Fatty Acid Digestion in Lactating Dairy Cows Fed Fats Varying in Degree of Saturation and Different Fiber Sources

Abstract

Six cannulated cows were assigned to six treatments in a 6 x 6 Latin square design to evaluate the effects of fat saturation and amount and source of effective fiber on fatty acid metabolism. Cows were fed a control diet with no added fat or diets with 5% added fat from saturated tallow, tallow, or animal-vegetable fat; the diets with animal-vegetable fat had three percentages of effective fiber: 40% forage, 40% forage plus 20% soyhulls, or 60% forage. Cows fed diets supplemented with fat tended to have more disappearance of total fatty acids in the rumen than did those fed the control diet. Disappearance of fatty acids from the rumen, especially C16 and C18, was higher for cows fed the low fiber diet. The apparent digestibility of fatty acids in the small intestine was higher for cows fed the control diet than for those fed supplemental fat. Apparent digestibility also was reduced as fat saturation increased, primarily because of saturated tallow. Digestibility of C18:1 in saturated tallow was reduced, apparently in association with other saturated fatty acids. Fiber source had no effects on apparent intestinal digestibility of fatty acids. Concentrations of C18:0 and C18:1 in milk fat increased as the degree of fat saturation decreased, reflecting higher unsaturated C18 intake and ruminal biohydrogenation of polyunsaturated C18 fatty acids.

Feeding micronized and extruded flaxseed to dairy cows: Effects on digestion and ruminal biohydrogenation of long-chain fatty acids

“…These results suggest disappearance of FA in the rumen, which is in agreement with others (Doreau and Ferlay 1994;Tice et al 1994;Hussein et al 1996;Pantoja et al 1996). Reduction in the duodenal flow of FA can be due to absorption in the rumen, degradation to shorter chains and/or underestimation of duodenal flow (Wu et al 1991).…”

“…Reduction in the duodenal flow of FA can be due to absorption in the rumen, degradation to shorter chains and/or underestimation of duodenal flow (Wu et al 1991). The higher duodenal flow of C 18:0 relative to intake for all dietary treatments is likely due to ruminal BH of unsaturated C 18 (Klusmeyer and Clark 1991;Pantoja et al 1996).…”

Digestion of fatty acids in ruminants: a meta-analysis of flows and variation factors. 1. Total fatty acids

“…Possibly, hydrogenated tallow may have low intestinal digestibility due to incomplete ruminal lipolysis, and low digestibility of FA from rapeseed may be related to their passing intact to the faeces. Moreover, the lower absorption of C14 (a trend), C16 and C18 from hydrogenated tallow was probably due to the increased flow of esterified FA at the ileum, given that these FA are less soluble in micelles (Pantoja et al, 1996;Elliott et al, 1999). Based on the database, mean apparent intestinal digestibility increased with increasing chain length from C12 to C16 and was similar for C16 and C18, although the absorption of C18 was a quadratic function of its duodenal flow.…”

Impacts of feeding lipid supplements high in palmitic acid or stearic acid on performance of lactating dairy cows

“…Total digestibility decreased in order of C12:0, C14:0, and C18:0 so that increasing dietary concentration of C18:0 resulted in the greatest reduction of whole-tract total FA digestibility. Decreases in lipid digestion when lipid intake increased were associated with a decrease in the digestibility of saturated FA (Wu et al 1991;Pantoja et al 1996aPantoja et al , 1996b. Recently, Schmidely et al (2008) did an exhaustive meta-analysis of FA digestion.…”

“…However, there are concerns with respect to digestibility of the medium-and long-chain FA by lactating cows related to carbon chain length and saturation (Doreau & Ferlay 1994;Pantoja et al 1996b;Dohme et al 2004;Glasser et al 2008;Schmidely et al 2008) that are associated with rumen inert fats. Even with more common feed fats, for example tallow and yellow grease, there was decreased postruminal digestibility of FA in particular saturated FA (Avila et al 2000).…”