Effect of amount and source of vegetable oils in a high fibrous cattle diet on in vitro rumen fermentation, nutrient degradability and rumen cis-9, trans-11 CLA concentration

Abstract

Four diets with two vegetable oils at two different levels were evaluated for their in vitro rumen fermentation pattern, nutrient degradability and cis-9, trans-11 CLA production using a rumen simulation technique (RUSITEC). Control diet (C) was having roughage to concentrate in the ratio of 65:35. Treatment diets were formed by supplementing with sunflower oil (SF) and soya bean oil (SB) at 4.5 (SF4.5, SB4.5) and 6.0% (SF6, SB6) levels and incubated in RUSITEC fermenters. After seven days of adaptation period, fermentation parameters, nutrient degradability and rumen cis-9, trans-11 concentration were assessed for the next 3 days. Cis-9, trans-11 conjugated linoleic acid (CLA) content was higher in effluent from diets supplemented with 6% oil compared to that of control and 4.5% oil. SF6 and SF4.5 were more effective in increasing rumen cis-9, trans-11 CLA compared with corresponding levels of soya bean oil. However, the degradability of dry matter, acid detergent fibre, neutral detergent fibre and hemicellulose was significantly (P<0.05) reduced in SF6 and SB6 diets. Significantly (P<0.05) higher pH, lower proportion of acetate and butyrate and higher proportion of propionate were indicative of the aforementioned changes in the corresponding fermenters. Rumen fermentation pattern and nutrient degradability were not affected in SF4.5 and SB4.5 diets. The study indicated that vegetable oil supplementation at 6% level was deleterious for rumen fermentation and nutrient degradability despite an increase in cis-9, trans-11 CLA.