Insect oils and chitosan in sheep feeding: Effects on in vitro ruminal biohydrogenation and fermentation

Abstract

Oils derived from insect defatting may represent novel alternatives to expand the range of lipid supplements in ruminant feeding, both to increase the energy density of diets and to improve the fatty acid (FA) profile of milk and meat through modulation of ruminal biohydrogenation. Furthermore, insect chitosans might also modulate FA biohydrogenation, as indicated for chitosans from crustaceans. Thus, this work was conducted to assess the potential of different insect oils (as an alternative to soybean oil), insect chitosan and their combinations to modulate ruminal biohydrogenation. A second objective was to evaluate the effect of these products on ruminal fermentation, to make sure that they would not detrimentally affect diet utilization. The trial followed a 5 × 2 factorial design (10 treatments in total): (1 control, without added oil, + 4 oil supplements) × (absence or presence of chitosan), and was conducted in vitro using batch cultures of rumen microorganisms. The incubation substrate was supplemented with 0 or 20 g/kg DM of oils from soybean, black soldier fly, cricket or silkworm, whereas chitosan (from black soldier fly) was added at 0 or 30 g/kg DM. Four cannulated ewes were used as inocula donors and treatment effects on in vitro ruminal biohydrogenation and fermentation parameters (i.e., gas production, ammonia concentration, volatile FA production and molar proportions, and dry matter disappearance) were examined after 16 h of incubation. Insect oils modulated FA biohydrogenation, with effects that were directly linked to their degree of unsaturation. Results supported that the three insect oils may conveniently substitute soybean oil because they would not exert negative effects on ruminal fermentation. In order to promote the ruminal accumulation of bioactive FA (e.g., trans-11 18:1 and cis-9 trans-11 18:2), cricket oil would represent the most interesting alternative to soybean oil, because it increased the potentially health-promoting trans-11 18:1 without altering trans-10 18:1 concentration. However, the negligible effect of black soldier fly oil on unsaturated FA profile suggested a lower interest of this fat to improve milk or meat FA profile. Furthermore, the dietary addition of insect chitosan did not seem to favorably modify ruminal FA biohydrogenation or fermentation parameters.