Evangelista Amauri Felipe, Valloto Altair Antônio, El Faro Lenira, Pereira Rodrigo Junqueira, Dias Laila Talarico, de Almeida Teixeira Rodrigo
Department of Animal Science, Federal University of Paraná, Curitiba, Brazil.
Holstein Cattle Breeders Association of Paraná, Curitiba, Brazil.
J Anim Breed Genet. 2025 Nov;142(6):753-764. doi: 10.1111/jbg.12944. Epub 2025 May 30.
In this study, we aimed to evaluate the genetic association between fertility traits, milk yield and the fat: protein ratio (FPR) on the test day in primiparous Holstein cows. The analysed traits were milk yield (TDMY) and FPR assessed on the test day, as well as the following fertility traits: period from calving to first service (CFS), days open (DO) and calving interval (CI). Genetic parameters were estimated through bivariate analysis, using a random regression model (considering fourth-order Legendre polynomials) and the Bayesian method, with GIBBS2F90 software. Heritability estimates varied between 0.11 and 0.22 for TDMY, between 0.16 and 0.30 for FPR and between 0.03 and 0.05 for the fertility traits. Correlation estimates between TDMY and fertility traits tended to increase from early lactation until approximately day 100, then decreased slightly before continuing to grow until the end of lactation. Genetic correlations between TDMY and FPR were negative throughout lactation, ranging from -0.04 on day 5 to -0.37 in the final third of this period. The genetic correlations between FPR and fertility traits were positive in early lactation and negative in late lactation (except for CFS). These results indicate that TDMY and FPR are heritable and can be used as selection criteria in Holstein cows in Brazil. However, for fertility traits, genetic gains through direct selection may be slow. Additionally, a high level of milk production and FPRs in early lactation negatively impact fertility traits.
在本研究中，我们旨在评估初产荷斯坦奶牛在测定日的繁殖性状、产奶量和乳脂率与蛋白质率之比（FPR）之间的遗传关联。分析的性状包括测定日的产奶量（TDMY）和FPR，以及以下繁殖性状：产犊至首次配种间隔（CFS）、空怀天数（DO）和产犊间隔（CI）。通过双变量分析，使用随机回归模型（考虑四阶勒让德多项式）和贝叶斯方法，借助GIBBS2F90软件估计遗传参数。TDMY的遗传力估计值在0.11至0.22之间，FPR的遗传力估计值在0.16至0.30之间，繁殖性状的遗传力估计值在0.03至0.05之间。TDMY与繁殖性状之间的相关性估计值从泌乳早期到大约第100天趋于增加，然后在继续增长直至泌乳结束前略有下降。TDMY与FPR在整个泌乳期的遗传相关性均为负，从第5天的-0.04到该时期最后三分之一的-0.37不等。FPR与繁殖性状之间的遗传相关性在泌乳早期为正，在泌乳后期为负（CFS除外）。这些结果表明，TDMY和FPR具有遗传性，可作为巴西荷斯坦奶牛的选择标准。然而，对于繁殖性状，通过直接选择获得的遗传进展可能较慢。此外，泌乳早期的高产奶量和FPR对繁殖性状有负面影响。
