Three experiments were conducted in the early grazing seasons of 1982–84 inclusive. Autumn-calved lactating British Friesian cows grazed a perennial ryegrass pasture either by strip grazing to leave 80 mm residual herbage (SG) or by rotationally grazing six paddocks on a fixed pre-determined cycle (PG). They were offered grazing only or grazing and average quality grass silage (S) or a 1: 1 mix of silage and ensiled brewers' grains (SB) given individually overnight in a cubicle house.
In experiment 1, cows received treatments SG or SGS. The intake of silage dry matter (DM) was 4·3 kg/day and the estimated intakes of herbage DM from measured animal performance were 15·2 and 8·9 kg/day respectively. Milk yields were 18·4 and 15·3 kg/day, the concentrations of fat and protein in the milk were 38·0, 41·8 and 33·3, 30·8 g/kg and live-weight change was +679 and +348 g/day for treatments SG and SGS respectively.
For experiment 2, cows received treatments SG, PG or PGS and grazing stocking rates were 5·2, 5·5 and 11·0 cows per ha respectively. Silage intake was 6·1 kg/day DM and the estimated intakes of herbage DM were 14·2, 15·3 and 7·7 kg/day respectively. Milk yields were 18·2, 18·2 and 16·1 kg/day, the concentrations of fat and protein were 41·6, 39·8, 42·3 and 33·3, 33·0, 30·4 g/kg and live-weight change was +325, +540 and +161 g/day for treatments SG, PG and PGS respectively.
For experiment 3, cows received treatments PG, PGS or PGSB and grazing stocking rates were 5·8, 11·6 and 11·6 cows per ha respectively. The intakes of silage and silage plus brewers' grains DM were 6·5 and 8·5 kg/day. The estimated intakes of herbage DM were 14·2, 7·2 and 7·3 kg/day, milk yields were 18·7, 14·6 and 18·9 kg/day, the concentration of fat and protein in the milk were 37·3, 42·1, 40·3 and 33·4, 32·6, 32·9 g/kg and live-weight change was +425, +415 and +441 g/day for treatments PG, PGS and PGSB respectively.
The results show that offering silage overnight allowed grazing stocking rates to be doubled, raised the concentration of fat in the milk and depressed the yields of milk and protein. When brewers' grains were given with the silage, yields of milk fat and protein were greater compared with when silage was offered alone and the yield of fat was greater than for herbage alone.