Milk Production in Hereford Cattle. I. Effects of Separation Interval on Weigh-Suckle-Weigh Milk Production Estimates

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Abstract
Milk production estimates were obtained from 117 Hereford cows during 1975 and 1976 using the weigh-suckle-weigh method. Separation intervals of 4, 8 and 16 hr were compared to determine their effect on estimates of milk production. Cows were assigned to a 3 × 3 Latin square and three estimates were obtained on three consecutive days, once at 7 to 21 days into lactation and once again at 28 to 56 days. Least-squares procedures were used to analyze data according to a model including year, square/year, cow/square/year, separation interval, day of separation, period, year × period interaction and day × period interaction as sources of variation. All effects were significant with the exception of year. Treatment means for the 4-hr, 8-hr and 16-hr intervals, respectively, were 9.2, 7.6 and 5.9 kg milk per 24 hours. Each mean differed significantly from the others. The 8-hr separation interval gave the best estimate of milk production during early lactation because it 1) had less measurement error and higher correlation with calf average daily gain than the 4-hr interval and 2) produced less observable irritation and discomfort in the cows and was closer to the natural interval than the 16-hr interval. Copyright © 1979. American Society of Animal Science . Copyright 1979 by American Society of Animal Science