Effect of dietary standardized ileal digestible lysine and copper density on growth performance, nutrient digestibility, blood profiles, fecal microbiota, backfat thickness and lean meat percentage in growing pigs

This study was conducted to evaluate the effect of dietary standardized ileal digestible lysine (SID Lys) and copper (Cu) density on growth performance, nutrient digestibility, blood profiles, fecal microbiota, backfat thickness and lean meat percentage in growing pigs. A total of 240 castrated male growing pigs [(Yorkshire x Landrace) x Duroc)] with an average BW of 22.7 +/- 0.11 kg were used in this 42-day trial. Pigs were randomly allocated to 3 treatments plus control based on the BW. Basal diet contained 100% SID Lys of the estimated NRC (2012) requirement and 17 mg/kg Cu. Dietary treatments included different SID Lys of the estimated NRC (2012) requirement (100, 103 and 106%) with an extra 150 mg/kg supplemental Cu. Final BW, ADG and estimated SID Lys intake in pigs fed diets with 103 and 106% SID Lys and supplemental Cu were increased (P < 0.05) compared with those fed control diet. With the increasing SID Lys level, final BW, ADG, ADFI, G: F and estimated SID Lys intake in supplemental Cu treatments increased (P < 0.05) linearly. The apparent digestibility of dry matter (DM), nitrogen (N) and gross energy (GE) in supplemental Cu treatments showed a linear increase (P < 0.05) in response to increasing SID Lys level. Pigs fed control diet had higher (P < 0.05) blood urea nitrogen (BUN) than those fed diets with 103 and 106% SID Lys and supplemental Cu. The creatinine in supplemental Cu treatments with 100% SID Lys group was increased (P < 0.05) compared with control, and the creatinine in supplemental Cu treatments increased (P < 0.05) linearly with the increasing SID Lys level. Fecal Escherichiacoli (E. coli) counts were linearly (P < 0.05) decreased by supplemental Cu treatments with the increasing SID Lys level. Taken together, increasing SID Lys in 150 mg/kg supplemental Cu treatments improved growth performance, nutrient digestibility, backfat thickness, but decreased fecal E. coli counts in growing pigs.