Watson A K, Nuttelman B L, Klopfenstein T J, Lomas L W, Erickson G E
Department of Animal Science, University of Nebraska-Lincoln, Lincoln 68583-0908.
J Anim Sci. 2013 Nov;91(11):5507-17. doi: 10.2527/jas.2013-6349. Epub 2013 Sep 17.
Cattle weights can be highly variable and are influenced by many factors, including time of weighing, ambient temperature, feed intake, and cattle handling. A protocol of limit feeding has been in use since the 1980s that was designed to reduce variation in gut fill due to differences in intakes. Cattle are penned and fed a 50% hay, 50% wet corn gluten feed or grain diet (DM basis) at an estimated 2% of BW for at least 5 d, after which weights are taken on 2 consecutive d and averaged for a limit-fed BW (LFW). For this analysis, full-fed weights (FFW) also were taken before the limit-feeding period while cattle had ad libitum intakes. Data from 18 experiments were used to analyze differences within 2-d LFW and between LFW and FFW. For 10 of the 18 experiments, FFW also were measured on 2 consecutive d. Cattle included in this summary were grazing cornstalks, smooth bromegrass pasture, Bermuda grass pasture, fescue pasture, native range, or in a dry lot on a 70% forage diet. The largest differences between FFW and LFW for individual cattle were -39 to +44 kg over all 18 experiments. Differences between 2 consecutive d of LFW were -23 to +24 kg for all 18 experiments. Differences between 2 d of FFW were -14 to +34 kg in the 10 experiments measuring FFW on 2 consecutive d. There was not a clear relationship between FFW and LFW; each weighing scenario had unique environmental conditions that led to different relationships. Differences in both beginning and ending BW were compounded when calculating ADG. Average daily gain was calculated for 15 of the experiments on the basis of either LFW or FFW. Differences between LFW and FFW ADG were -0.29 to +0.31 kg/d. The maximum ADG based on FFW was 1.62 kg/d. This large ADG, on a forage based diet, was likely due to changes in gut fill rather than tissue gain. These data suggest that handling cattle in a similar manner when weighing is more important than limiting intakes to decrease variance between weights. However, limiting intake before collection of beginning and ending BW better estimates empty body weight of cattle, allowing for a more accurate determination of actual body tissue weight gain. Measuring weights accurately becomes especially crucial when evaluating multiple components within a system (e.g., cornstalks to pasture to feedlot). Feeding a standard diet between these components of the system minimizes differences in gut fill due to treatment and allows for a more accurate determination of each component's contribution to the total system.
牛的体重变化很大，受许多因素影响，包括称重时间、环境温度、采食量和牛的管理方式。自20世纪80年代以来，一直采用限饲方案，该方案旨在减少因采食量差异导致的肠道充盈度变化。将牛关进栏舍，饲喂由50%干草、50%湿玉米麸质饲料或谷物组成的日粮（以干物质计），饲喂量约为体重的2%，至少持续5天，之后连续两天称重并计算限饲体重（LFW）的平均值。在本分析中，还在限饲期之前牛自由采食时记录全饲体重（FFW）。使用来自18项试验的数据来分析连续两天的LFW之间以及LFW与FFW之间的差异。在18项试验中的10项中，FFW也连续两天进行测量。纳入本综述的牛包括采食玉米秸秆、草地早熟禾牧场、百慕大草牧场、羊茅牧场、天然牧场的牛，或在干栏舍中采食70%粗饲料日粮的牛。在所有18项试验中，个体牛的FFW与LFW之间的最大差异为-39至+44千克。在所有18项试验中，LFW连续两天之间的差异为-23至+24千克。在连续两天测量FFW的10项试验中，FFW两天之间的差异为-14至+34千克。FFW与LFW之间没有明确的关系；每种称重情况都有独特的环境条件，导致不同的关系。在计算平均日增重（ADG）时，初始体重和终末体重的差异会叠加。在15项试验中基于LFW或FFW计算平均日增重。LFW和FFW的ADG之间的差异为-0.29至+0.31千克/天。基于FFW的最大ADG为1.62千克/天。在以粗饲料为基础的日粮上出现如此高的ADG，可能是由于肠道充盈度的变化而非体组织增加。这些数据表明，称重时以相似方式管理牛比限制采食量以减少体重差异更重要。然而，在记录初始体重和终末体重之前限制采食量能更好地估计牛的空腹体重，从而更准确地确定实际体组织增重。在评估系统内的多个组成部分（例如从玉米秸秆到牧场再到饲养场）时，准确测量体重尤为关键。在系统的这些组成部分之间饲喂标准日粮可最大程度减少因处理方式导致的肠道充盈度差异，并能更准确地确定每个组成部分对整个系统的贡献。
