Effects of Dietary Protein and Rapidly Fermentable Carbohydrate Contents on Microbial Fermentation Profile in the Hindgut of Weanling Pigs

Abstract Text: Protein fermentation in the hindgut of piglets leads to the production of potentially toxic metabolites such as ammonia, which may increase the risk of postweaning diarrhea. In this way, the objectives in this study were to determine the effects of dietary CP and dried citrus pulp (DCP, rapidly fermentable carbohydrate source) contents on short-chain fatty acids (SCFA), branched-chain fatty acids (BCFA), and ammonia concentrations in the colon digesta of weanling pigs. One hundred and eight barrows weaned at 21 d of age were blocked by initial BW (5.82 ± 0.16 kg) and randomly assigned to 1 of 4 treatments with 9 replicate pens per treatment and 3 pigs per pen. Treatments were arranged in a 2 x 2 factorial, with 2 CP contents (HCP and LCP, high- and low-CP diets, respectively) and 2 DCP contents (0 and 7.5%, as-fed basis). The HCP treatments consisted of feeding a 20 and 21% CP diet (as-fed basis) during the pre-starter I (1 to 14 d) and pre-starter II (15 to 28 d) phases, respectively. For the LCP treatments, diets were reduced by 4 percentage units compared with the HCP diets in both phases. The AA contents in the diets were balanced by supplementation with crystalline AA, such as L-Lys, DL-Met, L-Thr, L-Trp, L-Val, and L-Ile to maintain constant ratios in relation to standardized ileal digestible Lys. Colon digesta samples were collected from 1 randomly selected pig per pen on d 7 and 28 postweaning for determinations of SCFA and BCFA by gas chromatography, and ammonia concentrations by colorimetry. Statistical analyses were conducted using the MIXED procedure of SAS. Feeding pigs diets containing 7.5% DCP increased (P < 0.01) acetic acid concentrations, and decreased propionic (P < 0.05) and valeric (P < 0.01) acids concentrations, whereas butyric acid production was not affected (P > 0.05) by treatments. Dietary DCP inclusion increased (P < 0.05) isobutyric acid concentrations in the colon only at 28 d postweaning. Adding 7.5% DCP to the diet resulted in lower isovaleric acid (P < 0.01) and ammonia (P< 0.01) concentrations in the colon only for pigs fed the LCP diet. In conclusion, low-protein AA-supplemented diets with 7.5% DCP inclusion depresses harmful protein fermentation in the hindgut, and therefore may be contributing to enhance intestinal health of weanling pigs.

Keywords: intestinal health, piglets, protein fermentation