GANHO DE PESO PRÉ E PÓS-DESMAME NO DESEMPENHO REPRODUTIVO DE NOVILHAS DE CORTE AOS QUATORZE MESES DE IDADE

The objective of this experiment was to study the development and reproductive performance of sixty-six Charolais crossbred beef heifers bred at fourteen months of age, classified in four groups according to pre and postweaning average daily weight gain (ADG): AA= heifers that showed ADG > .54 kg and .73 kg, respectively; AB= heifers that showed ADG > .54 kg and .73 kg, respectively; BB= heifers that showed ADG < .54 kg and < .73 kg, respectively. Weight at the beginning and end of the breeding period, and the reproductive performance were influenced by ADG of the heifers during pre and postweaning phase. AA heifers showed better development in relation to the other groups, without difference between AB and BA. The AA group was superior to the others except for the reproductive performance of the group AB. Heifers that became cyclical showed higher development during the growing phase and mating period than acyclic heifers. Reproductive performance of heifers was positively correlated with weight and body condition at beginning and end of the mating period. Greater weight during pre and post-weaning improve the reproductive performance of beef heifers

Biological efficiency of Charolais beef cows of different body sizes

This study aimed to evaluate the production, reproductive performance, and productive efficiency of predominantly Charolais cows and their calves (Straightbred, ¾ C, ¼ N) according to body size at calving. Sixty-three cow-calf pairs were used and classified into three weight groups: Light (331.3±5.8 kg), Moderate (385.9±5.3 kg), and Heavy (424.4±6.2 kg). The classes were formed using half standard deviations above or below the average weight of the cows at calving. For each pair, the body weight was evaluated at calving, at weaning (63 days), at the beginning and at end of the reproductive period, and at 9 months for the calves. Pregnancy rates were similar (P > 0.05) between weight groups. The calves did not differ (P > 0.05) in terms of body weight and weight gain from calving until pregnancy diagnosis (210 days). The heavy cows had greater weight variations from 210 days to 270 days than the light cows. The calf production rate (kg calf/cow kept in herds) did not differ between weight groups. However, in relation to the weight of the cows at 210 days, light cows were 11.28% and 13.02% more productive (P < 0.05), than moderate and heavy cows, respectively. Light cows were more efficient than the other classes of cows at calving and at 210 days old. Our simulations showed that there were more kilograms for sale in herds of light cows (53.085 kg) than moderate and heavy cows (52.310 and 52.870 kg, respectively), while maintaining the structures of the herd constant. The size of the Charolais cow did not influence the weight of calves from calving until 7 months of age or their reproductive performance provided they were weaned early. The need for space for the maintenance of the cow-calf pair increased as the weight of the cows increased. In herds with smaller cows, higher numbers and a higher production of weight for sale are observed than in herds with moderate and heavy cows. Light cows were the most efficient at calving and during pregnancy diagnosis at 210 days

Development and reproductive performance of Hereford heifers of different frame sizes up to mating at 14-15 months of age

Body development and reproductive performance of a hundred forty-two 14 to 15-month-old heifers, classified at weaning according to frame size as small, medium, and large, were evaluated. The parameters evaluated were: body weight, hip height, body condition score, weight gain, ovarian activity, and pregnancy rate. At weaning, body weight and hip height were significantly different among frame scores, (small – 133.0 kg, 92.2 cm; medium – 158.5 kg, 96.6 cm; and large – 185.2 kg; 100.2 cm). After weaning, heifers grazed together on natural pastures during the autumn and on ryegrass (Lolium multiflorum La.) during the winter and spring. Frame score differences remained until the beginning of the breeding season (BS), starting on average at 14 months of age. Weight gain between weaning and the beginning of BS was not different among frame scores (0.740 kg/day, on average). Body weights at the beginning of the BS were significantly different, of 255.7 kg (53.3% of the mature weight) for small heifers, 285.0 kg (59.4%) for medium heifers, and 307.6 kg (64.1%) for large heifers. Ovarian activity at the beginning of the BS was not different among the three groups. The average weight gain values during the BS of 0.492, 0.472, and 0.421 kg/day for small, medium, and large heifers, respectively, were significantly different. Pregnancy rates were not different among groups (small, 71.4%; medium, 76.4%; and large, 76.5%). Frame score did not influence the reproductive performance of heifers, but the small and medium heifers conceived 29 and 20 days earlier, respectively, than the large heifers

Development and reproductive performance of Hereford heifers of different frame sizes up to mating at 14-15 months of age

Body development and reproductive performance of a hundred forty-two 14 to 15-month-old heifers, classified at weaning according to frame size as small, medium, and large, were evaluated. The parameters evaluated were: body weight, hip height, body condition score, weight gain, ovarian activity, and pregnancy rate. At weaning, body weight and hip height were significantly different among frame scores, (small – 133.0 kg, 92.2 cm; medium – 158.5 kg, 96.6 cm; and large – 185.2 kg; 100.2 cm). After weaning, heifers grazed together on natural pastures during the autumn and on ryegrass (Lolium multiflorum La.) during the winter and spring. Frame score differences remained until the beginning of the breeding season (BS), starting on average at 14 months of age. Weight gain between weaning and the beginning of BS was not different among frame scores (0.740 kg/day, on average). Body weights at the beginning of the BS were significantly different, of 255.7 kg (53.3% of the mature weight) for small heifers, 285.0 kg (59.4%) for medium heifers, and 307.6 kg (64.1%) for large heifers. Ovarian activity at the beginning of the BS was not different among the three groups. The average weight gain values during the BS of 0.492, 0.472, and 0.421 kg/day for small, medium, and large heifers, respectively, were significantly different. Pregnancy rates were not different among groups (small, 71.4%; medium, 76.4%; and large, 76.5%). Frame score did not influence the reproductive performance of heifers, but the small and medium heifers conceived 29 and 20 days earlier, respectively, than the large heifers

Grupo genético e presença de chifres em lesões e perdas econômicas de carcaças bovinas

Assessment of carcass bruises in steers and cull females, classified during truck unloading at the slaughterhouse according to genetic dominance in zebu and taurine cattle, and the presence of horns, including polled, horned  and mixed batches. We considered horned the batches that included more than 20% of horned animals and mixed the batches that included less than 20% horned animals. The data were collected in a commercial slaughterhouse and included 93 batches, with a total of 2,520  animals,  from different regions of South Brazil. After evisceration, the bruises were identified and recorded in  the different carcass regions: hip, round, ribs, forequarter and loin area per animal and batch. The weights of the removed tissue due to bruising was based on the average weights of various samples of bruises according to their degree of severity. Regarding the number of bruises per animal, no differences (P> 0.05) were observed between genetic groups, however, when comparing the total bruises per batch, differences were observed in all carcass regions, except for the forequarter, with more number of injuries in zebu than in taurine carcasses. The individual assessment showed 86.2% (P0,05) entre os grupos genéticos, porém, quando comparados os totais por lote, ocorreram diferenças em todas as regiões da carcaça, com exceção do dianteiro, com maior número de lesões nos zebuínos em relação aos taurinos. As avaliações individuais mostraram aumentos de 86,2% (P<0,05) de contusões para a região da costela dos animais aspados em relação aos mochos. Lotes aspados apresentaram maior média (P<0,05) de lesões em comparação aos mochos com aumento de 65,1; 131,7 e 132,8 % nas contusões totais na carcaça, na costela e no dianteiro, respectivamente. Os lotes mistos não diferiram dos mochos e aspados. Os zebuínos foram responsáveis pela maior perda da indústria totalizando 1,21 kg resultando economicamente numa perda de R$15,48 por carcaça. A presença de aspas resultou em maior perda em kg de carcaça (1,13 kg) com perda econômica de R$ 16,11 por carcaça. As contusões nas carcaças são reflexo do grupo racial e presença de aspas, com susceptibilidade dos grupos zebuínos e aspados ocasionando maiores perdas econômicas para a cadeia produtiva da carne

Grupo genético e heterose sobre medidas morfométricas durante o crescimento de bovinos de corte machos

In the present study, the effects of genetic group and heterosis on body measurements of purebreds (Charolais - C and Nellore - N), first-generation crossbreds (G1) (1/2C1/2N and 1/2N1/2C), and second-generation crossbreds (G2) (3/4C1/4N and 3/4N1/4C) males from rotational crossbreeding were evaluated at 8, 12, 18, and 24 months of age. Among the purebreds, the Nellore displayed greater rump height than the Charolais. The Charolais had greater thoracic perimeter than the Nellore, however this difference decreased gradually with advancing age, being equal between the two genetic groups at 24 months. For width of the rump, ischial opening and thoracic perimeter crossbred animals showed higher values than the purebred animals at all ages, but less pronounced at eight months of age. For all morphometric measurements, with exception of rump height, the differences of crossbreds males in relation to the purebreds, were more evident in relation to the Nellore. Heterosis was significant for morphometric measurements in male beef cattle. Morphometric measurements showed high correlation with each other and with body weight, thereby indicating that they are good indicators of body development.Foram avaliados os efeitos de grupo genético e heterose nas medidas corporais de machos puros (Charolês - C e Nelore - N); mestiços de primeira geração (G1) (½ CN e ½ NC); e mestiços de segunda geração (G2) ( ¾ C ¼ N e ¾ N ¼ C) oriundos de cruzamento rotativo. Os animais foram avaliados aos 8, 12, 18 e 24 meses de idade. Entre as raças puras, o Nelore apresentou maior altura da garupa do que o Charolês em todas idades. O Charolês foi superior ao Nelore em perímetro torácico, porém esta diferença decresceu gradativamente com o avanço da idade, sendo igual entre os dois grupos genéticos aos 24 meses. Para largura da garupa, abertura isquiática e perímetro torácico, os animais mestiços apresentaram valores médios mais elevados do que os machos puros, em todas as idades, porém menos acentuados aos oito meses de idade. Para as medidas avaliadas, com exceção para altura de garupa, as diferenças dos mestiços frente aos puros, foram mais evidentes em relação ao Nelore. A heterose se mostrou significativa para medidas morfométricas de bovinos de corte machos. As medidas corporais possuem alta correlação entre elas e com o peso corporal, sendo bons indicadores de desenvolvimento corporal