https://orcid.org/0000-0002-2073-2765
ABSTRACT
Dietary alfalfa hay could improve carcass and meat characteristics of lambs, however, information on hair breeds according to consumer demands is incomplete. This study aimed to evaluate the effect of dietary alfalfa hay and gender on carcass characteristics and physico-chemical properties of Katahdin × Pelibuey lmabs (F1). Thirty-six male and twenty-four female lambs were distributed in a completely randomized design with a 2 × 2 factorial arrangement: two diets, with or without alfalfa hay (AH) and two genders (male and female). Dry matter Intake (DMI) of male lambs was higher than females (1.360 vs 1.267 kg/d), daily weight gain (DWG) (0.262 vs 0.212 g), live slaughter weight (40.2 vs 37.8 kg), hot carcass weight (HCW) (20.0 vs 18.8 kg), temperature (9.57 vs 5.98°C) and highest pentadecanoic (1.42 vs 0.74%), linoleic (4.86 vs 3.04%) and tricosanoic acid content (2.43 vs 1.26%) in Longissimus lumborurm muscle (LLM). The meat pH ranged from 5.1 to 6.0. Protein and lipid average values were 19.2 and 5.1%, respectively. Lambs fed alfalfa diet had similar physicochemical characteristics than those fed concentrate feed, indicating the possibility of producing lamb meat using alfalfa. Meat of male lambs had the highest linoleic acid content, which provides positive health benefits to the consumers.
1. Introduction
Consumer demand for lamb cuts focuses more on quality traits than quantitys; however, there is no official definition of quality characteristics for lamb carcasses in Mexico. To meet the quality standards demanded by the market, it is necessary to perform meat quality evaluations and compare breeds and feeding systems to determine which one produces the best meat. Dorper and Katahdin have been introduced as pure or crossbred genotypes in national herds (Macías et al. Citation2010; Vázquez et al. Citation2011). Although satisfactory results have been obtained with these breeds, the genetic improvement of hair sheep has been slow and there is a deficit in meat characteristics and quality to satisfy consumer demand and compete with imported products. Therefore, it is essential to continue with the evaluation of these breeds in order to increase the knowledge of carcass quality and physicochemical properties of meat produced by these animals.
Moreover, feeding is one of the main factors affecting the meat characteristics and quality, such as color, internal fat depots, tenderness, and chemical composition (Alhidary et al. Citation2016; De Brito et al. Citation2016). Therefore, it is essential to establish feeding strategies to improve these attributes. This is important because improving meat characteristics and quality would improve human acceptance.
Intensive lamb fattening systems generally use commercial diets with high grain content (Muñoz et al. Citation2015; Camacho et al. Citation2018), which increases the costs of these production systems because of the high grain prices. Alfalfa (Medicago sativa) forage is a valuable alternative to be used in intensive lamb feeding because of its outstanding nutritional quality and high palatability (Chiquiní et al. Citation2018; McDonald and Min Citation2021) with a high protein content which is rapidly degradable (Al-Dobaib Citation2009). Alhidary et al. (Citation2016) reported improved carcass characteristics and meat quality (cooking loss, color, and pH) in lambs supplemented with alfalfa hay. Similarly, Ripoll et al. (Citation2012) noted that lambs fed alfalfa grass and concentrate increased meat shelf life by delaying lipid oxidation and meat myoglobin formation. The addition of high-protein forages is essential for improving the utilization efficiency of grain-based diets and obtaining better lamb carcass and meat characteristics. This study was conducted to investigate the effect of dietary alfalfa hay inclusion in the diet and gender on the physicochemical properties of meat from Katahdin × Pelibuey crossbred lambs (F1).
2. Materials and methods
The study was conducted at the Mocohá Experimental Station of the National Institute of Forestry, Agriculture and Livestock Research, located at 8 m.a.s.l., with a tropical sub-humid AW climate, according to Koopen classification, modified by García (Citation1973), with 900 mm of annual precipitation, distributed between June and November (Duch Citation2002), with maximum, average and minimum temperatures of 36, 26 and 18° C, respectively (UNAM Citation1991).
All procedures used in this study were performed according to the Mexican Official Standard-NOM-062-ZOO-Citation1999, Technical specifications for the production, care and use of laboratory animals.
2.1. Animals and diets
Thirty-six non-castrated male lambs and twenty-four Katahdin × Pelibuey females were used, with an average initial body weight ± standard deviation (SD) of 14.9 ± 2.9 and 13.4 ± 3.2 kg, respectively. The animals were distributed based on live weight and gender using a completely randomized design with a 2 × 2 factorial arrangement. The factors evaluated were diets with alfalfa hay (AH) and no alfalfa hay (NAH) and two genderes, male (M) and female (F). Alfalfa hay was used in pellet form and diets were designed to have similar protein and energy contents ( and ) and to provide all nutrients, according to NRC (Citation2007) recommendations. Each replicate consisted of one animal in a single pen (2 × 3.5 m), provided with a shaded area, drinker, and feeder. Lambs were internally dewormed and vaccinated against pneumonic pasteurellosis at the beginning of the experiment. Were fed ad libitum and received a mixture of trace minerals for free consumption. Sheep were subjected to a 14-day adaptation period to the diets and pens, and were weighed to determine DWG, after a 16-hour fast every 14 days, until the end of the measurement period, which lasted 84 days. Feed consumption was recorded, weighing (g) the feed offered and rejected daily, between 9 and 10 am. At the end of the experiment, all lambs were slaughtered after fasting for 16 h, according to the Mexican Official Standard established for slaughter and dressing of animals (NOM-033-SAG/ZOO-Citation2014).
Table 1. Ingredientes of the experimental diets (DM basis).
Table 2. Chemical composition of the experimental diets.
2.2. Carcass evaluation
After slaughtering, the head was cut off at the occipito-atloid joint, and the skin, feet, parts of the thoracic cavity (organs and glands), and contents of the abdominal and pelvic cavities (gastrointestinal contents) were removed. The weight of kidney fat (KF) and the hot carcass weight (HCW) were recorded to determine the carcass yield (CY). The carcass was refrigerated at 4°C for 24 h, a ribbed cut was made between the 12th and 13th ribs, and backfat (BF) thickness was measured using a stainless-steel ruler. The area of the Longissimus lumborurm muscle (LLM) was measured using a gridded plastic template according to the procedures established by The Ohio State University (Citation2011).
2.3. Physical characteristics of sheep meat
The pH and temperature were measured in the LLM using a HANNA multifunctional pH meter (HI99163N) equipped with a glass-tipped probe inserted one cm deep in the exposed muscle. The LLM was removed from the vertebral column (lumbar vertebrae), and samples of approximately 2.5 cm thickness were taken to determine drip loss (DL) at 24 and 48 h, 100 g of meat was weighed, placed in transparent plastic bags and suspended in a refrigerator at 4°C (Warner Citation2017). Drip loss was determined as the difference in weight of the sample before and after cooling and was expressed as percentage. Color was measured in samples collected immediately and after 20 min bloom with a Minolta colorimeter (CR-400) using the L*, a*, and b* scale system recommended by the CIE (Citation1986).
2.4. Chemical composition of sheep meat
Samples of approximately 2.5 cm thickness were taken from the LLM, vacuum-packed, and kept frozen at −60°C until chemical analysis. Before the analysis, the samples were thawed for 24 h at 4°C. After thawing, lean muscle tissue was minced using a knife and then ground for 15 s with a grinder (Bella Cucina, Model 10029) to determine moisture, weighing 5 g of sample, dried in a mechanical convection air oven at 105°C for 8 h (Pettinati et al. Citation1973), minerals using a muffle furnace (Pérez and Andujar Citation1980), crude protein (nitrogen × 6.25), using a nitrogen analyzer, as recommended by AOAC (Citation2016). The fatty acid profile was evaluated by gas chromatography, according to the method reported by AOAC (Citation2012). The fatty acids were extracted, subsequently saponified and derivatized for the formation of fatty acid methyl esters (FAMEs), using boron trifluoride in methanol. An Agilent Technologies 6890N Network Gas Chromatograph system was used. A Split injector was used at a temperature of 250°C, a FID detector at 260°C, and an SP-2560 column (100 m × 0.25 mm I.D., 0.20 µm) with an initial temperature of 140°C, using a ramp of 4°C/min until 240°C was reached for 15 min. Helium was used as carrier gas at a speed of 20 cm/s, injecting a volume of 1 µL, 100:1 split. A Standard 37-Component FAME Mix on SP™-2560 was used to identify the fatty acids and were quantified as a function of peak area by the area normalization method.
2.5. Statistical analysis
All data were analysed using a linear fixed-effects model (GLM of SAS), which included the effects of diet and gender, using SAS (Citation2003). The statistical model included the interaction of both effects (diet and gender); however, this interaction was not an important source of variation (P < 0.10). The animal was used as the experimental unit and the results were considered statistically significant if P ≤ 0.05.
3. Results
No effect of diet on DMI and DWG of lambs was found (P > 0.05). Male lambs had higher DMI (P = 0.021), DWG (P = 0.031) and live slaughter weight (P = 0.002).
3.1. Carcass evaluation
shows the effects of diet and gender on carcass characteristics. No effect of diet was observed (P > 0.05). The animals recorded an average ± standard error of the mean (SEM) HCW and CY of 19.57 ± 1.39 kg and 49.91 ± 1.91%, respectively. Male lambs had higher HCW (P = 0.004); however, females had higher KF (P = 0.001) and BF (P = 0.040). No interaction between diet and gender on the variables studied was observed (P > 0.05).
Table 3. Effect of diet and gender on the carcass characteristics of Katahdin × Pelibuey lambs.
3.2. Physical characteristics of meat
The physical properties of LLM were not affected (P > 0.05) by diets (). The pH and temperature average values (± SEM) found in LLM were 5.5 ± 0.33 and 8.0 ± 0.11°C. A light reddish color was observed in meat, with average values of L* = 36 (brightness), a* = 19 (red/green), and b* = 5 (yellow/blue) (P > 0.05). No significant changes were observed in the c* (saturation) and h* (hue) values of meat (P > 0.05).
Table 4. Effect of diet and gender on the physical properties of Longissimus lumborum muscle of Katahdin × Pelibuey lambs.
Meat of male lambs had higher temperatures (P = 0.007) and DL at 48 h (P = 0.038) in the LLM than in females. Likewise, higher L* (P = 0.017) and b* (P = 0.042) values were observed in the meat of the male lambs. No interaction was found between the main effects for these traits (P > 0.05).
3.3. Chemical composition of meat
No significant (P > 0.05) effect of diet was observed on the variables evaluated. The average values (± SEM) of moisture, crude protein, total lipids, and minerals in LLM for both diets were 72.25 ± 1.83, 19.2 ± 1.04, 5.1 ± 0.09, and 3.9 ± 0.41%, respectively. Data in show a higher concentration (19%) of saturated acids in LLM of female lambs (P = 0.041); however, male lambs had higher amounts of pentadecanoic (P = 0.011), linoleic (P = 0.008) and tricosanoic (P = 0.006) acids compared to females. The effects of diet and gender were independent for all variables evaluated (P > 0.05).
Table 5. Effect of diet and gender on the fatty acid composition of Longissimus lumborum muscle of Katahdin × Pelibuey lambs.
4. Discussion
Results of DMI are similar to those reported by Resendiz et al. (Citation2013) who observed a DMI of 1360 kg/d in lambs fed with 30% of alfalfa. Chiquiní et al. (Citation2018) reported lower values (1107 kg/d) in hair lambs fed with 50% alfalfa hay than those obtained in the present study. These authors did not find differences in DMI between lambs fed alfalfa hay and concentrate. The few variations found in DMI study may be because the inclusion of forage with high crude protein content (like alfafa) in diet improves the efficiency of utilization of diet (Bodine and Purvis Citation2003; Zhang et al. Citation2010) and therefore dry matter intake (Sanginés et al. Citation2014; Alhidary et al. Citation2016).
The DWG values found were higher than those reported by Norouzian et al. (Citation2011) in lambs fed diets based on cereal grains and 15% alfalfa hay and similar to those observed by Chiquiní et al. (Citation2018) using alfalfa hay (50%) and concentrate in the diet of hair lambs. It can be deduced that feeding alfalfa hay in addition with concentrate have beneficial impact on feed intake and consequently weight gain of lambs.
The effect of gender on carcass composition was evident, with males having a higher daily weight gain, slaughter weight, HCW and CY, and females had higher KF and BF. The regulation of adiposity and muscularity in animals has been attributed to gender steroid hormones (Clarke et al. Citation2012) where testosterone increases body mass (Kelly and Jones Citation2013), as was the case of male lambs. Also has been documented that carcass components are directly related to the degree of maturity and slaughter weight, with heavier animals having a higher carcass conformation (Salgueiro et al. Citation2009; Jacques et al. Citation2011), as demonstrated in the present study with male lambs and previous studies (Jaborek et al. Citation2018). Similar results were reported by Sun et al. (Citation2018) and Francisco et al. (Citation2019), who used diets containing different proportions of alfalfa hay, maize stover, and barley in growing lambs.
Diet did not affect the physical properties of the LLM. The average values of L*, a*, and b* indicate that the meat of the animals in both diets had a light red color and was within the parameters established for the color of fresh meat (Da Silva et al. Citation2005; Costa et al. Citation2009; Khliji et al. Citation2010). It has been reported that pH is related to meat color, mainly brightness (Priolo et al. Citation2001). In the present study, the average pH values were similar for both diets, which explains the few variations in meat color recorded. The pH and temperature values remained within the normal range for fresh meat (Maltin et al. Citation2003), indicating that there was sufficient muscle energy reserve (glycogen) for the meat maturation process (Aberle et al. Citation2001). Similar results were reported by other authors (Cohelho et al. Citation2019; Devincenzi et al. Citation2019) for lambs grazing on alfalfa pastures or supplemented with alfalfa hay. Holman et al. (Citation2021) also observed no significant effect of dietary treatment on the color of lambs fed wheat forage with or without alfalfa.
The higher DL (20%) observed in the meat of male lambs at 48 h after storage indicated that the meat of these animals began to lose its properties. DL is an indicator of the water holding capacity of meat, and a higher DL reduces tenderness, juiciness, and sensory quality of the meat, causing lower consumer acceptance (Wang et al. Citation2016; Guo and Darlympl Citation2017). The higher temperatures recorded in the meat of male lambs may have favoured water loss, which is in agreement with observations of Lonergan (Citation2009).
The higher values of L* found in the LLM of male lambs indicate that the meat was brighter than that of females. Calnan et al. (Citation2016) measured Longissimus muscle color from 8,265 lambs at 24 h post-mortem and found that male lambs produced loin meat with a 0.43 unit higher mean L* than female lambs. Teixeira et al. (Citation2005) found an effect of gender on brightness, with males having significantly higher brightness values than females. In beef muscle color, males showed higher color parameters (L*, a*, and b*) than females (Page et al. Citation2001) even with no difference between their muscle pH, as observed in the present study. The reasons why female lambs produced darker meat are not clear, perhaps due to an associated intrinsic muscle factor such as myoglobin concentration which is known to be strongly associated with meat color variables parameters, particularly L* (Calnan et al. Citation2016). Ripoll et al. (Citation2012) observed that there is a relationship between meat color categories and brightness, such that meat becomes redder and luminosity decreases.
The values for the chemical composition of lamb meat were similar to those reported by other authors (Echegaray et al. Citation2021; Gonzales-Barron et al. Citation2021). The minimal variations in parameters among the animals that consumed both experimental diets were in agreement with those described by Jacques et al. (Citation2017) in lambs fed concentrates and pastures. Previously, Bonanno et al. (Citation2012) evaluated alfalfa hay or concentrates in the diet of lambs and observed no effect on protein, fat, and ash content of meat.
The total saturated and monosaturated fatty acids were present in higher proportions, with the lowest proportions corresponding to polyunsaturated fatty acids. In ruminants, the synthesis of saturated fatty acids is favoured (45-55%), of which more than half are medium chains (10–16 carbons), whereas polyunsaturated fatty acids account for less than 5% (Vasta et al. Citation2009; Ribeiro et al. Citation2016). The higher saturated acids concentration observed in the LLM of female lambs may be due to the influence of gender hormones on lipolysis and fat deposition (Vargas et al. Citation2018). It has been documented that female lambs tend to deposit a greater amount of body fat (Díaz et al. Citation2003; Santos et al. Citation2008). This was confirmed in this study since female lambs had significantly higher KF and BF. Similar results were found when evaluating the fatty acid profile of the meat of ewe lambs and whole and castrated male lambs (Okeudo and Moss Citation2007; Malau-Aduli et al. Citation2016). These authors reported a higher proportion of myrstic acid and palmitate in ewe lambs than in males, although in the present study, no significant differences were found in the concentrations of these acids; ewe lambs tended to have a higher amount.
The higher linoleic acid content found in the LLM of male lambs differs from that reported by Díaz et al. (Citation2003), who indicated that female lambs have high levels of C18:2 n-6 and total PUFA; however, Nürnberg et al. (Citation1998) observed a high concentration of these acids in male lambs, which is in agreement with our findings. In addition, Tejeda et al. (Citation2008) reported minimal differences in the fatty acid composition of semimembranosus muscle of male and female lambs fed only concentrate. The published results on the effect of gender on fatty acid composition greatly differ. The controversy in these reports may be because the effect is related to the slaughter weight of the animals. Majdoub-Mathlouthi et al. (Citation2013) reported higher proportions of Eicosadienoic (C20:2 n-6) and Archidonic (C20:4 n-6) in the LLM of lambs slaughtered at a greater weight. Similarly, Tejeda et al. (Citation2008) found a higher amount of C16:0 and C18:2 n-6 in male lambs slaughtered at higher weights.
5. Conclusions
The results showed that it is feasible to use alfalfa hay in the diet of growing lambs to produce meat with physical and chemical characteristics similar to those of lambs fed concentrate feed. Male lambs had a higher content of linoleic acid in their meat, which represents a major benefit for consumers of this type of meat due to its beneficial effect on human health.
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No potential conflict of interest was reported by the author(s).
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References
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