Global warming has increased the frequency of heat stress in livestock. Although heat stress directly leads to negative effects on production and reproduction traits in dairy cattle, the transgenerational transition of these changes is poorly understood. We hypothesized that heat stress in pregnant cows might induce epigenetic modifications in the developing embryo germ cells, which, in turn, might lead to phenotypic effects in the offspring. Here, we examined whether transgenerational effects of heat stress contribute to the phenotypic expression of economic traits in Israel dairy cattle. Since heat stress in Israel occurs specifically between June and October, first we examined the association of the month of birth of F1 cows (pregnancy of the F0 dam) with the performance of the F2 and F3 female offspring. Then, we calculated an annual heat stress index and examined the association of the heat stress index during the pregnancy of the F0 dam with the performance of her F2 and F3 offspring. Finally, we examined intergenerational interactions of heat stress by comparing the performance of F3 cows according to the pregnancy seasons of the F0 and F1 animals. We found a significant association of the month of birth, season of pregnancy, and heat stress index of F0 females, with the performance of their F2 and F3 progenies, which suggests a true transgenerational effect. The most significant transgenerational effects were on fat yield and concentration, dystocia, still-birth, and maturation. These findings suggest that heat stress during pregnancy affects the performance of offspring, regardless of life circumstances in at least the last three generations. Therefore, heat stress can reduce selection efficiency in breeding programs and may have economic significance in livestock.

中文翻译：

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奶牛跨代热应激效应的广泛表型影响：连续四代研究

全球变暖增加了牲畜热应激的频率。尽管热应激直接对奶牛的生产和繁殖性状产生负面影响，但对这些变化的跨代转变知之甚少。我们假设怀孕母牛的热应激可能会诱导发育中的胚胎生殖细胞的表观遗传修饰，进而可能导致后代的表型效应。在这里，我们检查了热应激的跨代效应是否有助于以色列奶牛经济性状的表型表达。由于以色列的热应激特别发生在 6 月和 10 月之间，因此我们首先检查了 F1 母牛的出生月份（F0 母牛的妊娠）与 F2 和 F3 雌性后代的表现之间的关联。然后，我们计算了年度热应激指数，并检查了 F0 母猪怀孕期间的热应激指数与其 F2 和 F3 后代的表现之间的关联。最后，我们通过根据 F0 和 F1 动物的怀孕季节比较 F3 奶牛的表现来检查热应激的代际相互作用。我们发现 F0 雌性的出生月份、怀孕季节和热应激指数与其 F2 和 F3 后代的表现存在显着关联，这表明存在真正的跨代效应。最显着的跨代影响是脂肪产量和浓度、难产、死产和成熟。这些发现表明，怀孕期间的热应激会影响后代的表现，而与至少最后三代的生活环境无关。