São Paulo State University (UNESP), School of Agricultural and Veterinarian Sciences, Via de Acesso Prof. Paulo Donato Castelane, Jaboticabal, SP, 14884-900, Brazil.
São Paulo State University (UNESP), School of Agricultural and Veterinarian Sciences, Via de Acesso Prof. Paulo Donato Castelane, Jaboticabal, SP, 14884-900, Brazil.
Theriogenology. 2024 Dec;230:142-150. doi: 10.1016/j.theriogenology.2024.09.005. Epub 2024 Sep 6.
This study aimed to investigate the differences between productive and reproductive performance traits of sexually precocious and non-sexually precocious Nellore heifers and to evaluate the genetic correlation of sexual precocity with traits of economic importance. For this purpose, 300,000 Nellore heifers were evaluated for reproductive traits: heifer pregnancy (HP) at 14 (HP), 18 (HP), and 24 (HP) months; heifer rebreeding (HR); number of progenies up to 53 months (NP); and probability of the cow remaining in the herd until 76 months with at least 3 progenies (Stay). The growth-related traits evaluated included female yearling weight (YW); average daily gain from weaning to yearling (ADG); weight at maturity (MW); weaning weight of first progeny (WW); and female visual scores at yearling for conformation (Conf), precocity (Prec) and muscling (Musc). The effects of female YW and ADG in six categories on HP, HP, and HP were analyzed using Generalized linear mixed models (GLMM). Furthermore, a linear mixed model was used to evaluate the impact of HP on WW, MW, and reproductive performance (NP and Stay). Genetic correlations of HP evaluated in different months with growth and reproductive traits were estimated using a bivariate animal model. Precocious heifers (HP) were lighter for YW and MW but had greater ADG than HP and HP. The probability for HP, HP, and HP increased as the classes of YW and ADG increased. However, heifers weighing more than 326 kg had a slight reduction in the probability of becoming pregnant at HP and HP. Precocious heifers (HP and HP) produced their first progeny by 3 % lighter than HP, although they had a greater NP. Precocious heifers at 18 months (HP) were 3 % and 6.8 % more likely to remain in the herd than HP and HP heifers, respectively. Genetic correlations between growth traits (WW, YW, ADG and MW) and heifer pregnancy (HP, HP, and HP) ranged from weak (r = 0.27 ± 0.05) to moderate (r = -0.47 ± 0.07). The genetic correlation between HR and HP was stronger for HP (0.75) against HP (0.58) and HP (0.64). Although, the genetic correlation between NP and Stay with HP was higher (r = 0.53 and 0.45) than those observed for HP (r = 0.46 and 0.38) and HP (r = 0.35 and 0.39). The genetic correlation estimates between HP and visual scores were moderate and favorable for HP. Selecting HP is beneficial for production systems because it increases the NP during the productive life without compromising heifer productivity or reproductive performance. However, attention should be given to improving the HR of heifers who become pregnant early.
本研究旨在探讨早熟和非早熟尼洛雷牛的生产性能和繁殖性能之间的差异，并评估早熟与经济重要性状的遗传相关性。为此，对 30 万头尼洛雷小母牛的繁殖性状进行了评估：14 个月（HP）、18 个月（HP）和 24 个月（HP）的小母牛妊娠；小母牛再配种（HR）；53 个月以下的后代数量（NP）；76 个月时至少有 3 头后代的母牛留在牛群中的概率（Stay）。评估的生长相关性状包括雌性小母牛体重（YW）；断奶至小母牛的平均日增重（ADG）；成熟体重（MW）；第一头后代的断奶体重（WW）；小母牛在 1 岁时的形态学评分（Conf）、早熟（Prec）和肌肉（Musc）。使用广义线性混合模型（GLMM）分析了雌性 YW 和 ADG 在六个类别对 HP、HP 和 HP 的影响。线性混合模型用于评估 HP 对 WW、MW 和繁殖性能（NP 和 Stay）的影响。使用双变量动物模型估计了不同月份评估的 HP 与生长和繁殖性状的遗传相关性。早熟小母牛（HP）的 YW 和 MW 较轻，但 ADG 大于 HP 和 HP。随着 YW 和 ADG 类别的增加，HP、HP 和 HP 的概率增加。然而，体重超过 326 公斤的小母牛在 HP 和 HP 时怀孕的概率略有下降。早熟小母牛（HP 和 HP）的第一头后代比 HP 轻 3%，尽管 NP 更大。18 个月（HP）的早熟小母牛比 HP 和 HP 小母牛更有可能分别保持在牛群中，其可能性分别增加了 3%和 6.8%。生长性状（WW、YW、ADG 和 MW）与小母牛妊娠（HP、HP 和 HP）之间的遗传相关性从弱（r=0.27±0.05）到中度（r=-0.47±0.07）不等。HR 与 HP 的遗传相关性强于 HP（0.75）对 HP（0.58）和 HP（0.64）。尽管 NP 和 Stay 与 HP 的遗传相关性高于 HP（r=0.53 和 0.45）和 HP（r=0.46 和 0.38）和 HP（r=0.35 和 0.39）。HP 与视觉评分之间的遗传相关性估计适中，对 HP 有利。选择 HP 对生产系统有益，因为它可以提高生产寿命期间的 NP，而不会影响小母牛的生产力或繁殖性能。然而，应注意提高早熟小母牛的 HR。
