The impact of different dietary levels of fermentable substrates and calcium-phosphate on the intestinal microbiota in pigs

Saving the limited resources of phosphate rock and improving intestinal health of pigs represent major challenges of modern pig industry. Consequently, the present study addressed the impact of supplementing variable levels of calcium-phosphate (CaP) on the numbers of selected members of the intestinal microbiome in growing pigs. To investigate the impact of fermentable substrates on the microbiota, two protein sources potentially providing variable quantities of fermentable substrates for the gut microbiota were utilized.

A total of 31 growing pigs (initial BW 54.7 kg ± 4.1 kg) in 2 consecutive experiments were allocated to 4 treatments, fed either a corn-soybean meal or a corn-pea based diet, each diet containing a high and a low level of CaP (Ca: 4.4 vs. 8.3; P: 4.2 vs. 7.5 g/kg dry matter) After 9 weeks, animals were slaughtered, digesta samples from jejunum, caecum, and colon were removed and 16S rRNA gene copy numbers of Bifidobacterium spp., Enterobacteriaceae, Lactobacillus spp., and Roseburia spp. were analyzed by quantitative real-time PCR.

Low levels of CaP led to higher 16S rRNA gene copy numbers of all bacterial groups (P< 0.10) except Lactobacillus spp. in the jejunum. In contrast, numbers of caecal Roseburia spp. were lower (P< 0.05), when diets containing low CaP levels were fed, whereas colonic Bifidobacterium spp. (P< 0.05) were higher. Higher quantities of Roseburia spp. were detected in the jejunum (P< 0.05) when pea containing diets were fed, while feeding these diets resulted in lower numbers of this genus in the caecum (P< 0.10). Jejunal Lactobacillus spp. (P< 0.05) and caecal Bifidobacterium spp. (P< 0.05) were lower, whereas Enterobacteriaceae were higher in all investigated gut compartments as a result of feeding pea containing diets (P< 0.05).

In the present study, a reduction of dietary CaP resulted in higher numbers of bacteria with probiotic properties such as colonic Bifidobacterium spp. as well as higher numbers of jejunal Enterobacteriaceae including pathogenic members. Thus, an evaluation of potential effects of these diets on intestinal health is difficult. The utilization of pea meal instead of soybean meal containing diets led to higher numbers of Enterobacteriaceae in all investigated compartments, whereas probiotic Lactobacillus spp. and Bifidobacterium spp. were partly lower, indicating an assumed less favorable microbial composition. However, the observed effects cannot be assigned to P alone or to certain substrates because concentrations of Ca and P varied and diets contained different levels of various individual substrates.

Disclosure of Interest: None Declared.