Gutierrez Carlos G, Gong Jin G, Bramley Thomas A, Webb Robert
Departamento de Reproducción, Facultad de Medicina Veterinaria, Cd. Universitaria 04510, Mexico, DF, Mexico.
Anim Reprod Sci. 2006 Oct;95(3-4):193-205. doi: 10.1016/j.anireprosci.2005.09.015. Epub 2005 Oct 19.
Two studies were conducted to investigate the effect of selection on predicted breeding value (PBV) for milk production, and its associated metabolic and endocrine milieu, on follicular development and ovulation in the postpartum period. A total of 71 cattle from lines selected to differ in their PBV were used in two consecutive years. In Study 1 the first ovulation and commencement of normal luteal function occurred significantly earlier in low (L) line cows than high (H) line cows. In Study 2 average daily milk production during the study period did not differ (P>0.10) between cows in either the H (=31.0+/-1.5kg/day) or L (=30.2+/-1.7kg/day) PBV lines although, 305 days milk production was significantly different (P<0.01; H=6880+/-164kg versus L=5795+/-317kg). As in Study 1, first ovulation postpartum in Study 2 occurred earlier (P<0.01) in the L (day 19) versus the H line (day 28). Circulating concentrations of glucose and insulin were significantly lower, whilst concentrations of GH and BOHB were higher in cows from the high PBV line. No differences in gonadotrophin concentrations were seen between lines. Both changes in body weight and patterns of follicle development did not differ between lines. By day 15 postpartum all cows had follicles of all three-size categories (small, medium-sized and large). Small (P<0.07) and medium-sized follicle numbers increased (P<0.01) with day postpartum. However, the inclusion of predicted changes in body weight as a covariate in the analysis, demonstrated that changes in number of small and medium-sized follicles were associated with changes in body weight. In conclusion, selection on PBV for milk production is associated with a longer interval from parturition to first ovulation, independent of changes in follicular development, milk production and body weight implicating other factor(s) associated with genetic selection.
进行了两项研究，以调查选育对产奶预测育种值（PBV）及其相关代谢和内分泌环境的影响，以及对产后卵泡发育和排卵的影响。连续两年使用了71头来自选育品系、PBV不同的母牛。在研究1中，低（L）系母牛的首次排卵和正常黄体功能开始时间显著早于高（H）系母牛。在研究2中，尽管305天产奶量有显著差异（P<0.01；H=6880±164千克对L=5795±317千克），但研究期间H（=31.0±1.5千克/天）或L（=30.2±1.7千克/天）PBV品系母牛的日均产奶量无差异（P>0.10）。与研究1一样，研究2中产后首次排卵L系（第19天）早于H系（第28天）（P<0.01）。高PBV品系母牛的循环葡萄糖和胰岛素浓度显著较低，而生长激素（GH）和β-羟基丁酸（BOHB）浓度较高。品系间促性腺激素浓度无差异。体重变化和卵泡发育模式在品系间无差异。产后第15天，所有母牛都有三种大小类别的卵泡（小、中、大）。小卵泡数量（P<x0.07）和中卵泡数量随产后天数增加（P<0.01）。然而，在分析中纳入体重预测变化作为协变量表明，小卵泡和中卵泡数量的变化与体重变化有关。总之，对产奶PBV的选育与从分娩到首次排卵的间隔时间延长有关，与卵泡发育、产奶量和体重变化无关，这意味着与基因选育相关的其他因素。
