Silage and milk production: a comparison between three rates of high-protein concentrate supplementation of grass silages of two digestibilities

Grass silages made from first-harvest perennial ryegrass in mid-May and early-June and termed high-D and low-D respectively had mean DOMD values of 694 and 633 g kg^?1 and were offered ad libitum to twelve Ayrshire cows in a 16-week feeding experiment using a cyclic changeover design. The silages were supplemented with a concentrate containing 363g CP per kg DM at daily rates of 1.5, 3.0 and 4.5 kg per cow. The average daily intakes of silage DM were 12.6 and 11.1 kg per cow on the high- and low-D silage treatments respectively, and were not significantly different on the three concentrate treatments. The mean daily milk yields were 171, 18.6 and 21.0 kg per cow on the low-D silage treatments, and 19.6, 21.2 and 22.8 kg per cow on the high-D silage treatments at the 1.5, 3.0 and 4.5 kg rates of concentrate feeding respectively. Fat and lactose concentrations in the milk were not affected significantly by treatment, whereas the CP and SNF concentrations increased progressively and significantly as the rate of supplementary feeding increased. It is concluded that a high-protein concentrate supplement allows silage to make the maximum contribution in the diet, and gives a high response in terms of milk yield and composition.