Use of Crickets in a Bioassay of Forage Quality in Tall Fescue1

Abstract

Feeding trials were conducted to test the validity of using crickets (Acheta domesticus L.) to assay the quality of forages intended for ruminant feed. Diets of forage from diverse genotypes of tall rescue (Festuca arundinacea Schreb.) produced significant differences in survival and growth rate of crickets. Certain tall rescue genotypes were consistently ranked high on the basis of cricket performance compared to others that caused almost complete mortality in all trials. Survival and growth rate were not related to in vitro digestibility; tensile strength of the leaves; and concentration in the forage of lignin, acid detergent fiber, cellulose, and ash.A feeding trial was conducted to study the relationship between cricket performance and toxicity of tall rescue to cattle. Anion, cation, and neutral fractions, were prepared from extracts of two genotypes representing opposite extremes on the basis of cricket performance in earlier trials. These and other extracts of interest were included in cricket diets. Results indicated the presence of an inhibitory substance in the cation fraction of the genotype found to cause a high rate of mortality. This entity is probably not associated with “fescue foot” toxicity in cattle, because the toxic principle responsible for that syndrome is most likely in the anion fraction. However, the effect of the cation fraction and other forage attributes associated with cricket survival and growth on the performance of ruminants, merits additional study.