Fatty acid profiles of some insect oils and their effects on in vitro bovine rumen fermentation and methanogenesis

Abstract

This experiment aimed to establish the fatty acid profiles of oils from selected insect species and to evaluate their effects on in vitro rumen fermentation and methanogenesis. Insect samples, namely maggots, krotos, superworms, mealworms and crickets, were subjected to oil extraction using hexane in a Soxhlet apparatus. The fatty acid composition of the oils was subsequently determined. The insect oils were added at 5% dry matter to two kinds of diets, high forage (70% forage + 30% concentrate) and high concentrate (30% forage + 70% concentrate), which represented the diets of dairy cows and beef cattle, respectively. These diets, together with a control for each (without any addition of insect oil), were incubated in an in vitro rumen fermentation system, performed for three runs, with each run represented by two incubation units. Therefore, in total 2 × 6 treatments were incubated: the two types of diet (high forage and high concentrate) and the addition (or not) of insect oils (no addition, maggot, kroto, superworm, mealworm and cricket). The data were analysed by using two-way analysis of variance (ANOVA), followed by Tukey’s test. The results revealed that maggot oil was dominated by C12:0 (43.1% from total fatty acids), whereas the main fatty acids present in kroto oil were C18:1n-9 (38.8%) and C16:0 (20.8%). Superworm oil, mealworm oil and cricket oil were rich in C16:0 (19.5–31.2%), C18:1n-9 (25.8–44.6%) and C18:2n-6 (24.0–27.9%). In no case was the interaction between substrate and the addition of insect oil significant for any of the parameters. The addition of insect oil reduced the methane emission of the incubated substrates (p < .05) without altering total volatile fatty acid concentration, with mealworm oil resulting in the lowest level of methane among the insect oils. The oils had no significant effect on ruminal ammonia concentration. Generally, the addition of insect oil reduced the dry and organic matter digestibility of the substrates (p < .05). In conclusion, insect oils are rich in medium-chain and monounsaturated fatty acids (MUFA), and have the ability to mitigate enteric methane emission.Highlights Oils from various insects, namely maggots, krotos, superworms, mealworms and crickets, were extracted, characterised for their fatty acid profiles, and evaluated for their effects on in vitro rumen fermentation and methanogenesis. Maggot oil was dominated by C12:0, whereas the main fatty acids present in kroto oil were C18:1n-9 and C16:0. Superworm, mealworm and cricket oils were rich in C16:0, C18:1n-9 and C18:2n-6. The addition of all the insect oils reduced methane emissions in the high forage and high concentrate substrates, without altering total volatile fatty acid concentration.

Keywords

• insect
• fat
• fatty acid
• methanogenesis
• rumen fermentation