AbstractsBiology & Animal Science

Considerable evidence suggests that dietary macronutrients impact upon activities and conditions in the gastrointestinal tract (GIT) including: functions and processes, digestive enzymes secretion, microbial ecology and bacteria-derived metabolism. Knowledge about the modulation of canine intestinal microbiota, bacteria-derived metabolic products,intestinal inflammatory status and adaptive exocrine pancreatic secretion in response to macronutrients is limited. However, such information is necessary to investigate further the complex interplay between host and intestinal microbiota in response to changes of diet. The reasearch for this PhD thesis focused upon the changes of the intestinal microbiota,bacteria-ferivedmetabolicproducts,anintestinalinflammatorymarker and pancreatic enzyme profiles of five healthy Beagle dogs in response to being fed three different diets: high-carbohydrate starch (HCS), high-protein greaves-meal (HPGM), or a balanced dry commercial (DC) diet. Every diet was crossed-over and fed to each dog for three 21-day periods. The microbial deoxyribonucleic acid (DNA) was profiled according to its percentageoftheguanine-cytosinecontent(%G+C)inordertodetectthefluctuations in intestinal microbiota. Thereafter, 16S ribosomal ribonucleic acid (16S rRNA) gene amplicons were obtained from the most abundant %G+C peaks and analysed by sequence analysis. The DC diet sample was associated with high abundances of representatives of the orders Clostridiales, Lactobacillales, Coriobacteriales and Bacteroidales. Sequence diversity was highest for the DC diet samples and included representatives of the orders Lactobacillales and Bacteroidales, which were not detected in samples obtained for the HPGM and HCS diets. The HPGM and HCS diets also had reduced numbers of representatives of the family Lachnospiraceae; specifically Clostridium cluster XIVa. The HCS diet favoured the proliferation of representatives of the order Erysipelotrichales, specifically the Clostridium cluster XVIII, whereas the HPGM diet favoured representatives of the order Fusobacteriales. Bacterial metabolism and intestinal inflammatory status were assessed by determining dry matter, pH, ammonia, short-chained fatty acids (SCFAs), and faecal canine calprotectin concentrations. Faecal ammonia concentrations decreased with the HCS diet. All dogs fed the HPGM diet developed diarrhoea, which led to differences in faecal consistency scores and increased faecal pH. Moreover, decreases in propionic and acetic acids coupled with increases in branched-chain fatty acids and valeric acid caused changes in faecal total SCFAs. Faecal canine calprotectin concentration was also higher for the HPGM diet than with the other diets and correlated positively with valeric acid concentrations.8 Dietary effects on digestive enzyme composition in the serum, in jejunal fluid, and in the faeces were studied by determining the following factors: amylase activity, the concentrations of canine trypsin-like immunoreactivity (cTLI), canine pancreatic lipase immunoreactivity…