Abstract：
In tropical beef cattle production systems, animals are commonly raised on pastures, exposing them to potential stressors. The end of gestation typically overlaps with a dry period characterized by limited food availability. Late gestation is pivotal for fetal development, making it an ideal scenario for inter- and transgenerational effects of the maternal gestational environment. Intergenerational effects occur due to exposure during gestation, impacting the development of the embryo and its future germline. Transgenerational effects, however, extend beyond direct exposure to the subsequent generations. The objective of the present study was to verify these effects on the post-natal performance of zebu beef cattle. We extended the use of a reaction norm model to identify genetic variation in the animals\' responses to transgenerational effects. The inter- and transgenerational effects were predominantly positive (-0.09% to 19.74%) for growth and reproductive traits, indicating improved animal performance on the phenotypic scale in more favourable maternal gestational environments. Additionally, these effects were more pronounced in the reproductive performance of females. On average, the ratio of direct additive genetic variances of the slope and intercept of the reaction norm ranged from 1.23% to 3.60% for direct and from 10.17% to 11.42% for maternal effects. Despite its relatively modest magnitude, this variation proved sufficient to prompt modifications in parameter estimates. The average percentage variation of direct heritability estimates ranged from 19.3% for scrotal circumference to 33.2% for yearling weight across the environmental descriptors evaluated. Genetic correlations between distant environments for the studied traits were generally high for direct effects and far from unity for maternal effects. Changes in EBV rankings of sires across different gestational environments were also observed. Due to the multifaceted nature of inter- and transgenerational effects of the maternal gestational environment on various traits of beef cattle raised under tropical pasture conditions, they should not be overlooked by producers and breeders. There were differences in the specific response of beef cattle to variations in the quality of the maternal gestational environment, which can be partially explained by transgenerational epigenetic inheritance. Adopting a reaction norm model to capture a portion of the additive variance induced by inter- or transgenerational effects could be an alternative for future research and animal genetic evaluations.
摘要：
在热带肉牛生产系统中，动物通常在牧场上饲养，让他们面临潜在的压力。妊娠结束通常与以食物供应有限为特征的干旱期重叠。妊娠晚期是胎儿发育的关键,使其成为母体妊娠环境的代际和跨代影响的理想方案。代际效应是由于妊娠期间的暴露而发生的，影响胚胎及其未来种系的发育。代际效应,然而,超越了对后代的直接接触。本研究的目的是验证这些对Zebu肉牛产后表现的影响。我们扩展了反应规范模型的使用，以识别动物对跨代效应的反应中的遗传变异。生长和繁殖性状的代际和跨代效应主要为正(-0.09%至19.74%),表明在更有利的母体妊娠环境中，动物在表型尺度上的表现有所改善。此外,这些影响在女性的生殖表现中更为明显。平均而言,反应范数斜率和截距的直接加性遗传变异率直接为1.23％至3.60％，母体效应为10.17％至11.42％。尽管规模相对较小，这种变化被证明足以促使参数估计的修改。在评估的环境描述符中，直接遗传力估计的平均百分比变化范围从阴囊周长的19.3％到一岁体重的33.2％。所研究性状的远距离环境之间的遗传相关性通常对直接影响很高，而对母体影响则相去甚远。还观察到不同妊娠环境中父亲的EBV排名变化。由于母体妊娠环境对热带牧场条件下饲养的肉牛的各种性状的代际和跨代影响的多面性，生产者和育种者不应该忽视它们。肉牛对母体妊娠环境质量变化的具体反应存在差异,这可以部分解释为跨代表观遗传。采用反应规范模型来捕获由代际或跨代效应引起的加性方差的一部分，可能是未来研究和动物遗传评估的替代方案。
