Restrospective Methods of Estimating Individual Feed Costs

Abstract

Accuracies of four retrospective estimates of lactation feed cost were evaluated from 167 Holsteins in first lactation fed two mixed rations plus 1.8 kg alfalfa hay. Actual feed cost was regressed on each of the estimates. Method 1 (squared correlation .81) equated lactation feed cost to .43 of the milk value. Method 2 (.86) assigned a fixed cost, $.06 per Mcal, of estimated net energy (lactation) intake. Intake was estimated from body weight and production of the animal and National Research Council requirements for maintenance, production, and growth. Method 3 (.86) estimated lactation feed cost as a proportion of average actual feed cost. Methods 2 and 3 were superior to Method 1 because they also accounted for variation of maintenance and growth of cows. Method 4 (.92) was similar to Method 2 but allowed cost per megacalorie to vary, accounting for the differential cost of the two rations. Milk yield accounted for a substantial proportion of variation in actual feed cost, whereas accounting for maintenance and growth requirements and for differential proportion of grain in the mixed ration, each increased the accuracy of predicting actual feed cost by 5 and 6%. © 1982, American Dairy Science Association. All rights reserved.