Effects of feeding management and breed type on muscle chemical composition and relationships between carcass and muscle compositional traits in steers

Abstract

There is little published information on the chemical composition of muscle from beef steers produced in Irish production systems. The objective of this study was to determine the effects of feeding management and breed type on m. longissimus chemical composition of steers, and to examine relationships between selected carcass traits and measures of carcass and muscle composition. A total of 117 steers (65 Friesians and 52 Charolais  Friesians) were assigned on weight within breed type to a pre-experimental slaughter group and to one of 12 finishing groups (6 feeding treatments by 2 finishing periods). The 6 feeding treatments were: (1) silage only offered ad libitum (SO), (2) and (3) SO plus a low concentrate level, (4) and (5) SO plus a high concentrate level, (6) concentrates ad libitum. In Treatments 2 and 4, the silage and concentrates were offered separately whereas in Treatments 3 and 5 they were offered as a total mixed ration (TMR). The two finishing periods were 105 and 175 days. Mean low, high and ad libitum concentrate levels were proportionately 0.415, 0.732 and 0.927, respectively, of daily dry matter intake. Carcass weight, fat depth, fat proportion in the rib joint and m. longissimus lipid concentration all increased (P < 0.01) asymptotically with increasing concentrate level. Carcass fat class (P < 0.07), perinephric plus retroperitoneal fat weight (P < 0.001), fat depth (P < 0.06), fat proportion in the rib joint (P < 0.001) and m. longissimus lipid concentration (P < 0.001) were higher for Friesians than for Charolais crosses. Carcass weight increased (P < 0.001) with increased duration of the finishing period, as did carcass fat class (P < 0.06), fat proportion in the rib joint (P < 0.001) and m. longissimus lipid concentration (P < 0.001). Method of feeding had no effect on any of the traits measured.