Optimal Inclusion Levels of Cricket and Silkworm as Alternative Ruminant Feed: A Study on Their Impacts on Rumen Fermentation and Gas Production

Due to growing interest in alternative and sustainable high-quality feed sources for the livestock industry, we carried out a study to determine the optimal inclusion levels of two insect species ( Gryllus bimaculatus and Bombyx mori ) in a feed for ruminants, as well as evaluating their impacts on rumen fermentation characteristics and methane production. An experiment was performed using an in vitro model for 24 h with a ruminant diet (control group) of 60%:40% grass:concentrate, in order to investigate the effects of insect inclusion into the diet at 10, 20, 30, and 40%, through their substitution into the concentrate mixture. The rumen fermentation parameters indicated that each insect could be included in the diet up to 20% without adverse effects on nutrient digestibility, while increasing the production of ammonia-nitrogen. Increasing the inclusion level beyond 20% led to significant decreases ( p < 0.05) in the total gas production, nutrient digestibility, and volatile fatty acids production due to the high fat content in these dietary treatments. Therefore, G. bimaculatus and B. mori could be used as an alternative ruminant feed up to 20%, in order to replace high-quality feed ingredients. Formulating ruminant feed using insects as ingredients should take into consideration their fat content and the total dietary fat content.