Carlos Santos Gottschall

Perdas reprodutivas e reconcepção em bovinos de corte segundo a idade ao acasalamento

Reproductive performances of beef heifers mated at 14 months of age (14M), at 24 months of age (24M) and pluriparous cows (C), based on data from 4.012 animals were evaluated. The reproductive disorders were 19.3%, 11.6% and 7.6%, respectively, at 14M, 24M and for C; 14M was different from C (P<0.01). The occurrence of dystocia was 20.7%, 5.1% and 0.8% for the 14M, 24M and C, respectively. The 14M group was different from C (P<0.01). The mortality caused by dystocia was higher for 14M group 7.4% than for the C group 0.4% (P<0.01), respectively. The reconception rate was higher for the 14M (85.3%) and V (81.1%) than for the 24M group (70.7%) (P<0.01). The category which concentrated the parturition in the first period (until 09/19) (52.3%) was the 24M. Animals mated earlier tended to show high reproductive disorders and incidence of dystocia.

Resposta reprodutiva de vacas de corte associada a marcadores moleculares relacionados à fertilidade

The association between the reproductive performance, expressed by pregnancy rate at fixed timed artificial insemination and birth rate in the subsequent season in beef cows, and molecular markers linked to genes for IGF-1 receptor, LHβ, leptin, and FSH and LH receptors were evaluated. Data from 249 Aberdeen Angus adult cows were used in this study. One hundred and ninety-nine cows were subjected to four different protocols for FTAI, followed by clean-up bulls and 50 cows formed the control group, matted only with bulls for 90 days during the mating season. Body condition score (BCS) and ovarian condition score (OCE) were evaluated at the beginning of the breeding season. The birth rate in the following year was 75.5%, with no treatments influence. The BCS has influenced the birth rate, respectively 55.6%, 75.8% and 82.4% (P<0.05) for animals with BCS less than 2.5; 2.5 to 2.9; and greater than or equal to 3.0, at the beginning of the breeding season. The markers related to IGF-1 receptor gene (AFZ-1 and HEL5) were associated with the birth rate in beef cows. Cows homozygous for AFZ-1 marker showed 84.4% of birth rate, while heterozygous cows showed 71.5% (P <0.05). The presence of allele *161 to the HEL5 marker was negative on birth rate. Cows with this allele had only 33.3% of birth rate, while cows without this allele had 76.5% of birth rate (P <0.05). These results demonstrate a significant association between the markers involved with the IGF-1 receptor and reproductive performance of Aberdeen Angus beef cows.

Relationships between age, weight, average weight gain and days on feed of beef steers slaughtered at 15 or 27 months of age

The main objective of this research was to evaluate the relationship between age, weight, average weight gain and days on feed of beef steers slaughtered at 15 or 27 months of age. Four hundred and thirty two beef steers were divided in two groups: 267 younger steers (YY), confined at 12 and slaughtered at 15 months old; and 165 young steers (YS), confined at 25 and slaughtered at 27 months of age. Beginning weight (BW) was 296.98 and 352.04 kg to YY and YS, respectively (p<0.01). Steers were on feedlot until reach a minimum fat percentage, resulting on seven different values for DF. In the statistical analysis the BW and the DF were calculated as co-variables. YS reach higher AWG (1.351 vs 1.004 kg/day) and higher SW (441.88 vs 388.88 kg) (p<0.01) and lower (p<0.01) DF (66.87 and 94.20 days, respectively). Steers with higher BW were sold earlier, reaching lower DF. Both groups showed a decrease tendency of AWG as the DF increased. YS reached higher AWG, resulting in lower DF compared with YY. In both groups, while the DF increases, the AWG decreases. Steers with higher BW reached lower DF