INFLUENCE OF DIETARY LYSINE ON GROWTH-PERFORMANCE AND CARCASS CHARACTERISTICS OF LATE-FINISHING GILTS

We conducted two experiments evaluating the lysine requirement of 91- to 113-kg gilts. Gilts (PIC L326 x C-22) with initial body weights of 42 (Exp. 1) or 39 kg (Exp. 2) were blocked by weight in a randomized c omplete block design. Experiment 1 included 105 gilts, with seven gilt s per pen and five replications (pens) per treatment. Experiment 2 inc luded 125 gilts, with eight gilts per pen and four replications (pens) per treatment. Gilts were fed a corn-soybean meal diet (no crystallin e lysine) containing 1.0% total lysine from 39 to 68 kg and .80% total lysine from 68 to 91 kg. In Exp. 1, when the average weight of gilts within a block reached 91 kg, gilts were fed corn-soybean meal diets c ontaining .40, .55, or .70% total lysine. Increasing dietary lysine in creased (linear, P < .05) ADG, daily lysine intake (11.3, 15.1, and 19 .8 g/d), gain/feed, plasma urea N, and carcass lean percentage but dec reased 10th rib fat depth. Because of the linear responses in Exp. 1, Exp. 2 was conducted with corn-soybean meal diets containing .60, .70, .80, or .90% total lysine. Increasing total dietary lysine had no eff ect on ADG, gain/feed, 10th rib fat depth, or carcass lean percentage (P > .10). Daily lysine intake increased (linear, P < .01) with increa sing dietary lysine (18.1, 21.1, 23.9, 26.5 g/d). Based on these resul ts, the total dietary lysine requirement for 91- to 113-kg gilts is ap proximately .60% total lysine, which corresponds to approximately 18 g /d lysine intake.