摘要
Residual feed intake (RFI ) class differences in gut function and grazing intake were evaluated using 14 crossbred steer progeny of first parity dams with known RFI phenotypes and a commercially available Angus sire. Steers were housed in a drylot facility and fed a forage based complete feed ad libitum, a forage diet at maintenance (1.5% BW as fed), and a concentrate diet at maintenance in Exp. 1, 4, and 5 respectively. Voluntary DMI and solid and liquid passage rate were evaluated while grazing (Exp. 2 and 3, respectively). Plasma concentrations of albumin ( ALB ), urea nitrogen (UN ), cholesterol (CHOL ), glucose (GLU ), triglycerides (TG ), and VFA were assessed immediately pre- and at 3 h intervals for 12 h post-feeding as indicators of nutrient absorption in Exp. 1, 4, and 5 respectively. Rumen pH, ammonia (NH4 ), and VFA were evaluated 12 h post-feeding. Steers were classified as either positive (POS ; n = 8) or negative ( NEG ; n = 6) according to dam RFI (mean 0.46 kg TND/d; range -4.27 to 5.70 kg TDN/d). Rumen pH, ammonia, and VFA's did not differ based on RFI classification (P > 0.05) in any of the experiments. Plasma metabolite and VFA concentrations did not differ between RFI classes in Experiment 1 (P > 0.05); however, UN was greater in POS (12.80 vs. 12.14 mg/dL; P = 0.02) steers when fed a forage diet at maintenance (Exp. 4) and greater in NEG (16.74 vs. 15.42 mg/dL; P = 0.01) steers when fed a concentrate diet at maintenance (Exp 5). Plasma valerate and butyrate (P = 0.02 and 0.02, respectively) were greater in NEG steers in Exp. 1 and 5, respectively. Evaluation of RFI group differences by collection time revealed a significant (P = 0.04) interaction of RFI and Time for TG and plasma isobutyric acid in Exp. 1. Concentrations of TG were greater (P = 0.04) in NEG steers at 3 hours after feeding but did not differ at any other time points. Plasma isobutyric acid concentrations rarely differed from zero but were greater in POS steers 6 hours post-feeding. The opposite was true at 12 hours post-feeding. No other interactions between RFI and collection time were significant. Negative RFI steers consumed numerically 8.9% less DM per day while grazing than POS steers but did not differ in voluntary DMI (P = 0.74). Liquid passage rate was greater in NEG (7.16 vs. 6.32 % marker/hour; P = 0.04) steers but solid passage rate was not different (P = 0.88). These data indicate that RFI classification may be associated with variation in the regulation and absorptive capacity of the gastrointestinal tract.
摘要译文
使用第1奇偶水坝已知RFI表型和市售陛下安格斯杂交14后代转向肠道功能和放牧的摄入残留采食量（RFI）班的差异进行了评价。公牛被安置在一个drylot设施和饲喂饲草为主的全价饲料自由采食，饲草饲料的维修（1.5％25 BW为FED）和精料日粮在精通维修。1，4和5中。而放牧（实验2和3，分别）自愿DMI和固体和液体通过率进行了评价。白蛋白的血浆浓度（ALB），尿素氮（UN），胆固醇（CHOL），葡萄糖（GLU），甘油三酯（TG）和VFA进行了评估立即前和在3小时的时间间隔为12小时后馈送作为指标营养吸收的进出口。1，4和5中。瘤胃pH值，氨氮（NH4），以及VFA进行了评价12小时后饲喂。公牛被分类为阳性（POS; N = 8）或负（NEG; N = 6）根据大坝RFI（平均0.46千克TND /天;范围为-4.275.70千克TDN /天）。瘤胃pH值，氨和挥发性脂肪酸的没有不同根据RFI分类（P\u003e 0.05），在任何实验。等离子和代谢物浓度挥发性脂肪酸没有RFI课间实验1差异（P\u003e 0.05）;然而，联合国是更大的POS机（12.80与12.14毫克/升; P = 0.02）（详4）操纵时，在维护饲喂草料饲料和更大的NEG（16.74与15.42毫克/升; P = 0.01）当在维护饲喂精料日粮公牛（实验5）。等离子体戊酸和丁酸酯（P = 0.02和0.02）均大于在NEG操纵在进出口。，1和5。评价通过收集时间RFI组差异揭示RFI和时间TG和血浆异丁酸在精通的显著（P = 0.04）的相互作用。1. TG浓度分别为更大（P = 0.04）的NEG操纵3小时喂奶后却没有差异，在其他任何时间点。血浆异丁酸含量很少从零差异，但在POS均大于操纵后6小时喂养。相反是在12小时后，饲养真。RFI和集合时间之间没有其他的相互作用是显著。而比放牧肉牛POS负公牛RFI数字消费8.9％，每天25 DM较少，但在自愿的DMI（P = 0.74）没有显着差异。液体通过速度是更大的NEG（7.16与6.32％25标记/小时; P = 0.04）阉但固体通路率没有差异（P = 0.88）。这些数据表明，RFI分类可以与变化的调节和胃肠道的吸收能力有关。
Shaffer, Kevin S.. Identifying Potential Sources of Variation in Residual Feed Intake in Beef Cattle[D]. US: West Virginia University, 2012