Milk fat concentration and growth of rat pups

The relationship between milk fat concentration and the growth of rat pups from birth to the 20th day was investigated. A total of 36 first-time-lactating Wistar rats and 366 pups from litters of 8-12 were used. The concentration of milk fat was determined by the crematocrit method, on the 2nd, 5th, 10th, 15th, 20th and 25th day of lactation. A wide range of milk fat concentration with a great variability in each individual dam was observed during lactation. To correlate milk fat and pup's growth, the mean value of the milk fat of the individual mothers was calculated for the first 10 days from the values of the 2nd, 5th and 10th day of lactation, and for the second 10 days from the values of the 10th, 15th and 20th days. The results show that pups fed higher fat milk in the first 10 days of life grew faster than pups fed lower fat milk. A significant positive correlation (P < 0.001) was found between the fat concentration of milk and the weight gains of pups in the first 10 days, but not in the older groups. It indicates that the fat concentration of milk is important for the growth of pups mainly in the early postnatal period of life.