COMPARISON OF THE EFFECTS OF LAB CHOW AND CASEIN DIETS BASED ON BODY AND BRAIN-DEVELOPMENT OF RATS

1. In order to study the effects of protein quantity and quality on de velopment, Wistar rats were submitted to four different diets during l actation and post-lactation periods. Three isocaloric diets were utili zed with 6% (M), 16% (W16) and 20% (W20) of protein (casein), and the fourth diet (C) consisted of a commercial lab chow containing 22% prot ein. 2. During the lactation and post-lactation periods the body weigh ts of dams and pups were recorded weekly. On the 49th day of age (21 d ays of suckling and 28 days of ad libitum chow), all animals were sacr ificed and the brains removed and weighed. 3. Dams from all groups inc reased food intake during the lactation period, but dams of the M grou p consumed a lower amount of diet as compared with other groups. Only the body weight of M dams was affected by diet during the lactation pe riod, but the body weight of pups from the M and C groups was lower th an in the other two groups. At 49 days of age C and M pups showed a si gnificantly lower brain weight compared with W16 and W20 pups. 4. Thus , a commercial lab chow diet does not promote normal body and brain de velopment as compared with balanced diets containing 16 or 20% protein . These results emphasize the need for further studies in order to eva luate other biological and behavioral parameters that might be altered by a lab chow diet.