Lambs weaned from the ewe at 2 days of age were fed liberally or on a restricted level in each of three periods of growth according to a factorial design. In the first period restriction was achieved by giving less milk (5 as against 9 kg of milk replacer) and in the later periods by diluting one of the diets with 40% oat husks.
Milk restriction had no effect on performance from 15 to 35 kg or on the carcass composition as determined by dissection into fat, lean and bone. However, in the separate stages, 15·25 kg and 25·35 kg there was some indication that previous restriction of milk affected subsequent dry-matter intake and growth, particularly in the middle period of growth in lambs given the low energy diet.
Restriction after 15 kg, particularly from 15 to 25 kg, reduced overall performance to slaughter at 35 kg but had little effect on dissected carcass components. Restriction in the middle period affected performance in the final period and reduced food conversion efficiency. It is calculated that milk allowances for artificially reared lambs can be reduced without much effect on subsequent performance particularly where good diets are self-fed after 15 kg.
Restriction after 15 kg can be achieved by diet dilution but it has no apparently beneficial effect on carcass quality, as in pigs, and particularly if applied soon after 15 kg has been reached, can severely reduce growth and efficiency of feed conversion.