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Revista mexicana de ciencias pecuarias
versão On-line ISSN 2448-6698versão impressa ISSN 2007-1124
Rev. mex. de cienc. pecuarias vol.7 no.4 Mérida Out./Dez. 2016
Articles
Effect of sire breed on carcass traits of meat lambs in Hidalgo, México
a Colegio de Postgraduados-Campus Montecillo. 56230 Montecillo, Edo. de México. Tel/Fax: 595-9520279.
b INIFAP-Hidalgo, Pachuca, Hgo. México.
c CENID-Fisiología y Mejoramiento Animal, INIFAP. Ajuchitlán, Qro. México.
d Centro Universitario UAEM. Amecameca, Edo. de México.
e Instituto de Ciencias Agropecuarias, UAEH. Área Académica de Medicina Veterinaria y Zootecnia. Tulancingo, Hgo. México.
f Colegio Superior Agropecuario del Estado de Guerrero, CEP-Cocula, México.
g Departamento de Zootecnia, Universidad Popular de la Chontalpa. Cárdenas, Tab. México.
The objective of the study was to evaluate the effects of sire breed (Charollais, Dorset and Texel), utilizing Hampshire ewes, lamb sex and birth type, on carcass traits of the lambs. After weaning (74±8 d), 45 lambs from these crosses were fattened during 63 d, consuming a balanced diet with 14% CP and 2.82 Mcal of ME/kg of DM. Lambs were weighed and slaughtered at 137 d of age; later, measures on slaughter weight and yield of hot and cold carcass, rib eye area, subcutaneous fat, carcass length, leg length, and rump perimeter were taken and the carcass compactness index was calculated. In addition, the carcass regional composition (shoulder, chest-belly, anterior-loin, leg, neck, and rear-loin) was determined. Data were analyzed utilizing a mixed model. Charollais-sired lambs had the highest (P<0.05) rib eye area (20.1±0.5 cm2), while Dorset-sired lambs were superior (P<0.05) in carcass length (66.3±0.9 cm) and leg length (34.8±0.3 cm). Ram lambs surpassed ewe lambs (P<0.05) in most traits analyzed. Lambs born as singles had higher means than twin lambs (P<0.05) in subcutaneous fat and leg length. In general, crosses with Charollais and Dorset showed superiority in carcass traits.
Key words: Meat sheep; Paternal breeds; Crossbreeding; Carcass traits; Regional composition
El objetivo del estudio fue evaluar los efectos de la raza paterna (Charollais, Dorset y Texel), utilizando ovejas Hampshire, sexo y tipo de nacimiento de la cría, en características de la canal de los corderos. Después del destete (74±8 días), 45 corderos de estas cruzas se finalizaron durante 63 días, consumiendo una dieta balanceada con 14% de PC y 2.82 Mcal de EM/kg de MS. Los corderos se pesaron y se sacrificaron a los 137 días de edad; posteriormente, se tomaron medidas de peso y rendimiento de la canal caliente y fría, área del ojo de chuleta, espesor de grasa subcutánea, longitud de canal, longitud de pierna, perímetro de grupa y se calculó el índice de compacidad de la canal; además se determinó la composición regional de la canal (espaldilla, bajos, badal, pierna, cuello, y costillar). Los datos se analizaron utilizando un modelo mixto. Los corderos de padre Charollais tuvieron el mayor (P<0.05) área del ojo de chuleta (20.1±0.5 cm2), mientras que los de padre Dorset fueron superiores (P<0.05) en longitud interna de la canal (66.3±0.9 cm) y longitud de pierna (34.8±0.3 cm). Los machos superaron a las hembras (P<0.05) en la mayoría de las variables analizadas. Los corderos de parto sencillo tuvieron medias mayores que los de parto doble (P<0.05) en espesor de la grasa subcutánea y longitud de la pierna. En general, las cruzas con Charollais y Dorset mostraron superioridad en las características de la canal.
Palabras clave: Ovinos de carne; Razas paternas; Cruzamientos; Características de la canal; Composición regional
Introduction
Currently, the priority of the sheep production systems in Mexico is to meet the demand of meat for the domestic market, especially for elaboration of traditional dishes such as barbecue (95 %), which consumption per capita slightly exceeds the 1,000 g1. This, despite increases in recent years of other sheep dishes, such as broiled lamb, coffin, steaks and lamb chops as a substitute for roasted kid2.
Despite the improvement of the Mexican sheep industry, which enabled to produce 57,980 t of meat carcass in 20131, there is still a deficit of meat to supply the domestic consumption, covered by imports, as national production is not sufficient to satisfy the demand in a timely, efficient manner, and with the required quality. This has aroused the interest of producers and breeders for information of new breeds that have been introduced to the country, especially on aspects related to productive performance, its response to selection and crossbreeding systems3. Therefore, it is necessary to perform genetic evaluations and select breeds or crosses that meet the needs and expectations of producers, breeders, and the national market4. Exotic breeds have been introduced in the State of Hidalgo and their productivity has been evaluated by performance tests and simple crosses5 to assess the sire breed effect6. However, it lacks studies for assessing the carcass traits of economic importance, and the best crossing strategies for these breeds have not been evaluated in the main regions of the State.
Therefore, the objective of the study was to evaluate Charollais, Dorset, and Texel sires, mated to Hampshire ewes; additionally to evaluate the sex and type of birth effects on carcass characteristics of lambs, in a commercial production system in Hidalgo, Mexico.
Material and methods
The work was carried out on a private Ranch, located in the municipality of Cuautepec de Hinojosa, State of Hidalgo, 20° 5' N and 98° 17' W at an altitude of 2,261 m, in a temperate subhumid climate with rains in summer, an average annual temperature of 15 °C and a rainfall of 600 to 1,100 mm per year7.
Hampshire ewes with an average body condition (2.5 on a scale of 1 to 5) and second parity, who underwent a protocol for estrus synchronization with intravaginal sponges impregnated with 20 mg of fluorogestone acetate were used. The sires came from various production units, selected by their best productive performance, 5 Charollais sires, 2 Dorset and 3 Texel. Controlled mating and intrauterine artificial insemination was performed to breed the ewes. Males remained with the females for 45 d, to achieve the highest number of pregnant ewes. This mating produced 45 crossbred lambs: Charollais x Hampshire (n= 14), Dorset x Hampshire (n= 15), and Texel x Hampshire (n= 16). At 12 d after birth lambs were injected with 0.2 ml of selenium + vitamin E and tail linked. At 15 to 45 d of age the lambs received a nutritional supplement (creep-feeding)-based pellets with 18 % crude protein (CP). From 45 d of age until weaning (74 ± 8 d) they were provided with alfalfa hay, oats and a balanced diet with 15 % of CP.
After weaning, lambs were finished in confinement for 63 d. Upon entering this stage of completion, initial weights of the three groups of lambs were 25.5 ± 1.4 kg (Charollais x Hampshire), 26.4 ± 1.1 kg (Dorset x Hampshire x) and 26.5 ± 1.1 kg (Texel x Hampshire). In this phase lambs received a balanced diet with 14 % CP and 2.82 ME/kg Mcal of DM, with 2 % alfalfa, 8 % of barley grain, 10 % rolling corn and 80 % concentrate feed. Later, the lambs moved to a TIF abattoir where they remained 24 h before slaughter, receiving the same feed throughout the period. Twelve hours before slaughter water and food were completely suspended. Later, procedures were those established by the federal authorities. Weight was recorded before the slaughter.
Once obtained, the carcass was washed and taken to the aerate room during a period of 1 h; past this time the hot carcass weight was recorded and refrigerated for 24 h at 4 °C to register the cold carcass weight and its yield. The carcass morphometric evaluation was performed following procedures from the literature8, by measuring carcass length, leg length, rump perimeter, and the carcass compactness index was calculated, dividing the weight (kg) by the length (cm). Subsequently, it was the cutting of the carcass8; where carcasses were dissected to weigh and record percentages of the primary cuts (shoulder, chest-belly, anterior-loin, leg, neck, and rear-loin). The rib eye area was determined by a cross-section at the height of the 13th thoracic vertebra, the muscle contour was drawn in a paper acetate and the area was then measured with a digital planimeter (PLanix 6, Tamaya Technics Inc., Tokyo, Japan). Subcutaneous fat thickness was measured with a graduated strip at the height of the 13th rib, 4 cm from the dorsal midline.
Data were analyzed with a mixed statistical model using the MIXED procedure of the SAS package9, which included sire breed (Charollais, Dorset, and Texel), lamb sex (male, female), and type of birth of the lamb (single, twin) as fixed effects, in addition to the sire effect nested within sire breed, as a random effect. Analysis included only first-order interactions. In case of statistical significance (P 0.05), subclasses means were compared with the Tukey test10.
Results and discussion
Weight and carcass yield
Table 1 shows the mean (± standard deviation) of the variables analyzed and least squares means (±standard error) of the subclasses. There was no difference (P≥0.05) due to sire breed in most of the variables, but Charollais-sired lambs showed a pretty big rib eye area (20.1 ± 0.5 cm2), which was 8.1 % higher than that of the Dorset-sired lambs and 14.2 % higher than the Texel-sired lambs. This contrasts with results from other study, in which no differences were detected among genotypes, when they evaluated terminals crosses with Charollais and Romanov sires11, or Suffolk and Texel sires12 . Partially agrees with results of the evaluation of the crossbreeding of Katahdin ewes with Suffolk, Texel, Charollais and Dorper sires, where there were only differences (P≤0.05) between the offspring of Charollais and Texel sires13. The rib eye area is one of the most important of the carcass performance variables, since it correlates positively with the total proportion of muscle in the carcass14.
Table 1 Least-squares means (mean ± standard error) of carcass traits, according to sire breed, lamb sex, and lamb birth type
SW= slaughter weight, HCW= hot carcass weight, CCW= cold carcass weight, HCY= hot carcass yield, CCY= cold carcass yield, REA= rib eye area, SF= subcutaneous fat.
ab Different literals in the same row, within subclass, indicate differences (P<0.05). *: ± standard deviation.
Males outperformed females (P≤0.05) in slaughter weight (+ 15.9 %), hot carcass weight (+ 12.3 %) and cold carcass weight (+ 11.3 %), which coincides with the results from other authors15,16. The opposite occurred in the yield carcass, both hot and cold (Table 1), because the females had a yield 3 % higher than males (P≤0.05). This is consistent with other authors that assessed the effect of sex on terminal crosses15,17,18. It seems that females have an advantage due to the grater amount of fat in the carcass16, as well as by the greater weight of the viscera, head and skin of the males18. The carcass yield is useful because it indicates the proportion of live weight that markets as a final product (meat, fat and bone), information that complements with the evaluation of the regional and tissue carcass composition. On the other hand, the difference between hot carcass weight and cold carcass weight provides an insight of the waste that exists by airing and cooling procedures.
There were interactions in the hot carcass yield (P≤0.01) between sire breed and sex of lamb, as well as sire breed and type of birth. In the first interaction (Figure 1), there were no differences among the male lambs; while among females the Charollais-sired ewe lambs outperformed (P≤0.01) those from Dorset and Texel sires. First, this could be explained by the increased performance that females had on the hot carcass; secondly, because of the superiority of the lambs (males and females) from Charollais parent upon the lambs from Dorset and Texel sires in the rib eye area, which is associated with most of the carcass meat.
In another interaction (Figure 2), there were no differences (P≥0.05) among the three groupsof twin lambs. However, among the single lambs, offspring from Charollais and Texel sires had higher means (P<0.01) than Dorset-sired lambs. This could be explained because from the total single lambs, most were females, which outperformed males in hot carcass yield and, as already indicated, this superiority of females is attributed to the higher amount of fat in the carcass16, although in this study that was not evaluated.
Figure 2 Effect of the interaction between paternal breed x type of birth of lamb in hot carcass yield
An effect of the type of birth on the thickness of subcutaneous fat was also found, single-born lambs had a higher average than twin lambs (P<0.05). In part, this could be explained as single-born lambs are heavier than twin lambs at an adult age19. However, this effect appears to be non-definitive, since in other studies20,21 the type of birth had no influence on thickness of the subcutaneous fat. In addition, a sire breed by type of birth interaction effect (P≤0.01) on the thickness of the subcutaneous fat was found (Figure 3). There was no difference (P≥0.05) among the three groups of twin lambs. However, among the single-born lambs, Texel-sired lambs had more subcutaneous fat tan those from Charollais and Dorset sires, which can be explained, even if only partially, by the superiority that had the single-born lambs over the twin-born lambs in this trait (Table 1).
Carcass morphometric measures
Table 2 shows the overall mean (± standard deviation) dimensions of the carcass and the least squares means (± standard error) of the subclasses. Dorset-sired lambs had longer carcass and leg. A study that compared different genotypes21 determined that Texel lambs had higher averages (P≤0.05) in carcass length than Merino, Polwarth, Romney Marsh, and Corriedale lambs. Leg length was similar, which means a larger extension of the trunk, which could represent an advantage for the size of the loin, the cut with the highest carcass value. In contrast, another study12 indicated that Texel lambs are characterized by having shorter carcass and leg length, but their carcasses are more compact than in the Suffolk lambs, which is attributed to the smaller size and precocity of the Texel breed in comparison to the Suffolk.
Table 2 Least-squares means (mean ± standard error) of carcass morphometric measures, according to sire breed, lamb sex, and lamb birth type
CL= carcass length; LL= leg length; RP= rump perimeter; CCI= carcass compactness index.
ab Different literals in the same row, within subclass, indicate differences (P<0.05). *: ± standard deviation.
Males had longer carcass (P≤0.01) and leg (P≤0.05) length than females. In terms of the first variable, the results of this work are consistent with another study that evaluated Pelibuey lambs22. However, differ fromobservations from other authors that assessed terminal crosses with Dorset, Hampshire and Suffolk15 or Suffolk and precocious Merino sheep23, in which sex did not influence or, even, the females from Hampshire and Suffolk sires had longer carcasses (P≤0.05) than the males15. With regard to the extension of the leg, in studies with Canaria wool and hair sheep breed24, and in lambs of Churra Galega Bragançana breeds and early Merino and Suffolk cross23, no differences were detected in the leg length due to sex, possibly, because slaughter occurs at an early stage in which the percentage of mature weight reached was still low.
With respect to the effect of type of birth on the carcass dimensions, only the leg length shows differences, being slightly longer in single-born lambs (P≤0.05), partially explained because single-born lambs reach adulthood with larger size than twin lambs18. This agrees with results of other researchers25, who indicated that single-born lambs had longer leg since they are born, an advantage that remains until they reach adult age26. These same authors found that the type of birth affects the leg circumference, because Makuie Iranian lambs had higher values of this parameter (P≤0.05) in single-born lambs than in twins and triples. The importance of the leg size is because this piece is considered as a prime cut with a high economic value, which if it also has a wide circumference, it can improve the carcass quality, as the classification systems value better carcasses with rounded and convex leg profiles.
Regional composition of the carcass
Although some studies show a direct effect (P≤0.05) of genotype on the regional carcass composition27,28, this work did not show such effect (P≥0.05) due to sire breed, both in absolute and relative pieces of the carcass. Regarding the effect of sex, Tables 3 and 4 show that males outperformed females (P≤0.05) in the weight and percentage of the shoulder and anterior-loin, but females had higher percentage values in the leg and rear-loin (P≤0.01). These results contrast with studies that evaluated Jezersko-solèava x Romanov crossbred lambs28, Segureña lambs29 as well as pure Corriedale lambs and crosses30 where the sex did not influence any of these variables. This may be due to differences in the weight and age at slaughter of lambs in different works, because males getting closer to mature weight have higher percentage of muscle and bone than females, while these have more fat accumulating in the rump, abdomen and leg28,29.
Table 3 Least-squares means (mean ± standard error) of weights (kg) of major cuts of the left half carcass, according to sire breed, lamb sex, and lamb birth type
ab Different literals in the same row, within subclass, indicate differences (P<0.05). *: ± standard deviation.
Table 4 Least-squares means (mean ± standard error) of percentages of major cuts of the left half carcass, according to sire breed, lamb sex, and lamb birth type
ab Different literals in the same row, within subclass, indicate differences (P<0.05). *:± standard deviation.
In the proportion of leg, there was an interaction (P≤0.01) between sire breed and sex of lamb (Figure 4). There were no differences (P≥0.05) among the three female groups. However, among males, Dorset and Texel sired-lambs had higher percentages of the leg (P≤0.01) than Charollais-sired lambs, who had lower percentage (27.0 ± 2.2 %) among the three male groups. This can be attributed mainly to the superiority of females over males in the leg percentage (Table 4).
Conclusions and implications
The three crosses represent a good choice to be employed in these production systems because they have similar values in the majority of meat traits. However, the Charollais-sired lambs had a higher rib eye area, which associated with a greater amount of muscle in the carcass, can be a good comparative advantage. Males had higher slaughter and carcass weights than females, as well as the size of certain body pieces, but there were no differences attributed to sex in the carcass yield, rib eye area or subcutaneous fat thickness. It means that in the three terminal crosses both females and males can be earmarked to the supply, with similar carcass quality. Single lambs only outperformed twins in the subcutaneous fat thickness and leg length, which means that they had a good productive response at the growth stage, but the type of birth had an influence at the finishing stage. It is necessary to conduct more studies to evaluate other breeds under different production systems, studies of tissue composition and meat quality, assess survival, reproductive and health characteristics, and include more animals in testing, in order to have a sufficient, clear and convincing information for sheep producers in Hidalgo.
Acknowledgments
Grateful for the financing of the project CONACYT-FOMIX key 151194: “Evaluation of integrated production systems of lamb in different sheep-producing areas in the State of Hidalgo”.
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Received: May 27, 2015; Accepted: June 29, 2015
Este es un artículo publicado en acceso abierto bajo una licencia Creative Commons
