INFLUENCE OF DIET COMPOSITION ON THE MICROBIAL ACTIVITY IN THE GASTROINTESTINAL-TRACT OF DOGS .1. EFFECTS OF VARYING PROTEIN-INTAKE ON THE COMPOSITION OF THE ILEUM CHYME AND THE FECES

Protein-rich foodstuffs (greaves, soya protein and corn gluten) were fed to four intact dogs and four dogs with ileum fistulas (T-type) to study effects on some physical and chemical properties of the ileum chyme and the faeces. The products were offered either pure (not corn gluten), only supplemented with minerals and vitamins, or as part of a mixed diet (55 % of the respective protein source plus rice, soya oil, cellulose, vitamin/mineral supplement). Among observations on the compatibility of the diets, the composition of ileum chyme and faeces (crude nutrients and amino acids), and the precaecal and total apparent digestibilities, were evaluated. The palatability of al test diets was good, except for corn gluten, which was refused by the dogs when offered exclusively. Greaves, fed exclusively, led to soft and smeary faeces with a significant decrease in the faecal dry-matter content (32.7 %). If fed in the mixed diet (55 % greaves), faecal dry matter increased (36.8 %), but the consistency was still smeary compared with the vegetarian diets (37.1-40.1 % faecal dry matter). Frequency of defaecation (1-2/day) was not affected by the dietary treatment. The pH of the faeces was alkaline when feeding greaves, while with soya protein, and particularly with corn gluten, a decrease to an acidic range was observed (down to pH 6.4). In the ileum chyme, diet-related changes in the nutrient concentrations were observed. The crude protein concentration increased up to 650 g/kg DM after feeding of greaves, but when corn gluten was fed in the mixed diet only 218 g/kg DM were found. The apparent digestibilities of the organic matter were, precaecally, 84-97 % and, in total, 89-92 %. Precaecal protein digestibility was significantly lower if the dogs ingested greaves (85/81 %, isolated greaves/mixture) compared with the diets containing plant proteins (89-91 %). The total apparent digestibility of crude protein was 92-94 %, indicating relatively higher fermentation of greaves in the large intestine (8.3/11 % of intake with isolated greaves/mixture) compared with the soya or corn protein (around 3 % postileal apparent digestibility). The organic matter flowing from the ileum into the colon was 2.4-3.3 g/kg BW/day and greaves (isolated and as part of the mixture) increased the ileocaecal protein flow significantly. These investigations showed the influence of the amount and quality of the dietary protein source on the chemical composition of the ileum chyme and the faeces of dogs. The lower tolerance of dogs for diets containing animal protein may be related to the lower precaecal digestibility and effects on either intestinal micro-ecology or the metabolic activities of the gut flora.