27 Standardized ileal digestible lysine to metabolizable energy ratio equations for 12 to 127 kg boars, gilts, immunocastrated gilts and boars

Abstract

We aimed to determine the standardized ileal digestible (SID) lysine (Lys) to metabolizable energy (ME) ratio equations for 12 to 127 kg boars, gilts, immunocastred gilts (IC gilts), and barrows (IC barrows). An average of 3,545 split-gender pigs (PIC 337×Camborough, initially 11.98 ± 1.26 kg) were used in a 21-d trial followed by a 21-d wash-out period in 2 replicates, totaling six feeding periods. In feeding phase 6, both genders were immunized against gonadotropin-releasing hormone (administrated with Vivax, Zoetis, São Paulo, SP, Brazil). Pens of pigs were weighed, blocked by body weight, and randomly allotted to 1 of 5 treatments consisting of 80, 90, 100, 110, and 120% of PIC SID Lys:Mcal of ME recommendations for mixed gender between boars, barrows, and gilts for each phase. The treatment diets were corn-soybean-meal-based and contained 3,300 Kcal of ME/kg. There were six split-gender pens•treatment^-1•replicate^-1 •phase^-1 and 30 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) for average daily gain (ADG) and gain to feed ratio (G:F). There was no significant gender by quadratic coefficient interactions in all phases of this study (P > 0.05), then the mixed gender equation was determined, and the intact boars and gilts equation was estimated by the PIC overall difference in efficiency between genders. In the immunocastrated phase, after second dose, the mixed gender optimum level was determined and the equations for IC gilts and barrows was estimated by the differences in efficiency observed in the phase 6 of the two replicates. The SID Lys to calorie ratio recommended is based on the average for ADG and G:F (Table 1). Approximately 98.4% and 99.2% of maximum ADG and G:F were achieved at these levels, respectively, and these equations were similar compared with previous PIC biological requirements (Orlando et al., 2021).