The objective of this study was to examine the effect of two feeding systems (traditional concentrate plus
cereal straw vs. total mixed ration) on the fatty acid composition of beef in lean beef breeds slaughtered at
commercial weight. Two improved breeds, purebred Charolais (n = 60) and Limousine (n = 60), and one
unimproved indigenous breed, Retinta (n = 60), were raised on either an indoor concentrate system or a
unifeed system consisting of a mixture of maize silage and concentrate. Young bulls fed the total mixed
ration system showed a higher percentage of saturated fatty acid content than young bulls fed with
concentrate plus wheat straw. The intramuscular fat of Retinta bulls raised on a concentrate feeding
system showed higher monounsaturated (587.3 mg/100 g edible meat) and lower polyunsaturated fatty
acid (221.0 mg/100 g edible meat) than Retinta bulls that were fed with mixed ration. No feeding system
effect on fatty acid profile of fat was observed for the improved breeds. At commercial weight, the
percentage of fatty acid desirable for human health was higher (70.3%) from the unimproved breed than
the improved breeds (69.1%). The results obtained confirm that genetic background plays an important
role in the fatty acid profile of meat from cattle raised with different feeding systems.