Inclusion of oils in the in vitro fermentation of elephant grass (Pennisetum purpureum Schum. cv. Cameroon)

ABSTRACT The objective of this study was to assess the impact of incorporating vegetable oils into the in vitro fermentation of a tropical grass on the kinetics and digestibility of the fibrous fraction by rumen microorganisms. Treatments consisted of different inclusion levels (0, 2, 4, and 6% dry matter) of lipid sources, namely soybean oil, canola oil, and baru oil, mixed with tropical forage (Pennisetum purpureum Schum cv. Cameroon). A completely randomized design was employed, featuring a 3 × 4 factorial arrangement (three lipid sources at four inclusion levels), resulting in 12 treatments, each with three replications. We examined the kinetics of rumen fermentation using the semi-automatic in vitro technique of cumulative gas production. Oil inclusion levels had a significant impact on in vitro gas production and lag time (P<0.0001), with values decreasing as the oil inclusion levels were increased, with no effect of sources. Furthermore, the digestibility of forage neutral detergent fiber (NDF) was negatively affected by higher oil inclusion levels, with significant differences observed among the lipid sources tested (P<0.0013), with improved digestibility effect for baru oil. The production and profile of short-chain fatty acids were also influenced by oil inclusion level factors; however, the influence of different lipid sources was only evident in treatments with 6% inclusion. Baru oil can be a potential dietary alternative for ruminant supplementation in the intake of tropical forages, as it presented the lowest adverse effect on the in vitro digestibility of NDF among the lipid sources used, such as soybean oil.