PASTURE FOR YOUNG DAIRY STOCK: I. EFFECT OF PREVIOUS NUTRITIONAL LEVEL AND AGE ON GROWTH OF AYRSHIRE AND HOLSTEIN HEIFER CALVES AND YEARLINGS ON PASTURE

Abstract

Holstein and Ayrshire heifer calves were barn-fed at high or moderate planes of nutrition from birth until 2, 4 or 6 months of age and then turned to pasture for 2 months. During the first 2 months of the initial barn feeding period body weight and heart girth increases were significantly greater on the high plane of nutrition but differences in withers heights were not significant. However, in the second 2 months increases for all three growth criteria were significant on the high plane of nutrition. During the 2-month pasture period calves in each group grew satisfactorily except Ayrshires on the moderate plane of nutrition. Two-month-old calves on the high plane of nutrition retained their weight advantage over the comparable age group on moderate nutrition. A highly significant trend indicated weight increase to be inversely proportional to age for the first month of the pasture season but the reverse was true for the next month on pasture. Growth patterns to the end of a second pasture season showed that treatment differences had largely disappeared and all animals had attained weight, heart girth, and withers height to within ± 4 per cent of Ragsdale standards.