Comparative Effects of Casein and Amino Acid Mixture Simulating Casein on Growth and Food Intake in Rats

Abstract

In several feeding methods, the effect of the amino acid mixture simulating casein on rat growth was compared with that of intact casein. When diets were provided ad libitum, weight gain and food intake were lower for rats fed amino acid diets than those fed a casein diet at dietary nitrogen levels of 3.2 and 4.8%, whereas no difference was observed between both the nitrogen sources at 0.8 and 1.6% levels. The superiority of casein was also found in pair-feeding experiments in which casein diet was pair-fed with amino acid diet on a daily basis at a nitrogen level of 3.2%. When animals were space-pair-fed for 1 hour twice daily, however, both diets supported identical growth during the 14-day experimental period. Identical growth rates were also obtained by force-feeding the same amounts of both diets. These results indicate that the amino acid mixture simulating casein is nutritionally equivalent with intact casein under conditions of space-feeding twice daily to pair-fed partners.