Carcass and meat quality characteristics of purebred (hair) and crossbred (wool × hair) sheep lambs grazing fescue pasture as influenced by breed type, sex, and supplementation

ABSTRACT

The influence of breed type (purebred vs. crossbred), sex (short-scrotum ram vs. ewe lamb), and supplementation (pasture-only vs. pasture plus 2% soy hull) on carcass and meat quality of landrace hair (Barbados Blackbelly; BB and St. Croix; SX) and wool (Dorset; DO) × hair sheep lambs was evaluated. Forty-eight, mixed sex 5-mo old purebred hair (body weight (BW) = 17.9 ± 1.95 kg) and crossbred (wool × hair) sheep lambs (BW = 21.7 ± 2.56 kg) rationally grazed predominantly tall fescue pasture during summer with or without soy hull supplementation at 2% of BW. At the end of a 90-d grazing trial, lambs were harvested using the USDA standard procedures and their carcasses were evaluated. After 24 h chilling storge (2°C), longissimus muscle (LM) pH was measured, and carcasses were fabricated into primal cuts. Loin chops and fat depots were collected to analyse meat quality parameters. Supplementation rather than crossbreeding had more significant effect on carcass quality under the conditions of this experiment. Regardless of breed type, soy hull supplementation improved colour, lipid oxidation stability and texture properties of fresh lamb, whereas pasture-only lambs had healthier fatty acid profiles compared with those from supplemented lambs.

KEYWORDS:

• Hair sheep
• crossbreeding
• sex
• grazing
• soy hull
• carcass trait
• meat quality

Introduction

Over the past several decades, sheep flock sizes and farm numbers have contracted in the United States to an estimated 5.2 million head of sheep and lambs in 2020 (USDA-NASS 2020). However, consumer demand for healthy, premium quality lamb has steadily increased among ethnic groups and health-conscious consumers and led to a surging interest in hair sheep (NRC 2008; Shiflett 2020). Barbados Blackbelly and St. Croix sheep are landrace hair sheep breeds consider ‘easy-care’ because they can be raised with limited management inputs (Burke and Apple 2007; Weaver et al. 2022), though mature size and growth rates are generally smaller than in traditional wool sheep (Burke et al. 2003; Boughalmi and Araba 2016).

Crossbreeding has been used to improve the growth performance of hair sheep, but sire breeds need to be selected that complement nutritional management of a flock. Dorset sheep are considered a prolific breed with potential for use in accelerated mating systems (Lewis et al. 1996). Dorset rams achieved higher lambing rates in early summer matings than Suffolk rams, and were considered superior for use in a falling lambing system (Abdulkhaliq et al. 2007). Dorset sheep have been used under intensive rotational grazing conditions, and lambs achieved growth rate of 300 g/d, but these were lower than growth rates of contemporary Dorset lambs fed concentrate ad libitum (450 g/d) (Jaques et al. 2011). Though not a traditional terminal sire breed, Dorset-sired crossbred lambs from commercial wool cross ewes had similar growth rates to Dorper-sired lambs but lambs tended to have less fat at similar slaughter weights (Notter et al. 2004).

The success of a grass-based production system relies heavily on available forage and its quality. Producing heavier carcasses with premium quality lamb often requires additional protein and energy to maintain acceptable lamb performance due to the seasonal variation of forage quality and availability (Turner et al. 2014). Incorporating supplementation in grass-based pastures can enhance grazing performance and carcass quality. Soy hull is a by-product of soybean processing for oil and meal production. It is, high in digestible fibre, has a similar crude protein (CP) content to corn, and has been used as both an energy and fibre source in ruminant diets (Ipharraguerre and Clark 2003). In cattle soy hull supplementation improved growth similarly to corn (Van Elswyk and McNeill 2014). The effects of supplementing soy hull on animal performance and carcass quality in a grass-based hair sheep production system are not well document. In general, grass feeding affects meat quality and flavour, and, influences pH, intramuscular fat, and branch-chained fatty acids in edible tissues (Priolo et al. 2001). Sex also significantly affects carcass characteristics in sheep, including carcass yield, colour, and fatty acid compositions (de Araújo et al. 2017). The inclusion of concentrate supplementation on forage diets increased dressing percentage and fat content (Papi et al. 2011). The aim of this study was to determine the effect of crossbreeding, by-product supplementation, and lamb sex in rotationally grazed landrace hair sheep on carcass traits, chemical composition, and meat quality of lamb.

Materials and methods

All animals used in this grazing trial were managed according to the guidelines of Virginia State University’s Agricultural Animal Care and Use Handbook (VSU, Petersburg, VA, USA), and the experiment was approved by the Agricultural Animal Care and Use Committee at the University (AACUC Protocol #2014-02).

Grazing trail, carcass trait, and sampling

Experimental lambs were produced under accelerated mating (8-mo production cycle) in a flock of Barbados Blackbelly (BB) and St. Croix (SX) landrace hair sheep ewes managed in a pasture-based system. Ewes were mated to either like-breed sires or Dorset (DO) rams. Forty-eight, mixed sex, 5-mo old lambs, born on pastures in spring (April), were randomly selected to equally represent purebred hair (BB, body weight (BW) = 16.2 ± 1.9 kg; SX, BW = 19.5 ± 2.0 kg) and wool × hair crossbred (DO × BB, BW = 21.7 ± 2.3 kg; DO × SX, BW = 21.7 ± 2.9 kg) animals. Male lambs were rendered short-scrotum at weaning to facilitate co-grazing with ewe lambs. Over a period of 14 d lambs were allowed to adjust to the rotational grazing system and handling facilities; and were trained in the use of the Calan^© feeders to facilitate feeding of individual animals. During the experiment lambs grazed predominately Jesup tall fescue with Max-Q^© endophyte pasture (Table 1) for 90 d (May to August) as one group. Half of the lambs (n = 24), balanced by breed type and sex, were supplemented daily with soy hull (Table 1) at 2% of BW using the Calan^© gate feeders. Body weight (BW) was recorded over 2 consecutive days at the beginning and end of the trial before providing supplements, and averaged to determine initial and final weight for the determination of average daily gain (ADG). Furthermore, additional BW were recorded before providing supplements (9:00 am) in 14 d interval and intermediate weights used to adjust soy hull feeding levels.

Table 1. Chemical composition of tall fescue and soyhull.

Item	Tall fescue	Soyhull
Chemical composition, %DM
Dry Matter, DM	91.3	88.9
Ether extract, fat	2.00	1.17
Crude protein, CP	8.68	9.44
Ash	6.08	4.30
Acid detergent fibre, ADF	44.0	48.5
Total digestible nutrient, TDN	56.5	53.6
Fatty acid, %
C14:0	0.43	0.41
C16:0	19.88	13.23
C16:1n7	1.59	0.27
C18:0	1.91	5.62
C18:1n9	4.28	20.53
C18:2n6	13.56	47.65
C18:3n3	49.71	7.69

At the end of a 90-d grazing trial, lambs were transported to the Fort Valley State University (FVSU; Fort Valley, GA, USA) slaughter facility for harvest. Feed was withheld from lambs for 12 h before slaughter and fasting body weight (FBW) recorded. Lambs were stunned using a captive bolt, exsanguinated, and dressed according to industry-accepted procedures. Hot carcass weight (HCW) was recorded on the day of slaughter, and carcasses were chilled at 2°C for 24 h. Cold carcass weight (CCW) and carcass shrink were determined, and dressing percentage (DP) reported as the proportion of weight that remained in the carcass. Ultimate muscle pH was measured between the 12th and 13th ribs at 24-h postmortem using a portable pH meter (Fisher Scientific, Pittsburgh, PA, USA) with a penetrating probe (Pakton^® Model OKPH1000N, Fisher Scientific). On day 2 postmortem, carcasses were fabricated into primal cuts, and portion of primal cuts was recorded. Three different fat depots (subcutaneous, intramuscular and kidney fats) were collected from each carcass for fatty acid analysis. Longissimus muscle (LM; intramuscular fat) and subcutaneous fat were excised and removed from the loin area. All fat samples were individually ground with liquid nitrogen, placed in polyethylene bags (NASCO Inc., Fort Atkinson, WI, USA), and stored at −80°C for further analysis. Loin from each carcass was sliced into 2.5-cm loin chops and then used to measure fresh meat colour (CIE L* a* b*) and to determine Warner-Bratzler shear force (WBSF) values and cooking losses.

Laboratory analysis

The Commission Internationale de l’Eclairage (CIE) L* a* b* colour coordinate values were measured on the surfaces of four loin chops from each carcass after a 45-min bloom time at 4°C using a HunterLab Color instrument (Minolta Chromameter, Model CR-200, Minolta, Japan) with illuminant D65 as a light source. After measuring colour coordinate values, the four chops were cooked according to the procedures described by Lee et al. (2012). The difference in weight of chops before and after cooking was reported as percentage cooking loss. Two cores were taken from each cooked chop, and Warner-Bratzler shear force (WBSF) values assessed using a TA-XT2 texture analyzer fitted with a Warner-Bratzler shear attachment (Texture Technologies Corp., Scarsdale, NY, USA).

Myoglobin (Mb) and percent metmyoglobin (MetMb) contents were determined using the ground LM sample (5.0 g) according to the method of Krzywicki (1982). Both contents were measured at 525, 572, and 700 nm using a Shimadzu (model UV-2401 PC) spectrophotometer, and the concentration of Mb (mg/g muscle) and percent MetMb (%) were calculated using Krzywicki’s equation (Krzywicki 1982). The thiobarbituric acid reactive substances (TBARS) assay was performed on the ground LM sample (0.5 g) as described by Buege and Aust (1978) using 1,1,3,3- tetramethoxypropane (TMP) for preparation of a standard curve of malondialdehyde (MDA). The TBARS were calculated from the standard curve of MDA and expressed as mg MDA/kg sample.

Proximate composition of LM samples was analysed according to AOAC (1995) methods. Total lipids were extracted from 3.0 g of LM or 0.1 g of fat depot samples with chloroform/methanol (2:1 v/v), using a homogenizer (Cyclone IQ², Virtis Co., Gardiner, NY, USA) for 3 × 30 s at 30,000 rpm (Lee et al. 2008). Extracted lipid was saponified and esterified according to the AOCS method (1993) of preparation of fatty acid methyl esters (FAME). The prepared FAME were analysed using a Thermo Electronic (Austin, TX, USA) gas chromatography (Model TRACE GC Ultra) equipped with an automatic sampler Model AS-3000 (Thermo Electronic Co.). A 0.25-mm i.d. by 30-m long fused silica SP-2380 capillary column (Supelco, Inc., Bellefonte, PA, USA) was used to separate the methyl esters, which were detected with a flame ionization detector (FID). The injection temperature was 240°C and the column temperature was programmed from 130°C to 220°C at 4°C/min. Helium was the carrier gas, with a flow rate at 1.6 mL/min and a split ratio of 30:1. The identification and quantitation of individual FAME in the sample were completed according to the AOCS method (1993).

Statistical analysis

Data were analysed as a completely randomized design with a 2 × 2 × 2 factorial treatment arrangement, and individual animal was considered as the experimental unit using MIXED procedure of SAS (SAS Institute Inc., Cary, NC, USA). The effects of breed type (pure- and cross-bred), sex class (female and short-scrotum male) and supplementation (pasture only and pasture plus soy hull), as well as their interaction were considered as fixed. Significant differences between means were determined by the least squares means generated and separated using the PDIFF options of SAS for main and interaction effects. Differences at P < 0.05 were considered significant.

Results and discussion

Body weight gains and carcass traits

Average daily gain (ADG) was affected (P < 0.0001) by breed type, sex, and diet (Table 2), with crossbred lambs growing faster than purebred lambs, male lambs growing faster than female lambs, and supplemented lambs growing faster than pasture-only lambs. The greatest effect was achieved through supplementation that more than doubled ADG. There were no interactions (P = 0.204) for the three main effects for ADG. Fasting body weight (FBW) reflected ADG and was greater (P < 0.0002) for crossbred, male, and supplemented lambs than purebred, female, and pasture-only lambs with again the biggest difference resulting from supplementation (29.86 and 21.35 ± 0.602 kg for supplemented and pasture-only lambs. As a result, hot and cold carcass weight, loin area, and primal cuts of crossbred, male, and supplemented lambs were again greater (P < 0.001) than those of purebred, female, and pastured-only lambs with some variations (Table 2).

Table 2. Daily weight gain and carcass traits in purebred (hair) and crossbred (wool × hair) hair sheep lambs grazed on tall fescue pastures with or without soy hull supplementation.

	Treatment						P-value
	Breed type, B		Sex, S		Diet, D		Main			Interaction
Item	Purebred	Crossbred	Ram	Ewe	Pasture-only	Pasture + soy hull	B	S	D	B × S	B × D	S × D	B × S × D
Average daily gain (ADG), g	83.4	111.8	112.4	82.7	57.5	137.7	0.0001	0.0001	0.0001	0.4765	0.1605	0.0668	0.2038
Fasting body weight (FBW), kg	22.18	29.03	27.47	23.74	21.35	29.86	0.0001	0.0002	0.0001	0.0231	0.1293	0.1211	0.0128
Hot carcass weight, kg	9.31	12.05	11.39	9.97	8.33	13.03	0.0001	0.0020	0.0001	0.0547	0.0537	0.0808	0.0393
Cold carcass weight, kg	8.82	11.39	10.79	9.42	7.81	12.41	0.0001	0.0019	0.0001	0.0566	0.0573	0.0989	0.0252
Carcass shrink, %	5.49	5.54	5.25	5.79	6.21	4.82	0.9555	0.5673	0.1460	0.7453	0.7545	0.3566	0.2028
Dressing percentage, %	41.70	41.09	41.02	41.77	39.10	43.69	0.4059	0.3100	0.0001	0.8134	0.4470	0.4105	0.4429
Loin area, cm^2	8.64	10.51	9.91	9.23	8.29	10.85	0.0001	0.1030	0.0001	0.2254	0.0979	0.0398	0.4629
Primal cut, kg
Neck	0.77	0.98	1.00	0.75	0.71	1.03	0.0001	0.0001	0.0001	0.3023	0.0958	0.0042	0.0652
Shoulder	1.65	2.41	2.03	2.04	1.49	2.57	0.0135	0.9642	0.0008	0.9267	0.3036	0.9369	0.7762
Fore shank	0.40	0.51	0.50	0.42	0.39	0.52	0.0001	0.0004	0.0001	0.1453	0.3421	0.0380	0.0850
Breast	0.97	1.24	1.19	1.03	0.83	1.38	0.0001	0.0051	0.0001	0.1044	0.2036	0.0475	0.0508
Rack	1.10	1.40	1.17	1.34	0.93	1.57	0.0001	0.0057	0.0001	0.0129	0.0325	0.4195	0.0987
Loin	0.63	0.83	0.78	0.68	0.55	0.90	0.0001	0.0012	0.0001	0.0135	0.0738	0.3000	0.0157
Flank	0.33	0.45	0.40	0.38	0.25	0.53	0.0001	0.3146	0.0001	0.2372	0.1001	0.3593	0.0508
Leg	3.17	4.15	3.87	3.46	2.88	4.45	0.0001	0.0072	0.0001	0.0822	0.0804	0.1840	0.0192
Hind shank	0.50	0.62	0.61	0.52	0.49	0.64	0.0002	0.0048	0.0001	0.3348	0.6958	0.1419	0.0815

Note: Within a row, least squares means differ significantly at P < 0.05.

A wide range in ADG associated with terminal sir use, sex and supplementation have been reported for landrace hair sheep in different environments and management systems. The range in ADG of 60 to 140 g/d observed was larger thanpreviously recorded for purebred lambs at our location (56 to 75 g/d; Wildeus et al. 2005) and were similar to those reported for St. Croix lambs in the Virgin Islands (79 g/d; Dodson et al. 2005) and Arkansas (119 g/d; Burke and Apple 2007). Crossbreeding landrace hair sheep lambs with Dorset sires resulted in an increase of ADG by 34% here, and was higher than observed for Dorper-sired crossbred lambs on pasture (14%, Dodson et al. 2005) and feedlot (20%; Burke et al. 2003), or in lambs on concentrate diets using wool breed terminal sires (Texel: 25%, Romanov: 20%; Phillips et al. 2005). In contrast, no significance differences in ADG were observed by Godfrey and Collins (1999) between purebred St. Croix lambs and crossbred lambs sired by Suffolk and Gulf Coast native rams fed concentrate at 4% BW and tropical grass hay. The difference in ADG of in ram lambs compared ewe lambs was of a similar magnitude (36%) to that of breed type. No difference was reported between ewe and wether lambs in earlier grazing trials with these landrace breeds (Dodson et al. 2005; Wildeus et al. 2005), but no information is available on co-grazing of short-scrotum ram and ewe landrace hair sheep lambs. In a trial with wool breed lambs growth rates were similar in wether and ewe lambs, but lower than intact and short-scrotum lambs (Wellington et al. 2003), which again had similar growth rates. Providing lambs with supplement while on pasture had a more dramatic impact on ADG compared to breed type and sex, and increased ADG by 139%. The authors are not aware of other studies with a design that allowed a direct comparison of non-supplemented and supplemented lambs on the same pasture. Earlier growth trials at our location showed an ADG of landrace hair sheep lambs of 67 and 92 g/d during spring/summer grazing and supplementation with corn/soybean meal at 0.75% and 1.5% BW, respectively (Wildeus et al. 2005). Dodson et al. (2005) reported ADG of 79 g/d for St. Croix lambs rotationally grazing tropical pasture, which was higher than for the lambs in this study (57 g/d). This difference likely results from the higher crude protein (CP) and total digestible nutrient (TDN) in pasture in their study (11.5% and 61%), compared to the dormant tall fescue pasture during summer grazing in this study (8.7% and 56%, respectively). At the same location St. Croix lambs raised in dry lot on tropical grass hay pasture and supplement at 4% BW had an ADG of 108 g/d, which was lower than in the supplemented lambs here (138 g/d). In Arkansas, St. Croix lambs grazing Bermuda grass pasture and receiving 680 g/d of a corn/soybean meal supplement had an ADG of 119 g/d, again lower than the supplemented lambs in this study. There were no significant interactions of the main effects for ADG. Brown and Mayeux (2005) reported a higher ADG in Dorset × St. Croix crossbred lambs under feedlot conditions, but not on pasture. The level and type of supplementation used here likely did not allow for an expression of this interaction.

The effects of breed type, sex, and diet on FBW generally mirrored that for ADG (Table 2). Supplementation resulted in the greatest increase (8.5 kg; P < 0.0001) in FBW compared to pasture-only lambs, followed by crossbred compared to purebred lambs (6.9 kg; P < 0.0001), and finally male compared to female lambs (3.7 kg; P < 0.0002). In contrast to ADG, there were significant interactions (P < 0.05) of breed type with sex and the three-way interaction of breed type, sex and diet. This discrepancy likely reflected that ADG only represented the performance of lambs during the feeding trial, whereas FBW also accounted for the pre-weaning differences resulting from breed type and sex. Within breed type, FBW was greater (P < 0.03) for ram than ewe lambs in crossbred lambs (32.0 vs. 26.1 ± 0.009 kg) but sex had no effect in purebred lambs (23.0 vs. 21.4 ± 0.009 kg). When also considering diet (three-way interaction), FBW was greater (P < 0.02) for supplemented crossbred ram lambs than for supplemented crossbred ewe lambs, whereas FBW of crossbred ewe lambs were not greater than that of either purebred ram or ewe lambs. These interactions reflected the improved growth potential associated with male lambs and supplementation. The lambs in this study were slaughtered at target age (8 mo; born within a 14 d window) rather than a target weight, hence comparison of a final body with other studies is confounding. The range in FBW (21 to 30 kg) in this experiment was general lower than reported for lambs of similar breed types, however lambs in these other studies were on trial longer (Dodson et al. 2005; Wildeus et al. 2005; Burke and Apple 2007) or were fed concentrate rations (Burke et al. 2003; Godfrey and Weiss 2005; Phillips et al. 2005).

Differences in hot and cold carcass weight among treatments reflected those for FBW. Carcass shrink was not affected by any of the treatments and ranged from 4.8% to 6.2% (Table 2). The difference in carcass shrink was most pronounced between pasture-only and supplemented lambs (1.4%) but was not statistically significant. Dressing percentage (DP) of lambs in this study (Table 2) were lower (39.7% to 43.1%) than generally reported for sheep (44% to 50%) and is influenced by age, body weight and fat cover (Hopkins 1991). There were no effects of breed type and sex on DP, but it increased (P < 0.001) by 4.6% in supplemented compared to pasture-only lambs. In ruminants, forage diets generally increase digestive tract size and decrease external fat cover that results in lower DP in carcasses (Gardner et al. 2015). Ates et al. (2020) also reported that lambs grazed on pastures had heavier intestinal weights and thinner layers of external fat cover than those fed concentrates.

In the present study, breed type, diet, and a sex × diet interaction significantly affected loin areas in carcasses from experimental lambs. Crossbred and supplemented lambs had larger (P < 0.0001) loin areas than purebred and pasture-only lambs (10.51 vs. 8.64 ± 0.284 cm²; 10.85 vs. 8.29 ± 0.285 cm²), respectively. Within the breed type, loin areas were not different (P > 0.05) between male and female crossbred lambs (11.10 and 9.92 vs. ± 0.403 cm²), whereas crossbred male lambs had greater (P < 0.05) loin areas than any of purebred lambs (8.55 to 8.73 ± 0.403 cm²). Similar to ADG and carcass yield, use of a terminal sire and supplementation translated to a larger loin. However, there was no effect sex for loin eye area in the present study.

Breed type, sex, and supplementation significantly affected (P < 0.01) all primal cuts from because of weight differences in BW and carcass weight at slaughter. Carcasses from crossbred male, and supplemented lambs produced heavier (P < 0.01) neck, fore-shank, breast, rack, loin, leg, and hind-shank cuts compared with those from purebred, female, and pasture-only lambs. Weights of shoulder and flank cuts were greater (P < 0.01) for crossbred and supplemented lambs than purebred and pasture-only lambs. These two primal cuts, however were not affected by sex, or two- nor three-way interactions of breed type, sex, and supplementation. The general perception in livestock that males develop greater muscularity in shoulder and neck areas, than castrated males, with the least development in females de Rezende et al. (2020) reported that shoulder and neck areas were developed more rapidly in rams than ewes. However, in the present study, such differences were not found in the shoulder cuts.

Primal cuts of rack and loin from lamb carcasses showed a significant interaction between breed type and sex. Within the breed type, weights of rack cuts were greater (P < 0.01) for male than female crossbred lambs (1.57 vs. 1.24 ± 0.060 kg), but were not different (P > 0.05) in purebred lambs (1.11 vs. 1.09 ± 0.060 kg). No significant differences were found in the weights of rack cuts from crossbred female and purebred lambs (regardless of their sex). Within breed type, weights of loin cuts were greater (P < 0.01) in male than female crossbred lambs (0.91 vs. 0.74 ± 0.028 kg), but were not different (P > 0.05) in purebred lambs (0.65 vs. 0.62 ± 0.028 kg). Crossbred short-scrotum ram lambs had heavier loin cuts and purebred ewe lambs. Crossbred ewe- and purebred male lambs had intermediate weights and were not different. An interaction between breed type and diet was only found (P < 0.05) in rack cuts. Within the supplemented groups, crossbred lambs had heavier rack cuts (1.79 vs. 1.36 ± 0.059 kg) than did purebred lambs, but no differences were found for breed type in rack cut weights in pasture-only lambs (1.02 and 0.85 ± 0.059 kg). Crossbred male lambs supplemented with soy hull had the heaviest weights of rack cuts, and pasture-only lambs, regardless of breed, had the lightest. Purebred, supplemented lambs had intermediate values.

Sex and supplementation had significant effects on primal cuts of neck, fore-shank and breast from lamb carcasses. Neck cuts from supplemented male lambs were heavier (P < 0.01) than those from either supplemented ewe lambs or pasture-only rams and ewe lambs (1.23 vs. 0.84 or 0.76 and 0.66 ± 0.049 kg). Weights of neck cuts from these three groups were not significantly different. Within supplemented groups, male lambs had heavier weights of fore-shank cuts (0.59 vs. 0.46 ± 0.021 kg) than did ewe lambs, but no differences in sex were found in the weights of rack cuts (0.41 and 0.37 ± 0.021 kg) in the pasture-only lambs. Supplemented male lambs had the heaviest weights of fore-shank cuts and pasture-only lambs, regardless of sex, had the lightest. No significant differences were found in the weights of fore-shank cuts from supplemented ewe- and pasture-only male lambs. For breast cuts, supplemented male lambs had the heaviest weight (1.52 ± 0.052 kg) and pastured-only lambs had the lightest weight, regardless of sex (0.81 to 0.86 kg). Supplemented ewe lambs (1.25 ± 0.052 kg) had intermediate weights, which were greater than pasture only-lambs (regardless of sex) but lower than supplemented male lambs.

Loin and leg cuts were affected (P < 0.05) by a breed type × sex × diet interaction. Within the supplementing treatment, weights of loin and leg cuts were greater for crossbred male than crossbred ewe lambs, whereas those from crossbred ewe were not greater than those of either purebred male or female supplemented lambs (Table 2). For pasture-only lambs loin cuts, in crossbred male lambs were heavier weights than in purebred lambs regardless of sex , whereas the weights of loin cuts were not different between crossbred ewe lambs and either crossbred male lambs or purebred lambs. Leg cuts in pasture-only groups, crossbred male lambs were heavier than in purebred female lambs, whereas the leg cut weights were not different between crossbred ewe lambs and either crossbred or purebred male lambs. Breed type, sex, and supplementation, as well as some of their interactions affected loin cuts in a similar fashion as were observed for weight gains and other carcass traits.

Quality characteristics of lamb chops

Quality characteristics of fresh and cooked loin chops are presented in Table 3. The CIE L* (lightness), a* (redness) and b* (yellowness) values of lamb chops were affected by sex and supplementation, and their interaction. A significant three-way interaction (breed type × sex × supplementation) was also found for the CIE b* values. Breed type had no significant colour of fresh lamb, and, agrees with findings of Suliman et al. (2021), who reported that the CIE L*, a* and b* colour coordinate values of fresh lamb were not affected by breed differences indigenous sheep raised under similar management conditions. Loin chops from male lambs had higher (P < 0.01) CIE L*, a* and b* values than ewe lambs. Supplemented lambs had lower CIE L* and b* values, but higher CIE a* values in the lamb chops than did pasture- only lambs., but the lamb chops had higher CIE a* values in supplemented lambs.

Both genetic and environmental factors such as breed, sex, age of animal at slaughter, slaughter weight and nutrition, affect meat production and quality in lambs (Lewis and Emmans 2007). The visual appearance of fresh meat is an important criterion used to evaluate meat quality by consumers, which is based on colour, marbling, and water-holding capacity (Andersen et al. 2005). Both genetic and environmental factors are also relevant for the concentration of myoglobin, moisture, and fat in fresh meat. In the present study breed type did not affect the CIE L* (lightness), a* (redness) and b* (yellowness) of lamb chops, nor was the concentrations of myoglobin, moisture, and fat in LM were not significantly different (Tables 3 and 4). Both sex and supplementation significantly influenced the CIE colour parameters of fresh lamb chops in this study. These results contradict the findings of Tejeda et al. (2008), who reported that fresh meat colour of lambs raised under similar management conditions were not affected by sex. This discrepancy can be explained by differences in the myoglobin and proximate composition contents in these lamb.

Table 3. Quality characteristics of loin chops from purebred (hair) and crossbred (wool × hair) hair sheep lambs grazed on tall fescue pastures with or without soy hull supplementation.

	Treatment						P-values
	Breed, B		Sex, S		Diet, D		Main			Interaction
Parameter	Purebred	Crossbred	Ram	Ewe	Pasture-only	Pasture + soy hull	B	S	D	B × S	B × D	S × D	B × S × D
Fresh
L* value, lightness	42.47	42.16	43.76	40.87	44.07	40.57	0.3860	0.0001	0.0001	0.2909	0.6051	0.0035	0.2103
a* value, redness	12.16	11.79	11.58	12.37	11.69	12.26	0.1274	0.0012	0.0209	0.5578	0.3952	0.0187	0.2918
b* value, yellowness	12.35	12.40	12.76	11.99	12.82	11.92	0.8256	0.0006	0.0001	0.8240	0.1933	0.8359	0.0027
Myoglobin (Mb), mg/g	3.72	3.67	3.71	3.68	3.44	3.95	0.7408	0.8282	0.0019	0.4089	0.0181	0.2354	0.0608
Metmyoglobin (MetMb), %	24.75	24.64	26.99	22.40	23.25	26.13	0.9527	0.0182	0.1345	0.0385	0.0946	0.1689	0.0973
TBARS, mg/kg	0.32	0.27	0.30	0.30	0.30	0.30	0.0157	0.8089	0.8974	0.1765	0.8320	0.9654	0.4431
Ultimate pH	5.55	5.64	5.57	5.62	5.63	5.57	0.0659	0.3097	0.2136	0.7052	0.4129	0.8245	0.3589
Cooked
Cooking loss, %	20.41	19.70	20.10	20.01	20.32	19.79	0.4089	0.9201	0.5433	0.0859	0.4093	0.3916	0.6821
WBSF, kg/cm^3	2.23	2.37	2.46	2.14	2.40	2.20	0.0672	0.0001	0.0113	0.0128	0.0231	0.0036	0.3712

Note: Within a row, least squares means differ significantly at P < 0.05.

Table 4. Least squares means for proximate and fatty acid composition of longissimus muscle (LM; intramuscular fat) from purebred (hair) and crossbred (wool × hair) hair sheep lambs grazed on tall fescue pastures with or without soy hull supplementation.

	Treatment						P-values
	Breed type, B		Sex, S		Diet, D		Main			Interaction
Item	Purebred	Crossbred	Ram	Ewe	Pasture-only	Pasture + soy hull	B	S	D	B × S	B × D	S × D	B × S × D
Proximate Composition, %
Moisture	75.18	75.48	75.56	75.10	76.12	74.54	0.0505	0.0034	0.0001	0.8178	0.3879	0.3156	0.2999
Crude Protein	22.06	21.77	21.78	22.04	21.42	22.41	0.2182	0.2768	0.0001	0.4397	0.9076	0.3263	0.7038
Ether extracted, fat	1.70	1.65	1.75	1.59	1.47	1.88	0.7436	0.2684	0.0079	0.4929	0.7688	0.0100	0.0926
Ash	1.16	1.20	1.20	1.16	1.19	1.18	0.2033	0.2067	0.7790	0.7169	0.3646	0.1324	0.0126
Fatty acid, %
C10:0	0.92	0.73	0.88	0.77	1.14	0.51	0.5337	0.7059	0.0398	0.9715	0.1576	0.1043	0.2251
C12:0	0.25	0.25	0.26	0.24	0.34	0.16	0.9101	0.6741	0.0025	0.1057	0.7372	0.2572	0.2718
C14:0	3.63	3.67	3.52	3.78	3.57	3.73	0.8435	0.1413	0.3447	0.3777	0.4418	0.5323	0.6654
C14:1n5	0.62	0.64	0.69	0.57	0.68	0.58	0.7783	0.0789	0.1363	0.5525	0.1249	0.6774	0.3642
C16:0, iso	0.39	0.37	0.34	0.42	0.39	0.37	0.8479	0.4552	0.8724	0.9111	0.3609	0.7397	0.2404
C16:0	21.41	22.27	22.09	21.59	21.71	21.97	0.2589	0.5007	0.7306	0.4136	0.4901	0.4494	0.6205
C16:1n7, trans	1.14	0.97	1.04	1.07	1.03	1.08	0.0027	0.5271	0.3934	0.6766	0.3736	0.4124	0.5966
C16:1n7	1.41	1.53	1.57	1.37	1.39	1.55	0.2917	0.0919	0.1980	0.4530	0.2047	0.5745	0.6622
C17:0	1.22	1.17	1.28a	1.11b	1.13	1.26	0.4815	0.0211	0.0802	0.7124	0.2540	0.6546	0.5658
C17:1n7	0.75	0.76	0.76	0.75	0.62	0.88	0.9501	0.8264	0.0001	0.5234	0.3933	0.9904	0.3191
C18:0	19.79	19.88	19.07	20.60	19.06	20.61	0.8572	0.0057	0.0050	0.6398	0.7617	0.6448	0.9512
C18:1n9, trans	0.26	0.28	0.29	0.26	0.27	0.27	0.7487	0.1997	0.9365	0.3928	0.0875	0.1652	0.7616
C18:1n11, trans	1.15	1.16	1.23	1.08	1.21	1.10	0.8101	0.0452	0.1598	0.7026	0.5182	0.3503	0.7480
C18:1n9	33.46	32.73	31.61	34.58	30.91	35.27	0.5196	0.0129	0.0005	0.6139	0.9929	0.4358	0.6841
C18:2n6, trans	0.37	0.36	0.41	0.32	0.39	0.34	0.6729	0.0092	0.0870	0.7230	0.3786	0.6411	0.8791
C18:2n6	6.04	5.86	6.55	5.35	7.03	4.87	0.6541	0.0067	0.0001	0.6747	0.4974	0.7135	0.9334
C18:2, c9,t11	0.31	0.35	0.33	0.33	0.39	0.27	0.4613	0.9885	0.0354	0.6888	0.7825	0.5992	0.5312
C18:3n3	1.21	1.24	1.42	1.03	1.51	0.94	0.7876	0.0028	0.0001	0.8311	0.5771	0.3707	0.6613
C18:3n6	0.76	0.72	0.79	0.69	0.75	0.73	0.6451	0.2315	0.7458	0.8289	0.8161	0.5198	0.4982
C20:1n9	0.30	0.34	0.35	0.29	0.36	0.28	0.2774	0.0609	0.0214	0.0812	0.3866	0.5881	0.2457
C20:2n6	0.68	0.72	0.84	0.56	0.93	0.48	0.7131	0.0118	0.0002	0.6360	0.6531	0.6043	0.5200
C20:4n6	3.14	2.97	3.58	2.25	3.87	2.23	0.6561	0.0088	0.0001	0.7003	0.9801	0.5058	0.8713
C20:5n3	0.35	0.34	0.38	0.31	0.34	0.34	0.7405	0.0288	0.8983	0.5133	0.0848	0.4871	0.8141
C22:5n3	1.06	1.01	1.23	0.84	1.35	0.73	0.6767	0.0071	0.0001	0.7191	0.9834	0.4267	0.9669
C22:6n3	0.34	0.34	0.39	0.30	0.44	0.24	0.9682	0.1071	0.0014	0.7242	0.5767	0.9873	0.6925

Note: Within a row, least squares means differ significantly at P < 0.05.

Male lambs had a higher (P < 0.05) moisture content in LM muscle, but notmyoglobin (Table 3) or fat contents (Table 4) than female lambs. Higher moisture content in LM muscle from male lambs could limit the absorption of visible lights, leading to an increase reflectance on the surface of lamb chops, and may explain higher CIE L* values in loin chops from the male lambs in this study. Carraspiso and García (2005) also reported that the lightness (CIE L*) of biceps femoris muscle increased as the moisture content in muscle increased.

The differences in CIE a* and b* values in male and female lambs observed here, however could not be explained by myoglobin and proximate composition. Many environmental factors influence the colour of fresh red meat, such as light, temperature, relative humidity, and presence of specific bacteria during the post-mortem processing (Luciano et al. 2009). Lambs fed low-energy diets alos tended to have meat that is darker (lower CIE L* values) in both lean and fat colour than those fed high-energy diets (Priolo et al. 2002; Ekiz et al. 2012). In contrast, LM from pasture-only lambs here had a lighter coloured (higher CIE L* values) fresh meat than supplemented lambs. Reasons for these opposing results could be differences in myoglobin and proximate composition contents of LM muscle. The higher moisture content observed in LM from pasture-only lambs could explain this higher CIE L* value because of increasing reflectance on the meat. The lower myoglobin concentration of pasture-only lambs could also have lowered the absorption of visible lights, leading to an increase reflectance (higher CIE L* values) on the surface of lamb chops. The higher CIE a* value of LM of supplemented lambs was in line with the higher amounts of myoglobin.

Loin chops of supplemented lambs had significantly lower yellowness (CIE b*) values than pasture-only lambs because of higher intermuscular fat contents. This result agrees with that of Lee et al. (2008) reporting that small ruminants fed a hay diet had a yellower coloured (higher CIE b* value) LM muscle than those fed on a concentrated diet. An interaction between sex and diet was detected for CIE L* and a* values. Regardless of supplementation, CIE L* values were higher (P < 0.05) in LM from male than ewe lambs. The LM from pasture-only male lambs had the highest CIE L* value and supplemented female lambs had the lowest value (46.04 and 39.65 ± 0.352, respectively). Pasture-only female and supplemented male lambs had intermediate L* values (42.09 and 41.49 ± 0.352, respectively), were higher than those from supplemented female lambs but lower than those from pasture-only male lambs. The CIE a* values of supplemented lambs were higher (P < 0.05) than pasture-only lambs (12.15 vs 11.00 ± 0.240), but not different from female lambs (grazing only and supplementing; 12.38 and 12.37 ± 0.240, respectively). Regardless of supplementation, female lambs had higher CIE a* values of LM than those from pasture-only and supplemented male lambs. There was a 3-way interaction for CIE b* values. Purebred pasture-only male lambs had higher (P < 0.05) CIE b* values of LM than purebred supplemented lambs regardless of sex. There were no significant differences in the CIE b* values of LM from pasture-only crossbred and purebred supplemented lambs regardless of sex.

Neither breed type, sex, diet, nor any interactions of these influenced ultimate pH of LM in the experimental lambs (Table 3). In general, muscle pH declines to reach approximately 5.3 to 5.8 in fresh lamb at 24 h postmortem (Savell et al. 2005). It is known that ultimate pH of red meat can be affected by factors such as breed, age, diet, and stress level (England 2018). However, such factors did not significantly impact the ultimate muscle pH of lambs in the current study. Perhaps this discrepancy can be explained by differences in glycogen levels in muscles and pre-slaughter stress among different studies. This suggested that glycogen levels in muscles and pre-slaughter stress among breed type, sex, and supplementation were not different in the present study.

Cooking losses of loin chops from the experimental lambs were not affected by either breed type, sex, diet, or any interaction involving these three main effects (Table 3). Cooking loss can be affected by muscle pH and proximate composition, as well as aging time and cooking temperature of meat (Aaslying et al. 2003; Abdullah and Qudsieh 2009). There is overwhelming evidence that water holding capacity (WHC) is negatively corrected with cooking loss in edible tissues (Watanabe et al. 2018). The WHC is also affected by muscle pH and intramuscular fat in a reverse relationship (Cannata et al. 2010), and muscle pH more significantly affected WHC than did intramuscular fat content (Watanabe et al. 2018). In present study, the absence of differences in cooking losses among breed type, sex and supplementation factors might be explained by the lack of difference in ultimate muscle pH in fresh lamb (Table 3), even though LM from supplemented lambs had more intermuscular fat than that from pasture-only lambs (Table 4).

The Warner-Bratzler shear force (WBSF) values of cooked loin chops were influenced (P < 0.05) by sex and supplementation, but not breed type. All two- (breed type × sex; breed type × diet; and sex × diet) interactions significantly affected the WBSF values of cooked loin chops from experimental lambs. The acceptable limit for lamb tenderness is around a 3 kg/cm³ WBSF to Australian and New Zealand consumers (Webb et al. 2005). The WBSF values of cooked chops from the current study ranged from 1.85 to 2.73 kg/cm³ (not presented in Table 3), which were all lower than 3 kg/cm³. Accordingly, fresh lamb from experimental lambs was objectively very tender. Meat tenderness can be affected by genetic and environmental factors like breed, sex, age of animal at slaughter, diet, and processing condition (Webb et al. 2005). In our study, loin chops from male lambs had higher (P < 0.05) WBSF than those from female lambs; moreover, the WBSF of loin chops from pasture-only lambs were higher (P < 0.05) than those from supplemented lambs. No significant differences were found in the shear values of cooked chops between breed types. Previous studies reported that breed might affect tenderness of fresh lamb (Fisher et al. 2004; Shackelford et al. 2012). Perhaps this discrepancy might be due to the lack of differences in the development of connective tissue and hypertrophy in muscles between the two breed types in our study. It is known that lambs fed concentrate diets have generated more tenderized meat than those grazed only on pasture (Priolo et al. 2002; Ekiz et al. 2012). The higher WBSF of cooked chops from male and pasture-only lambs in the present study are probably due to their carcasses being more prone to cold shortening than those from female or supplemented lambs. Compared with ewe or supplemented lambs, male and pasture-only lambs may have a higher calpastain activity or intramuscular fat content, and a higher collagen content and lower solubility (Lee et al. 2008). A breed type × sex interaction for WBSF values was noticed in cooked loin chops. Crossbred male lambs had higher (P < 0.05) WBSFr values of cooked chops compared to purebred male and female lambs, and crossbred ewe lambs (2.62 vs. 2.29, 2.17 and 2.12 ± 0.077 kg/cm³, respectively), while differences among these three groups were not significantly different. A breed type × diet interaction for WBSF values was also present in cooked chops of experimental lambs. The shear values of cooked chops were higher (P < 0.05) for crossbred pasture-only lambs than pasture-only and supplemented purebred lambs (2.56 vs. 2.24, 2.22 and 2.18 ± 0.078 kg/cm³, respectively), while WBSF was not different between three groups. In a sex × diet interaction, WBSF cooked chops from supplemented ewe was lower (P < 0.05) than those from male pasture-only and supplemented (1.93 vs. 2.47, 2.44 and 2.36 ± 0.077 kg/cm³, respectively), again differences between these three groups were not significantly different.

Supplemention and its interaction with breed type (breed type × diet) had significant effects on myoglobin (Mb) contents in LM (Table 3). Supplemented lambs had higher (P < 0.05) Mb concentrations in LM than pasture-only lambs. The LM from supplemented crossbred lambs had a higher (P < 0.05) concentration of Mb than that from pasture-only crossbred lambs (4.11 vs. 3.22 ± 0.156 mg/g muscle). Supplemented and pasture-only purebred lambs had the intermediate contents of Mb (3.78 or 3.66 ± 0.156 mg/g muscle), with no difference in crossbred lambs regardless of diet. Mean Mb content of LM muscle ranged from 3.22 to 4.21 mg/g (not presented in Table 3), and was lower than the average concentration of Mb of 6.64 mg/g muscle in the major meat production types of lambs in Australia (Pannier et al. 2014). In general, genetic factors like species, maturity, sex, and muscle groups are known to influence the content of Mb in livestock. Moreover, muscles used for greater physical activity often have more Mb content (Santos et al. 2015). However, in our study only diet and its interaction with breed type affected the concentration of Mb in LM muscle, and might be related with heavier carcass or muscle weights. Previous studies reported that lean growth animals had a less oxidative muscle type with a paler appearance (Wegener et al. 2000; Gardner et al. 2007). Muscles with lower proportions of oxidative myofibers might have lower concentrations of Mb and fewer mitochondria within these muscles (Lefaucheur 2010).

The percentages of metmyoglobin (MetMb) in the LM were significantly influenced by sex and its interaction with breed type (breed type × sex). The concentration of MetMb in LM from male lambs were higher (P < 0.05) than that from Female lambs. The LM from crossbred male lambs had a higher (P < 0.05) percentage of MetMb than that from crossbred female lambs (28.93 vs. 20.34 ± 1.882%), while purebred lambs either sex had an intermediate contents of MetMb (25.04 or 24.46 ± 1.882%), which were not different from crossbred lambs. As previously noted, the colour of fresh red meat is affected by the concentration of Mb, and greatly influenced by the oxidation state of Mb, which is presented in any of three redox forms, mainly deoxymyoglobin (DeoxyMb), oxymyoglobin (OxyMb), and metmyoglobin (MetMb). Their proportion depends on the level of saturation Mb with oxygen (Mancini and Hunt 2005). Formation of MetMb occurrs in the interior of the fresh cut red meat because of the lack of oxygen penetrating below the surface (Ranken 2000). Such a low oxygen concentration may induce oxidation of Mb to MetMb and is associated with meat discolouration. In the present study, the MetMb content was higher in male compared female lambs. Perhaps MetMb reducing enzyme systems in the male lambs might be lower than those in the female lambs, followed by slow conversion of MetMb to DeoxyMb, and subsequently accumulated MetMb upon analysing.

The thiobarbituric acid reactive substance (TBARS) values of LM were only affected by breed type. The TBARS values from purebred lambs were higher than those from crossbred lambs. In general, TBARS are useful to determine the degree of lipid oxidation occurred in meat products. Lipid oxidation results in the productions of free radicals, which may lead to the oxidation of meat pigments and generation of rancid odours and flavours (Tejeda et al. 2008). In the present study, lipid oxidation of meat was only affected by breed types. However, higher TBARS values in LM were not expected in loin chops from crossbred lambs because limitated variation in fatty acid composition in the LM from both breed types, especially unsaturated fatty acids. Additional factors, such as light, temperature, relative humidity, muscle pH, and the presence of specific bacteria, also influence the stability of meat pigments (Luciano et al. 2009). Several researchers proved a strong relationship between lipid oxidation and myoglobin oxidation levels (McKenna et al. 2005), whereas this relation was not present in our study. It remains unclear why higher MetMb concentrations in TBARS values were observed in the LM of male purebred lambs as compared to female crossbred lambs in the present study.

Chemical composition of longissimus muscle (LM) and fat depots

Proximate composition of LM from lambs on the study purebred and crossbred lambs with or without supplementing soy hull are summerized in Table 4. Moisture content of the LM was affected by sex and diet, but not breed type. The moisture percentages of LM from pasture-only lambs were higher (P < 0.05) than those from supplemented female lambs. The concentrations of protein in LM from supplemented lambs were higher (P < 0.0001) than those from pasture-only lambs, but was not affected by breed type and sex. Supplementation and its interaction with sex (sex × diet) had significant effects on the fat content in the LM. Supplemented lambs had a higher (P < 0.01) concentration of fat in the LM than pasture-only lambs. The LM from supplemented male and female lambs had a higher (P < 0.01) content of fat than that from pasture-only female lambs (1.76 or 1.99 vs. 1.18 ± 0.146%), while pasture-only male lambs had an intermediate fat content (1.75 ± 0.146%). There was a 3-way interaction (breed type × sex × diet) for ash content in the LM was detected, but ash content was immediately affected by breed type, sex, or diet. Crossbred pasture-only lambs had a higher (P < 0.05) ash content in the LM than pasture-only male lambs or supplemented purebred female lambs and supplemented male lambs or pasture-only crossbred female lambs. Supplemented crossbred female lambs, as well as supplemented male lambs and purebred pasture-only female lambs had the intermediate ash contents.

Proximate composition of muscle in ruminant animals is influenced by diet and breed, as well as age and sex (Wood et al. 2008). Development of muscle depends on nutrient composition and utilization, thereby the energy contents of the diet might partially explain the difference in proximate composition of LM in the present study. Compared with pasture-only lambs, supplemented lambs had higher concentrations of fat and protein, but a lower concentration of moisture in the LM, regardless of breed type and sex. Numerous studies reported higher muscle fat contents in animals that received higher proportions of concentrate in the diet (Geay et al. 2001; Roberts et al. 2009). The lower moisture content in the LM from supplemented lambs might be due to the higher lipid content compared to pasture-only lambs in the present study. Higher crude protein contents of LM from supplemented lambs could be due to the differences in the availability of nutrient and its utilization between forage and forage with supplement diets. Typically, crossbred sheep has a higher muscle fat content than that purebred sheep (Arvizu et al. 2011), and meat from ewes contains a higher amount of fat than that from rams (Santos et al. 2007). However, none of these expected trends was observed in the present study, and this lack of agreement might be attributed to the landrace breeds on the maternal side used in this study.

Consumption of red meat has been considered a health risk factor because of its high levels of saturated fat, derived from hydrogenation of dietary unsaturated fat in the rumen (Wolfram 2003; Khaldari and Ghiasi 2022). Accordingly, the fatty acid composition of edible tissues of lambs plays an important role to determine the healthier quality of fresh lamb, associated with intrinsic and extrinsic factors, such as breed, sex, slaughter weight, age and quality and quantity of feed (Wood et al. 2003, p. 2008). By far the most effective way to modify the fatty acid composition of fresh lamb is manipulating dietary regimes. As indicated in Tables 4–6, fatty acids identified in intramuscular (LM), subcutaneous, and kidney fats from experimental lambs, consisted of seven saturated (SFA: C10:0, C12:0, C14:0, C16:0 iso, C16:0, C17:0, and C18:0), eight monounsaturated (MUFA: C14:1n5, C16:1n7t, C16:1n7, C17:1n7, C18:1n9t, C18:1n11t, C18:1n9, and C20:1n9), and ten polyunsaturated (PUFA: C18:2n6t, C18:2n6, C18:2c9,t11, C18:3n3, C18:3n6, C20:2n6, C20:4n6, C20:5n3, C22:5n3, and C22:6n3) fatty acids. The identified fatty acids are only discussed for the main effects, breed type, sex, and diet as there were no significant interactions in regard to in intramuscular (LM) fat (Table 4). However, some of 2-way and 3-way interactions were found in the individual fatty acids from subcutaneous and kidney fats (Tables 5 and 6).

Table 5. Least squares means for fatty acid composition, weight percent of fatty acid methyl esters, of subcutaneous fat from purebred (hair) and crossbred (wool × hair) hair sheep lambs grazed on tall fescue pastures with or without soy hull supplementation.

	Treatment						P-value
	Breed type B		Sex, S		Diet, D		Main			Interaction
Fatty acid, %	Purebred	Crossbred	Ram	Ewe	Pasture-only	Pasture + soy hull	B	S	D	B × S	B × D	S × D	B × S × D
C10:0	1.08	0.90	1.05	0.93	1.07	0.90	0.2258	0.4553	0.2618	0.1381	0.7379	0.9816	0.1302
C12:0	0.57	0.40	0.58	0.38	0.68	0.29	0.1443	0.0819	0.0016	0.8659	0.3249	0.9449	0.3223
C14:0	4.44	4.69	4.42	4.70	4.60	4.53	0.2366	0.1824	0.7346	0.0453	0.3078	0.0630	0.0622
C14:1n5	0.96	1.09	1.09	0.96	1.09	0.96	0.1490	0.1345	0.1314	0.4182	0.0294	0.6047	0.0306
C16:0, iso	0.34	1.08	0.78	0.63	1.12	0.30	0.0277	0.6444	0.0166	0.5327	0.1536	0.1835	0.0352
C16:0	19.21	25.79	22.57	22.42	24.82	20.17	0.0001	0.9211	0.0044	0.0304	0.0979	0.0257	0.8931
C16:1n7, trans	1.31	0.93	1.11	1.13	1.05	1.19	0.0001	0.8351	0.0998	0.6392	0.4058	0.0003	0.1981
C16:1n7	1.99	2.16	2.10	2.04	1.77	2.38	0.1952	0.6490	0.0001	0.3385	0.4892	0.4227	0.3485
C17:0	1.29	1.33	1.28	1.34	1.27	1.36	0.5039	0.3221	0.1609	0.5464	0.8552	0.6037	0.8106
C17:1n7	1.14	1.12	1.12	1.14	0.82	1.45	0.7529	0.8014	0.0001	0.4618	0.8713	0.1520	0.3554
C18:0	19.16	19.06	19.50	18.72	18.04	20.18	0.9367	0.5377	0.0970	0.8936	0.6144	0.5368	0.5634
C18:1n9, trans	0.34	0.23	0.28	0.29	0.30	0.27	0.0382	0.7510	0.6374	0.2868	0.1464	0.9275	0.2143
C18:1n11, trans	0.93	0.77	0.83	0.87	0.92	0.79	0.0728	0.6038	0.1276	0.2348	0.6259	0.8185	0.2122
C18:1n9	35.66	30.50	32.91	33.25	29.68	36.48	0.0002	0.7789	0.0001	0.0204	0.2854	0.0258	0.5882
C18:2n6, trans	0.57	0.42	0.45	0.54	0.61	0.38	0.0587	0.2604	0.0055	0.5075	0.0833	0.4502	0.5461
C18:2n6	3.74	3.30	3.72	3.33	3.67	3.37	0.2871	0.3467	0.4626	0.3136	0.1887	0.2566	0.2380
C18:2, c9,t11	0.46	0.46	0.41	0.51	0.63	0.29	0.9030	0.0856	0.0001	0.5056	0.3031	0.0630	0.4074
C18:3n3	1.03	0.80	0.91	0.92	0.96	0.87	0.012	0.9287	0.2236	0.6540	0.6783	0.0066	0.2175
C18:3n6	0.64	0.63	0.64	0.62	0.73	0.53	0.8980	0.8277	0.0153	0.7128	0.6711	0.7281	0.6648
C20:1n9	0.51	0.58	0.29	0.80	0.88	0.21	0.8665	0.1825	0.0778	0.8722	0.9129	0.2122	0.9241
C20:2n6	0.47	0.43	0.40	0.49	0.59	0.31	0.6525	0.2651	0.021	0.2375	0.4487	0.4323	0.3388
C20:4n6	2.76	2.41	2.59	2.58	3.03	2.14	0.4210	0.9786	0.0506	0.3373	0.4348	0.9341	0.3856
C20:5n3	0.58	0.46	0.44	0.60	0.61	0.43	0.2650	0.1589	0.1107	0.9071	0.5042	0.0893	0.6449
C22:5n3	0.55	0.38	0.34	0.60	0.79	0.15	0.5520	0.3490	0.0329	0.7169	0.6849	0.3717	0.9458
C22:6n3	0.27	0.16	0.17	0.25	0.32	0.11	0.2392	0.4073	0.0458	0.994	0.4277	0.3076	0.1392

Note: Within a row, least squares means differ significantly at P < 0.05.

Table 6. Least squares means for fatty acid composition, weight percent of fatty acid methyl esters, of kidney fat from purebred (hair) and crossbred (wool × hair) hair sheep lambs grazed on tall fescue pastures with or without soy hull supplementation.

	Treatment						P-value
	Breed type, B		Sex, S		Diet, D		Main			Interaction
Fatty acid, %	Purebred	Crossbred	Ram	Ewe	Pasture-only	Pasture + soy hull	B	S	D	B × S	B × D	S × D	B × S × D
C10:0	1.10	1.22	1.55	0.77	1.33	0.99	0.6746	0.0083	0.2209	0.9466	0.9497	0.1713	0.3575
C12:0	0.18	0.17	0.21	0.14	0.20	0.15	0.622	0.0169	0.0859	0.6383	0.1950	0.1142	0.6071
C14:0	4.33	3.97	4.28	4.02	4.11	4.19	0.0025	0.0230	0.4589	0.1147	0.6348	0.3848	0.1220
C14:1n5	1.15	1.13	1.23	1.05	1.38	0.90	0.8378	0.0873	0.0001	0.8831	0.3943	0.3024	0.7297
C16:0, iso	0.52	0.41	0.52	0.41	0.69	0.24	0.0827	0.0829	0.0001	0.2914	0.5482	0.5933	0.5590
C16:0	22.55	20.56	21.14	21.97	19.25	23.86	0.0876	0.4604	0.0003	0.2548	0.5501	0.6096	0.4773
C16:1n7, trans	0.68	0.60	0.65	0.62	0.54	0.74	0.3333	0.6672	0.0139	0.0505	0.7170	0.5127	0.1691
C16:1n7	2.24	2.32	2.29	2.28	2.12	2.45	0.1323	0.9065	0.0001	0.1084	0.7056	0.3062	0.9222
C17:0	1.53	1.38	1.49	1.42	1.37	1.54	0.0048	0.1726	0.0022	0.5003	0.1840	0.8840	0.8314
C17:1n7	1.16	0.96	0.99	1.13	0.82	1.30	0.0275	0.0922	0.0001	0.0434	0.0230	0.0529	0.1381
C18:0	21.32	21.08	21.45	20.95	21.07	21.33	0.6967	0.4138	0.6703	0.1805	0.1143	0.6584	0.3302
C18:1n9, trans	0.23	0.23	0.24	0.22	0.21	0.25	0.9998	0.2967	0.0826	0.5179	0.0874	0.0678	0.5401
C18:1n11, trans	0.86	0.79	0.90	0.75	0.79	0.85	0.3792	0.0813	0.4593	0.5226	0.0684	0.2423	0.8136
C18:1n9	30.65	33.79	31.41	33.04	34.43	30.01	0.0653	0.3267	0.0117	0.2683	0.0938	0.2726	0.3119
C18:2n6, trans	0.54	0.50	0.52	0.52	0.60	0.44	0.0908	0.9635	0.0001	0.9285	0.6730	0.8420	0.1390
C18:2n6	4.46	4.47	4.51	4.42	4.15	4.78	0.9558	0.2676	0.0001	0.2399	0.3572	0.7283	0.5287
C18:2, c9,t11	0.47	0.48	0.49	0.46	0.65	0.30	0.9041	0.3523	0.0001	0.1462	0.0059	0.8386	0.8417
C18:3n3	1.72	1.60	1.68	1.64	1.72	1.60	0.0023	0.2610	0.0011	0.7350	0.5575	0.6591	0.7299
C18:3n6	0.64	0.64	0.64	0.64	0.65	0.62	0.8994	0.9322	0.3727	0.6798	0.1541	0.9261	0.6055
C20:1n9	0.40	0.43	0.43	0.40	0.49	0.35	0.2827	0.1392	0.0001	0.2457	0.3165	0.6894	0.8559
C20:2n6	0.52	0.54	0.54	0.51	0.61	0.44	0.2490	0.0356	0.0001	0.0990	0.1097	0.8851	0.8588
C20:4n6	2.13	2.14	2.17	2.10	2.17	2.10	0.8250	0.2223	0.2387	0.9403	0.1558	0.5226	0.5376
C20:5n3	0.38	0.35	0.38	0.35	0.35	0.38	0.1316	0.1888	0.1035	0.4763	0.1049	0.3246	0.5090
C22:5n3	0.13	0.14	0.16	0.11	0.16	0.10	0.8560	0.1629	0.0757	0.7580	0.2142	0.1250	0.7089
C22:6n3	0.11	0.13	0.17	0.07	0.16	0.08	0.6346	0.0695	0.1763	0.9904	0.0716	0.4215	0.4472

Note: Within a row, least squares means differ significantly at P < 0.05.

In intramuscular fat (LM), only trans-7-hexadeanoic acid (C16:1n7t) was significantly affected by breed factors (Table 4). The LM from purebred lambs had a higher (P < 0.01) concentration of C16:1n7t than that from crossbred lambs. Sex had significant effects on long chain fatty acids containing C17 to C22 carbons in the LM from experimental lambs. Compared with female lambs, male lambs had higher (P < 0.05) concentrations of margaric (C17:0), vaccenic (C18:1n11t), linolelaidic (C18:2n6t), linoleic (C18:2n6), α-linolenic (C18:3n3), eicosadienoic (C20:2n6), arachidonic (C20:4n6), eicosapentaenoic (C20:5n3) and docosapentaenoic (C22:5n3) acids in the LM, but lower (P < 0.01) concentrations of stearic (C18:0) and oleic (C18:1n9) acids. Medium (C10 to C12) and long chain (C17 to C22) fatty acids in the LM were significantly affected by supplementation. Of the medium chain fatty acids, concentrations of capric (C10:0) and lauric (C12:0) acids of the LM of pasture-only lambs were higher (P < 0.05) than that of supplemented lambs. For long chain fatty acids, pasture-only lambs had higher (P < 0.05) percentages of linoleic (C18:2n6), α-linolenic (C18:3n3), eicosenoic (C20:1n9), eicosadienoic (C20:2n6), arachidonic (C20:4n6), docosapentaenoic (C22:5n3), and docosahexaenoic (C22:6n3) acids, but lower (P < 0.05) percentages of heptadecenoic (C17:1n7), stearic (C18:0), and oleic (C18:1n9) acids than supplemented lambs.

The major fatty acids in the LM of experimental lambs were palmitic (C16:0), stearic (C18:0) and oleic (C18:1n9) acids (Table 4). Dietary saturated fatty acids including myristic (C14:0) and palmitic (C16:0) acids are hypercholesteremic and associated with the increased incidence of coronary heart diseases (Wolfram 2003; Khaldari and Ghiasi 2022). In the present study, these dietary saturated fatty acids were not significantly different in the LM. Fatty acid composition of fresh lamb is influenced by breed, sex, and diet (Wood et al. 2008). However, no significant differences were found in the concentrations of individual fatty acids presented in the LM from the two breed types, except for hexadeanoic acid (C16:1n7t). Previous studies reported that breed might affect the fatty acid composition of fresh lamb (Marino et al. 2008; Miguélez et al. 2008; Mazzone et al. 2010). This dabsence might be due in genetic factors influencing muscle growth and development in landrace hair sheep. In general, sex differences in lambs significantly influence the fatty acid composition of edible tissues (Tejeda et al. 2008). Previous research indicated that intact male lambs had higher amounts of polyunsaturated fat in their intramuscular fat than female lambs, whereas female lambs had higher contents of monounsaturated fat, mainly oleic (C18:1n9) acid (Tejeda et al. 2008; Mazzone et al. 2010). Similar results were found in the intramuscular fat from male and female lambs here. Basically, edible tissues from forage-fed ruminants contain a similar amount of saturated fat, a lower proportion of monounsaturated fat, and a higher percentage of polyunsaturated fat than those from concentrate-fed ruminants (Webb et al. 2005). Lambs grazing on pastures had higher concentrations of omega-3 PUFA and conjugated linoleic acids (CLA) in fresh lamb (Webb and O’Neill 2008). Diet rich in forage promote the growth of fibrolytic microorganisms that are responsible for the hydrogenating process in the rumen that increases the production of C18:1 trans11 (precursor of CLA in tissue) and CLA (Kotsampasi et al. 2017; Dias et al. 2023). The LM from pasture-only lambs here had lower levels of saturated (mainly C18:0) and monounsaturated (C18:1n9) fat, and higher amounts of polyunsaturated fat (omega-3 and -6 PUFA) than that from supplemented lambs and maybe associated with reduced the ruminal biohydrogenation or dietary forage containing lower amounts of C18:0 and C18:1n9 (Table 1).

In subcutaneous fat, there were no significant differences in pooled mean concentrations of any of individual fatty acids between male and female lambs (Table 5). However, some of medium (C10 to C12) and long chain (C16 to C22) fatty acids were affected by breed type and diet. Pooled mean concentrations of myristic (C14:0), myristoleic (C14:1n5), iso-palmitic (16:0, iso), palmitic (16:0), trans-7-hexadecenoic (16:1n7t), oleic (18:1n9), α-linolenic (C18:3n3) were affected by either two- or three-way interaction of breed type, sex, and diet. Among three C16 fatty acids present in the subcutaneous fat, crossbred lambs had higher (P < 0.05) concentrations of iso-palmitic (16:0, iso) and palmitic (16:0) acid, but trans-7-hexadecenoic (16:1n7t) acid concentration was a higher (P < 0.0001) in purebred lambs. Compared with crossbred lambs, purebred lambs had higher (P < 0.05) pooled mean concentrations of C18:1n9t, C18:1n9, and C18:3n3 in the subcutaneous fat.

In general, compared with heavy meat breed lambs, leaner sheep breeds have a relatively high proportion of PUFA, but low percentages of SFA and MUFA (Marino et al. 2008; Miguélez et al. 2008; Juárez et al. 2009). However, the present study showed that the purebred (lean) lamb had higher proportions of MUFA (16:1n7t, C18:1n9t and C18:1n9) and PUFA (C18:3n3), but lower concentrations of SFA (16:0, iso and 16:0) than the crossbred (heavy) breed type. This discrepancy might be due to the differences in physiological condition and digestive ability of type of sheep used in our study. Supplementation influenced the concentrations of individual fatty acids presented in the subcutaneous fat. Compared with supplemented lambs, pasture-only lambs had higher (P < 0.05) levels of C12:0, C16:0, iso, C16:0, C18:2n6t, CLA (C18:2c9,t11), γ-linolenic (C18:3n6), C20:2n6, C20:4n6, C22:5n3 and C22:6n3 in the subcutaneous fat, but lower (P < 0.05) levels of C16:1n7, C17:1n7, and C18:1n9. The subcutaneous fat from pasture-only lambs had higher (P < 0.05) concentrations of omega-3 and −6 PUFA and CLA than that from supplemented lambs. This result agrees with that of Webb and O’Neill (2008) reporting that lambs grazed on pastures had higher concentrations of omega-3 PUFA and CLA in their fat depots than those supplemented with grains. An interaction between breed type and sex was present in the mean concentrations of C14:0, C16:0 and 18:1n9 in the subcutaneous fat (Table 5). The pooled mean concentration of C14:0 of the subcutaneous fat from purebred male lambs was lower (P < 0.05) than that from either crossbred male or female lambs, or purebred female lambs (4.08 vs. 4.76 or 4.61, or 4.80 ± 0.185%, respectively). The level of C16:0 of purebred male lambs was lower (P < 0.05) than that of crossbred male and female lambs (17.57 vs. 27.57 and 24.00 ± 0.1549%, respectively); moreover, purebred (20.84 ± 0.1549%) or crossbred female lambs had intermediate levels of C16:0 and were not significantly different. The concentration of C18:1n9 of the subcutaneous fat of purebred male lambs was higher (P < 0.05) than that of either crossbred male or female lambs (36.97 vs. 28.10 or 31.27 ± 1.242%, respectively). Pure- and crossbred female lambs had intermediate levels of C18:1n7 and were not significantly different. A significant interaction between breed type and diet was found in the concentration of C14:1n5 in subcutaneous fat. The subcutaneous fat from crossbred pasture-only lambs had a higher (P < 0.05) pooled mean concentration of C14:1n5 than that in pure- and crossbred supplemented lambs, and purebred pasture-only lambs (3.25 vs. 2.99 and 2.93, and 2.93 ± 0.086%, respectively). An interaction between sex and diet was found in the concentrations of 16:0, 16:1n7t, 18:1n9 and C18:3n3. The level of C16:0 in the subcutaneous fat of male pasture-only lambs was higher (P < 0.05) than that of male supplemented lambs. The mean concentrations of C16:0 between female lambs with or without supplementation were not significantly different (21.86 vs. 22.98 ± 1.549%). The pooled mean concentration of 16:1n7t of the subcutaneous fat from male supplemented lambs was higher (P < 0.001) than that from male pasture-only lambs and female supplemented lambs(1.35 vs. 0.87 and 1.03 ± 0.074%, respectively). Female with or without (1.23 ± 0.074%) supplementation had intermediate levels of 16:1n7t and were not significantly different. The subcutaneous fat from male supplemented lambs had a higher (P < 0.05) mean concentration of C18:1n9 than that from male and female pasture-only lambs (37.72 vs. 28.10 and 32.15 ± 1.242%, respectively). Female lambs with or without supplementation had intermediate levels of C18:1n9, and were not significantly different. The mean concentration of C18:3n3 of the subcutaneous fat from female pastures-only lambs was higher (P < 0.01) than that from female supplemented lambs (1.05 vs. 0.78 ± 0.067%, respectively). The levels of C18:3n3 male lambs fed with or without supplement were not significantly different (0.97 or 0.86 ± 0.067%). Mean concentrations of C14:1n5 and 16:0, iso of the subcutaneous fat from experimental lambs were influenced by a three-way interaction (breed type × sex × diet). The concentration of C14:1n5 of the subcutaneous fat of crossbred male supplemented lambs was higher (P < 0.05) than that of purebred either male pasture-only lambs or female lambs fed the supplement (1.42 vs. 0.85 or 0.85 ± 0.105%). However, there were no significant differences found in the level of C14:1n5 for crossbred female lambs with or without supplementation (0.90 or 1.07 ± 0.105%), crossbred male supplemented lambs (0.95 ± 0.105%), and purebred male supplemented lambs and female pasture-only lambs (1.14 and 1.02 ± 0.105%). The subcutaneous fat from crossbred male pasture-only lambs had a higher (P < 0.05) percentage of 16:0, iso than that from purebred male lambs with or without supplementation and supplemented female lambs, and crossbred supplemented male lambs (2.47 vs. 0.27 or 0.35 and 0.05, and 0.04 ± 0.404%, respectively).

In Table 6 summarizes individual fatty acids in the kidney fat from experimental lambs. Selected fatty acids affected by breed type, sex and diet. Concentrations of any other fatty acids in the kidney fat were not different (P > 0.1) between breed types. Sex had significant effects on medium (C10 to C12) and long chain fatty acids containing C14 and C20 carbon. Compared with female lambs, male lambs had higher (P < 0.01) concentrations of C10:0, C12:0 and C14:0, as well as C20:2n6 in the kidney fat.

Differences in the breed type induced difference in concentrations of individual fatty acids in subcutaneous fats in our study, and fatty acid composition of kidney fat from experimental lambs were affected in the similar manner. Our study showed that the purebred (lean) lamb had higher proportions of SFA (C14:0 and C17:0), MUFA (C17:1n7) and PUFA (C18:3n3) than the crossbred (heavy) one. Long chain fatty acids containing C14 to C20 carbons in the kidney fat were significantly affected by supplementation. Pooled mean concentrations of C16:0, C16:1n7t, C16:1n7, C17:0, C17;1n7 and C18:2n6 of the kidney fat of pasture-only lambs were lower (P < 0.01) than that of lambs supplemented with soy hull. However, compared with supplemented lambs, pasture-only lambs had higher (P < 0.01) mean concentrations of C14:1n5, C16:0 iso, C18:1n9, C18:2n6t, C18:2c9,t11, C18:3n3 and C20:2n6. The kidney fats from pasture-only lambs had higher amounts of polyunsaturated fat (omega-3 and -6 PUFA) and CLA than those from supplemented lambs, whereas the concentration of C18:1n11t was not different diets. As indicated in the ruminal biohydrogenation of C18 PUFA (linoleic and linolenic acids), a large amount of trans forms of C18:1 isomers are derived and accumulated in adipose tissues (Webb and O’Neill 2008; Kotsampasi et al. 2017). Furthermore, a large portion of C18:1 trans11 (vaccenic acid) generated from ruminal microorganisms can be partially converted to C18:2 CLA (rumenic acid) in the adipose tissue of ruminants by the action of Δ−9 desaturatase enzyme (Webb and O’Neill 2008; Dias et al. 2023). In our study, omega-3 and −6 PUFA and CLA were present at higher concentrations in the kidney fat from pasture-only lambs when compared with supplemented lambs because of the suppression of ruminal biohydrogenation. A significant interaction between breed type and sex was detected in the concentration of C17:1n7 in the kidney fat from experimental lambs (Table 6). The kidney fat from crossbred male lambs had a lower (P < 0.05) mean concentration of C17:1n7 than that from purebred male and crossbred female lambs. An interaction between breed type and diet was found in the mean concentrations of C17:1n7 and 18:1n11t. The pooled mean concentration of C17:1n7 purebred supplemented lambs was higher (P < 0.05) than that from crossbred lambs with or without supplementation and purebred pasture-only lambs (1.49 vs. 1.11 or 0.82 and 0.82 ± 0.082%). In the kidney fat the mean concentration of 18:1n11t of either pure- or crossbred pasture-only lambs from was higher (0.61 or 0.69 ± 0.0259%) than that pure- or crossbred supplemented lambs (0.34 or 0.26 ± 0.0259%).

Conclusion

Considerable research has been conducted to evaluate the effects of breed, sex, and diet on the carcass and meat characteristics of lambs over the past 60 years. However, a complete understanding of the influence of these individual factors on the carcass and meat properties of lambs is still needed, and it is challenging to evaluate breed, sex, and diet effects and their interactions. Consequently, there have been many differening results reported stemming from variations in animal types and confounding environmental factors. It is widely accepted that high energy diets can produce heavier live and carcass weights and more heavily muscled, fatter carcasses compared to low energy diets. Regarding sex, rams are typically leaner than ewes and wethers, ewes have a greater amount of carcass fats, as well as yield and quality grades. Our findings indicated that supplementation significantly improved growth performance of lambs on pasture and crossbreeding also improved growth rate. Furthermore, supplementation rather than terminal sire mating had more significant effect on carcass quality under the conditions of our experiment. Supplementation also enhanced colour, stability of lipid oxidation, and texture property of fresh meat regardless of breed type. In general, supplementary feeding of grazing lambs can improve weight gain, carcass characteristics, and meat quality. However, fresh meat from pasture-only lambs had healthier fatty acid composition compared with that from supplemented lambs, again regardless of breed type. For a more complete understanding of the effects of breed type, sex, and supplementation on carcass and meat quality, additional studies are needed. These can be designed to evaluate more address interactions observed here, and specifically address carcass conformation and yield, the effects of lamb nutrition and the feed intake of the lambs, as well as the industry and consumer acceptance of resulting fresh lamb.

Acknowledgements

This research was conducted within the agricultural research station project at Virginia State University and Fort Valley State University, funded by the USDA-NIFA-2013-38821-21118.

Disclosure statement

No potential conflict of interest was reported by the author(s).

Additional information

Funding

This work was supported by the National Institute of Food and Agriculture [grant number 2013-38821-21118].