Effect of breed (hair and wool), weight and sex on carcass quality of light lambs under intensive management

Abstract

Eighty carcasses of Canaria Hair breed (CHB) and Canaria breed (CB) were evaluated; 10 carcasses by sex, breed and slaughter weight (15.8 ± 0.66 kg and 24.9 ± 0.76 kg live weight, respectively). Breed effect was observed in measurements, fatness, commercial category and tissue composition of the carcass. CHB presented carcasses with more leg length and rump perimeter (but only in 25 kg lambs), heaviest shoulder and more muscle percentage. CB showed carcasses more fatness (8.18 ± 1.66 vs. 6.63 ± 1.46) and with more fat depth (3.90 ± 1.35 vs. 2.86 ± 1.15). CB increases its fatness faster because 16 kg lambs of CB showed similar values that 25 kg lambs of CHB (7.45 vs. 7.26, respectively). All carcass measurements, conformation, compactness indices and carcass fatness were affected by weight; 25 kg lambs showed higher values. Weight effect was also found in the tissue composition; 25 kg lambs showed more intermuscular fat (IF) percentage and less bone percentage. Sex effect was observed in first category joints, in total fat and IF; females showed higher percentages than males. In relation to carcass quality, we conclude that CB could be more commercially attractive in light carcasses because this breed increases its fatness faster and CHB more commercially attractive in heavy lambs.

Keywords:

• carcasses quality
• sheep
• hair breed
• intensive system

1. Introduction

There are three autochthonous sheep breeds in the Canary Islands: Canaria breed (CB, wool), Palmera breed (wool) and Canaria Hair breed (CHB). The three local breeds are considered under special protection (RD. 2129/2008). The wool breeds are milk-type breeds (González et al. 2007). CHB is a meat-type breed (Camacho et al. 2007). This hair breed is considered the origin of hair sheep breeds Iberoamerican (Delgado et al. 1998), and this breed is the only hair breed in Europe (Bermejo et al. 2010). According to the latest Common Agricultural Policy (CAP) proposals, rare breed conservation is one of the most important issues of the reform. In the new CAP, supplementary premiums for preserving rare breeds and for promoting high-quality food products can be obtained (Canali 2006). In disadvantaged rural areas, conservation of animal genetic resources could make a positive contribution to improving the livelihoods of local farmers (Rege & Gibson 2003).

In the last years the demand of sheep meat has increased in the Canary Islands. This is positive for the conservation and expansion of local breeds, which can satisfy part of that market. Given this fact, it is advisable to study and characterization the different meat products. This manuscript studies the two breeds with more animals present: CB and CHB. Intrinsic factors such as breed, sex and slaughter weight (SW) influence the carcass quality (Alfonso et al. 2001) giving rise to different types of commercial products (Civit et al. 2009). The different ethnic origin of these breeds can be reflected in differences on carcass quality, which can influence the production management of the breeds. Also knowing the quality of lambs of native breeds is an important instrument to promote the consumption of meat in the local population (Hernández-Castellano et al. 2013). This study is a part of the project aiming to determine the carcass and meat quality characteristics in intensive system of two native breeds of sheep (hair vs. wool). In this part, the carcass quality of CB and CHB under an intensive feeding system was investigated comparatively, statistically analysing the effect of breed, SW and sex parameters on carcass quality.

2. Material and methods

This study has complied with the rules of the Committee of Research Ethics and Animal Well-being of the University of La Laguna (RD 1201/2005; L 14/2007).

2.1. Experimental site

This study was carried on a farm located in Tenerife (Canary Island, Spain; 28°07′ latitude N and 16°35′ longitude W) at 200 m above sea level. During the experiment, the average temperature was 21°C (max. 25°C, min. 17°C), the average rain precipitation was 114 mm per year and the average relative humidity was 72%.

2.2. Experimental design, animal management and slaughter procedures

Eighty carcasses of CHB and CB were evaluated; 10 carcasses by sex, breed and SW – 15.8 ± 0.66 kg live weight (69.8 days) and 24.9 ± 0.76 kg live weight (136.8 days). Purebred sheep (sires and dams) were used for breeding of lambs. Animals of both breeds were born and raised in permanent confinement, at the same time. During the first week of age, all the lambs received vitamins A, D₃ and E, and they were also vaccinated against enterotoxemia. All lambs received only maternal milk until 15 days of age. After day 15, milk feeding was continued and free access to forage (ray-grass hay), concentrate (1530 kilocalories of net energy and 18% crude protein) and water was initiated. Dams were fed with ray-grass hay ad libitum and concentrate (1638 kilocalories of net energy and 19% crude protein). Lambs were separated from the dams at 16 kg of live weight.

When animals reached SW, they were transported to the slaughterhouse, located approximately 100 km from the farm, according to EU regulations (Council Regulation, EEC No 1/2005). All animals were weighed twice, first at the farm and once again at the slaughterhouse (slaughterhouse live weight, SLW) in order to determine losses due to transport. In the slaughterhouse, the animals were fasted for approximately 12 h, only water was provided (RD 54/1995). After weighing (SW), lambs were electrically stunned and slaughtered according to standard commercial procedures. The fast loss was also determined (SLW – SW/SLW × 100). Transport loss and fast loss were the total loss.

Each lamb's head, feet, skin, liver, heart, lung-trachea, spleen, thymus, testicle-penis, ovary-uterus, full and empty gastrointestinal tract were weighed. The carcass included the kidneys, pelvic-renal fat and beefy portion of the diaphragm; however, the head (cut at occipital-atlantoidal articulation) and the limbs were not included (cut at the carpo-metacarpal and tarso-metatarsal joints). Carcasses were weighed (hot carcass weight, HCW) and hung by the Achilles tendon after processing. Subsequently, the carcasses were cooled at 4°C for 24 h. After chilling, the carcasses were weighed again (cold carcass weight, CCW), and the carcass yield (CCW/SW × 100) and drip loss (HCW – CCW/HCW × 100) were calculated.

2.3. Measures and carcass classification

After cooling, various carcass measurements were determined to assess the carcass morphology, including the carcass length (K) (Boccard et al. 1964), rump width (G) (Palsson 1939), maximum width at rib level (Wr) (Barton et al. 1949) and rump perimeter (B) (Robinson et al. 1956). Half carcasses were obtained according to the procedure described by Colomer-Rocher et al. (1988) and the half-carcass internal length (L) and leg length (F) were determined according to the method of Palsson (1939) and McMeekan (1939), respectively. The carcass compactness index (CCW/L) (Palsson 1939) and leg compactness index (G/F) (Thwaites et al. 1964) were calculated.

The subjective classification of conformation was evaluated using the description of Colomer-Rocher et al.(1988) and photographic standards (Colomer-Rocher 1984), considering 15 categories [1 = P–, 2 = P (poor), 3 = P+, 4 = O–, 5 = O (normal), 6 = O+, 7 = R–, 8 = R (good), 9 = R+, 10 = U–, 11 = U (very good), 12 = U+, 13 = E–, 14 = E (excellent) and 15 = E+]. The carcass fatness was classified according to the EU scale (EEC Regulation 1278/94, 1994) for light lamb carcasses, which has 12 categories [1 = 1–, 2 = 1 (very scarce), 3 = 1+, 4 = 2–, 5 = 2 (scarce), 6 = 2+, 7 = 3–, 8 = 3 (medium), 9 = 3+, 10 = 4–, 11 = 4 (important), 12 = 4+]. Carcasses were ribbed between the 12th and 13th thoracic vertebrae to measure (with a manual calliper) fat thickness carcass (fat depth). Subsequently, carcasses were weighed and split down the dorsal midline. The left-half of carcasses were also weighed and disjointed (Colomer-Rocher et al. 1988) into seven anatomical parts: leg, loin, anterior ribs, shoulder, breast, neck and tail. Each joint was weighed and expressed as percentage of CCW. The joints were vacuum packed, frozen and maintained at –20°C until dissection. The joints were grouped into three categories, including the first category (leg + loin + anterior ribs), second category (shoulder) and third category (breast + neck + tail). Prior to dissection, joints were defrosted in trays placed inside a refrigerator. Dissection method of Colomer-Rocher et al. (1988) was followed to determine the tissues' components [muscle (M), subcutaneous fat (SF), intermuscular fat (IF), bone and remainders]. Bone, fat and muscle percentages were calculated. Furthermore, muscle/bone (M/B), muscle/fat (M/F) and subcutaneous fat/intermuscular fat (SF/IF) indices were determined.

2.4. Statistical analysis

The multivariate analysis was designed base on two questions: (1) Does the interaction breed × weight produce a distinct product? (2) What variables have the most discriminatory? These questions were resolved by the canonical discriminant analysis (Everitt & Dunn 1991), which gave us information about the differences or similarities in carcass quality of the different products obtained. The analysis resulted in a graphic representation of the location of the observations in the space formed by the first two functions obtained. Data were analysed by conducting analysis of variance. The fixed effects of the model included the breed, weight, sex and the interactions breed × weight and breed × sex. Differences among means in the interaction breed × weight were determined by Bonferroni test. All analyses were performed using the SPSS 15.0 (SPSS Inc. 2006) for Windows.

3. Results and discussion

3.1. Discriminant analysis

Canonical discriminant analysis provided results regarding the possibility of differentiating among different meat products based on the breed. It is important to determine which variables involved in the analysis have the greatest effect on the quality of the final product. This is additional information that could be extracted from the present study.

Table 1 shows the results obtained from de canonical discriminant analysis. All of functions of canonical discriminate analysis were significant. The first function explains 90.6% of variance. Carcass compactness index was the variable more discriminatory in function 1 (R = 0.382; Table 2). Both breeds increase their carcass compactness index with SW increasing (Figure 1). Analysis of variance showed that the effect of variation in axe 1 was breed and weight (Table 3). The productive aptitude and morphology of the breed may result differences in carcass quality (Martínez-Cerezo et al. 2002). Also, SW of lambs has corresponded with significant differences in the carcass compactness in others breeds (Peña et al. 2005; Santos-Silva et al. 2007).

Figure 1. Discriminate functions and centroids for carcass quality of breed × weight interaction.

Table 1. Lambda of Wilks and the signification of the different functions.

Function	Lambda of Wilks	Chi-Cuadrado	Variance	Significance
1	0.010	310.847	90.6	0.001
2	0.241	95.956	8.0	0.001
3	0.736	20.654	1.4	0.037

Table 2. Combined intra-group correlations between discriminate variables and canonical discriminate functions.

	Function
Variables	1	2	3
Muscle percentage	−0.034	−0.578	0.031
Intermuscular fat percentage	−0.026	0.556	0.087
Total fat percentage	0.032	0.524	0.130
Carcass conformation	0.115	0.352	0.106
Fat depth	0.156	0.350	−0.183
Bone percentage	0.010	−0.213	0.127
Second category	−0.022	−0.183	−0.084
Subcutaneous fat percentage	0.060	0.069	0.065
Carcass compactness index	0.382	−0.034	0.599
Carcass yield	−0.107	0.031	0.598
Leg compactness index	0.050	0.032	−0.333
Remainders percentage	−0.054	−0.232	0.243
First category	0.018	0.077	0.194
Third category	0.001	0.033	−0.116

Bold represents as: canonical correlation coeffient of most important variables. Correlation coeficient >0.3 in function 1 and correlation coeficiente >0.5 in function 2.

Table 3. Means and effect of the functions 1 and 2.

	Breed
	Canaria		Canaria Hair		Effect
Function	16 kg	25 kg	16 kg	25 kg	Breed	Weight	Breed × weight
1	−4.242	4.893	−5.004	4.559	0.019	0.001	ns
2	1.182^a	1.455^a	−1.091^b	−1.777^b	0.001	ns	0.039

Note: Different letters are significant at P ≤ 0.05.

ns, not significant.

In the function 2, the variables more discriminatory were muscle percentage, IF percentage and total fat (TF) percentage (Table 1). Analysis of variance showed that the effect of variation in axe 2 was the breed (Table 3). Carcasses of CHB tended to be leaner and less fat than CB carcass (Figure 1). The different origin of these breeds (hair vs. wool) could explain their different tissue composition.

3.2. Yield, measurements, conformation and fatness of the carcass

The higher percentage of total weight loss in CB (8.79 vs. 7.31; P < 0.001) led to differences in SW (P < 0.011; Table 4). According to Carter and Gallo (2008), fasting of the animals causes weight loss mainly due to the reduction of intestinal contents. Thus, increased gastrointestinal emptying may explain the lower SW of CB. Only 25 kg lambs showed significant differences between breeds for HCW and CCW: the hair lambs presented higher weights in hot and cold carcasses (interaction breed × weight). Significant differences between breeds in weight of the skin explain these differences in 25 kg lambs (2.37 CB vs. 1.61 CHB; P < 0.001).

Table 4. Carcass weights and yield (means) in CB and CHB.

	Breed
	Canaria		Canaria Hair		Sex			Effect
Characteristics	16 kg	25 kg	16 kg	25 kg	Male	Female	SEM	Breed	Weight	Sex	Breed × weight	Breed × sex
Farm weight (kg)	15.85	24.78	15.76	25.04	20.35	20.02	0.5	ns	***	ns	ns	ns
Slaughterhouse live weight (kg)	15.36	24.03	15.40	24.44	19.78	19.50	0.5	ns	***	ns	ns	ns
Slaughter weight (kg)	14.62	22.41	14.75	23.00	18.62	18.46	0.4	*	***	ns	ns	ns
Total weight loss (%)	7.89	9.74	6.50	8.21	8.41	7.71	0.1	***	***	ns	ns	ns
Hot carcass weight (kg)	7.40^a	10.40^b	7.18^a	10.97^c	8.93	8.91	0.2	ns	***	ns	**	ns
Cold carcass weight (kg)	7.24^a	10.23^b	6.96^a	10.77^c	8.73	8.73	0.2	ns	***	ns	**	ns
Drip loss (%)	2.21	2.15	2.99	1.78	2.52	2.07	0.2	ns	ns	ns	ns	ns
Carcass yield (%)	49.49^b	45.67^a	47.22^ab	46.83^a	47.13	47.55	0.3	ns	**	ns	**	ns

Note: Means in the same row showing different letters are significantly different (P ≤ 0.05).

SEM, standard error of mean; ns, not significant (P > 0.05).

*P < 0.05; **P < 0.01; ***P < 0.001.

The breed affected leg length (F), half-carcass length (L), rump perimeter (B), fatness and fat depth (Table 5). The hair lambs' carcasses were significantly longer than wool lambs' in half-carcass length (L) and leg length (F). Although leg length (F) and rump perimeter (B) were significantly different between breeds, these differences were only in heavy lambs (interaction breed × weight), so 25 kg hair lambs' carcasses had longer leg length, higher rump perimeter but shorter carcass length (K) than wool lambs. Martínez-Cerezo et al. (2002) relate the morphology of the carcass to the productive orientation of the breed, where dairy breeds show longer and narrower carcass.

Table 5. Carcass traits (means and SEM) of CB and CHB.

	Breed
	Canaria		Canaria Hair		Sex			Effect
Characteristics	16 kg	25 kg	16 kg	25 kg	Male	Female	SEM	Breed	Weight	Sex	Breed × weight	Breed × sex
Leg length (F), cm	26.28^a	28.25^b	25.94^a	30.07^c	27.57	27.55	0.2	**	***	ns	***	ns
Rump width (G), cm	12.57	14.50	12.64	14.86	13.56	13.64	0.1	ns	***	ns	ns	ns
Half carcass length (L), cm	44.83	52.12	46.75	53.29	48.84	49.39	0.4	***	***	ns	ns	ns
Carcass length (K), cm	45.18^a	53.08^c	45.59^a	52.13^b	48.65	49.10	0.4	ns	***	ns	*	ns
Rump perimeter (B), cm	43.88^a	49.83^b	43.62^a	51.45^c	47.04	47.07	0.4	*	***	ns	**	ns
Maximum width ribs (Wr), cm	14.40	17.50	14.18	17.60	15.73	16.00	0.2	ns	***	ns	ns	ns
CCW/L, kg cm^−1	0.16^b	0.20^c	0.15^a	0.20^c	0.17	0.17	0.0	ns	***	ns	**	ns
G/F	0.48	0.51	0.48	0.49	0.49	0.49	0.0	ns	*	ns	ns	ns
Conformation (1–15 points)	7.00	9.70	6.10	10.63	8.46	8.10	0.3	ns	***	ns	ns	ns
EUROP	O+	R+	O+	U–	R	R	–	–	–	–	–	–
Fatness (1–12 points)	7.45	8.90	6.00	7.26	7.68	7.16	0.1	***	***	ns	ns	ns
Fat depth (mm)	3.02	4.83	2.31	3.47	3.32	3.46	0.1	***	***	ns	ns	ns

Note: Means in the same row showing different letters are significantly different (P ≤ 0.05).

SEM, standard error of mean; CCW, cold carcass weight; ns, not significant (P > 0.05).

EUROP = scale 1–15 points: 1 = P–, 2 = P (poor), 3 = P+, 4 = O–, 5 = O (normal), 6 = O+, 7 = R–, 8 = R (good), 9 = R+, 10 = U–, 11 = U (very good), 12 = U+, 13 = E–, 14 = E (excelent), 15 = E+.

*P < 0.05; **P < 0.01; ***P < 0.001.

Fatness and fat depth were significantly smaller in hair lambs than in wool lambs. According to Bueno et al. (2000), thickening found in these breeds allows the good conservation the carcass and meat. Bunch et al. (2004) observed highest fat depth in wool breeds vs. hair breeds (6.4 vs. 4.2 mm) when lambs were slaughtered at heavy weights (>45 kg live weight). Dransfield et al. (1990) and Sañudo et al. (1998) have suggested there are differences between breeds in precocity and therefore in the deposition of fat in carcasses. In this study, the differences between breeds in carcass fatness suggests that both breeds have different precocity, CB would be an earlier maturity breed according to higher amount of carcass fat.

The SW affected all variables as shown in Table 4, except shrink losses. The heaviest carcasses (25 kg) showed lower carcass yield (P < 0.001). Sanz et al. (2008) in Churra Tensina breed also observed lower carcass yield in heavier lambs, which was attributed to the faster growth of the digestive system in heavier lambs. The more time passed from suckling to ruminant explain the faster growth of the digestive system in 25 kg lambs and therefore its lower carcass yield. Carcass yield decreased when increasing the SW only in CB (interaction breed × weight; P = 0.026). In this study, animal management was the same for both breeds; therefore, the different evolution of carcass yield suggests differences from pass suckling to ruminant, it would be faster in the CB and would be associated with their aptitude dairy. The acetic acid produced in the rumen by the microbial activity promotes the synthesis of milk fat (Fuller 2004). An early rumen development permits greater intake of forage that would be positive for the synthesis of fat.

The weight affected all variables as shown in Table 5. In agreement with other breeds (Martínez-Cerezo et al. 2002; Peña et al. 2005), all measurements of carcass and indexes (CCW/L and (G/F) increased in both breeds as animals growth. Because the fat tissue grows faster in later phases (Addullah & Qudsieh 2009), carcass fatness and fat depth increased with the growth of lambs.

3.3. Commercial category and tissue composition

Breed did affect the second commercial category (shoulder). Hair lambs had a significantly higher proportion of second category joints than wool lambs (Table 6). Several authors, in breeds of same productive aptitude, reported breed effect on the second commercial category (Gutiérrez et al. 2005; Miguélez et al. 2006). Snyman and Olivier (2002) comparing carcass traits of hair and wool lambs found that hair-type lambs had a higher shoulder that wool lambs (P < 0.001). Higher shoulder proportion in hair lambs could be explained by breed-specific morphology characteristic of CHB, more than by their productive aptitude.

Table 6. Carcass composition (means) of CB and CHB.

	Breed
	Canaria		Canaria Hair		Sex			Effect
Characteristics	16 kg	25 kg	16 kg	25 kg	Male	Female	SEM	Breed	Weigh	Sex	Breed × weight	Breed × sex
Category (%)
1^a(leg + loin + anterior ribs)	60.72	60.78	60.20	60.50	60.16	60.95	0.2	ns	ns	*	ns	ns
2^a(shoulder)	17.27	17.05	18.04	17.57	17.72	17.25	0.1	*	ns	ns	ns	ns
3^a(breast + neck + tail)	20.14	20.29	19.87	20.13	20.44	19.76	0.2	ns	ns	ns	ns	ns
Components (%)
Muscle (M)	48.95	49.03	53.85	55.34	52.33	51.06	0.5	***	ns	ns	ns	*
Total fat (TF)	24.66	25.57	17.61	19.16	20.67	23.03	0.5	***	ns	***	ns	ns
Subcutaneous fat (SF)	10.79	9.71	7.03	7.23	8.68	8.79	0.3	***	ns	ns	ns	ns
Intermuscular fat (IF)	13.87	15.86	10.57	11.92	11.98	14.24	0.3	***	**	***	ns	ns
Bone (B)	21.69	20.27	22.55	20.29	21.75	20.66	0.1	ns	***	***	ns	ns
Remainders	1.94	1.51	2.14	1.78	1.91	1.78	0.0	ns	**	ns	ns	ns
M/TF	2.06	1.95	3.14	2.95	2.66	2.36	0.0	***	ns	*	ns	ns
M/B	2.26	2.42	2.39	2.74	2.42	2.48	0.0	***	***	ns	ns	ns
SF/IF	0.83	0.64	0.68	0.63	0.77	0.63	0.0	ns	*	*	ns	ns

SEM = standard error of mean; ns = not significant (P > 0.05).

*P < 0.05; **P < 0.01; ***P < 0.001.

There were significant differences between breeds in muscle, TF, SF and IF, but not in bone and remainder (Table 6). The hair lambs showed a higher proportion of muscle but a lower proportion of TF than wool lambs; therefore; the relationship between muscle and total fat (M/TF) and the relationship between muscle and bone (M/B) were higher for CHB (P < 0.001; P < 0.001). Several authors also have observed higher muscle percentage in hair breeds vs. wool breed and vs. wool × hair crossing (Rubio et al. 2004; Gutiérrez et al. 2005). Although, a high muscle:bone ratio is a common finding in carcasses with the best conformation (Álvarez et al. 2013), in this study has not been so.

Beriain et al. (2000) indicate that dairy breeds have more fat tissue that meat breeds and Sañudo et al. (1997) relate the higher fat percentage with the precocity of the breed. The higher fat proportion observed in tissue composition of carcass of CB would be related to their productive aptitude and their precocity, because no significant differences were observed between breeds in the age of the lambs, aspect strongly related to the fat content of the carcass (Pollot et al. 1994). This result in fat tissue content points to an important differentiation in the carcass quality of the two groups of sheep (CB vs. CHB), which is key in the commercial value of the carcass (Sañudo et al. 2000).

Slaughter weight affected IF, bone and remainders; 25 kg lambs showed a significantly higher proportion of IF and therefore lower SF/IF proportion than the 16 kg lambs. Between 16 and 25 kg IF has more growth than SF in the two breeds. It is known that fatty deposits increase with increasing SW because it implies an increase in age and therefore increased late tissue development (Jeremian 2000). The growth decreased the bone percentage, so 25 kg lambs showed a significantly lower proportion of bone and higher L/B ratio than 16 kg lambs. The development of bone tissue has its peak in the early stages of the animal's life (Butterfierd 1988), so different authors found that weight affects bone tissue percentage independently of the breed (Martínez-Cerezo et al. 2002).

There were significant differences between sexes in the proportion of first category joints; females showed the highest proportion due to the greater proportion of ribs (32.28% female vs. 24.67% male). This result would be associated with greater slaughter age of the females (114.5 vs. 91.6 days), due to slower average dairy weight (163 vs. 200 g), and therefore greater development of the ribs, which is considered a piece of late development (Díaz 2001).

Significant differences between sexes in bone, TF, IF and M/TF and SF/IF ratios were found (Table 6). In agreement with others studies (Peña et al. 2005; Luaces et al. 2007), females had lower bone percentage and greater fat proportion. Females displayed a greater tendency to accumulate fat from a very early age (Velasco et al. 2000); furthermore in this study, females were older than males when slaughtered. This would also explain the lower bone percentage in these carcasses. Females showed lower M/TF and SF/IF ratios owing to their higher TF and IF percentages, respectively.

4. Conclusions

In this study, the breed, SW and sex affected the carcass quality, especially the characteristics of fatness. CB showed carcasses more fatness; this breed increases fatness faster than the CHB. Heavy lambs presented carcasses more fatness and with less bone percentage. Females had lower bone percentage and greater fat proportion. Differences between breeds were observed in the morphology of the carcass, especially for heavy carcasses. We conclude finally that heavy hair breed lambs could be more attractive than wool breed lambs; however, the wool breed could produce better light carcasses.

Additional information

Funding

This work has been made possible by funding from the INIA [grant number RTA/2006-00174-00-00] and the slaughterhouse of Tenerife and the farm GORON SUR.