In captivity the diversity of prey items for obligate insectivores is limited and nutritionally inadequate, leading to nutrient deficiencies. Zoological institutions utilize gut-loading, an insect supplementation technique, to compensate for these nutrient shortcomings. This study developed a gut-loading diet (GLD) to enhance the nutritive quality of the domestic house cricket (Acheta domestica) for insectivorous amphibians and reptiles, with the requisite that it also met cricket foraging and palatability needs. Gut-loaded cricket analysis established its effectiveness such that the targeted level of most nutrients required by the end consumers were met after consuming the diet for 24 hrs (Ca:P of 1.127; vitamin A (retinyl acetate) level of 12,607 IU/kg; vitamin E level of 342 IU/kg and a linoleic fatty acid level of 4.62%), peaking at 2 days for some and remained above targeted amounts for at least 4 days. A list of cricket gut-loading optimization husbandry procedures has also been recommended.

Captive insectivores may consume invertebrates as all, or part of their overall diet. The challenge with feeding captive insectivores involves the limited number of invertebrate species that are commercially available, and the lack of key nutrients provided by these insects. Among these insects, a naturally occurring low concentration of calcium and an inverse calcium to phosphorus ratio may put insectivores at the risk of developing hypocalcemia. A strategy to correct this nutrient imbalance involves supplementing the insect diet with high concentrations of targeted nutrients – a term referred to as gut-loading. Current industry guidelines recommend feeding a supplemented diet for 48 to 72 h before offering the insect to an insectivore. In the present study, the mineral profile of adult crickets (Acheta domesticus) offered a maintenance diet (1.58% Ca, DMB) are compared to crickets offered a supplemented diet (11.32% Ca, DMB) over 120 h. The supplemented diet produced a cricket with significantly higher calcium concentration compared to the maintenance diet. The calcium concentration of crickets offered the supplemented diet was highest at 48 h (0.63%), but did not achieve a 1:1 Ca:P ratio nor meet the lowest reported nutrient requirements of carnivorous reptiles, omnivorous reptiles, or an insectivorous bird at various life stages. Although the supplemented diet improved the whole body calcium concentration in feeder crickets, the crickets do not provide adequate calcium, iron, or manganese to meet the requirement of insectivores. As evidenced by the current study, the supplemented crickets are not recommended to serve as the sole source of nutrition for an insectivore.