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.
Effects of dietary supplementation with increasing doses of lactose on faecal bacterial populations and metabolites and apparent total tract digestibility in adult dogs
Abstract The effect of increasing dietary doses of lactose on canine faecal microbiota and apparent digestibility was evaluated. Fourteen adult healthy dogs [1–5 years of age, mean body weight (BW) of 19.0 kg] were fed with an extruded diet containing silica (5 g/kg) as a digestion marker. After a 20 d adaptation period, increasing doses of lactose were added to the dogs’ diet (0.5, 1 and 2 g/kg BW0.75/d) during three consecutive 20-d supplementation periods. Faeces were collected at the end of each period for analyses. Four dogs refused the diet added with lactose at 0.5 g/kg BW0.75/d and were excluded from the trial, as well as two dogs, which developed acute diarrhoea when lactose was fed at 1 g/kg BW0.75/d. Conversely, eight dogs remained healthy throughout the study. Faecal moisture was influenced by lactose (quadratic, p = .001), while faecal pH and ammonia were not affected by treatments. Lactose supplementations tended to linearly decrease isovalerate (p = .051) and quadratically influence n-valerate (p = .056) in canine faeces. No changes in faecal microbial populations were observed. Apparent digestibility of dry matter, Ca, K, Mn and Fe was influenced by lactose supplementation (quadratic, p < .05). Increasing doses of lactose linearly decreased Mg digestibility (p < .05). Furthermore, coefficients of crude protein, crude ash, P, Mg and Zn digestibility were tendentially affected (quadratic, p = .055, .089, .091, .065 and .065, respectively). In conclusion, 8 of 14 dogs displayed a good tolerance (absence of gastrointestinal signs) up to the highest dose of lactose (2 g/kg BW0.75/d). An evident prebiotic effect was not observed.
Studies on disaccharidase activities of the small intestine of the domestic cat and other carnivorous mammals.
1. 
1. The hydrolysis of disaccharides by homogenates of small intestinal mucosa from five carnivorous mammals was investigated. Maltase, sucrase and lactase activities were present in the small intestine of the domestic cat, lion, ferret, dog and polar bear. Trehalase activity was absent from the intestine of the domestic cat and lion, but was present in the other carnivores. 
 
2. 
2. A detailed investigation was made of intestinal lactase levels in cats of various ages. Lactase activity was high at birth and decreased to relatively low levels in the adult animal. The decline in activity occurred most rapidly during 4–7 weeks of age, which coincides with the weaning period. 
 
3. 
3. Evidence for the existence of at least two intestinal β-galactosidases in the domestic cat was obtained. One is a soluble enzyme which hydrolyses ortho-nitrophenyl β-galactoside but not lactose; the other is a particulate enzyme which catalyses the hydrolysis of both substrates.