摘要
This 3-yr study used 490 steers to determine whether feedlot steers changed their feed efficiency (FE) ranking when fed a grower diet, then a finisher diet. The steers were crossbreds and were between 5 to 7 mo of age. There were 2 feeding periods each year. Within each year, approximately 90 steers had their diet switched from a grower to a finisher diet (feed-swap group), whereas another 90 steers were fed either the grower (grower-fed group) or the finisher (finisher-fed group) diet throughout the feeding trial. Each feeding test lasted for a minimum of 10 wk, and all steers were fed ad libitum. Individual animal feed intakes were collected using the GrowSafe feeding system, and BW were measured every 2 wk. Residual feed intake (RFI), G:F, and Kleiber ratio (KR) were computed at the end of each feeding period. For each measure of efficiency, animals were classified as low, medium, or high based on 0.5 SD from the mean. The majority of steers did not maintain the previous efficiency class in the second period. Approximately 58, 51, and 51% of steers in the feed-swap group, finisher-fed group, and the grower-fed group, respectively, changed their RFI measure by 0.5 SD. A low rank correlation occurred in all test groups but was less in the feed-swap group. Spearman rank correlations between the 2 feeding periods in the feed-swap group were 0.33, 0.20, and 0.31 for RFI, G:F, and KR, respectively. Classifications based on G:F and KR showed that a greater number of steers (P < 0.05) in the feed-swap group did not maintain their FE class from 1 feeding regimen to the other, whereas classification based on RFI did not show any difference (P > 0.05) between the proportions of individuals that changed or maintained their FE class. In the groups without a feed-swap, there was no difference (P > 0.05) in the proportion of steers that changed or maintained the same FE class for all FE measures. Our results suggest that diet type and feeding period affect the FE ranking in beef steers. A feedlot diet is ideal for evaluating the FE potential of steers for feedlot profitability; however, we suggest that tests involving less dense diets should be examined in an effort to understand the relationships between FE and feeder profitability.
摘要译文
这项为期3年的研究使用了490个阉牛来确定饲养场阉牛是否在饲喂种植者饲料时改变了饲料效率（FE）排名，然后是饲养者饮食。阉牛是杂交种，年龄在5到7个月之间。每年有2个喂养期。在每年内，大约90名阉牛的饮食从种植者转为终结者饮食（饲料交换组），而另外90名阉牛饲喂种植者（种植者喂养组）或终结者（育肥喂养组）饮食整个喂养试验。每次喂养测试持续至少10周，所有操舵随意喂食。使用GrowSafe饲喂系统收集个体动物饲料摄入量，并且每2周测量BW。在每个喂养期结束时计算残留采食量（RFI），G：F和Kleiber比率（KR）。对于每种效率测量，动物根据平均值0.5 SD分类为低，中或高。大多数阉牛在第二阶段没有保持以前的效率等级。饲料交换组，育肥饲料组和种植者饲养组中大约58％，51％和51％的阉牛分别将其RFI指标改为0.5 SD。在所有测试组中发生低等级相关，但在饲料交换组中较少。对于RFI，G：F和KR，饲料交换组中2个喂养期之间的Spearman等级相关性分别为0.33,0.20和0.31。基于G：F和KR的分类显示，饲料交换组中更多的阉牛（P <0.05）没有将FE等级从1个喂养方案维持到另一个，而基于RFI的分类没有显示任何差异（P> 0.05）改变或维持其FE类别的个体比例。在没有饲料交换的组中，对于所有FE测量，改变或维持相同FE类的转向比例没有差异（P> 0.05）。我们的研究结果表明，饮食类型和喂养时间会影响牛肉阉牛的FE排名。饲养场日粮是评估饲养场盈利能力的潜力的理想选择;然而，我们建议应该检查涉及低密度饮食的测试，以便了解FE和饲养者盈利能力之间的关系。
O. N. Durunna;F. D. N. Mujibi;L. Goonewardene;E. K. Okine;J. A. Basarab;Z. Wang;S. S. Moore. Feed efficiency differences and reranking in beef steers fed grower and finisher diets[J]. Journal of Animal Science, 2011,89(1): 158-167