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Impact of combinations of dietary palmitic, stearic, and oleic acids on rumen fermentation and fiber digestibility.

F. Batistel

Events

06-23-2020

Abstract:

181
Impact of combinations of dietary palmitic, stearic, and oleic acids on rumen fermentation and fiber digestibility.
O. Gonzalez1, A. Sears1, J. de Souza2, F. Batistel*1. 1Department of Animal, Dairy and Veterinary Sciences, Utah State University Logan, UT, 2Perdue Agribusiness Salisbury, MD.

Previous research demonstrated that palmitic and/or oleic acid enhanced fiber digestibility. Since palmitic, stearic, and oleic acids are the main fatty acids (FA) present in ruminal bacteria cells we hypothesized that readily available 16- and 18-carbon FA from the diet are incorporated into rumen bacterial membranes supporting growth. Thus, our objective was to evaluate the effect of combinations of palmitic, stearic, and oleic acid on fiber digestibility and rumen fermentation. Continuous culture fermenters (n = 8) were used in a replicated 4 � 4 Latin square design. Treatments were: 1) Control diet with no supplemental FA (Total FA: 2.2%; Control); 2) Control diet plus 0.9 g of palmitic acid (Palmitic); 3) Control diet plus 0.29 g of palmitic, 0.56 g of stearic, and 0.05 g of oleic acid (Pal/Ste/Ole); and 4) Control diet plus 0.83 g of stearic, and 0.07 g of oleic acid (Ste/Ole). All FA treatments were supplemented at 1.5% DM diet. Treatment 2 was the positive control; treatment 3 mimicked the bacterial phospholipid 16- and 18-carbon FA profile, while treatment 4 mimicked the bacterial phospholipid 18-carbon FA profile. The control diet (40 g DM/day) was a 50:50 orchardgrass hay:concentrate mixture that provided 8.7 g CP, 21 g NDF, 11 g starch, and 1.5 g FA fed twice daily. Data were analyzed using a mixed model including the fixed effect of treatments, and the random effects of period and fermenter. Data are reported as least squares means with differences declared at P ≤ 0.05. Three pre-planned contrasts were tested: 1) Control vs. Pal/Ste/Ole; 2) Pal/Ste/Ole vs. Ste/Ole; and 3) Pal/Ste/Ole vs. Palmitic. Compared with control, Pal/Ste/Ole increased NDF digestibility (43.8 vs. 39.5%, P = 0.05). Furthermore, Pal/Ste/Ole increased NDF digestibility compared with Ste/Ole (43.8 vs. 36.2%, P < 0.01). Compared with control, Pal/Ste/Ole increased total VFA production (198 vs. 169 mmol/d, P = 0.04). Ammonia concentration was not affected by treatments. Our preliminary results indicate that supplying dietary fatty acids that mimics the bacterial phospholipid 16- and 18-carbon FA profile favors ruminal fiber digestibility and VFA production.

Keywords: fatty acids, rumen, fiber.