Department of Animal and Aquacultural Sciences, Norwegian University of Life Sciences, NO-1432 Ås, Norway.
Department of Animal and Aquacultural Sciences, Norwegian University of Life Sciences, NO-1432 Ås, Norway; Tine SA, NO-1431 Ås, Norway.
J Dairy Sci. 2017 Sep;100(9):7602-7612. doi: 10.3168/jds.2016-12018. Epub 2017 Jul 6.
Today's Norwegian Red (NR) is markedly different from the one that existed 25 yr ago due to the continuous genetic improvement of economically important traits. Still, current national recommendations on replacement heifer rearing largely are based on results from Danish studies from the late 1980s to the mid 1990s. The objectives of the present study were to gain information on (1) growth and growth profiles of modern NR replacement heifers in commercial dairy herds and (2) how growth during the rearing period affects the heifers' milk yield during their first lactation. To this end, we conducted a field study on 5 high-producing and 5 low-producing commercial dairy farms from each of 3 geographical regions in Norway. On these 30 farms, we combined repeated onsite registrations of growth on all available females from newborn to calving with registrations deriving from the Norwegian Dairy Herd Recording System. Each herd was visited 6 to 8 times over a period of 2 yr. At each visit, heart girth circumference on all available young females was measured. Registrations were made on a total of 3,110 heifers. After imposing restrictions on the data, growth parameters were estimated based on information from 536 animals, whereas 350 of these animals had the required information needed to estimate the relationship between growth and test-day milk yield. Our findings pointed toward an optimal ADG of 830 g/d from 10 to 15 mo of age that would optimize first-lactation yield of heifers in an average Norwegian dairy herd. The optimum will likely increase from selection over time. Utilizing simple proportionality, the ADG between 5 and 10 mo of age ideally should be 879 g/d, taking into account the fact that animal growth rate is higher at low ages and that a high prepubertal growth rate had no negative effect on first-lactation yield. When such a rearing practice is used to meet the requirements of today's genetically improved NR heifer, heifers can both optimize production in their first lactation and enter the milking herd earlier than the current average age of 24.8 mo.
今天的挪威红牛（NR）与 25 年前的品种有很大的不同，这是由于其经济重要性状的持续遗传改良。尽管如此，目前关于后备奶牛饲养的国家建议主要还是基于 20 世纪 80 年代末至 90 年代中期丹麦的研究结果。本研究的目的是为了获得以下两方面的信息：（1）现代 NR 后备奶牛在商业奶牛场的生长和生长曲线；（2）育肥期的生长情况如何影响后备牛在其第一次泌乳期的产奶量。为此，我们在挪威的 3 个地理区域的每个区域选择了 5 个高生产性能和 5 个低生产性能的商业奶牛场进行了实地研究。在这 30 个农场中，我们将新生牛到配种期间所有可用雌性牛的生长情况进行了多次现场记录，并结合了从挪威奶牛 herd recording system 中获得的注册信息。每个牛场在 2 年期间被访问了 6-8 次。每次访问时，都会测量所有可用的年轻雌性动物的心围周长。总共对 3110 头小母牛进行了注册。在对数据进行限制后，根据 536 头动物的信息估计了生长参数，而其中 350 头动物具有估计生长与测试日产奶量之间关系所需的信息。我们的研究结果表明，从 10 到 15 月龄时，ADG 最佳为 830 克/天，这将使平均挪威奶牛场的后备牛在第一次泌乳期的产奶量达到最佳。随着时间的推移，这个最佳值可能会增加。利用简单的比例关系，5 到 10 月龄的 ADG 理想值应为 879 克/天，这是因为动物的生长速度在低龄时更高，并且青春期前的高生长速度对第一次泌乳期的产奶量没有负面影响。当采用这种饲养方式来满足当今遗传改良的 NR 后备牛的要求时，后备牛不仅可以优化其第一次泌乳期的生产性能，而且可以比目前 24.8 月龄的平均进入泌乳牛群的时间更早。
