Net Energy Value for Lactation of a High and Low Concentrate Ration Containing Corn Silage

Abstract

Rations containing corn silage and either 30 or 60% of the dry matter from concentrate were fed to Holstein cows in amounts calculated to minimize body tissue change. Complete energy balance measurements were made at 6-week intervals throughout the lactation cycle. Digestibility of energy in the 30 and 60% concentrate ration declined from 72 and and 75% at maintenance down to 63 and 64% at 4× maintenance. Smaller losses of energy as methane and urine partially compensated for greater fecal loss, but metabolizability of both rations decreased (P