安大略省肉用小母牛中，种公牛阴囊周长对产犊年龄的影响。
Effects of scrotal circumference of sire on age of calving in Ontario beef heifers.
作者信息
Thompson J A, Etherington W G, Wilton J W, Johnson W H
出版信息
Can Vet J. 1992 Jun;33(6):386-9.
Calving records for daughters of 667 Record of Performance tested sires were examined to study factors related to age at first calving. For the 3025 heifers analyzed, mean age (+/- SD) at first calving was 791.5 +/- 161.6 days (26.4 +/- 5.4 months). There were significant effects of the breed of sire on age of heifer at first calving. Daughters of Angus sires calved earlier than daughters of Charolais, Hereford, Limousin, and Simmental sires. Mean ages at first calving for daughters of Hereford, Limousin, and Simmental bulls were significantly (p < 0.05) correlated with the sire's end-of-test age-adjusted scrotal circumference, but these correlations were not significant when farm effects were controlled. It appears that unknown herd level factors are more important in determining age at first calving in Ontario herds than using early maturing sires as determined by scrotal circumference measurements.
对667头经过性能记录测试的种公牛的女儿们的产犊记录进行了检查，以研究与首次产犊年龄相关的因素。对于分析的3025头小母牛，首次产犊的平均年龄（±标准差）为791.5±161.6天（26.4±5.4个月）。种公牛的品种对小母牛首次产犊的年龄有显著影响。安格斯种公牛的女儿比夏洛来、赫里福德、利木赞和西门塔尔种公牛的女儿产犊更早。赫里福德、利木赞和西门塔尔公牛的女儿首次产犊的平均年龄与种公牛测试结束时年龄校正后的阴囊周长显著相关（p<0.05），但在控制农场效应后，这些相关性并不显著。看来，在安大略省的牛群中，未知的畜群水平因素在决定首次产犊年龄方面比使用通过阴囊周长测量确定的早熟种公牛更为重要。
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