Evaluation of nutritional strategies to slow growth rate then induce compensatory growth in 90-kg finishing pigs

Two 44-d experiments were conducted to evaluate nutritional strategies with different concentrations of dietary lysine (and other amino acids) on growth rate and subsequent compensatory gain of 90-kg finishing pigs. Three diets were formulated to contain 0.70 (control), 0.50% and 0.18% standardized ileal digestible (SID) Lys. In Exp. 1, 356 pigs (Line 241 × 600, DNA; initially 89.0 ± 1.10 kg) were used with four treatments. From d 0 to 28, pigs received either the control or the 0.50%-Lys diet. On d 28, pigs either remained on these diets or were switched the 0.18%-Lys diet until d 44. There were 18 pens per treatment from d 0 to 28 and 9 pens per treatment from d 28 to 44. From d 0 to 28, pigs fed the 0.50%-Lys diet had decreased (P < 0.001) ADG and G:F compared to those fed the control diet. From d 28 to 44, pigs switched to the 0.18%-Lys diet had decreased (P < 0.05) ADG and G:F compared to pigs that remained on the control or 0.50%-Lys diets. From d 0 to 44, pigs fed 0.50%-Lys diet for 44-d had decreased (P < 0.05) ADG, G:F, and percentage carcass lean compared to pigs fed the control diet. Pigs fed the 0.50%-Lys diet then the 0.18%-Lys diet had decreased (P < 0.05) ADG and G:F compared to other treatments. Pigs fed the 0.50%-Lys diet for 44-d and pigs fed the control diet then 0.18%-Lys diet had decreased (P < 0.05) ADG, G:F, and percentage carcass lean compared to control pigs. In Exp. 2, 346 pigs (Line 241 × 600, DNA; initially 88.6 ± 1.05 kg) were used to evaluate compensatory growth after varying durations of dietary lysine restriction. A total of four treatments were used including pigs fed the control diet for 44-d or fed the 0.18%-Lys diet for 14, 21, or 28-d and then fed the control diet until the conclusion of the experiment on d 44. There were nine pens per treatment. On average, pigs fed the 0.18%-Lys diet grew 49% slower than the control. Compared to the control, ADG of pigs previously fed the 0.18%-Lys diet increased (P < 0.05) 28% during the first week after switching to the control diet and 12% for the rest of the trial. Despite this improvement, overall ADG, G;F, final BW, and percentage carcass lean decreased (linear, P < 0.05) as the duration of Lys restriction increased. In summary, feeding Lys-restricted diets reduced the ADG and G:F of finishing pigs. Compensatory growth can be induced in Lys-restricted finishing pigs, but the duration of restriction and recovery influences the magnitude of compensatory growth.