Department of Agricultural, Food and Nutritional Science, University of Alberta, Edmonton, Alberta T6G 2P5, Canada.
J Anim Sci. 2012 Mar;90(3):734-41. doi: 10.2527/jas.2011-4264. Epub 2011 Oct 14.
The objective of the study was to examine whether residual feed intake (RFI) reranking exists between 2 consecutive periods in replacement heifers fed the same diet. The study collected feed intake and BW data from 190 crossbred heifers over a 3-yr period (61 in 2007, 68 in 2008, and 61 in 2009) during the winter-spring season. The heifers were fed a roughage-based diet (90% barley silage and 10% rolled barley grain) throughout the feeding trial, which was broken down into 2 feeding periods with ADG of 0.94 and 0.90 kg•d(-1) in the first and second periods, respectively. The RFI was calculated for the entire period using different models, which included ADG, mid-metabolic BW, body composition, and feeding activity. Gain:feed ratio and Kleiber ratio were also calculated. Rank correlations among the RFI calculated from different models were obtained, as well as rank correlations between the 2 feeding periods for the feed efficiency measures. Including body composition and feeding activity only improved the R(2) by 1 to 5%. The rank correlations among the different models were high (90 to 95%) for RFI calculated for the entire feeding period. However, the RFI calculated within the second feeding period had greater rank correlation than the RFI calculated from the entire feeding period. Compared with G:F and Kleiber ratio, RFI gave lesser reranking between periods 1 and 2. About 49% of the heifers maintained their RFI class, whereas 51% of the heifers had a different RFI class in period 2. Furthermore, 41% of the heifers changed their RFI in period 2 by <0.5 SD, whereas the rest of the heifers changed by ≥0.5 SD. These results indicate that reranking exists in heifers despite receiving the same diet in the 2 feeding periods and that the reranking may be more serious in heifers (28%) with extreme RFI performances in each period.
本研究旨在检验在给后备牛饲喂相同饲粮的情况下，连续两个时期之间是否存在残余采食量（RFI）的再分级。研究收集了 190 头杂交后备牛在冬季-春季期间 3 年的数据（2007 年 61 头，2008 年 68 头，2009 年 61 头），这些后备牛整个试验期间饲喂以粗饲料为主的饲粮（90%大麦青贮和 10%压扁大麦），该饲粮分为两个采食期，第一和第二期的平均日增重（ADG）分别为 0.94 和 0.90kg/d。使用不同模型（包括 ADG、代谢中体重、体组成和采食活动）计算整个时期的 RFI。还计算了增重/饲料比和克莱伯比。获得了不同模型计算的 RFI 之间的秩相关，以及两个采食期之间饲料效率衡量指标的秩相关。仅包含体组成和采食活动，RFI 的 R2 提高了 1%至 5%。整个采食期 RFI 的不同模型之间的秩相关度较高（90%至 95%）。然而，第二期 RFI 的秩相关度大于整个采食期 RFI 的秩相关度。与增重/饲料比和克莱伯比相比，RFI 在两个采食期之间的再分级较小。约 49%的后备牛保持了相同的 RFI 等级，而 51%的后备牛在第二期有不同的 RFI 等级。此外，41%的后备牛第二期 RFI 的变化小于 0.5SD，其余后备牛的变化大于 0.5SD。这些结果表明，尽管后备牛在两个采食期接受相同的饲粮，但仍存在再分级，并且在每个时期 RFI 表现极端的后备牛（28%）中，再分级可能更严重。
