Ruminal fermentation in vivo as influenced by long-chain fatty acids.
Responses of ruminal microbes to long-chain fatty acids in forms of free acids, calcium salts, or triglycerides were measured in trials with rumen cannulated heifers. Addition of fatty acids at 10% to a basal diet of 50% corn silage and 50% grain increased fat content 3 to 10 to 12%. Long-chain fatty acids with a high melting point (stearic acid) and calcium salts of long-chain fatty acids (vegetable fat and tallow) decreased acetate:propionate by about 20%. Long-chain fatty acids with a low melting point (oleic acid) and the triglyceride form of long-chain fatty acid (tallow) decreased acetate to propionate ratio by 50 to 60%. Even though they were not completely inert in the rumen, responses with the hard long-chain fatty acids (stearic acid) and with calcium salts of long-chain fatty acids confirm that these are efficacious for protecting ruminal microbes from adverse effects of fat. With calcium salts of long-chain fatty acids, dietary buffers may be needed to maintain ruminal pH so that dissociation of salts does not occur. Long-chain fatty acid supplementation at 10% of the diet is probably more than the amount needed to optimize productivity and health. With most diets, 6 to 8% supplemental long-chain fatty acid is probably sufficient.
D000818:Animals; D002417:Cattle / Q000502:physiology*; D004041:Dietary Fats / Q000378:metabolism* / Q000494:pharmacology; D005227:Fatty Acids / Q000378:metabolism / Q000494:pharmacology; D005285:Fermentation; D019301:Oleic Acid; D009829:Oleic Acids / Q000494:pharmacology*; D012417:Rumen / Q000187:drug effects / Q000378:metabolism*; D013229:Stearic Acids / Q000494:pharmacology; D014280:Triglycerides / Q000494:pharmacology*
D004041:Dietary Fats; D005227:Fatty Acids; D009829:Oleic Acids; D013229:Stearic Acids; D014280:Triglycerides; D019301:Oleic Acid; C031183:stearic acid