Estimating nutritional status of German cockroaches, Blattella germanica (L.) (Dictyoptera: Blattellidae), in the field

Nutritional status of German cockroaches from the field (HUD apartments) was estimated using uric acid content to measure amount of protein consumed, and respiratory quotient (RQ) to measure fat and carbohydrate metabolized. Initial trials demonstrated the stability of these two indicators as nymphal cockroaches grow and with timing of meals. Nutrient consumption (and presumed availability) was estimated by comparing uric acid content and RQ of nymphal cockroaches collected from kitchens of HUD apartments with those reared in the laboratory and provided a series of meridic diets. Uric acid content was linearly related to percentage of dietary protein (y=6.2x-32.07, r²=0.96)and RQ was linearly related to log₁₀(% fat:% carbohydrate) (y=- 0.148Log(x)+0.790, r²=0.68). Field-collected German cockroaches contained 10.9±7.7 to 22.9±5.1 μg/mg uric acid and RQ of 0.770±0.024 to 0.803±0.260. Comparatively, cockroaches provided rodent chow had greater uric acid content (125.1±9.6 μg/mg) and RQ (0.878±0.022). Employing linear calibration and these regressions, diet consumed by German cockroaches in the field was estimated at 7±3% to 9±3% protein and equivalent amounts of carbohydrates and fat as an energy source. German cockroaches in the field consume less protein and carbohydrates, and more fat compared to those provided a standard laboratory diet such as rodent chow. Diet available in the field is considered suboptimal, resulting in physiological stress; the biological implications of this stress are discussed.