Impacts of a limit-feeding procedure on variation and accuracy of cattle weights.

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.