Xi Y M, Wu F, Zhao D Q, Yang Z, Li L, Han Z Y, Wang G L
Institute of Dairy Science,Nanjing Agricultural University,Nanjing 210095,China.
Animal. 2016 Aug;10(8):1311-8. doi: 10.1017/S1751731116000343. Epub 2016 Mar 3.
Residual feed intake (RFI), defined as the difference between an animal's actual feed intake and expected feed intake over a specific period, is an inheritable character of feed conversion efficiency in dairy cows. Research has shown that a lower RFI could improve the profitability of milk production. This study explored variation in RFI by comparing the differences in body size, milk performance, feeding behavior, and serum metabolites in 29 Holstein cows in mid lactation. The cows were selected from a total of 84 animals based on their RFI following feedlot tests. Selected cows were ranked into high RFI (RFI >1 SD above the mean, n=14) and low RFI (RFI<1 SD below the mean, n=15). The low RFI cows (more efficient) consumed 1.59 kg/day less dry matter than the high RFI group (P<0.01), while they produced nearly equal 4% fat-corrected milk. The milk : feed ratio was higher for the low RFI group than for the high RFI group (P<0.05). The levels of milk protein (P<0.01), total solids (P<0.05), and nonfat solids (P<0.05) were also higher for the low RFI group, whereas milk urea nitrogen was lower (P<0.01). The daily feeding duration was shorter for the low RFI group than for the high RFI group (P<0.01). No significant differences were found in levels of glucose, β-hydroxybutyrate, prolactin, insulin, IGF-1, growth hormone or ghrelin, but the level of neuropeptide Y was higher (P<0.01) and levels of leptin and non-esterified fatty acid (P<0.05) were lower for the low RFI group than for the high RFI group. There were substantial differences between cows with different RFI, which might affect the efficiency of milk protein metabolism and fat mobilization.
剩余采食量（RFI）定义为动物在特定时期内的实际采食量与预期采食量之间的差值，是奶牛饲料转化效率的一个可遗传特性。研究表明，较低的RFI可以提高牛奶生产的盈利能力。本研究通过比较29头泌乳中期荷斯坦奶牛的体尺、产奶性能、采食行为和血清代谢物的差异，探讨了RFI的变化。这些奶牛是在育肥试验后根据其RFI从总共84头动物中挑选出来的。挑选出的奶牛被分为高RFI组（RFI高于平均值1个标准差，n = 14）和低RFI组（RFI低于平均值1个标准差，n = 15）。低RFI组（效率更高）的奶牛每天消耗的干物质比高RFI组少1.59千克（P < 0.01），而它们生产的4%乳脂校正乳几乎相同。低RFI组的乳料比高于高RFI组（P < 0.05）。低RFI组的乳蛋白（P < 0.01）、总固体（P < 0.05）和非脂固体（P < 0.05）水平也更高，而乳尿素氮更低（P < 0.01）。低RFI组的每日采食持续时间比高RFI组短（P < 0.01）。在葡萄糖、β-羟基丁酸、催乳素、胰岛素、IGF-1、生长激素或胃饥饿素水平上未发现显著差异，但低RFI组的神经肽Y水平更高（P < 0.01），瘦素和非酯化脂肪酸水平更低（P < 0.05）。不同RFI的奶牛之间存在显著差异，这可能会影响乳蛋白代谢和脂肪动员的效率。
