CARBOHYDRATE-METABOLISM OF THE CAT .3. DIGESTION OF SUGARS

The total digestibility of glucose (5.1 g/kg body weight/d), galactose (5.6 g/kg body weight/d), lactose (1.3 and 4.5 g/kg body weight/d) and sucrose (7.2 g/kg body weight/d) and the prececal digestibility (post-mortem experiments using chromic oxide as a marker) of lactose and sucrose were determined in 12 adult cats. The effect of these sugars on protein and fat digestibility as well as their impact on intestinal metabolism (water, pH, organic acids) was tested. Apparent total digestibility of all sugars amounted to nearly 100%. Prececal digestibility of lactose (higher dose) averaged 70.5% and of sucrose 98.8%. Apparent protein digestibility was reduced by all diets containing sucrose or lactose by 4 to 5% compared to the carbohydrate-free diet. Glucose and galactose had no significant influence on fecal pH (glucose 7.15, galactose 6.96, carbohydrate-free 7.22), other sugars caused varying degrees of acidification (sucrose 6.00, lactose high dose 5.36, low dose 6.38). Lactose and sucrose showed similar effects on the pH in the large bowel, while stomach and small intestinal pH remained unchanged. With the exception of the sucrose diet the concentration of short chain fatty acids (SCFA) in the feces decreased following the intake of sugars, while lactate concentration increased in all sugar diets. These changes were most marked in the high lactose diet (carbohydrate-free diet: SCFA 307, lactate 0.71 mmol/kg feces; high lactose diet: SCFA 58, lactate 14.27 mmol/kg). While both monosaccharides led to an increase of fecal dry matter percentage, there was a more or less marked reduction after the intake of disaccharides. Similar effects of lactose and sucrose were seen in the chyme of the small and large intestine.