Effect of indigestible dietary protein on growth performance and health status of weaned pigs

Feeding diets containing excess dietary protein (DP) is associated with increased hindgut protein fermentation, often resulting in post-weaning diarrhea. However, the response to DP content has been variable in piglets. The indigestible dietary protein (IDP) content of diets may be more related to negative health and performance outcomes than total DP. The objective of this study was to evaluate the impact of diet IDP content on performance, immune response, and fecal consistency score (FCS) in newly weaned pigs. Eighty mixed-sex weaned pigs with an average initial body weight of 8.1 ± 0.31 kg were housed in groups of 5 pigs/pen and randomly assigned to 1 of 2 dietary treatments in a completely randomized design (n = 8 pens/treatment) for 28 d. Diets were formulated to contain similar total crude protein (22% [phase I] and 20% [phase II]), net energy, and to meet or exceed all other nutrient requirements, but differ in IDP content (low IDP, 2.74% [LIDP] or high IDP, 4.2% [HIDP]). During the first 7 d, FCS was visually scored, followed by a weekly FCS and growth performance measurements. On d 9 post-weaning, blood, digesta from ileum, cecum, and colon, and fecal samples were collected in the morning from 1 pig/pen without prior fasting. Additional blood was also collected from 1 pig/pen on d 28. There was no effect of IDP on feed intake (P > 0.10). Low IDP increased average daily gain by 7% during phase II and 4% during the overall period compared to HIDP (P < 0.05). Gain:feed was lower and higher in LIDP-fed pigs during phases 1 and 2, respectively, compared to HIDP (P < 0.05). Pigs fed LIDP diet had improved FCS on d 6 and overall compared to HIDP (P < 0.01). Plasma superoxide dismutase concentration was higher in LIDP-fed pigs compared to HIDP (P < 0.05). There was neither IDP, Day, nor their interaction effect on serum albumin, interleukin (IL)-6, IL-1β, and plasma alkaline phosphatase (P > 0.10). Oxidized glutathione (GSSG) was higher on d 28 in LIDP-fed pigs compared to d 9 (P < 0.05); but GSSG in pigs fed HIDP on both days. In the cecum, LIDP increased the concentrations of cadaverine, spermine, allantoin, creatinine, and N1-acetylspermidine (P < 0.05) and reduced phenylethylamine, tryptamine, and choline (P < 0.05). High IDP increased valerate concentration in the colonic digesta (P < 0.05). The results indicate that feeding LIDP diet improved growth performance and oxidative status, reduced diarrhea severity, while increasing some biogenic amines in nursery pigs.