Blood transport and tissue metabolism of lipids in the preruminant calf given a milk diet containing coconut oil or beef tallow

摘要

Blood transport and tissue metabolism of lipids in the preruminant calf given a diet containing coconut oil (rich in medium chain fatty acids) or beef tallow (rich in long chain saturated and unsaturated fatty acids) is discussed. Coconut oil results in hyperlipidaemia by increasing concentrations of cholesterol and phospholipids. C12:0 and C14:0 of coconut oil are specifically transported by triglyceride- (38%) and cholesterol- (44%) rich lipoproteins. Uptake of coconut oil fatty acids by the liver leads to hepatic steatosis due to a marked deposition of triglycerides (X18). This may be the result of a higher process of elongation of products generated by the oxidation of medium chain fatty acids (C12:0), a lower capacity of oxidation associatedwith a higher capacity of esterification of long chain fatty acids (C18:1 n-9) into triglycerides, and of low and non-inducible capacity of triglyceride secretion. Muscle fatty acid oxidation and lipogenic potentiality of adipose tissues are not modifiedby dietary fatty acids. C12:0 and C14:0 provided by the coconut oil diet accumulates in muscle and adipose tissues at the expense of C18:1 n-9, increasing the degree of saturation of fatty acids in stored lipids. It is concluded that the use of coconutoil as the sole source of lipids in the milk diet of the preruminant calf is not recommended since it induces hepatic steatosis, does not improve zootechnical performances, and decreases meat quality for consumers by favouring the deposition of atherogenic saturated fatty acids.