Abstract

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 BW^0.75 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 BW^0.75 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 BW^0.75 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.

中文翻译：

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饲喂水平对高、低残食肉牛采食效率的影响

摘要

比较随意采食 ( ADLIB ) 和限制 ( RESTRICT ) 饲喂期后的产热，可以深入了解剩余采食量 ( RFI ) 组如何根据以前的饲喂水平改变其能量需求。在这项研究中，作者试图解释限制饲料后高和低 RFI 阉牛的效率变化。为了确定 RFI 分类，将 56 头初始体重 ( BW ) 为 350 ± 28.7 kg 的安格斯交叉公牛单独圈养，随意获取总混合日粮，并记录 56 天的每日摄入量。RFI 定义为干物质摄入量回归中期测试 BW 的残差^0.75和平均每日收益。高和低 RFI 组被定义为分别高于或低于零平均值 > 0.5 SD。在随后的 56 天 RESTRICT 期间，从每个高组和低组 ( n = 28) 中选择了14 头阉牛。在 RESTRICT 期间，在 BW ^{0.75 的}基础上，摄入量限制为之前随意摄入量的 75% ，所有其他条件保持不变。在 RESTRICT 期之后，两个 RFI 组都降低了维护能源需求。然而，低 RFI 组在 BW ^{0.75 的}基础上降低了 32% 的维持能量需求，更多（P< 0.05) 比高 RFI 组降低了维护需求 (18%)。因此，经过一段时间的进料限制后，低 RFI 公牛仍然更有效率。我们得出的结论是，饲料限制降低了受限制程度相同的高和低 RFI 组的维持能量需求。