Effect of Errors in Body Weight upon Computerized Formulation of Feeding Guidelines for Dairy Cows

Abstract Computerized least-cost rations were simulated for 15 dairy herds from herd-average body weights either reported by Dairy Herd Improvement or by taping heart girths of cows. Differences between simulated rations were predicted for feed costs, intakes of crude protein and net energy, and gain in body weight. Weights reported by Dairy Herd Improvement were 68±37kg per cow less than taped weights. The 360 taped cows averaged 633±39kg body weight. The use of reported mean body weights in the formulation of rations for the milking herd increased predicted intakes of net energy and gains in body weight. The effect upon predicted feed costs and intakes of crude protein was not significant. To compensate for differences in estimations of body weight does not appear to be practical. The error in estimation of body weight is small as compared with other possible errors which affect management decisions.