Comparative Antirachitic Value of Field–Cured Hay, Barn–Dried Hay, and Wilted Grass Silage for Growing Dairy Calves

Abstract

Alfalfa from the same field and harvested simultaneously as wilted silage, barn-cured hay and field-cured hay was fed to 3 groups of calves to study the effect of methods on conservation on growth of calves and the antirachitic properties of the forage. Wilted silage fed as the sole roughage to growing dairy calves produced gains as good or better than those observed in calves fed barn-cured and field-cured hay. The calves that were fed the wilted silage were sleek and excellent in appearance. Wilted silage, made in 2 different yrs., contained sufficient vitamin D to prevent rickets in growing calves that were kept out of sunlight when the silage was fed at the rate of 1.2 to 1.7 lb. per 100 lb. of body wt. on the hay-equivalent basis (3 to 4 lb. per 100 lb. body wt. on the silage basis). Barn-cured hay made one yr. contained sufficient vitamin D to prevent rickets in calves that were kept out of sunlight when it was fed at the rate of 1.2 to 1.7 lb. per 100 lb. of body wt: Rat bioassays of the forages fed for vitamin D, which confirmed the results of the calf-feeding expt., showed that they contained sufficient vitamin D to prevent rickets in growing calves. While further fundamental data must be collected on the factors affecting the vitamin D content of forages harvested with a minimum exposure to the sun, it seems quite likely that barn-cured hay and wilted silage, at least as conserved under Beltsville conditions, contain sufficient vitamin D for growing calves to prevent rickets if fed at the usual levels of roughage feeding.