Proximate, mineral and fatty acid composition of semimembranosus and cardiac muscles from grass- and grain-fed and zeranol-implanted cattle

Chemical composition (proximate, minerals, and fatty acids) of semimembranosus (SM) and cardiac muscle from cattle fed grass (G) and grain on grass without (GG) or with (GGP) zeranol implant were determined. The protein content of SM muscle from GG and GGP cattle was higher (p≤0.05) while the moisture content was lower (p≤0.05) than that from G cattle. The lipid content of cardiac muscle from GG cattle was higher (p≤0.05) compared to that of G cattle. Grain supplementation (GG and GGP) increased the potassium level in SM muscle while a decrease was observed in cardiac muscle. Grain supplementation also increased linoleic acid but decreased polyunsaturated (PUFA) fatty acids in both muscles. There was 3 times more PUFA, particularly linolenic and arachidonic acids, in cardiac muscle than in SM muscle irrespective of the feed type. The concentrations of PUFA in SM and cardiac muscle were higher for G cattle than for GG and GGP cattle, which could make muscles from G cattle more prone to oxidation.