Developmental changes in the composition of Beagle dog milk.

The concentrations of iron, copper, zinc, manganese, calcium, magnesium, protein, carbohydrate, and fat were analyzed in dog milk during the first 45 days of lactation. The concentration of iron decreased significantly from 13 microgram/ml on day 0 to 6 microgram/ml. Zinc concentration decreased only slightly from 9.6 microgram/ml to 8.7 microgram/ml. Calcium concentration increased significantly during early lactation, from 1,366 microgram/ml to 1,757 microgram/ml on day 10, but changed little thereafter. Protein concentration increased throughout lactation, from 4.3% early in lactation to 6.3% late in lactation. Fat concentration increased from 2.4% to 4.5% in early lactation, and then decreased to 2.7% in late lactation. The concentrations of copper, manganese, magnesium, and carbohydrate did not show strong developmental patterns; average values were 1.8 microgram/ml, 0.14 microgram/ml, 59 microgram/ml, and 4.5%, respectively, throughout lactation. These data indicated that the nutrient intake of the pup changed markedly during the early neonatal period and that these changes should be taken into account in evaluating studies of suckling dogs.