Evaluation of the Lysine Requirement of 11- to 23-Kg Nursery Pigs

A total of 1,200 PIC 337×1050 barrows and gilts (11.4±1.4 kg) were placed in a wean-to-finish facility. The 5 dietary treatments were: 1.10, 1.20, 1.30, 1.40, and 1.50% SID lysine. Dietary treatments were randomly allotted to pens (25 pigs/pen) blocked by gender and average pen BW. Pigs were started on experimental diets at approximately 11.4 kg BW. Prior to the study, pigs were placed on a common diet that met the lysine requirement based on BW. All diets were corn-soy based and were formulated to meet or exceed NRC requirements (NRC, 2012). Pen weights and feed intake information were collected at each phase for calculation of average daily gain (ADG), average daily feed intake (ADFI), and gain:feed (G:F). Mortalities and removals were weighed and recorded. Data were analyzed as a RCBD using the PROC MIXED procedure of SAS with pen as experimental unit, treatment as fixed effect, and body weight block as random effect. Results were considered significant at P≤0.05 and a trend at P>0.05 and P≤0.10. Competing requirement estimation models were: quadratic polynomial (QP), broken-line linear (BLL), and broken-line quadratic (BLQ) using PROC NLMIXED. Models that differed in their bayesian information criterion values by at least 2 points were considered to have meaningful differences in their data fit (Raftery, 1996). There were no significant differences detected in BW at the conclusion of the 21-d study (P>0.16). There were no differences detected in ADG based on dietary treatment (P>0.12). Feed intake was linearly reduced (P<0.003) as SID Lys level increased. Consequently, G:F was linearly improved (P<0.02) as SID Lys increased. For ADG, the QP model was determined to be the best fit (15.5 + 153.3 × SID Lys – 60.6 × SID Lys²) with an estimated SID Lys requirement of 1.26%. Gain to feed was best modeled by the linear broken line model (1/(145.7 + 19.1 × [1.40 – SID Lys])) with an estimated requirement of 1.40% SID Lys. In conclusion, the SID Lys requirement for ADG is 1.26% and G:F is 1.40% 11- to 23 –kg BW pigs.

Table 1. Evaluation of lysine requirement in 11-23 kg nursery pigs
	Trt 1	Trt 2	Trt 3	Trt 4	Trt 5		Probability, P <
SID Lys:	1.1	1.2	1.3	1.4	1.5	SEM	Linear	Quad.
ADG	0.50	0.52	0.50	0.51	0.49	0.01	0.34	0.12
ADFI	0.76	0.77	0.75	0.74	0.72	0.02	0.003	0.18
G:F	0.663	0.671	0.671	0.695	0.687	0.010	0.02	0.85