95 Effects of increasing standardized ileal digestible valine:lysine ratio on growth performance in finishing pigs

Abstract

Abstract Two experiments evaluated the effects of increasing standardized ileal digestible (SID) Val:Lys ratio on the growth performance of 38 to 67 kg (Exp. 1) and 90 to 116 kg (Exp. 2) finishing pigs. In Exp. 1, pigs (n = 647; DNA 600 × 241) were randomly allotted to 1 of 6 dietary treatments with 8 or 9 pigs per pen and 12 replications per treatment. Diets were corn-soybean meal-based, and low and high Val diets were manufactured and blended to create intermediate Val:Lys ratio diets. Diets were formulated to contain 0.90% SID Lys, and treatments consisted of SID Val:Lys ratios of 60%, 63%, 66%, 69%, 72%, and 75%. At the conclusion of the 27-d study, all pigs were fed a common diet for 30 d and then randomly re-allotted to 1 of 6 diets formulated to contain 0.65% SID Lys and SID Val:Lys ratios of 63%, 66%, 69%, 72%, 75%, and 78% (Exp. 2). In both experiments blood samples were collected from 3 pigs per pen on d 15 for plasma urea nitrogen (PUN) analysis. In Exp. 1, final body weight (BW), average daily gain (ADG), and average daily feed intake (ADFI) increased (quadratic, P < 0.05) as Val:Lys increased (Table). Pigs fed the diet with 66% SID Val:Lys ratio had the greatest ADG, whereas pigs fed 72% SID Val:Lys ratio had the greatest ADFI. As the Val:Lys ratio increased, gain to feed ratio (G:F) decreased (linear, P < 0.05). Valine and Lys intake increased (quadratic, P < 0.05) as the Val:Lys ratio increased with the greatest intake observed at 72% SID Val:Lys. Valine and Lys intake per kg of gain increased (linear, P < 0.05) as the level of Val in the diet increased. Plasma urea nitrogen decreased (linear, P < 0.05) as the Val:Lys ratio increased. In Exp. 2, ADG and ADFI increased (linear, P < 0.05) as Val:Lys increased. However, for ADG there was little improvement from feeding greater than 69% SID Val:Lys. There were no linear or quadratic effects (P > 0.05) for SID Val:Lys on G:F or PUN. Valine intake, Lys intake, and Val intake per kg of gain increased (linear, P < 0.05) as the Val:Lys ratio increased. There were no differences (P > 0.05) observed in Lys intake per kg of gain. Based on the results of this study, it appears that 66% SID Val:Lys ratio maximizes ADG in 38to 67 kg pigs, and only small increases in ADG were observed when feeding greater than 69% SID Val:Lys for 90 to 116 kg finishing pigs.