Whole dried black soldier fly (Hermetia illucens) larvae are acceptable, palatable, and do not negatively affect health when fed to healthy, adult horses at low inclusion rates

Abstract

Black soldier fly larvae (BSFL) have the potential to be incorporated into equine feed as a sustainable and nutritionally dense insect-derived source of protein and fat. The purpose of this study was to investigate the suitability of whole dried BSFL as a novel protein source in equine diets based on acceptability, palatability, and various health parameters. Seventeen horses (15.2 ± 7.0 years; 596 ± 122 kg body weight (BW) (mean±SD)) and three ponies (19.7 ± 0.6 years; 364 ± 53 kg) were separately fed a BSFL-based supplement (TRT) and a roasted soybean-based supplement (CON) (0.75 g crude protein per kg BW^0.75) for 28-days using a cross-over study design. Feed intake was recorded throughout the feeding periods to assess the acceptability of the novel ingredient. Body weight, body condition score (BCS), plasma biochemistry, and complete blood counts were assessed at the beginning and end of each treatment period as markers of health status. After the cross-over study, two-bowl tests were used to assess the palatability of the BSFL supplement, with or without the presence of other concentrates. Minimal differences were observed between treatment groups for biochemical analytes and complete blood counts, and BW and BCS did not change throughout the study period. Both supplements were willingly consumed by the horses over the 28-day feeding periods, though feed intake was 8% greater in the CON compared to the TRT group (P<0.01). For the palatability tests, horses first approached (P=0.03) and first consumed (P=0.03) the CON more frequently than the TRT supplement when the supplements were supplied with other concentrates. When the supplements were offered in the absence of other concentrates, there was no difference in which bucket was approached first, but horses tended to first consume the CON rather than the TRT supplement. Overall, these data indicate that dietary consumption of BSFL for 28 days at a low-inclusion rate results in no negative health outcomes in horses; however, longer-term studies are warranted to further examine physiological effects of consuming BSFL and at higher inclusion rates. Though horses did favour the CON supplement based on palatability parameters, horses willingly consumed the BSFL supplement, indicating that BSFL at low inclusion rates may be considered a palatable ingredient in equine diets.