Competition between Food Particles and Rumen Bacteria in the Uptake of Long‐chain Fatty Acids and Triglycerides

S ummary . Suspensions of mixed rumen bacteria were incubated with long‐chain fatty acids and their corresponding triglycerides in the presence and absence of the food particles present in the rumen. The uptake of free fatty acids and triglycerides by the bacteria was due largely to physical adsorption. With increasing unsaturation of the free fatty acids, less adsorption occurred and in all instances the presence of food particles reduced greatly the extent to which the fatty acids were adsorbed on the bacteria. The triglycerides were adsorbed to the bacteria to a much less extent than their corresponding free fatty acids, more of the substrate remaining in the supernatant fraction. The presence of food particles had little effect on the extent to which the triglycerides became adsorbed to the bacteria, but reduced greatly the amount of triglyceride present in the supernatant fraction. The decrease in amount of free fatty acid associated with the bacteria and the decrease in the amount of triglyceride in the supernatant liquid when food particles were present, was wholly accounted for by the increase in amount of these substrates associated with the food particles. The implications of these findings with respect to the metabolism of lipids in the rumen is discussed.