Use of mealworm (Tenebrio molitor) oil in a concentrate-base diet for lamb fattening: Effect on in vitro ruminal biohydrogenation and fermentation

There is a global need for the search for alternative energy sources for livestock, with insect oils being a promising option. The use of Tenebrio molitor oil (TMO) in ruminant feeding has barely been investigated. However, its inclusion in fattening lamb diets could be of interest not only as an energy source, but also as a potential modulator of ruminal biohydrogenation (BH). This study was conducted to assess the effects of replacing soybean oil (SBO) and palm distillate fatty acids (PFA) by TMO on in vitro ruminal BH and fermentation. A 10:90 forage:concentrate substrate, mimicking a diet typically used for lamb fattening, was supplemented with 2% DM of TMO, SBO or PFA and incubated for 8 h using batch cultures of rumen microorganisms. A comprehensive analysis of the TMO allowed the identification of several minor FA that are rarely reported (e.g., iso 15:0, anteiso 15:0, cis -9 trans -11 18:2, 10-oxo-18:0). Effects on the digesta fatty acid (FA) composition were mainly related to the contribution to the rumen digesta of the major FA provided by the lipid supplements (e.g., 16:0 with PFA, cis -9 18:1 and 14:0 with TMO, and cis -9 cis -12 18:2 with SBO) or to the BH of dietary unsaturated FA (e.g., trans -11 18:1 and other trans -MUFA with SBO and TMO, and cis -MUFA with TMO). Results of ruminal fermentation suggest no significant negative effects of TMO compared to PFA and SBO. Overall, the use of 2% DM of TMO could be a suitable alternative energy source to replace PFA and SBO in diets for fattening lambs.