Moser D W, Bertrand J K, Benyshek L L, McCann M A, Kiser T E
Animal and Dairy Science Department, University of Georgia, Athens 30602-2771, USA.
J Anim Sci. 1996 Sep;74(9):2052-7. doi: 10.2527/1996.7492052x.
Nine pairs of Limousin bulls from nine contemporary groups were acquired, with each pair consisting of one large scrotal circumference (SC) bull and one small SC bull. Average adjusted yearling scrotal circumferences were 36.3 cm (SD 1.6 cm) and 28.5 cm (SD .9 cm) for large SC (LP) and small SC (SP) bulls, respectively. In addition to the phenotypic grouping, non-parent SC EPD were used to group bulls into high (HE, > .53 cm), average (AE), and low (LE, < -.61 cm) lines. Each bull was mated to a randomly assigned group of 15 to 20 Brangus x Hereford cows each yr for 1 to 3 yr. Birth weights, weaning and yearling weights and heights, and ultrasound measurements for backfat and ribeye measurements were taken on 407 progeny. Blood samples were collected on 210 heifer progeny when they averaged 11, 13, and 15 mo of age to determine whether they had reached puberty. When subjected to a breeding soundness exam (BSE), LP bulls scored higher (P < .01) for motility as well as total BSE score. The LP calves had heavier birth weights (P < .05) and greater testicular mass at weaning (P < .01) than SP calves. The HE and AE bull calves had greater (P < .02) testicular mass than did the LE bull calves. A greater (P < .05) percentage of HE heifers had reached puberty by the 11- and 13-mo measurements than either the AE or LE heifers. The HE heifers reached puberty at a younger age than AE (P < .01) or LE (P < .001) heifers. Selection using SC EPD was more effective than phenotypic selection in reducing age at puberty in daughters.
从九个当代组中选取了九对利木赞公牛，每对由一头阴囊周长较大（SC）的公牛和一头阴囊周长较小的公牛组成。大阴囊周长（LP）公牛和小阴囊周长（SP）公牛的平均校正一岁阴囊周长分别为36.3厘米（标准差1.6厘米）和28.5厘米（标准差0.9厘米）。除了表型分组外，还使用非亲本阴囊周长预期子代差异（EPD）将公牛分为高（HE，>.53厘米）、中（AE）和低（LE，< -.61厘米）三个品系。每年将每头公牛与一组随机分配的15至20头婆罗门牛×赫里福德牛母牛交配，持续1至3年。对407头后代进行了出生体重、断奶和一岁体重与身高测量，以及背部脂肪和肋眼的超声测量。在210头小母牛后代平均年龄为11、13和15月龄时采集血样，以确定它们是否已达到青春期。在进行繁殖健全性检查（BSE）时，LP公牛在活力以及总体BSE评分方面得分更高（P <.01）。LP犊牛的出生体重比SP犊牛更重（P <.05），断奶时的睾丸重量更大（P <.01）。HE和AE公牛犊的睾丸重量比LE公牛犊更大（P <.02）。在11月龄和13月龄测量时，达到青春期的HE小母牛的百分比高于AE或LE小母牛（P <.05）。HE小母牛比AE（P <.01）或LE（P <.001）小母牛更早达到青春期。使用阴囊周长EPD进行选择在降低女儿青春期年龄方面比表型选择更有效。
