Yerex R P, Young C W, Donker J D, Marx G D
Department of Animal Science, University of Minnesota, St. Paul 55108.
J Dairy Sci. 1988 May;71(5):1355-60. doi: 10.3168/jds.S0022-0302(88)79693-9.
First lactation records from a herd of Holstein cows bred for either high production and large size or for high production and small size were examined to estimate effects of selection for size and feed efficiency. Selection was among progeny-tested bulls available from the artificial insemination industry. Three rations were fed that differed for ratios of concentrate to milk. After three generations, groups of cows bred for large or small size differed by 50.2 kg in weight, 5.6 cm in wither height, 6.4 cm in length, 2.1 cm in depth, and 5.9 cm in chest circumference; most differences were due to a decrease in the size of the small cows. On the basis of total lactations, cows bred for small size were 2.8% more feed efficient than cows bred for large size. During the first 90 d of lactation cows fed the low concentrate ration were more efficient than those fed the high concentrate ration. Season of calving had an effect on feed efficiency between d 30 and 120 of lactation. During this period cows calving between December and May were more efficient.
对一群为追求高产和大体型或高产和小体型而培育的荷斯坦奶牛的首次泌乳记录进行了检查，以评估体型选择和饲料效率的影响。选择是在人工授精行业提供的经过后裔测定的公牛中进行的。投喂了三种精粗比不同的日粮。三代之后，培育的大体型和小体型奶牛组在体重上相差50.2千克，体高相差5.6厘米，体长相差6.4厘米，体深相差2.1厘米，胸围相差5.9厘米；大多数差异是由于小体型奶牛的体型减小所致。基于总泌乳量，培育的小体型奶牛比大体型奶牛的饲料效率高2.8%。在泌乳的前90天，投喂低精料日粮的奶牛比投喂高精料日粮的奶牛效率更高。产犊季节对泌乳第30天至120天之间的饲料效率有影响。在此期间，12月至5月产犊的奶牛效率更高。
