Evaluation of the Dairy Herd Improvement Association Record System

Abstract

Two problems currently facing the dairy industry are the evaluation of new methods of measuring milk quantity and quality, and the production testing of more cows. Productiontesting problems center around labor costs and the limited number of farmers serviced by one Dairy Herd Improvement Association (DHIA) technician. Increasing the length of the testing interval would proportionally increase the number of farmers serviced by a technician, reduce the labor costs per farmer, and possibly increase the income of the technician. The evaluation of new milking devices and the adoption of different testing intervals is dependent upon the accuracy of the new methods relative to a standard. The standard for comparison of methods of production testing has been the actual daily production of the cow smnmed over all the days in the lactation. The accuracy needed in measuring test-day production should depend upon the influence of test-day production on the variation of the estimate of lactation production. Unbiasedness is also an important property for evaluating any method of production testing. Erb et al. (5) studied five methods of testing, using the daily production records of 19 cows. Thompson et al. (9) estimated the bias and the variance of the estimate of lactation production. The reader is referred to Erb et al. (4, 5) for a review of the early literature on testing methods and the accuracy of various testing methods. The purpose of this investigation was to determine the magnitude of the daily variation in milk yield and evaluate various methods of testing and estinmting lactation yield.