Systems of concentrate allocation for dairy cattle. 4. A comparison of two amounts and two patterns of allocation

Abstract

ABSTRACTFor 25 weeks starting at week 3 post partum autumn-calving dairy cows were offered either a flat rate of concentrates in which all cows received the same daily amount throughout the experiment (F), or a variable rate based on their individual milk yield at 2 weeks post partum, and which was reduced at weeks 10, 15 and 20 of the experiment (V). Two mean amounts of concentrates were compared, 11 kg/day (11) and 7 kg/day (7) and grass silage was available ad libitum. For treatments 11F, 11V, 7F and 7V respectively, mean milk yields were 26·2, 24·5, 21·5 and 21·3 kg/day, mean live-weight changes were +0·18, +0·07, -0·09 and -0·05 kg/day, and mean silage dry-matter intakes were 8·0, 7·1, 9·4 and 9·0 kg/day. Differences between systems of allocation were not significant, but differences between amounts of concentrates offered were significant. Due to the greater milk yield and milk fat concentration of the F system of allocation, milk fat yield was significantly greater than for the V system. The substitution rate of concentrates for silage dry matter was significantly greater during the first 10 weeks of the experiment than during the succeeding 15 weeks. In the residual period (3 weeks indoors and 14 weeks grazing), there were no significant effects on performance. The mean 305-day milk yields for 11F, 11V, 7F and 7V respectively were 6957, 6388, 5862 and 5901 kg.