The objective of this study was to estimate genetic parameters for first calving reproductive traits and growth curve characteristics in Japanese Black cattle. The Gompertz growth function was fitted to body weight–age data to obtain the mature weight (MWT) and rate of maturing (ROM) of cows. Data of reproductive traits including the first service conception rate (CR) for heifers, age at the first calving (AFC), and gestation length for the first calving were collected. Records of 3,204 animals were used for analysis. Genetic parameters were estimated using a linear uni‐ and bivariate animal model. The heritability estimates were moderate (0.29 for ROM) and high (0.57 for MWT) for growth curve parameters and low (0.03–0.11) for reproductive traits. There was a negative genetic correlation between MWT and ROM (−0.26), suggesting that an animal with a faster ROM would show a lower MWT. CR was negatively correlated with MWT (−0.42) but significantly and positively correlated with ROM (0.91). There was a negative genetic correlation between AFC and MWT (−0.49). These results suggest that a heifer with a faster ROM and lower MWT would show a higher CR. Meanwhile, a heifer with a lower MWT would show a higher AFC.

中文翻译：

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日本黑牛头胎繁殖性状与生长曲线特征的遗传关联

本研究的目的是估计日本黑牛初产犊繁殖性状和生长曲线特征的遗传参数。将 Gompertz 生长函数拟合到体重-年龄数据以获得奶牛的成熟体重 (MWT) 和成熟率 (ROM)。收集了繁殖性状数据，包括小母牛的首次配种受孕率 (CR)、初产年龄 (AFC) 和初产妊娠时长。3,204 只动物的记录被用于分析。使用线性单变量和双变量动物模型估计遗传参数。生长曲线参数的遗传力估计为中等（ROM 为 0.29）和高（MWT 为 0.57），而生殖性状的遗传力估计为低（0.03-0.11）。MWT 和 ROM 之间存在负遗传相关性 (-0.26)，表明 ROM 较快的动物会显示较低的 MWT。CR 与 MWT (-0.42) 呈负相关，但与 ROM (0.91) 呈显着正相关。AFC 和 MWT 之间存在负遗传相关性 (-0.49)。这些结果表明，具有较快 ROM 和较低 MWT 的小母牛会表现出较高的 CR。同时，MWT 较低的小母牛会表现出较高的 AFC。