Effect of Commercial Diets on the Nutritional Value and Mortality Rates of Dubia Roaches (Blaptica dubia)

Abstract Dubia roaches ( Blaptica dubia ) are a popular feeder insect but, like most other insects, have an inverse calcium to phosphorous (Ca:P) ratio. A plethora of insect diets claim to correct this inverse ratio, but limited evidence-based data exists. The goals of this study were to determine whether diets claiming to correct the Ca:P ratio can do so, to determine the effect of diet on the nutritional value and mortality of dubia roaches, and to determine the fasting period required to empty the gut of dubia roaches. In phase one, nymphal roaches were fasted (24 h) and randomly divided into a control group ( n = 6, baseline) and two experimental groups ( n = 6 each). Each cohort represented approximately 75–80 roaches. Roaches in the experimental groups were fed either 50 g of a high calcium diet or low calcium diet (24 h). The Ca:P ratio was significantly higher ( P < 0.001) in the high calcium group compared with the control and low calcium diet groups. In phase two, adult roaches (25.4–31.8 mm) were fasted (24 h) and then gut-loaded for 24 or 168 h on a high calcium or low calcium diet ( n = 6/group). The Ca:P ratio was significantly higher ( P < 0.001) in the high calcium group compared with the low calcium diet group, regardless of time. No significant difference (all P > 0.06) in mortality occurred across diets or overtime. In phase three, adult roaches were fasted (24 h), gut-loaded on the high calcium diet (24 h), and then fasted for 24, 48, or 72 h ( n = 3). The Ca:P ratio did not decrease over time ( P = 0.092). These results confirm that a high calcium diet can increase the Ca:P ratio in dubia roaches; however, not all gut-loading diets can alter the Ca:P ratio.