Magnesium balance in adult cats fed a dry food rich in lactose.
The question addressed was whether lactose consumption would stimulate apparent magnesium absorption in adult cats. In a cross-over study, eight cats were fed dry diets without or with 10% lactose, which was added at the expense of the glucose component. Urine and faeces were quantitatively collected and the balance of magnesium, calcium and phosphorus was determined. Lactose feeding did not affect mineral absorption. The dry matter content of faeces was unchanged after lactose consumption. Urinary excretion of galactose represented 0.2% of the intake. It is concluded that lactose ingestion at a level of 1.2 g/kg body weight has no effect on mineral absorption and on the consistency of faeces in adult cats.
Blood sugar levels and renal sugar excretion after the intake of high carbohydrate diets in cats.
The effect of starch and sugars on blood sugar level and renal excretion of sugars and galactitol was investigated. Fifty-nine adult cats were divided into seven dietary groups (carbohydrate content in dry matter): STARCH (29-37% starch, decomposed or raw), SUC (36% sucrose), LAC1 and LAC2 (11 and 28% lactose, respectively), GLUC (40% glucose), GAL (39% galactose) and a carbohydrate-free control diet, FAT. Diet STARCH did not significantly influence postprandial blood glucose level (3.65 +/- 0.68 mmol/l +/- SD, n = 16) compared with diet FAT (3.20 +/- 0.77 mmol/l, n = 14) 1, 3 or 6 h after feeding (weighted means). Diet GLUC led to a steep rise in blood glucose concentration 1 h after feeding (5.08 +/- 0.69 mmol/l, n = 6). Diet SUC induced a mild persistent hyperglycemia without marked postprandial changes (4.52 +/- 0.52 mmol/l, n = 15, weighted mean of 0, 3 and 6 h post-prandially). Diet GAL induced persistent hypoglycemia before and after feeding (2.58 +/- 0.38 mmol/l, n = 13) and considerable postprandial galactosemia (3.26 +/- 1.38 mmol/l, n = 7). In the groups STARCH and FAT, glucose was only detectable in traces in urine, whereas all diets containing sugars led to glucosuria. In group SUC, fructose and sucrose were found in urine and in both lactose groups galactose and lactose were found. Diet GAL led to galactosuria (140 mmol galactose/l). In group LAC1, and especially in group GAL, galactitol was detected in urine. These results point to a rather limited capacity of the cat to metabolize sugars.
Production of xylanase by Aspergillus awamori on complex medium in stirred tank and airlift tower loop reactors
Abstract Aspergillus awamori was cultivated on complex medium containing wheat bran as sole carbon source in the precultures as well as in the main cultures in stirred tank and airlift tower loop reactors. The decomposition of the wheat bran particles by α -amylase and xylanase produced by the fungus was investigated by monitoring the enzyme activities, the CO 2 production rate, the concentrations of reducing sugars, glucose, xylose, phosphate and ammonium as well as by applying transmission electron microscopy. By applying synthetic medium in the preculture, the time lag was longer, the growth faster, the xylanase activity higher in the main culture, than by using wheat bran in the preculture. With increasing the stirrer speed the intimate contact between the pellets and the wheat bran was reduced, which caused a decrease of the growth and the xylanase production. By applying ground wheat bran, filamentous mycelium was formed, the growth and the substrate uptake rates increased, but the xylanase production decreased due to the less intimate contact between the fungus and the wheat bran. In the airlift tower loop reactor filamentous mycelium was formed due to the low specific power input. In spite of the high medium viscosity, high xylanase productivity was obtained. With ground wheat bran the particles were completely covered by filamentous mycelium, medium viscosity strongly increased and as consequence the growth and xylanase production decreased.