Huhtanen Pekka, Bayat Ali-Reza
Animal Nutrition, Production Systems, Natural Resources Institute Finland (LUKE), 31600 Jokioinen, Finland.
Animal Nutrition, Production Systems, Natural Resources Institute Finland (LUKE), 31600 Jokioinen, Finland.
J Dairy Sci. 2025 Jul 31. doi: 10.3168/jds.2025-26683.
Residual feed intake (RFI), calculated as a difference between observed and predicted intake, is a commonly used estimate of feed efficiency (FE). Determination of FE in practical dairy herds is challenging, as it requires accurate estimation of feed intake of individual cows. Alternatively, FE could be estimated as a difference between observed and predicted metabolic losses derived from gas exchanges. The objectives were to compare respiration chambers (RC) and the GreenFeed (GF) system in estimating FE based on the gas data, and to compare FE estimated from measured feed intake or gas data. The study was conducted using 32 Nordic Red dairy cows (DIM 159 ± 63, BW 634 ± 60 kg, and milk yield 28.9 ± 6.7 kg/d) fed a grass silage-based diet (CP 152 g/kg DM, NDF 395 g/kg DM). The study included two 14-d periods with the GF system with a 1-wk period in RC chambers (3-d measurements) between the GF periods. Residual CO production (RCO), residual O consumption (RO) and residual heat production (RHP) were estimated as observed minus predicted values derived from energy requirements. Root means squared errors of DMI prediction were smaller for models based on CO or O and ECM yield compared with ECM + BW model both with RC and GF data with minor differences between the methods. The relationship between GF and RC was slightly better for RO (R = 0.68) and RHP (R = 0.67) compared with RCO (R = 0.59). Seventy-five percent of the top 50% (12/16) cows in GF were ranked among the top 50% in RC. Repeatability values of different FE traits were similar or higher for the data based on gas data measured by GF compared with the corresponding values based on measured feed intake. Residual CO production explained 57% of variation in residual ME intake (RMEI). Gross FE expressed as ECM/CO explained 82% of gross FE expressed as ECM/DMI. When the cows were divided into low, medium, and high RCO groups, the differences in various FE traits were consistent with those based on measured feed intake. The difference in RMEI between the Low- and High-RCO cows was 15 MJ/d. Low-RCO cows produced 13% less methane per kilogram ECM, had higher diet digestibility, and produced less heat than high-RCO cows. It is concluded that estimating FE from gas data measured by the GF system has a potential to rank the cows according to FE in farm conditions without requiring measuring feed intake.
剩余采食量（RFI）通过观察到的采食量与预测采食量之间的差值计算得出，是常用的饲料效率（FE）估计值。在实际奶牛群中确定饲料效率具有挑战性，因为这需要准确估计每头奶牛的采食量。另外，饲料效率可以通过观察到的气体交换产生的代谢损失与预测值之间的差值来估计。本研究的目的是比较呼吸室（RC）和GreenFeed（GF）系统在基于气体数据估计饲料效率方面的差异，并比较根据实测采食量或气体数据估计的饲料效率。本研究使用了32头北欧红牛奶牛（泌乳天数159±63天，体重634±60千克，日产奶量28.9±6.7千克），给它们饲喂以青贮草为基础的日粮（粗蛋白152克/千克干物质，中性洗涤纤维395克/千克干物质）。研究包括两个为期14天的GF系统阶段，在两个GF阶段之间有一个为期1周的RC室阶段（3天测量期）。剩余二氧化碳产生量（RCO）、剩余氧气消耗量（RO）和剩余产热量（RHP）通过观察值减去根据能量需求得出的预测值来估计。基于二氧化碳或氧气以及能量校正乳产量的模型对干物质采食量（DMI）的预测均方根误差比基于能量校正乳产量+体重的模型更小，在RC和GF数据方面两种方法差异不大。与RCO（R = 0.59）相比，RO（R = 0.68）和RHP（R = 0.67）的GF与RC之间的相关性略好。GF中排名前50%（12/16）的奶牛中有75%在RC中也排名前50%。与基于实测采食量的数据相比，基于GF测量的气体数据得出的不同饲料效率性状的重复性值相似或更高。剩余二氧化碳产生量解释了剩余代谢能摄入量（RMEI）变化的57%。以能量校正乳/二氧化碳表示的总饲料效率解释了以能量校正乳/干物质采食量表示的总饲料效率的82%。当奶牛被分为低、中、高RCO组时，不同饲料效率性状的差异与基于实测采食量的差异一致。低RCO组和高RCO组奶牛的RMEI差值为15兆焦/天。低RCO组奶牛每千克能量校正乳产生的甲烷量少13%，日粮消化率更高，产热比高RCO组奶牛少。研究得出结论，根据GF系统测量的气体数据估计饲料效率，有可能在农场条件下根据饲料效率对奶牛进行排名，而无需测量采食量。
