Survival of hamsters fed graded levels of two protein sources

Two protein sources (supplemented casein and lactalbumin), which were well-utilized by Syrian hamsters in previous 3-week experiments, were fed in long-term studies. Casein supplemented with methionine and cysteine was fed for 20 weeks at levels of 4, 20, and 40 g/100 g diet. The lowest level did not support normal growth and resulted in the highest mortality rate during the first 10 weeks of feeding. The higher levels caused increased mortality in females, in association with decreasing body weights between 16 and 20 weeks. Kidney weights and incidences of lower nephron nephrosis at 20 weeks were elevated in both sexes fed the 40 g/100 g levels of supplemented casein by comparison with the 10 g/100 g level. In a separate experiment, lactalbumin was fed for life at 10, 20, and 40 g/100 g diet levels, and its effects compared to those with a commercial diet. The lactalbumin diet supported somewhat slower growth rates, but improved survival when compared to commercial diet-fed groups. Survival was longest in both sexes fed the 20 g lactalbumin/100 g diet levels for life.