The retention time of digesta in the rumen of cattle grazing tropical forages is long and extensive biohydrogenation occurs. The conjugated linoleic acid (CLA) levels that are found are low but would still result in a significant level in the products so formed. Many supplements contain low levels of lipids or even if found in a high concentration in the supplement, are fed at a low level with the end result being that the supplement cannot markedly change the fatty acid profile in the rumen fluid. Some small but significant changes can occur e.g. with coconut oil and fish oil. The level of CLA that is found and the likely level of inhibitory isomers of CLA suggest that this would not result in an inhibition of lipid synthesis especially given the long retention time and biohydrogenation of unsaturated fatty acids.
