Influence of gender on carcass yield of twin lambs Blackbelly x Pelibuey at 56 days of age / Influência do gênero no rendimento de carcaça em cordeiros gêmeos Blackbelly x Pelibuey aos 56 días de idade

The aim of this study was to determine the influence of gender on pre-weaning growth, yield and weight of primal cuts of the carcass of Blackbelly x Pelibuey lambs. 16 twin lambs were used. The lamb gender was the fixed factor. The variables evaluated were: body weight at birth and at weaning, average daily weight gain, weight and yield of carcass and primal cuts: neck, arm, thorax, abdomen and leg. Gender did not affect (P>0.05) body weight at birth. However, the pre-weaning average daily weight gain and body weight at weaning were affected (P<0.05) by the gender. Hot carcass yield and weight and primal cuts were not affected (P>0.05) by the gender of the lamb. Nevertheless, the area of the Longissimus dorsi muscle and cavity fat were different between males and females (P<0.05) 11.5±0.73cm2 and 198±0.05 g vs 9.3±0.73cm2 and 282±0.05g, respectively. In conclusion, in twin lambs Blackbelly x Pelibuey males had greater average daily weight gain and body weight at weaning than females. Carcass yield and weight and primal cuts were not affected by the gender of the lamb. However, males had greater area of the L. dorsi muscle than females and these in turn had a greater amount of cavity fat than males.(AU)

Objetivou-se determinar a influência do gênero no crescimento pré-desmame, no rendimento e no peso dos cortes primários de carcaça de cordeiros Blackbelly x Pelibuey. Utilizaram-se 16 cordeiros gêmeos. Os dados foram analisados em um desenho completamente ao acaso, em que o gênero dos corderos foi o fator fixo. As variáveis avaliadas foram: peso vivo ao nascimento e ao desmame, ganho diário de peso, peso e rendimento de carcaças e dos cortes primários: pescoço, braço, tórax, abdômen e perna. O gênero não afetou (P>0,05) o peso vivo ao nascimento. No entanto, o ganho diário de peso e o peso vivo ao desmame foram afetados, sendo esses valores superiores nos machos (P<0,05). O peso e o rendimento das carcaças quentes e dos cortes primários não foram afetados (P>0,05) pelo gênero do cordeiro. Entretanto, a área do músculo Longissimus dorsi e a gordura cavitária foram diferentes entre machos e fêmeas (P<0,05): 11.5±0.73cm2 e 198±0.05g vs. 9.3±0.73cm2 e 282±0.05g, respectivamente. Em conclusão, nos cordeiros gêmeos Blackbelly x Pelibuey, os machos tiveram maior ganho diário de peso e maior peso vivo ao desmame do que as fêmeas. O peso e o rendimento da carcaça bem como os cortes primários não foram afetados pelo gênero do cordeiro. Todavia, os machos tiveram maior área do músculo L. dorsi que as fêmeas e estas tiveram maior quantidade de gordura cavitária que os machos.(AU)

Genetic and non-genetic effects on productive and reproductive traits of cows in dual-purpose herds in southeastern Mexico

Data on productive and reproductive performance of cows in dual-purpose herds were analyzed to determine the effect of some environmental and genetic factors on saleable milk yield (SMY), lactation length (LL), daily saleable milk per lactation (DMYL), calving interval (CI), and daily saleable milk per calving interval (MYCI) in dual-purpose herds in Yucatan, Mexico. Repeatabilities (re) for these traits were also estimated. Data were obtained from monthly visits to 162 herds from 1996 to 2000. The fixed factors studied were: region (central, eastern and southern), parity number (1 to 6), calving year (1996 to 2000) and calving season (dry, rainy and windy and rainy), genetic group (low- (< 0.50%), medium- (50%) and high- (> 50%) grade cows with European genes). About 2700 to 7700 cows were evaluated for each trait. All factors had significant effects (P < 0.05) on the traits except for region on CI and calving season on DMYL. The overall means for SMY, LL, DMYL, CI, and MYCI were: 1322.3 +/- 80.5 kg, 224.8 +/- 1.3 days, 5.8 +/- 0.1 kg, 555.1 +/- 16.5 days, and 3.0 +/- 0.1 kg, respectively. The re values for SMY, LL, DMYL, CI, and MYCI traits were: 0.19 +/- 0.03, 0.08 +/- 0.04, 0.16 +/- 0.04, 0.00 +/- 0.08, and 0.08 +/- 0.07, respectively. First parity cows had lower SMY, shorter LL, longer CI, and lower MYCI means than cows with more than one parity. Medium grade cows produced more SMY, DMYL and MYCI and had shorter CI than low- and high-grade cows. Therefore, under Yucatan conditions medium-grade cows should be exploited, and more attention should be given to first parity cows in order to improve the productivity in the herd. The relatively high re estimates for SMY and DMYL can be used to calculate most probable producing abilities, in order to identify which cows should be culled.