CONCENTRATION OF MICROBIAL METABOLITES IN THE GASTROINTESTINAL-TRACT OF BROILER RABBITS

A very large spectrum of microorganisms can live and develop in the gastrointestinal tract of rabbits. Microbial metabolites constitute a large nutritional potential which acts upon the metabolism and health of the host, In our study, the concentration of microbial metabolites was measured in stomach, small intestine, caecum and colon of broiler rabbits (New Zealand x Californian breed). Seven suckling rabbits, four weeks old, were kept with the doe. Rabbits had free access to a commercial granulated feed containing 17.6 % of crude protein, 2.2 % of fat and 12.6 % of crude fiber. Eleven rabbits, three months old, were fed granulated concentrate feed containing 14.7 % of crude protein, 2.2 % of fat and 13.2 % of crude fiber. The rabbits were killed approx. four hours after the morning feeding. The pH was measured immediately and samples of digesta were stored under CO2 in hermetically sealed bottles at -40-degrees-C until analyzed. Lactic acid was oxidized to acetaldehyde and measured by using Conway microdiffusion chambers. Ammonia was determined colorimetrically using Nessler reagent. Volatile fatty acids (VFA) were determined by titration after steam distillation. Their molar ratio was measured by gas liquid chromatography. Variable concentrations of lactic acid were found in the stomach and small intestine of rabbits (5.3 - 22.5 mmol/g, on average). The highest concentration of ammonia was found in the caecum (600 +/- 97 and 510 +/- 70 mug N/g, for suckling and adult rabbits, resp.). The lowest concentration of ammonia was in the stomach. The average pH values of the gastric contents were 2.88 and 2.58 in suckling and adult rabbits, resp. In the other parts of the gastrointestinal tract the average pH varied from 5.5 to 7.1. The gastric content of suckling rabbits contained 29.2 +/- 6.6 mmol VFA per 1 g. These VFA (acetate and butyrate) were probably of milk origin. No VFA were found in the stomach of adult rabbits. The highest concentrations of VFA were found in the caecum: 126 +/- 35 and 190 +/- 40 mmol/g, for suckling and adult rabbits, resp. The VFA concentrations in the colon were lower: 81 +/- 14 and 44 +/- 8 mmol/g, for suckling and adult rabbits, resp. Acetate and butyrate were principal acidic metabolites in the hindgut. Propionate was relatively less important.