Abstract: 【Aim】 This study aims to explore the effects of dietary protein level on the nutrient utilization and nitrogen metabolism in Blattella germanica, so as to provide new ideas for the development of cockroach bait. 【Methods】 The nutritional efficiency parameters and nitrogen utilization rate in male adults of B. germanica fed on four diets containing different protein levels (5%, 25%, 45% and 65%) were evaluated by using standard gravimetric procedure method. The activities of xanthine oxidase, glutamic oxaloacetic transaminase, glutamic pyruvic transaminase and uric acid in male adults of B. germanica fed on the diets containing different protein levels were determined by using spectrophotometric method. 【Results】 The male adults of B. germanica fed on the diet containing 65% protein had the highest relative consumption rate. The efficiency of conversion of ingested food, efficiency of conversion of digested food and relative growth rate of male adults fed on the diet containing 45% protein were significantly higher than those fed on the diets containing 5% and 65% protein. The nitrogen content, fecel nitrogen content, nitrogen consumption rate, nitrogen excretion rate, nitrogen production rate, nitrogen assimilation efficiency, xanthine oxidase activity and uric acid content in male adults increased with the increase of protein content in diets. However, the male adults fed on the diet containing 65% protein had the lowest nitrogen utilization rate. Besides, the group fed on the diet containing 45% protein had the highest glutamic oxaloacetic transaminase activity. The glutamic pyruvic transaminase activities in male adults fed on the diets containing 25% and 45% protein were significantly higher than those in male adults fed on the diets containing 5% and 65% protein. 【Conclusion】 Diets containing moderate protein level are beneficial to the utilization of food and nitrogen in B. germanica adults, and under the condition of high protein content the activities of glutamic oxaloacetic transaminase and glutamic pyruvic transaminase decrease, suggesting that high protein level will increase the burden of metabolism of B. germanica and is unfavorable to its utilization of food.

Key words: Blattella germanica, protein level, enzyme activity, nutritional utilization, nitrogen