In a previous experiment it was found that when concentrates were given in large amounts with a fixed ration of hay, cows receiving starchy concentrates gave more milk but with a lower fat concentration than cows receiving the same amount of high quality fibrous concentrates of a similar metabolisable energy (ME) concentration. The purpose of the present experiment was to examine the effects of varying the starch:fibre ratio of the concentrates on milk yield and composition and on hay intake.

Sixty-one Friesian cows in their second or later lactation were given a standard ration for the first two weeks of lactation and were then allocated to one of eight experimental treatments for the following 18 weeks. All the cows were given 13.5 kg/d of one of four concentrates of similar crude protein and estimated ME concentrations. The concentrates varied from high starch (S) based on barley, wheat and cassava to high fibre (F) based on high-quality by-products (citrus pulp, molassed sugar beet pulp and wheatfeed) with two intermediate types (SF and FS).