132. The Nutritive Value of Proteins for Milk Production

Abstract

1. As regards their nutritive value for milk production, the proteins of spring grass are markedly superior to those of autumn grass. This is shown not only from a study of milk yield, but from the increased excretion of N and S in the urine, the increased creatine excretion, and the lower biological value given by autumn grass.2. A study of the N and S metabolism of cows receiving fresh and artificially dried grass fails to reveal any significant differences in the nutritive value as a result of artificial drying. There are no significant differences between the biological values of the proteins of fresh and of artificially dried autumn grass. A comparison of the mean biological values of the proteins of fresh and of artificially dried spring grass indicates that the latter has an inferior value for milk production, but the differences largely disappear when the biological values are calculated to a common standard.