In the growing rats weighting between 70 and 300 g, when 20% of the total daily energy intake consists either of 'lard (with 36% oleic acid) or sunflowerseed oil (with 61% linoleic acid)', lipogenesis, proteinogenesis, feed efficiency ratio and body compositions are identical. With the nutritional conditions used during these experiments, the occurrence of a high level of polyunsaturated fatty acids level in the diet cannot be considered as an exogenous factor able to modify the parameters studied.