Evaluation of the productive and reproductive performance of sexual precocity at different ages in Nellore heifers

IF 2.4 2区 农林科学 Q3 REPRODUCTIVE BIOLOGY
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Abstract

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 (HP14), 18 (HP18), and 24 (HP24) months; heifer rebreeding (HR); number of progenies up to 53 months (NP53); 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 (ADGW-Y); weight at maturity (MW); weaning weight of first progeny (WWprog); and female visual scores at yearling for conformation (Conf), precocity (Prec) and muscling (Musc). The effects of female YW and ADGW-Y in six categories on HP14, HP18, and HP24 were analyzed using Generalized linear mixed models (GLMM). Furthermore, a linear mixed model was used to evaluate the impact of HP on WWprog, MW, and reproductive performance (NP53 and Stay). Genetic correlations of HP evaluated in different months with growth and reproductive traits were estimated using a bivariate animal model. Precocious heifers (HP14) were lighter for YW and MW but had greater ADGW-Y than HP18 and HP24. The probability for HP14, HP18, and HP24 increased as the classes of YW and ADGW-Y increased. However, heifers weighing more than 326 kg had a slight reduction in the probability of becoming pregnant at HP14 and HP18. Precocious heifers (HP14 and HP18) produced their first progeny by 3 % lighter than HP24, although they had a greater NP53. Precocious heifers at 18 months (HP18) were 3 % and 6.8 % more likely to remain in the herd than HP14 and HP24 heifers, respectively. Genetic correlations between growth traits (WW, YW, ADGW-Y, and MW) and heifer pregnancy (HP14, HP18, and HP24) ranged from weak (rg = 0.27 ± 0.05) to moderate (rg = −0.47 ± 0.07). The genetic correlation between HR and HP was stronger for HP24 (0.75) against HP14 (0.58) and HP18 (0.64). Although, the genetic correlation between NP53 and Stay with HP14 was higher (rg = 0.53 and 0.45) than those observed for HP18 (rg = 0.46 and 0.38) and HP24 (rg = 0.35 and 0.39). The genetic correlation estimates between HP and visual scores were moderate and favorable for HP14. Selecting HP14 is beneficial for production systems because it increases the NP53 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.

评估内洛尔母牛不同年龄性早熟的生产和繁殖性能
本研究旨在调查性早熟和非性早熟内洛尔母牛的生产性能和繁殖性能性状之间的差异,并评估性早熟与重要经济性状之间的遗传相关性。为此,对 300,000 头内洛尔母牛的繁殖性状进行了评估:14 个月(HP14)、18 个月(HP18)和 24 个月(HP24)的小母牛怀孕率(HP);小母牛再繁殖率(HR);53 个月以内的后代数(NP53);母牛在牛群中存活至 76 个月并至少有 3 头后代的概率(Stay)。评估的生长相关性状包括雌性一岁体重(YW)、断奶至一岁的平均日增重(ADGW-Y)、成熟体重(MW)、第一胎后代的断奶体重(WWprog)以及雌性一岁时的体型(Conf)、早熟(Prec)和肌肉(Musc)视觉评分。使用广义线性混合模型(GLMM)分析了六类雌性 YW 和 ADGW-Y 对 HP14、HP18 和 HP24 的影响。此外,还使用线性混合模型评估了HP对WWprog、MW和繁殖性能(NP53和Stay)的影响。使用双变量动物模型估算了不同月份评估的HP与生长和繁殖性状的遗传相关性。早熟小母牛(HP14)的YW和MW较轻,但ADGW-Y高于HP18和HP24。随着YW和ADGW-Y等级的增加,HP14、HP18和HP24的概率也在增加。然而,体重超过 326 千克的母牛在 HP14 和 HP18 怀孕的概率略有下降。虽然早熟母牛(HP14 和 HP18)的 NP53 较大,但其生产的第一头后代比 HP24 轻 3%。与 HP14 和 HP24 母牛相比,18 个月的早熟母牛(HP18)留在牛群中的可能性分别高出 3% 和 6.8%。生长性状(WW、YW、ADGW-Y 和 MW)与小母牛妊娠(HP14、HP18 和 HP24)之间的遗传相关性从弱(rg = 0.27 ± 0.05)到中等(rg = -0.47 ± 0.07)不等。与 HP14(0.58)和 HP18(0.64)相比,HP24(0.75)的 HR 与 HP 之间的遗传相关性更强。不过,NP53 和 Stay 与 HP14 的遗传相关性(rg = 0.53 和 0.45)高于 HP18(rg = 0.46 和 0.38)和 HP24(rg = 0.35 和 0.39)。HP和视觉评分之间的遗传相关性估计值适中,对HP14有利。选择 HP14 对生产系统是有益的,因为它在不影响小母牛生产性能或繁殖性能的情况下,提高了生产期的 NP53。不过,应注意提高早孕母牛的HR。
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来源期刊
Theriogenology
Theriogenology 农林科学-生殖生物学
CiteScore
5.50
自引率
14.30%
发文量
387
审稿时长
72 days
期刊介绍: Theriogenology provides an international forum for researchers, clinicians, and industry professionals in animal reproductive biology. This acclaimed journal publishes articles on a wide range of topics in reproductive and developmental biology, of domestic mammal, avian, and aquatic species as well as wild species which are the object of veterinary care in research or conservation programs.
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