Carlos Miguel Jaume

Body condition score to predict the postpartum fertility of crossbred beef cows

A relacao entre as modificacoes no escore de condicao corporal (BCS) e a fertilidade de vacas de corte durante o pos-parto foi examinada em grupos organizados em funcao das datas dos partos. Foram efetuadas quatro avaliacoes com inicio em torno de um mes pos-parto. Na segunda avaliacao, as vacas receberam pessarios impregnados com acetato de medroxi-progesterona e uma injecao de benzoato de estradiol. Na sua remocao, foi efetuada a terceira avaliacao e separacao dos terneiros durante quatro dias. Durante esse periodo foi observado cio duas vezes ao dia, sendo as inseminacoes realizadas 12 horas apos. Depois do retorno dos terneiros as vacas, foram introduzidos touros ate completar 60 dias de estacao reprodutiva. As distribuicoes dos BCS diferiram significativamente entre grupos de paricao e momentos de avaliacao. Os resultados indicaram que apenas vacas com BCS 3 (escala de 1 a 5) em torno do primeiro mes pos-parto podem ser incluidas em programas de inseminacao artificial com possibilidade de ficarem prenhas. Nao foi observada diferenca estatisticamente significativa entre grupos de paricao quanto a taxa de prenhez. A evolucao do BCS durante o pos-parto pode ser empregada para ajustar a estacao reprodutiva a melhor epoca do ano, visando maiores taxas de gestacao.

Características da lactação de vacas Hereford criadas em um sistema de produção extensivo na região da campanha do Rio Grande do Sul

Milk yield of primiparous and multiparous Hereford cows grazing native pastures was studied using 144 lactations from four different years (1995, 1998, 2000, 2001). Estimates of milk yield were obtained every 21-day interval from birth to weaning (189 d) by the weigh-suckle-weigh technique. Effects of year, calving order, pregnancy, calf sex, and sire breed were studied. Multiparous cows (8.27+0.26 kg/d) yielded more milk than primiparous cows (5.81+0.25 kg/d) at peak of lactation (42 d). Total milk yield also was higher for multiparous (1,158.34+25.51 kg/d) compared to primiparous (915.44+24.47 kg/d). Therefore, the main difference between multiparous and primiparous lactation curves was production at peak although similar lactation persistence was found. All remaining effects did not affect milk yield in the present trial. Milk met calf requirements for maintenance and growth in the first 2 months of lactation and only maintenance requirements until the fourth month.

Produção de leite e desempenho pós parto de vacas Hereford em distintas condições reprodutivas criadas extensivamente

Milk production and pospartum performance from 52 multiparous Hereford cows, with the same body condition score (3 in a 1 to 5 scale), pregnant (45) or not pregnant (24), was studied in 69 lactations during two years, 2000 (42) and 2001 (27) under range conditions. Estimates of milk yield were obtained during six intervals (three 21d and three 42d), by the weigh-suckle-weigh technique, from birth to weaning (189d). Effects studied were year, pregnancy, calf sex and sire breed. None of the effects studied affected (P>0.05) milk production parameters: daily milk production, total milk yield, lactation peak and persistency. Body weight at calving was greater (P<0.05) in 2001 (417.49 ± 6.94kg) that in 2000 (353. 97 ± 5.57kg) and was not affected by the other effects. Body weight at conception (99d; 432.10 ± 5.78 and 399,37 ± 7.92kg) and at weaning (189d; 433.30 ± 6.36 and 393.46 ± 8.70kg), were greater (P<0.05) in pregnant cows than in non-pregnant animals, respectively. Sex of calf had a significant effect (P<0.05) on calf birth weight (41.75 ± 1.21kg and 37.6 ± 1.13kg for males and females, respectively). All studied effects affected significantly calf weaning weight (P<0.05) and pregnant cows had heavier calves at weaning (194.22 ± 3.41kg) than non-pregnant cows (177.43 ± 4.67kg). The greatest performance of pregnant beef cows with similar milk yield and body condition score from calving to weaning can be explained by the superior adaptation characteristics of these cows.

Reproductive deficiency in bulls from synthetic breeds according to the type of crossbreed and the morphology of the Y chromosome

We used 550 Braford and 214 Brangus-Ibage bulls to study the association between Y chromosome morphology and the evaluation of breeding-soundness, karyotyping and breeding records were used to assess Y chromosome morphology. In general, no direct association was detected between the individual type of Y chromosome and reproductive fitness as previously estimated through breeding soundness examination. The type of breeding strategy used to form the synthetic breeds was also analyzed. The Braford breed is about 3/8 Zebu (Bos taurus indicus) and 5/8 Hereford (Bos taurus taurus) but when the breeding strategy used 1/4 Zebu animals to produce Braford bulls which were 3/8 Zebu a greater percentage of the bulls had to be culled due to reproductive problems. Our study shows that certain interactions between genotypes can be detrimental to the reproductive efficiency of 3/8 Zebu animals and that breeding strategies avoiding or favoring certain genotypes can be used to reduce the percentage of bulls from synthetic breeds that are culled due to problems with semen quality.