Effect of Days Carried Calf, Days Dry, and Weight of First Calf Heifers on Yield

Open Access
Publisher Website
Google Scholar
Abstract
Effects of days carried calf, days dry, and weight of first calf heifers were studied using records of Holstein cows processed at the Northeast Dairy Records Processing Laboratory [Ithaca, New York, USA] between July 1980 and August 1984. Multiplicative factors were estimated for days carried calf for milk fat, and protein using a model that adjusted for the age-month and herd-year of freshening. Factors developed show a close relationship between protein and milk with fat factors being smaller. Factors also are smaller than others reported in the literature. First lactation factors differed from second and third lactation factors. Analysis of days dry indicated that optimum number days dry between lactations 1 and 2, 2 and 3, and 3 and 4 for maximized subsequent yield was 51 to 60 d dry for all lactations. Calculated F values showed greater significance for days dry than age-month of freshening. Optimum freshening weight of a first calf heifer to maximize first lactation milk yield is between 544 and 567 kg. The F values for weight at freshening were more significant than age-month of freshening.