Department of Dairy Science, University of Wisconsin-Madison, Madison 53706.
USDA Dairy Forage Research Center, Marshfield, WI 54449.
J Dairy Sci. 2019 May;102(5):4041-4050. doi: 10.3168/jds.2018-15504. Epub 2019 Mar 7.
The objective of this study was to determine the growth, feed efficiency, and manure excretion of prebred dairy heifers with differing predicted genomic residual feed intakes (RFI) when offered diets differing in energy density. Prebred Holstein heifers (n = 128, ages 4 to 8 mo) were blocked by weight (low, medium-low, medium-high, or high) with 32 heifers per block. Heifers in each weight block were grouped by RFI and randomly assigned to obtain 2 pens of high (HRFI) and 2 pens of low RFI (LRFI) heifers within each block (8 heifers/pen). Heifers with LRFI were hypothesized to have greater feed efficiency than HRFI heifers. Dietary treatments were a high-energy diet (HE; 66.6% total digestible nutrients, 14.0% crude protein, and 36.3% neutral detergent fiber, dry matter basis) and a low-energy diet (LE; 63.8% total digestible nutrients, 13.5% crude protein, and 41.2% neutral detergent fiber, dry matter basis). Each pen of heifers was randomly assigned to a treatment to obtain a 2 × 2 factorial arrangement (2 RFI levels × 2 diet energy densities). Diets were offered in a 120-d trial. Dry matter intake was not affected by diet, RFI, or their interaction. Average daily gain (ADG) was affected by diet, with heifers fed HE having greater ADG than heifers fed LE. In addition, RFI affected ADG, with LRFI heifers having greater ADG than HRFI heifers, whereas the interaction of RFI and diet was not significant. Feed efficiency was improved for heifers fed the HE diet, but it was not affected by RFI or the interaction of RFI and diet. Overall, feed efficiency of prebred heifers was not dependent on predicted genomic RFI, because the greater ADG of LRFI heifers was accompanied by slightly higher dry matter intake. Feed efficiency of heifers was reduced when heifers were fed the LE diet, but this resulted in more optimal ADG compared with the HE diet fed for ad libitum intake.
本研究旨在确定在提供能量密度不同的日粮时，具有不同预测基因组残余采食量（RFI）的后备奶牛的生长、饲料效率和粪便排泄情况。将后备荷斯坦奶牛（n = 128，年龄 4 至 8 月龄）按体重（低、中低、中高或高）分组，每组 32 头。每个体重组的奶牛按 RFI 分组，并随机分配，以获得每个分组内 2 个高 RFI（HRFI）和 2 个低 RFI（LRFI）的牛栏（每组 8 头）。假设 LRFI 的奶牛比 HRFI 的奶牛具有更高的饲料效率。日粮处理为高能日粮（HE；总可消化养分 66.6%，粗蛋白 14.0%，中性洗涤纤维 36.3%，干物质基础）和低能日粮（LE；总可消化养分 63.8%，粗蛋白 13.5%，中性洗涤纤维 41.2%，干物质基础）。每组奶牛随机分配到一个处理组，以获得一个 2×2 因子排列（2 个 RFI 水平×2 个日粮能量密度）。试验期为 120 天。日粮不影响干物质采食量、RFI 或它们的互作。日增重（ADG）受日粮影响，饲喂 HE 的奶牛 ADG 大于饲喂 LE 的奶牛。此外，RFI 影响 ADG，LRFI 的奶牛 ADG 大于 HRFI 的奶牛，而 RFI 和日粮的互作不显著。饲喂 HE 日粮提高了奶牛的饲料效率，但 RFI 或 RFI 和日粮的互作对其没有影响。总体而言，后备奶牛的饲料效率不依赖于预测的基因组 RFI，因为 LRFI 奶牛的更高 ADG 伴随着略高的干物质采食量。当奶牛饲喂 LE 日粮时，奶牛的饲料效率降低，但与自由采食饲喂 HE 日粮相比，ADG 更理想。
