194 Supplementation of feed grade essential and non-essential amino acids to control levels in pigs fed reduced crude protein (RCP) diets meeting the SID His:Lys ratio requirement maintained growth performance and carcass composition in growing/finishing swine

Previous research indicates aggressive feeding of AA to growing/finishing pigs results in reduced intake, gain, and fatter carcasses. This study investigated the role of dietary essential AA, nonessential AA, and electrolyte balance on these outcomes. PIC C29 × 380 pigs (n= 196) were blocked by BW and treatments assigned to gender-balanced pens within block. Treatments were: 1) corn-soybean meal diets formulated to meet a constant Trp:Lys ratio (20) without feed grade Trp (PC); 2) RCP diets meeting the His:Lys ratio requirement (32) without added feed grade His but with feed grade indispensable AA added to control levels (Met+Cys:Lys, 60 to 65; Thr:Lys, 65 to 68; Trp:Lys, 20; Ile:Lys, 73 to 78; Val:Lys, 79 to 88; His:Lys, 45 to 51; EAA); 3) as 2 but with feed grade Glu and Gly (67:33) added to the same N in PC (NEAA), or 4) as 3 but with diets formulated using NaHCO3to create the same dietary electrolyte balance as PC (dEB). All diets met the SID AA:Lys ratio requirement for each phase (23 to 41, 41 to 59, 59 to 82, 82 to 104, and 104 to 131 kg BW). Ractopamine (10 mg/kg) was fed during the last 3 wk. Pig BW and pen feed disappearance data were used to calculate ADG, ADFI, and G:F for each pen. HCW, LM and fat-depth (10th rib) were captured by Fat-O-Meter at slaughter. Pig growth performance and carcass composition were maintained by adding feed grade EAA to the RCP diet. ADG, ADFI, G:F and carcass characteristics did not respond to NEAA or NaHCO3additions. These results suggest the reduced performance of growing/finishing pigs fed RCP diets formulated to meet the His:Lys requirement without using feed grade His in previous studies may be attributed to improper AA:Lys ratios and not from total N or dietary electrolyte balance.