Effect of dietary supplements of propionic acid, siliceous earth or a combination of these on the energy, protein and amino acid digestibilities and concentrations of microbial metabolites in the digestive tract of growing pigs

Abstract

A total of six barrows (Yorkshire X Lacombe), with an average body weight of 50 kg, were surgically fitted with two simple T-cannulas, one at the distal ileum and one in the cecum. Following recovery, four of the pigs were fed one of four diets according to a 4 × 4 Latin square design. The basal diet (Treatment 1) contained 15% soya-bean meal, 61.9% barley, 10% wheat bran, 10% beet pulp, 2.6% of a vitamin-mineral mixture and 0.5% chromic oxide as a digestibility marker. Treatments 2, 3 and 4 were the basal diet supplemented with 2% propionic acid (PA), 2.5% siliceous earth (SE), and a combination of 2% PA and 2.5% SE, respectively. The pigs were fed twice daily: the daily dietary allowances were 1.8 kg, 1.84 kg, 1.85 kg and 1.88 kg for Treatments 1, 2, 3 and 4, respectively. Each experimental period lasted 12 days. Following an 8 day adaptation period, feces were collected for 2 days followed by a 12 h collection of cecal digesta on Day 11 and a 12 h collection of ileal digesta on Day 12. Apparent ileal digestibilities of dry matter, organic matter, crude protein, ash or energy were not affected ( P > 0.05) when PA or a combination of PA and SE, were supplemented. However, the supplementation of PA improved ( P < 0.05) the apparent ileal digestibilities of several of the indispensable amino acids (arginine, histidine, leucine, phenylalanine and valine). The supplementation of SE decreased ( P < 0.05) the ileal digestibility of two of the indispensable amino acids (arginine and valine). With the exception of histidine, the supplementation of a combination of PA and SE did not affect ( P > 0.05) the ileal amino acid digestibilities. The supplementation of PA or SE, or a combination of these, had little effect on the apparent amino acid digestibilities when these were measured with the fecal analysis method. There was no effect ( P > 0.05) on the concentration of putrescine, cadaverine and ammonia in ileal digesta when PA, SE or a combination of these were supplemented. However, the supplementation of PA decreased ( P < 0.05) the concentration of cadaverine in cecal digesta; the supplementation of PA in combination with SE decreased the concentrations of both cadaverine and putrescine. There is no clear indication that SE functions as an adsorbent for PA to be released during its passage through the gastrointestinal tract.