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Effect of Forage-Concentrate Ratio in Complete Feeds Fed Ad Libitum On Energy Intake in Relation to Requirements by Dairy Cows¹

Department of Animal Sciences, Purdue University, Lafayette, IN 47907

ABSTRACT

Energy intake for each of 37 Holstein cows from 4 wk prepartum through 44 wk of lactation was determined by measuring the quantity of feed consumed ad libitum and estimating the energy available in each of four complete feeds of: (a) 75:25, (b) 60:40, (c) 45:55, and (d) 30:70 forage:concentrate dry matter.

The greatest need for energy occurred during the first trimester while peak energy consumption occurred during the second trimester. Factors affecting energy requirements accounted for 64% of the variation in consumption over a complete lactation for the 30:70 feed but only 27% in the 45:55 feed.

Although none of the cows consumed enough energy to meet her requirements during the early weeks of lactation, cows in the groups fed higher concentrate feeds achieved energy balance earlier. Once energy balance was achieved, cows in each group remained in positive balance. Cows in the latter stages of lactation did not appear to regulate their intake according to physiological requirements for milk production.

¹ Journal Paper No. 5365. Purdue University Agricultural Experiment Station.

² Visiting Professor from Cornell University