In chicks fed rations containing 15% rapeseed oil (RSO) or soybean oil (SBO) a gradual increase in the lipid content of heart tissue was found from 1 to 10 days of age. The finding that feeding high levels of RSO to chicks did not cause excessive accumulation of fat in cardiac tissue supports the contention that it is inappropriate to extrapolate from one species to another (e.g. from rats to humans) as has been done by some workers with respects to RSO utilization. 2. Inclusion of RSO in the ration caused an increase in the total omega-9-monounsaturated fatty acid concentration in heart tissue. The increase in C 20:1 fatty acid concentration in heart tissue noted in the RSO-fed chicks suggests beta-oxidation of erucic acid (delta13 22:1) to eicosenoic acid (delta11 20:1). The rapid decrease in the oleic acid (delta9 18:1) concentration of liver tissue of chicks found during the period 1 to 10 days of age suggests the importance of oleic acid as a source of energy for the chicken.
