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Twelve Yorkshire barrows with a mean initial body weight of 21.5 ± 0.75 kg were received in 2 equal batches and were housed individually in metabolism crates. Pigs were allowed to adapt to their new environment and were offered a conventional pig starter diet for 1 wk before the study. At least 3 d before surgery, 6 pigs were assigned, following a randomized complete block design, to each of the 2 dietary treatments: a cornstarch and soybean meal-based diet (Control) or the Control diet with 12% pectin added at the expense of cornstarch (Pectin). The diets were formulated to contain similar standardized ileal digestible AA:NE ratios while ignoring the potential effect of pectin on ileal AA digestibility.
Among AA other than valine in digesta- and mucosa associated microbes on the last day of infusion, 15N enrichment was highest in alanine ( mole percent excess (MPE) ranging from 0.051% for mucosa associated microbes in Pectin pigs to 0.056% for digesta associated microbes for Control pigs; P > 0.10), lowest in lysine and threonine (MPE ranging from <0.001% for lysine and threonine in mucosa-associated microbes to 0.018% in threonine for digesta- associated microbes for Pectin pigs), and intermediate in the other AA. There was no effect of dietary treatment on 15N enrichment in AA in either digesta- or mucosa associated microbes (P > 0.10). For both Control and Pectin pigs, 15N enrichment of most AA in digesta-associated microbes was similar to that in mucosa-associated microbes (P > 0.10), except for lysine, threonine, and aromatic AA. More than 92% of valine in microbial protein in the upper gut was derived from preformed AA from endogenous and DP, suggesting that the novo synthesis makes only a small contribution to microbial AA.
It is concluded that the 92% of valine in microbial protein in the upper gut was derived from preformed AA from endogenous and dietary protein, suggesting that the contribution of de novo synthesis to microbial AA, and thence to the host’s AA supply, is small.
AJO Libao-Mercado, CL Zhu, JP Ct, H Lapierre, JN Thibault, B Sève, MF. Fuller, and CFM de Lange. 2009. Journal of Nutrition. 139:1088-1094.
