PS5-3. Effects of Dietary Standardized Ileal Digestible Lysine on Growth Performance and Economical Outcomes of Intact Male Pigs Weighing 26 to 42 kg

Abstract Immunological castration takes advantage of the production benefits associated with raising intact male pigs prior to administration of the GnRF immunization. Objectives of this experiment were to determine the effects of standardized ileal digestible (SID) lysine on growth performance and economical outcomes of intact male pigs weighing 26 to 42 kg. The experiment consisted of 1, 008 pigs (PIC 800 sire line × PIC Camborough F1 sows) randomly assigned to one of 48 pens (21 pigs/pen). Six dietary treatments were designed in a titration manner with equidistant treatments. Treatments for SID lysine levels (as-fed) were 0. 95%, 1. 04%, 1. 14%, 1. 24%, 1. 34%, or 1. 44%. Net energy was formulated to equivalent levels of 2. 36 Mcal/kg. Minimum ratios of 30% Met: Lys, 60% Met+Cys: Lys, 66% Thr: Lys, 21% Trp: Lys, 70% Val: Lys, 56% Ile: Lys, and 102% Leu: Lys on a SID basis were used for all diets. Diets were formulated to meet or exceed other nutrient requirements established by NRC (2012). Diet costs were estimated using commercial costs in Canada during 2024 (i. e. , where and when the experiment took place) and were CAD477 for the 0. 95% SID lysine diet, CAD499 for the 1. 04% SID lysine diet, CAD521 for the 1. 14% SID lysine diet, CAD543 for the 1. 24% SID lysine diet, CAD565 for the 1. 34% SID lysine diet, and CAD587 for the 1. 44% SID lysine diet. Data were analyzed as a randomized complete block design with pen as the experimental unit. Dietary SID lysine level served as the fixed effect and pen replicate served as a random effect. Two single-degree of freedom orthogonal contrasts were used to test the linear or quadratic effects of increasing SID lysine level. Linear effects (P 0. 01) were observed for average daily feed intake (ADFI), average daily gain (ADG), gain: feed (G: F), and estimated income over feed costs. Quadratic effects (P 0. 01) were observed for ADG, G: F, and estimated income over feed costs. Average daily feed intake decreased linearly from 1. 91 kg/d to 1. 68 kg/d as SID lysine level increased. Average daily gain increased linearly from 1. 01 kg/d to 1. 15 kg/d as SID lysine levels increased from 0. 95% to 1. 14% and plateaued at SID lysine levels greater than 1. 14%. Gain: feed increased linearly from 0. 533 to 0. 675 as SID lysine levels increased from 0. 95% to 1. 34% and was not different between SID lysine levels of 1. 34% and 1. 44%. Estimated income over feed costs increased linearly from CAD9. 36 to CAD11. 55 as SID lysine levels increased from 0. 95% to 1. 14% and plateaued at SID lysine levels greater than 1. 14%. In conclusion, the greatest levels of performance and estimated income over feed costs were achieved at SID lysine levels of 1. 14% to 1. 34% for 26 to 42 kg intact male pigs.