The effect of dietary P and Ca level, phytase supplementation and ileal infusion of pectin on the chemical composition and carbohydrase activity of fecal bacteria and the level of microbial metabolites in the gastrointestinal tract of pigs

¹ Institute of Animal Nutrition, University of Hohenheim, 70599 Stuttgart, Germany
² Institute of Agricultural and Nutritional Sciences, Martin-Luther-University Halle-Wittenberg, 01608 Halle (Saale), Germany

^* To whom correspondence should be addressed. E-mail: rhmosenth{at}uni-hohenheim.de.

	Abstract

Two experiments with growing pigs were conducted to determine the effects of dietary P and Ca level, phytase supplementation and ileal pectin infusion on ileal and fecal P and Ca balance, chemical composition of fecal mixed bacterial mass (MBM), and bacterial metabolic activity. Pigs (initial BW = 30 kg) were fitted with simple T-cannulas at the distal ileum. They were fed a low-P corn-soybean meal control diet (3 g P/kg), and the control diet supplemented with monocalcium phosphate (MCP; 7 g P/kg; Exp. 1) or 1,000 FTU phytase/kg (Exp. 2). The daily infusion treatments consisted of 60 g pectin dissolved in 1.8 L demineralized water or 1.8 L demineralized water as control infusion, infused via the ileal cannula. In each experiment, 8 barrows were assigned to 4 dietary treatments according to a double incomplete 4 x 2 Latin square. The dietary treatments in Exp. 1 were the control (Con-) diet with water infusion; control (Con+) diet with pectin infusion; MCP diet with water infusion; MCP diet with pectin infusion. In Exp. 2, the pigs received the same Con- and Con+ treatments as in Exp. 1 and, in addition, the phytase supplemented diet in combination with water or pectin infusion. After a 15-d adaptation period, feces were collected for 5 d followed by ileal digesta collection for twice every 12h. In Exp. 1, supplemental MCP increased (P 0.003) ileal and fecal P and Ca recovery as well as P and Ca content of the MBM. Pectin infusion increased the N content of the MBM (P = 0.054) and polygalacturonase activity (P = 0.032) in feces. In addition, pectin decreased (P = 0.049) ileal and tended (P < 0. 079) to increase fecal VFA concentrations. In Exp. 2, phytase decreased ileal and fecal P recovery (P < 0.001) and the P content of the MBM (P = 0.045), while the N content of the MBM (P = 0.094) and fecal cellulase activity (P = 0.089) tended to decrease. Similarly, pectin infusion decreased (P = 0.036) fecal cellulase activity, but increased (P < 0.001) polygalacturonase activity. In conclusion, these data indicate that bacterial P and Ca assimilation and metabolic activity depend on P and Ca availability in the large intestine and on the availability of fermentable substrate such as pectin. Thus, increasing dietary P and Ca levels increases bacterial P and Ca assimilation due to greater intestinal P and Ca availability, while decreasing intestinal P availability through phytase addition to low-P diets reduces bacterial P incorporation and seems to decrease bacterial activity.

Key Words: bacteria, large intestine, pectin, phosphorus, phytase, pig