PSII-10 Ammonium Phosphate is an Appropriate Nitrogen Source in Nitrogen-Limiting Diets for Growing Pigs

Abstract

Abstract The use of low protein (LP) diets is common in swine production, but there is potential for reduced dietary N for the endogenous synthesis of non-essential amino acids (NEAA), impacting overall animal growth. It has been previously demonstrated that inclusion of non-protein nitrogen (NPN) in a diet with an increased essential amino acid-nitrogen:total nitrogen (EAA-N:TN) ratio (i.e. limiting in total N) reduced the Lys requirement and maximum NR in growing pigs. The objective of this study was to determine the impact of NPN inclusion and Lys content on growth performance of growing pigs. A total of 240 growing pigs (120 gilts and 120 barrows) with an initial body weight (BW) of 20.2 ± 2.18 kg were housed in groups of 5 pigs/pen. Pens were randomly assigned to 1 of 6 dietary treatments over 3 blocks (n = 8 pens/treatment) in a 2 × 3 factorial design, with factors of NPN inclusion (no ammonium phosphate [NAP] or ammonium phosphate inclusion at 1.7% [AP]) and dietary lysine (Lys; 1.03%, 1.15% or 1.27% standardized ileal digestible). The AP and NAP diets were formulated to have an EAA-N:TN ratio of 0.48 and 0.54, respectively. All diets were corn and soybean meal-based and formulated to meet or exceed NRC (2012) nutrient requirements. The experimental period was 28 d, with individual BW and per pen feed intake determined weekly. On d 28, backfat and lean depth were measured on 2 pigs per pen, one male and one female. Data were analyzed using a mixed model with fixed effects of N content, Lys, and their interactions, and block as a random effect. Backfat and lean depth analysis included sex as a fixed effect. Inclusion of NPN reduced feed intake and increased gain:feed compared with pigs fed NAP diets (P < 0.05). Overall ADG and d 28 BW increased with increasing Lys, but were not impacted by dietary NPN content (P > 0.05). Pigs fed AP diets had increased lean depth (P < 0.05) and reduced backfat. Overall, NPN, as ammonium phosphate, can improve feed efficiency and increase lean depth while maintaining similar ADG and final BW.