Nugent R A, Notter D R, Beal W E
Virginia Polytechnic Institute and State University, Blacksburg 24061-0306.
J Anim Sci. 1991 Jun;69(6):2413-21. doi: 10.2527/1991.6962413x.
Body measurements on Angus- (n = 374) and Polled Hereford-sired (n = 438) calves were used to quantify calf shape via multivariate factor analysis, and measurements on Polled Hereford-sired calves were further used to investigate relationships between calf shape and sire expected progeny differences (EPD) for birth weight and first-calf calving ease. Calf birth weight, head circumference, shoulder width, hip width, heart girth, cannon bone circumference and length, and body length were recorded at 24 h postpartum. Sire birth weight EPD was positively associated (P less than .05) with all calf measures but only with head and cannon circumference after adjustment for phenotypic birth weight and gestation length. Thus, at constant birth weight, calves from higher birth weight EPD bulls tended to have larger cannon and head circumferences. Calving ease EPD was negatively related (P less than .05) to all calf measures except shoulder width. After adjustment for birth weight, only cannon circumference was associated with calving ease EPD, and this effect was removed by additional adjustment for birth weight EPD. Thus, at constant birth weight, bulls with higher EPD for calving ease sired calves with smaller cannon circumference, but at constant birth weight EPD, body measures were not associated with calving ease EPD. Factor analysis defined underlying skeletal width and frame components of shape (independent of birth weight) for both sire breeds. Calf shape differed among sires and was in part explained by birth weight EPD. No additional variation in shape was explained by calving ease EPD. Calf shape seemed to add no information for prediction of dystocia to that provided by birth weight EPD.
对安格斯牛（n = 374）和无角海福特牛（n = 438）所产犊牛进行体尺测量，通过多变量因子分析来量化犊牛体型，并且对无角海福特牛所产犊牛的测量数据进一步用于研究犊牛体型与出生体重和头胎产犊难易度的父系预期后代差异（EPD）之间的关系。产后24小时记录犊牛的出生体重、头围、肩宽、臀宽、胸围、管围和管长以及体长。父系出生体重EPD与所有犊牛测量指标均呈正相关（P < 0.05），但在对表型出生体重和妊娠期长度进行调整后，仅与头围和管围呈正相关。因此，在出生体重恒定的情况下，来自出生体重EPD较高公牛的犊牛往往具有更大的管围和头围。产犊难易度EPD与除肩宽外的所有犊牛测量指标均呈负相关（P < 0.05）。在对出生体重进行调整后，只有管围与产犊难易度EPD相关，而通过对出生体重EPD进行额外调整，这种影响被消除。因此，在出生体重恒定的情况下，产犊难易度EPD较高的公牛所产犊牛的管围较小，但在出生体重EPD恒定的情况下，身体测量指标与产犊难易度EPD无关。因子分析确定了两个父系品种犊牛体型的潜在骨骼宽度和框架组成部分（与出生体重无关）。犊牛体型在不同父系之间存在差异，部分原因可由出生体重EPD解释。产犊难易度EPD并未解释体型的额外差异。犊牛体型似乎并未为预测难产提供比出生体重EPD更多的信息。
