Department of Agricultural, Food and Nutritional Science, University of Alberta, Edmonton, Alberta, T6G 2P5, Canada.
J Anim Sci. 2011 Jan;89(1):158-67. doi: 10.2527/jas.2009-2514. Epub 2010 Sep 3.
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.
这项为期 3 年的研究使用了 490 头阉牛，以确定育肥期饲料改为育肥后期饲料后，育肥后期饲料的育肥效率（FE）排名是否会发生变化。这些阉牛是杂交品种，年龄在 5 至 7 个月之间。每年有 2 个饲养期。在每年，大约有 90 头阉牛的饲料从育肥期饲料切换到育肥后期饲料（饲料交换组），而另外 90 头阉牛则在整个饲养试验中一直喂食育肥期饲料（育肥期饲料组）或育肥后期饲料（育肥后期饲料组）。每次饲养试验至少持续 10 周，所有阉牛均可自由采食。使用 GrowSafe 饲养系统收集个体动物的饲料摄入量，每 2 周测量一次体重。在每个饲养期结束时计算残余饲料摄入量（RFI）、增重效率（G:F）和克莱伯比（KR）。根据平均值的 0.5SD，对每种效率测量将动物分为低、中或高。大多数阉牛在第二阶段没有保持之前的效率等级。在饲料交换组、育肥后期饲料组和育肥期饲料组中，分别约有 58%、51%和 51%的阉牛通过 0.5SD 改变了他们的 RFI 测量。在所有测试组中都存在低阶相关性，但在饲料交换组中相关性较小。在饲料交换组中，两个饲养期之间的斯皮尔曼等级相关系数分别为 0.33、0.20 和 0.31，用于 RFI、G:F 和 KR。基于 G:F 和 KR 的分类表明，在饲料交换组中，更多的阉牛（P<0.05）无法维持从一种饲养方案到另一种饲养方案的 FE 等级，而基于 RFI 的分类则没有显示出个体改变或维持其 FE 等级的比例有任何差异（P>0.05）。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 等级的阉牛比例没有差异（P>0.05）。我们的结果表明，饲料类型和饲养期会影响肉牛的 FE 排名。育肥后期饲料是评估育肥后期饲料对育肥盈利能力的 FE 潜力的理想选择；然而，我们建议应检查涉及密度较低的饲料的测试，以努力了解 FE 与饲养者盈利能力之间的关系。
