Effect Of Supplementing Fish Oil And Sunflower Oil On Ruminal Fiber Digestion And Fibrolytic Enzyme Activities

Dietary combinational addition of fish oil and sunflower oil is one of the best strategies to enhance conjugated linoleic acid in ruminant product. It was reported that polyunsaturated fatty acid would exert negative effects on rumen function, thus affect fiber digestion. The study on dietary fish oil and sunflower oil combination's influence on fiber digestion was scarcely reported. This study is designed to evaluate these effects.Experiment 1. Four three site cannulated China Nooxi steers were used in a 4 x 4 Latin square study to determine the effects of including different levels of fish oil (FO) and sunflower oil (SFO) on fiber digestion when high forage diets were fed. Treatments were basal diet (forage to concentrate was 65:35, control), or basal diet with 3% SFO plus 1% FO (SF1), or basal diet with 2.5% SFO plus 1.5% FO (SF2), or basal diet with 2% SFO plus 2% FO (SF3). The steers were fed a relatively lower DMI that just met maintenance nutrition requirement. DM, OM, ADF and NDF digestion across rumen was not affected by treatments. Although SF3 tended to increase total tract digestion, the results from this study suggest fish oil inclusion does not decrease fiber digestion.Experiment 2. Four three site cannulated China Holstain dairy cows were used in a 4 x 4 Latin square study to determine the effects of DHA and/or free linoleic acid on fiber digestion when high forage diets were fed. Treatments were basal diet (forage to concentrate was 65:35, control), or 2.73% free linoleic acid (RFLA), or 2.73% free linoleic acid plus 0.45% DHA (RFLAO), or 0.45%DHA (RFFO). DM, OM, ADF and NDF digestion across rumen or arcoss the whole tract was not affected by treatments, while DHA seems to level up ruminal fibrolytic enzyme activities.Based on the results above, we conclude that when fed high forage diet, addition of fish oil or its active componet DHA into diet does not decrease fiber digestion, while fibrolytic enzyme activities tend to increase. For the two experiments were conducted under high forage condition, much attention should be paid when extended to other situations such as high production dairy cows or finishing beef cattle.