Effect of pasture feeding levels on the responses of lactating dairy cows to high energy supplements

Abstract

Stall-fed dairy cows were fed amounts of pasture ranging from 6.7 to 11.8 kg DM/cow.day and supplemented with either 0, 2.2 or 4.5 kg DM/cow.day of pelleted concentrates. Twenty-eight cows in their third month of lactation and 29 cows in their eighth month of lactation were fed in this manner for about 5 weeks. Stage of lactation had a major influence on responses obtained from feeding a high energy supplement to pasture-fed cows. In early lactation, for cows fed 6.8 kg DM, marginal responses from feeding an additional kg DM of concentrates were 1.85, 0.053 and 0.059 kg milk, milk fat and milk protein, respectively; if they were fed 11.7 kg DM of pasture, marginal responses from concentrates were more than halved (0.58 kg milk, 0.019 kg milk fat and 0.027 kg milk protein per kg DM). The latter response to concentrates, where high levels of pasture were fed to cows in early lactation, were less than those obtained in late lactation at any level of pasture feeding.