Effect of feed-grade amino acid supplementation in reduced crude protein (RCP) diets formulated on a NE basis on performance and carcass characteristic of growing-finishing pigs

Abstract Text: Barrows and gilts (n=216) were used to test the effects of feed grade AA supplementation of RCP diets (formulated on a NE basis) on performance and carcass traits. Pigs were blocked by BW, and pens (3 barrows and 3 gilts/pen) within blocks were assigned randomly to either control corn-soybean meal diets (C) or 1 of 3 RCP diets supplemented with feed-grade AA to meet SID AA ratios during each of the 5 feeding phases (23 to 41, 41 to 59, 59 to 82, 82 to 104, and 104 to 127 kg BW). Paylean (10 mg/kg) was included in all diets during the last 3 wk of finishing. Pig BW and pen feed disappearance were recorded at the end of each feeding phase to calculate ADG, ADFI, and G:F. Additionally, 10^th rib backfat depth (10RFD) and LM depth (LMD) were measured ultrasonically on 1 randomly selected barrow and gilt/pen at the end of each phase. ADG was similar (P>0.22) among treatments in phase 1, 2 and 4 but decreased at the highest level of CP (linear effect (P≤0.02) in phases 3 and 5, as well as across the entire feeding trial. ADFI increased, then decreased (quadratic, P=0.06) at the highest level of CP reduction during phase 2, but reductions were greater in pigs fed RCP3 diets during phases 4 and 5, and across all 5 feeding phases (linear effect, P≤0.02). Feeding RCP diets reduced G:F during phase 3 (linear, P=0.05), but increased G:F (linear, P=0.06) across the feeding trial. Linear increases (P≤0.07) in 10RFD with decreasing dietary CP were observed at the end of each feeding phase, whereas LMD was reduced (linear, P=0.06) by RCP diets only at the end of phase 4.  Results suggested that CP can be replaced with feed grade AA to meet the requirement of the first 5 limiting AA (RCP2) without negatively impacting growth performance or carcass traits when diets are formulated on NE basis; however, further CP reductions resulted in more variable performance.

 

CP (added L-lysine HCl) of experimental diets for each feeding phase (% as fed)
Phase	C	RCP1	RCP2	RCP3
1	20.64 (0.350)	18.82 (0.512)	18.43 (0.549)	16.68 (0.716)
2	19.38 (0.334)	16.85 (0.558)	16.50 (0.590)	14.70 (0.763)
3	16.75 (0.285)	14.68 (0.468)	14.08 (0.523)	12.48 (0.675)
4	14.99 (0.253)	13.05 (0.424)	12.61 (0.464)	11.11 (0.607)
5	17.98 (0.300)	16.60 (0.424)	16.20 (0.462)	14.60 (0.614)

Keywords: Reduced crude protein, Amino acid supplementation, Swine, Performance