Influence of a low carbohydrate diet on performance of pregnant and lactating dogs.

Beagle bitches, obtained 3 weeks post-conception, were fed one of two diets; diet 1 contained 44% of metabolizable energy from carbohydrate and diet 2 contained 0% of metabolizable energy from carbohydrate. Bitches consumed similar amounts of energy from the two diets. Plasma glucose levels were similar in bitches fed the two diets, except in the week before whelping. At this time, plasma glucose levels as low as 15--20 mg/dl were observed in several bitches fed diet 2. None of the bitches fed diet 1 exhibited hypoglycemia. Bitches fed diet 2 also had depressed plasma levels of alanine and lactate and elevated levels of free fatty acids and B-hydroxybutyrate near the end of gestation. Total number of pups whelped by the bitches was unaffected by diet, but fewer pups from bitches fed diet 2 were alive at birth (63%) than from bitches fed diet 1 (96%). Only 35% of the pups whelped by bitches fed diet 2 were alive at 3 days of age. Milk from bitches fed diet 2 had a lower percentage of energy from lactose and a higher percentage of energy from fat than did milk of bitches fed diet 1. Growth of pups, however, was unaffected by composition of diet fed to the bitches. We concluded that pregnant bitches require dietary carbohydrate for optimal reproductive performance.

Influence of prolonged fasting in the dog on glucose turnover and blood metabolites.

Glucose turnover and blood metabolites were measured in eight adult female beagles in the fed state, at 1 day of fasting, and at 7, 14, and 21 days of fasting. Glucose utilization decreased significantly from 1 to 7 days of fasting, but remained constant from 7 to 21 days, while blood ketones and plasma free fatty acids rose significantly during the same period. Plasma alanine, serine, and glycine fell with fasting, with the greatest decrease in alanine levels occurring between 7 to 14 days. Plasma branched chain amino acids rose significantly with fasting. It was concluded that the shifts in plasma metabolites and decreased glucose utilization could be indicative of decreased energy demands of the fasting dogs and/or a shift in substrate utilization with progressive fasting.

Influence of meal frequency on in vivo hepatic fatty acid synthesis, lipogenic enzyme activity, and glucose tolerance in the chicken.

Chicks were allowed access to food for 2 hours per day (meal-fed) or were fed ad libitum. Tritiated water was administered intravenously, and the incorporation of tritium into fatty acids was used to estimate in vivo rates of fatty acid synthesis. Allowing the meal-fed chick access to a meal increased the hepatic rate of fatty acid synthesis up to 50-fold. Hepatic activities of malic enzyme and fatty acid synthetase were similar before and after the meal. The rate of fatty acid synthesis was greater in the fed meal-eater than in the ad libitum-fed chichen. Plasma free fatty acid levels were decreased and plasma triglyceride levels were increased when the meal-eater was fed. Oral and intravenous glucose tolerance tests were conducted. Meal-feeding did not impair glucose tolerance in the chicken, as has been reported in meal-fed humans. Unlike in the rat, intravenous glucose tolerance was not greatly influenced by meal pattern in the chicken. Oral glucose tolerance was improved in one of two experiments as a consequence of meal-eating. These results suggest that the chicken does respond to a shift in meal pattern.