Play behavior in young animals has been used to evaluate the condition (health) of livestock. We investigated age, sex, and genetic differences of Japanese Black calves in relation to frequency of play behaviors (galloping, leaping, turning, bucking, head butting objects, and head shaking) and examined how these relationships might affect growth during the suckling stage. Locomotor play behaviors (galloping, leaping, turning, and bucking) and head butting objects gradually declined with the age for both sexes. The frequency of head butting was significantly higher in males than females. We found that significant interaction effects (age × MAOA polymorphism) in play behaviors (except head shaking) and the frequencies of locomotor play in calves without the wild-type allele were significantly higher than those in younger calves (2 and 6 weeks of age). Weight gain was significantly correlated with the frequency of locomotor play in females, but not in males. This study suggests that play in Japanese Black calves gradually declines as they mature and that play may be controlled by variations in the MAOA gene. In addition, the frequency of locomotor play may be an indicator of health in female calves.

中文翻译：

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与日本黑小牛的游戏行为有关的性别，年龄或遗传差异。

幼兽的游戏行为已用于评估牲畜的状况（健康）。我们调查了日本黑小牛的年龄，性别和遗传差异，这些行为与玩耍行为的频率（舞动，跳跃，转弯，屈曲，头撞物体和摇头）有关，并研究了这些关系在哺乳阶段如何影响生长。随着男女年龄的增长，运动行为（奔跑，跳跃，转弯和屈曲）和头部撞物体逐渐减少。男性的头撞频率明显高于女性。我们发现，在没有野生型等位基因的小牛中，游戏行为（头部摇晃除外）中的显着相互作用效应（年龄×MAOA多态性）和运动行为的频率显着高于年轻小牛（2周龄和6周龄） 。体重增加与女性运动能力的频率显着相关，而男性则没有。这项研究表明，日本黑牛犊的成熟度会随着它们的成熟而逐渐下降，并且这种运动可能受到MAOA基因变异的控制。另外，运动运动的频率可能是雌性犊牛健康的指标。这项研究表明，日本黑小牛的游动随着它们的成熟而逐渐下降，并且该游动可能受到MAOA基因变异的控制。另外，运动运动的频率可能是雌性犊牛健康的指标。这项研究表明，日本黑小牛的游动随着它们的成熟而逐渐下降，并且该游动可能受到MAOA基因变异的控制。另外，运动运动的频率可能是雌性犊牛健康的指标。