ABSTRACT
Beef cattle breeding programs offer genetic evaluations and consulting services on animal breeding practices to help breeders improve the genetic merit of their herds. Some breeders are more willing to apply best practices and technologies than others. Consequently, the average genetic merit and genetic trends differ across herds. We benchmarked some parameters of an average herd (AVE) and the corresponding parameters of herds with higher genetic merit (TOP), both participating in a commercial Nellore breeding program. Expected progeny differences (EPD) for growth, reproductive and carcass traits and a selection index (SI) of animals born from 2005 to 2019 on 128 farms located in Brazil, Bolivia and Paraguay were used to compute the AVE parameters. The 20 herds with higher mean SI of animals born in the last five birth seasons were classified as TOP herds. The mean SI and EPD of animals born in the last five seasons in the TOP herds were, respectively, 89% and 79% to 206% higher (p ≤ 0.001) than those of animals from the AVE herd. Genetic trends over the entire period were also higher (50% for SI and 31% to 88% separately for each trait, p ≤ 0.006) in the TOP herds compared to the AVE herd. Although the difference in the numbers of cows, bulls and calves between the TOP and AVE herds did not reach statistical significance (p = 0.175, p = 0.273 and p = 0.061, respectively), the numbers of progeny per cow and per bull were 21% (p = 0.012) and 26% (p = 0.047) higher in the TOP herds, respectively. Multiple ovulation and embryo transfer and in vitro fertilization and embryo transfer (MOET/IVF) accounted for a higher percentage of births in the TOP herds compared to AVE (24.6% vs. 12.5%, p = 0.002). The generation interval was 17% shorter (p < 0.001) in the TOP herds compared to AVE. The average inbreeding coefficient of animals from the TOP herds (1.08 ± 0.52%) did not differ (p = 0.78) from that of AVE animals (1.26 ± 0.96%). In general, AVE herds are evolving in the desirable direction but differences in genetic merit between AVE and TOP herds are increasing over time. The more frequent use of MOET/IVF, a lower cow-to-bull ratio, and a larger family size (progeny per cow or per bull) can help achieve larger selection differentials and increase genetic trends and average genetic merits of TOP herds compared to AVE herds.
Subject(s)
Benchmarking , Reproduction , Pregnancy , Female , Cattle/genetics , Animals , Male , Reproduction/genetics , Parturition , Inbreeding , Phenotype , DairyingABSTRACT
Trinta e dois cordeiros (¹/2 Texel + » Bergamácia + » Corriedale), 16 machos inteiros e 16 fêmeas, foram alimentados durante 71 dias com dietas isoenergéticas (72 por cento NDT), variando os níveis protéicos (12, 16, 20 e 24 por cento PB) em baias individuais, com avaliaçäo de carcaça após abate. O rendimento verdadeiro médio da carcaça foi 54 por cento, enquanto o rendimento comercial médio foi 48 por cento. Verificou-se que os níveis protéicos entre 12 e 24 por cento näo afetaram o peso da carcaça quente e fria; o rendimento comercial da carcaça, o índice de compacidade da carcaça e do pernil, bem como a condiçäo corporal, conformaçäo, cobertura de gordura, consistência da gordura, cor da carne, espessura de gordura e deposiçäo de gordura. Os animais terminados com dietas com 12 por cento de proteína bruta foram os que apresentaram maior rendimento verdadeiro de carcaça
