Effect of feeding reduced CP, amino acid supplemented diets, on dietary nitrogen and energy utilization and volatile fatty acid excretion in wean-to-finish swine

Abstract Text: Thirty-two barrows (initial BW 8.66 ±0.136 kg) were used to evaluate the effect of feeding reduced CP, amino acid (AA) supplemented diets, on nutrient and VFA excretion. Pigs were randomly allotted to the following diets: 1) Control: Corn-SBM-DDGS diets with no synthetic AA, 2) 1X reduction in CP, 3) 2X reduction in CP, and 4) 3X reduction in CP. Diet 4, the 3X reduction in CP, was balanced on the 7^thlimiting AA. Diets 2 and 3 were then formulated to have stepwise and equally spaced reductions in CP between Diets 1 and 4. Diets 2-4 were supplemented with synthetic amino acids as needed to meet amino acid needs based on NRC (2012) requirements. All diets were formulated to have identical ME content. Feed was supplied twice daily at ~95% of ad libitum intake for each dietary phase to minimize orts. Four nursery phases (d 0-7, d 7-14, d 14-28, d 28-42) and 5 grow-finish phases (21 d phases) were fed. Pigs were housed in stainless-steel metabolism pens (1.22m²) equipped with a nipple waterer and stainless steel feeder. Two pigs were housed per pen during the nursery phase, with one pig being removed on d 42 post-weaning. Collections started with nursery phase 3 and during nursery phases pigs were allowed an eight day adjustment period to the diets followed by a 3 d total collection of feces, urine, and orts. During the Grow-Finish phases pigs were acclimated to diets for the first 10 d of each phase, and then feces, urine, and orts were collected for 3 d. Acetic (P <0.001), propionic (P <0.04), and butyric acid (P <0.04) concentrations in the feces were linearly decreased by 26.5, 11.0 and 14.8%, respectively as dietary CP was reduced from control to 3X. Calculated DE and ME values based on analyzed GE content of feed, feces and urine were linearly reduced (P < 0.05) with increasing reductions in dietary CP (DE: 3736, 3658, 3662, 3526 kcal/kg; ME: 3694, 3612, 3616, 3499 kcal/kg). A tendency (P = 0.08) for a linear reduction in dietary N intake (25.2% lower in 3X vs. Control) was observed, which was partially responsible for the 36.5% linear reduction (P < 0.05) in N excretion (28.1, 21.3, 17.9 and 17.8 g/d). In conclusion, low CP diets with synthetic AA result in lower DE and ME values for the diet, but significantly reduce N and VFA excretion.

 Keywords: Swine, Nitrogen Retention