Hansen L B, Cole J B, Marx G D, Seykora A J
Department of Animal Science, University of Minnesota, St. Paul 55108, USA.
J Dairy Sci. 1999 Apr;82(4):795-801. doi: 10.3168/jds.S0022-0302(99)75298-7.
Holstein cows were compared for direct and correlated responses to selection for large versus small body size. The divergent selection lines differed for body weight, body dimensions, and birth weight of calves but did not differ for production or calving ease. Also, cows in the small line required fewer services to conception during first lactation than did cows in the large line. Cows in the body size lines differed for three reasons for disposal: udder conformation, which favored cows in the large line; problems with legs and feet, which favored cows in the small line; and a miscellaneous category, which included internal infections and favored cows in the small line. Productive life to a maximum of 6 yr was 87.7 d (15.4%) longer for cows in the small line than for cows in the large line. Continued selection for larger Holstein cows in North America might not be economically justifiable.
对荷斯坦奶牛进行了比较，以研究针对大体型与小体型选择的直接反应和相关反应。不同选择品系的奶牛在体重、体尺以及犊牛出生体重方面存在差异，但在生产性能或产犊难易程度上并无差异。此外，小型品系的奶牛在首次泌乳期间受孕所需的配种次数比大型品系的奶牛少。体型品系的奶牛在淘汰原因上存在三方面差异：乳房形态，大型品系的奶牛更具优势；腿脚问题，小型品系的奶牛更具优势；其他类别，包括内部感染，小型品系的奶牛更具优势。小型品系奶牛的最长6年生产寿命比大型品系奶牛长87.7天（15.4%）。在北美，持续选择培育更大体型的荷斯坦奶牛在经济上可能不合理。
