Effects of dietary protein content and addition of locust powder on the nitrogen balance

Locust (Inago, Oxya japonica) is an insect traditionally eaten for long years in Japan. A locust powder was added 3% to normal protein diet or low protein diet and was examined to the effects on nitrogen balance of rats. Twenty-four Wister strain 3-week-old male rats were divided into four groups by difference of protein levels (normal; 20% casein or low; 7% casein) and by additive or non-additive locust powder. The four groups are showed as follows, the 20% casein diet group (20%), the additive locust powder to 20% casein diet group (20%I), the 7% casein diet group (7%) and the additive locust powder to 7% casein diet group (7%I). At the third week of experiment, the nitrogen (N) balance test was conducted for four days, and then at the end of fourth week, rats were dissected. The body weight gain and organ weights (liver, kidney and spleen) of the 7% casein diet groups were lower than these of the 20% casein groups, and the effect of locust on these values were not observed. The amount of feces N excretion of the locust additive groups were higher than that of the locust non-additive groups, but the dietary protein level did not affect the amount of feces N excretion. The N absorption rate of the 7% casein diet groups were lower than that of the 20% casein diet groups, and the N absorption rate of the locust additive groups were lower than that of the locust non-additive groups. The amounts of N absorption and retention of the 7% casein diet groups were lower than that of the 20% casein groups. The effects of locust on the amount of N absorption and retention were not observed. These results showed that the addition of 3% locust powder to normal protein diet or low protein diet, which is 1/3 of normal level, did not affect N absorption and retention.