130 Effects of Increasing Dietary Standardized Ileal Digestible Lysine Levels on Growth Performance of 102- to 127-kg Immunocastred Gilts and Boars

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Abstract Our objective was to determine the effects of increasing dietary standardized ileal digestible (SID) lysine (Lys) on growth performance of immunocastrated gilts and boars. A total of 3,519 split gender pigs [PIC 337×Camborough, initial body weight (BW) = 101.7 ± 3.89 kg] were used in a 21-d trial in 2 replicates. Following the immunization against gonadotropin-releasing hormone (administrated with Vivax, Zoetis, São Paulo, SP, Brazil) in both genders, pens of pigs were weighed, blocked by BW, and randomly allotted to 1 of 5 treatments. Treatments consisted of 1.69, 1.90, 2.11, 2.32, and 2.53 g of SID Lys:Mcal of ME, which corresponded to 80, 90, 100, 110, and 120% of PIC SID Lys recommendations for mixed gender between barrow and gilts. This resulted in 0.56, 0.63, 0.70, 0.77, and 0.84% SID Lys given that the treatment diets were corn-soybean-meal-based and contained 3,300 Kcal of ME/kg. There were 6 split gender pens∙treatment-1∙replicate-1 and 29 pigs/pen. Data were analyzed using generalized linear and nonlinear mixed models with a pen as the experimental unit. Competing models included linear, quadratic polynomial (QP), broken-line linear (BLL), and broken-line quadratic (BLQ). There was no evidence of linear or quadratic SID Lys concentration by gender interaction (Table). Increasing SID Lys concentration improved average daily gain (ADG; quadratic, P < 0.01) and gain-to-feed ratio (G:F; quadratic, P < 0.01). The QP, BLL, and BLQ had a similar fit for the ADG and G:F. In the QP model, 95% and 100% of the ADG were achieved at 0.64 and 0.76% of SID Lys, respectively, and at 0.61 and 0.75% for G:F. The BLL and BLQ models estimated the breakpoint at 0.70% (95% CI: 0.65-0.74%) and 0.68% SID Lys (95% CI: 0.50-0.85%), for ADG, respectively. For G:F, the BLL, and BLQ models estimated the breakpoint at dietary SID Lys of 0.69% (95% CI: 0.52-0.86%) and 0.68% (95% CI: 0.58-0.78%), respectively. There was no evidence that increasing dietary SID Lys levels impacted the average daily feed intake or the removal and mortality rate. In the current trial the estimated optimum SID Lys:Mcal of ME ratio for 102- to 127-kg immunocastrated gilts and boars ranged from 2.06-2.30 (0.68-0.76% SID Lys based on a 3,300 kcal of ME/kg diet), depending on the statistical model.