Grass as a feed for calves.

Thirty-two Friesian calves were randomly assigned to four treatment groups in each of 3 years, and weaned on to an ail-grass diet at either 6, 9, 12 or 15 weeks of age. In the first 2 years, whole milk was fed for 4 weeks and skim milk until calves were weaned on to grass. In the third year whole milk was fed for 5 weeks and concentrates were fed until weaning on to grass. All calves were individually fed indoors for 26 weeks. Freshly cut grass was fed ad lib daily after 1 week. Calves weaned on to an all-grass diet at an early age had a lower rate of liveweight gain (p<0.01) than calves fed skim milk or concentrates for longer periods in addition to grass. Average daily gains (kg/day) from 0 to 26 weeks were 0.50, 0.56, 0.57, 0.64 in the first year, 0.54, 0.54, 0.59, 0.62 in the second year and 0.58, 0.54, 0.61, 0.64 in the third year, for calves weaned on to grass at 6, 9, 12 and 15 weeks, respectively. These daily gains differed significantly in the first and third year but not in the second year. Immediately after the calves were weaned on to an all-grass diet, their intake of grass dry matter increased (p<0.01). Age at weaning had no effect on subsequent daily dry matter intake from grass. Body measurements showed no consistent trend between treatments in any year.