Insects as Novel Ruminant Feed and a Potential Mitigation Strategy for Methane Emissions

SIMPLE SUMMARY: In the last decade, there has been a growing interest in using edible insects as animal feed due to their high nutritive value and environmental advantages over the conventional livestock feeds. Insects have been used in the diets of some animals (poultry, fish, and swine) however, their evaluation in ruminants is still limited. The current in vitro study evaluated the usage of four different kinds of edible insects to partially substitute soybean meal as an example to the conventional high-quality expensive protein sources in ruminants’ diets. This study showed that the evaluated insects had high protein and fat contents. Substitution of 25% of soybean meal with the tested insects in a ruminant diet had no adverse effect on rumen fermentation profile or nutrient digestibility. Moreover, the inclusion of some species in the diet led to a reduction of the methane production up to 16–18% which is an additional environmental benefit. The findings of this study are encouraging for further work in this promising area to improve the sustainability of livestock industry. ABSTRACT: This study is the first to evaluate the chemical composition and impacts of four different edible insects, Acheta domesticus (A.d), Brachytrupes portentosus (B.p), Gryllus bimaculatus (G.b), and Bombyx mori (B.m), on the digestibility, rumen fermentation, and methane production when used as a substitute for 25% of the soybean meal (SBM) in a ruminant diet through in vitro incubation. The dietary treatments were 100% grass hay, 60% grass hay + 40% SBM, 60% grass hay + 30% SBM + 10% A.d, 60% grass hay + 30% SBM + 10% B.p, 60% grass hay + 30% SBM + 10% G.b, and 60% grass hay + 30% SBM + 10% B.m. The experiment was conducted as a short-term batch culture for 24 h at 39 °C, and the incubation was repeated in 3 consecutive runs. Chemical analysis of the insects showed that they were rich in fat (14–26%) with a high proportion of unsaturated fatty acids (60–70%). Additionally, the insects were rich in protein (48–61%) containing all essential amino acids and the amino acid profiles of the insects were almost the same as that of SBM. The inclusion of insects did not affect nutrient digestibility or the production of volatile fatty acids but did increase the production of ammonia-nitrogen. The addition of G.b and B.m led to decrease in methane production by up to 18% and 16%, respectively. These results reveal that substitution of 25% SBM in the diet with the tested insects had no negative impacts, and their potential to reduce methane production is an environmental benefit.