Making a pest useful: Can dermestid beetles help evaluate pet food protein quality?

Current pet food ingredient utilization studies test general macronutrient bioavailability using vertebrate models such as rats or chicks for target species of companion animals, which require approval and regulations from the Institutional Animal Care and Use Committee (IACUC) as stated in the US Animal Welfare Act. Currently, the only invertebrate evaluated under IACIC are cephalopods; hence, insects may be model candidates of interest. We hypothesized that certain dermestid beetles may be useful in protein quality evaluations because they are natural pests of protein rich stored products including pet foods. Three dermestid larvae were selected, Trogoderma variabile (warehouse beetle), Trogoderma inclusum (larger cabinet beetle), and Dermestes maculatus (hide beetle), as models since they efficiently transform the energy from food sources at measurable growth rates and are known to have high protein content diets. Thirty beetle larvae of each species were placed on treatment diets including a control containing a known and complete protein composition or no protein composition (negative control). Larval weight at a common growth stage, second instar, were compared to test protein efficiency ratio (PER), which reflects their protein conversion efficiency. Initial experimental data showed that the larvae had too long of a feeding period as they grew to the next instar. This interfered with the study; however, one species showed a much better PER than the others in comparison. Preliminary experimental results suggest that hide beetles are a prospective new model organism for evaluating protein quality in pet foods and could serve as an alternative to vertebrate models.