Fatty acid profile and oxidative stability of the perirenal fat of bulls fattened on grass silage and maize silage supplemented with tannins, garlic, maca and lupines

Carcass fat composition of cattle fed a forage-based diet might be inferior with maize silage compared to grass-silage based systems. This was quantified using complete diets with concentrate. To test whether supplements may influence carcass fat properties as well, the maize-silage diet was additionally supplemented either with Acacia mearnsii tannins, garlic, maca or lupines, feeds rich in secondary metabolites. The perirenal fat of 6 × 6 bulls fed these six diets was analysed for fatty acid profile and shelf life. The n−6/n−3 ratio was always higher than 11 with the maize silage treatments and 2 with grass silage. The supplements did not affect the occurrence of biohydrogenation intermediates, including rumenic acid. Shelf life, being twice as long with maize compared to grass silage, was either unaffected or tended to be impaired, especially with supplementary garlic. Overall, supplementation was not efficient in improving carcass fat properties of maize-silage fed bulls.

► The studies directly compares fattening on forage-based diets relying on grass- or on maize-type forages. ► Grass-based feeding led to a fatty acid profile favourable in a human nutritional sense. ► Shelf life was reduced un the grass-based system. ► Unexpectedly, plants rich in secondary compounds did not alter carcass fat profile. ► These findings give important indications on how to produce a healthy beef.