Supplemental value of soybean protein to rice as measured by growth rate of rats

Weanling male Sprague-Dawley rats were randomly assigned to 9 groups of 8 animals each and were given diets containing 8 per cent protein supplied from rice flour and soybean protein in the following ratios: 8:0; 7:1; 6:2; 4:4; 2:6; l:7 and 0:8. A diet containing 8 per cent protein from casein and a non-protein diet served as controls. The supplementary value of soybean protein to rice flour was evaluated during a 28-day growth period and a 7-day nitrogen balance study.

Growth rate. protein efficiency ratio, nitrogen balance, biological value and net protein utilization increased with increasing amounts of soybean protein in a rice/soybean mixture from 8:0 to 4:4. An all soybean protein diet (0:8) supported little or no growth. Rats fed an all rice diet equaled the growth of rats fed the diet containing 7:1 of rice and soybean. It appears that a ratio of 6:2 and 4:4 of rice: soybean possesses the best protein value among the other combinations. No statistically significant difference was observed between the combinations of 6:2 or 4:4 of rice and soybean. However, the diet containing 75 per cent rice flour and 25 per cent soybean in a total of 8 per cent protein, would probably be the best combination to recommend because from an economic viewpoint, such a diet, having less protein, would be less expensive. Moreover this diet because of its higher rice content, would undoubtedly be more acceptable to populations in which rice is the major dietary staple.