The utilization of lysine by young pigs from nine protein concentrates compared with free lysine in young pigs fed ad lib.

1. Pigs (n 195) between 21 and 49 d of age were given a basal diet containing wheat, wheat gluten and cotton-seed meal which was supplemented with one of nine protein concentrates or free L-lysine. The diets were given ad lib. in two experiments. 2. Increasing the lysine content of the diets from 6.9 to 10.1 g/kg increased the weight gains of the pigs from 89 to 317 g/d in the first experiment. In the second experiment the weight gains were increased from 68 to 213 g/d by increasing the lysine content of the diets from 5.9 to 9.5 g/kg. 3. The utilization of lysine from the protein concentrates was compared with the utilization of free L-lysine. 4. The utilization of lysine fro weight gain compared with free lysine was 0.86-0.88 for meat meals, 0.95-0.99 for soya-bean meal, 0.69-0.75 for cotton-seed meal, 0.90 for lupins (Lupinus augustifolius) and 0.99 for milk.