Mineral composition of muscles of 1- to 6-year-old steers

The diaphragm, longissimus, psoas major, semitendinosus and transversus abdominus muscles from eight or nine Angus steers were evaluated at each age of slaughter including 12, 18, 24, 30, 36, 48, 60 and 72 mo. The content of K, Fe, and Zn varied (P less than .01) with age of the steers. Ca, Na and Mg were not affected. The K content on a fat-free basis decreased from a high of 392 mg/100 g wet tissue at 24 mo of age to a low of 332 mg/100 g at 72 mo. Fe content increased with age from 2.00 mg/100 g of tissue at 12 mo to 3.73 mg/100 g at 72 mo. Concentrations of all minerals varied (P less than .01) among the five muscles evaluated. Feeding regimen had a significant effect on K, Fe and Zn, Steers fed entirely ad libitum had a higher K (17 mg/100 g more) and Fe (.19 mg/100 g more) content in their muscles than did the steers that were fed to gain .45 kg/d or those fed ad libitum for the last 6 mo before slaughter. Where significant, the magnitude of the difference in mineral content among age groups, muscles and feeding regimens was large enough to require that maturity, muscle and feeding regimen be specified when values for mineral content were reported.