Abstract Objectives of this study were to determine the effects of standardized ileal digestible (SID) lysine on growth performance and economical outcomes of immunologically-castrated male pigs weighing 106 to 138 kg. The experiment consisted of 1, 050 pigs (PIC 800 sire line × PIC Camborough F1 sows) randomly assigned to one of 50 pens (21 pigs/pen). Five dietary treatments were designed in a titration manner with equidistant treatments. Treatments for SID lysine levels (as-fed) were 0. 35%, 0. 41%, 0. 46%, 0. 52%, or 0. 57%. Net energy was formulated to equivalent levels of 2. 48 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 CAD413 for the 0. 35% SID lysine diet, CAD415 for the 0. 41% SID lysine diet, CAD417 for the 0. 46% SID lysine diet, CAD421 for the 0. 52% SID lysine diet, and CAD425 for the 0. 57% SID lysine diet. Pigs were administered the second dose of the GnRF analogue 15 d prior to the start of experiment. Data were analyzed 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. 05) were observed for average daily gain (ADG), gain: feed (G: F), and estimated income over feed costs and quadratic effects (P 0. 05) were observed for G: F and estimated income over feed costs. Average daily feed intake was unaffected (P = 0. 22). Average daily gain increased linearly from 1. 36 kg/d to 1. 46 kg/d as SID lysine level increased from 0. 35% to 0. 52% but was not further increased at the SID lysine level of 0. 57%. Gain: feed increased linearly from 0. 298 to 0. 321 as SID lysine level increased from 0. 35% to 0. 52% and was not different between SID lysine levels of 0. 52% and 0. 57%. Estimated income over feed costs increased linearly as SID lysine level increased from 0. 35% to 0. 52% and was not different between SID lysine levels of 0. 52% and 0. 57%. In conclusion, the greatest levels of performance and estimated income over feed costs were achieved at SID lysine levels of 0. 52% for immunologically castrated male pigs weighing 106 to 138 kg.
Bohrer et al. (Wed,) studied this question.