Effects of Increasing Standardized Ileal Digestible (SID) Lysine on Performance of 11 to 23 Kg Nursery Pigs.

A 21-d study was conducted to determine the effects of increasing SID LYS on growth performance parameters. Twenty-one days post-weaning, a total of 822 [PIC TR4 x (FAST LW x PIC L02); 11.22 kg BW] mixed-sex pigs were allotted to one of five dietary treatments in a randomized complete block design using previous treatment and weight as blocking criteria. There were 26-28 pigs per pen with 6 replications per treatment. Experimental diets were corn-soybean meal based with 10% DDGS, formulated to be iso-caloric, and fed in pellet form (3.17 mm). The 5 dietary treatments consisted of 1.10, 1.175, 1.25, 1.325, and 1.40% SID LYS and were achieved by increasing primarily soybean meal and secondarily crystalline AA (L-Lysine HCl, Methionine Hydroxy Analogue, L-Threonine, L-Tryptophan, L-Valine) levels maintaining a constant SID Ile:Lys of 0.55 for all treatments without adding crystalline isoleucine. Data were analyzed using general linear and NLIN procedures of SAS with initial BW used as a covariate for all response variables. Overall (Table 1.), pigs fed increasing SID LYS had improved ADG and G:F (Linear, P < 0.001). There were no quadratic effects of increasing SID LYS (P > 0.19) for any response variable. Average daily gain was not a fit for any NLIN models and may indicate that the estimate is greater than 1.40%. The piecewise linear model was the best fit for G:F and estimated the requirement to be 1.32%. Mean separation indicates that the minimum SID LYS level to optimize ADG is at least 1.25%, and 1.325% for G:F.

Table 1. Effect of SID LYS on growth performance (d 0-21)
SID LYS, %	1.10	1.175	1.25	1.325	1.40	SEM
Expected Total LYS, %	1.23	1.31	1.39	1.48	1.56	-
Analyzed Total LYS, %	1.27	1.36	1.41	1.47	1.56	-
Soybean meal, %	20.9	23.6	26.3	29.0	31.8	-
Crystalline LYS, %	0.47	0.48	0.50	0.51	0.53	-
ADG, g1	552b	545b	575ab	593a	607a	13.53
ADFI, g	802	772	775	775	779	13.67
G:F1	.69c	.71c	.74b	.77a	.78a	.007
BW Gain, kg1	11.59b	11.44b	12.08ab	12.45a	12.75a	0.28
abcd Within a row, means without common superscript differ (P <0.05). 1 Linear effect SID LYS (P < 0.001)