Department of Animal Science, University of California, Davis, Davis, CA.
J Anim Sci. 2020 Oct 1;98(10). doi: 10.1093/jas/skaa286.
Comparing heat production after ad libitum (ADLIB) and restricted (RESTRICT) feeding periods may offer insight into how residual feed intake (RFI) groups change their energy requirements based on previous feeding levels. In this study, the authors sought to explain the efficiency changes of high- and low-RFI steers after feed restriction. To determine RFI classification, 56 Angus-cross steers with initial body weight (BW) of 350 ± 28.7 kg were individually housed, offered ad libitum access to a total mixed ration, and daily intakes were recorded for 56 d. RFI was defined as the residual of the regression of dry matter intake on mid-test BW0.75 and average daily gain. High- and low-RFI groups were defined as >0.5 SD above or below the mean of zero, respectively. Fourteen steers from each high and low groups (n = 28) were selected for the subsequent 56-d RESTRICT period. During the RESTRICT period, intake was restricted to 75% of previous ad libitum intake on a BW0.75 basis, and all other conditions remained constant. After the RESTRICT period, both RFI groups had decreased maintenance energy requirements. However, the low-RFI group decreased maintenance energy requirements by 32% on a BW0.75 basis, more (P < 0.05) than the high-RFI group decreased maintenance requirements (18%). Thus, the low-RFI steers remained more efficient after a period of feed restriction. We conclude that feed restriction decreases maintenance energy requirement in both high- and low-RFI groups that are restricted to the same degree.
比较自由采食（ADLIB）和限制采食（RESTRICT）后热产生量，可能有助于了解残留采食量（RFI）群体如何根据之前的采食水平改变其能量需求。在这项研究中，作者试图解释高和低 RFI 牛在限制采食后的效率变化。为了确定 RFI 分类，将 56 头初始体重（BW）为 350±28.7kg 的安格斯杂交公牛单独饲养，自由采食全混合日粮，并记录 56 天的日采食量。RFI 定义为干物质采食量对中测 BW0.75 和平均日增重回归的残差。高和低 RFI 组分别定义为高于或低于平均值 0.5SD。从每个高和低 RFI 组中选择 14 头牛（n=28）进行随后的 56 天限制采食期。在限制采食期间，根据 BW0.75 将采食量限制在前一个自由采食期的 75%，其他条件保持不变。在限制采食期后，两组 RFI 均降低了维持能量需求。然而，低 RFI 组的维持能量需求减少了 32%，比高 RFI 组减少了 18%，更显著（P<0.05）。因此，低 RFI 牛在限制采食期后仍然更有效率。我们得出结论，限制采食降低了高和低 RFI 组的维持能量需求，这些组都受到相同程度的限制。
