The Effects of Length of Feeding, Dietary Electrolyte Balance, and Energy Source on Ileal Endogenous Amino Acid Losses in Pigs Fed Nitrogen-Free Diets

An experiment was conducted to investigate the effect of dietary factors on ileal endogenous amino acid losses (EAA) in pigs fed a N-free diet (NFD). Sixteen cannulated pigs were used to evaluate the effect of length of feeding, dietary electrolyte balance (DEB, low vs. high), and energy source (corn starch vs. dextrose) on ileal EAA losses. Pigs were fed 4 diets for 2 periods in a crossover design with 4 blocks of 4 pigs per block within each of the 2 periods. The average initial BW in periods 1 and 2 were 28.3±0.95 and 30.6±1.09, respectively. Each period lasted 7 d with a 12-h ileal digesta collection on d 3 and 4 and 6 and 7. Pigs received a daily feed allowance of approximately 4% of their BW. There were no 3- or 2- way interactions except for DEB x energy source where low DEB and dextrose resulted in higher (P < 0.05) endogenous loss of N, Arg, Lys, Ala, Gly, Pro, and total AA compared to losses from pigs fed a NFD with high DEB and dextrose. The length of feeding of NFD was not significant for most of the amino acids except for Arg, Gly, Pro, total AA, and N where feeding for 6-7 d resulted in higher (P < 0.05) losses. Low dietary DEB resulted in higher (P < 0.05) Thr, Cys, Gly, and Ser losses. Dextrose as a source of energy resulted in higher endogenous losses for most of the AA except for Arg, Lys, Ala, Gly, Pro, and total AA. The effect of length of feeding was most pronounced for Pro where endogenous loss increased by 82% (2,620 vs. 4,780 mg/kg DMI) with increasing length of feeding. Finally, dextrose resulted in higher EAA loss and the length of feeding of NFD could be reduced to 3 to 4 days without any significant effects on losses compared to when the diet if fed for 6 to 7 days.