Date of this Version
The response time to cimaterol (CIM), a P-adrenergic agonist, by broiler chickens for carcass characteristics, muscle composition, muscle fiber size, catheptic enzyme activity, and tenderness was determined. Two trials were conducted in which chickens were fed a control diet (CON) containing 0 ppm of CIM or a diet containing 1 ppm of CIM. Trial 1 consisted of 55, 31-d-old broiler chickens individually fed for up to 48 h. At 0, 6, 12, 18, 24, and 48 h, five CON and five CIM-fed chickens were killed. Trial 2 consisted of 160, 33-d-old broiler chickens group-fed for up to 14 d. At 2,4,6, 8, 10, 12, and 14 d, 10 CON and 10 CIM-fed chickens were killed. The breast muscle (BM) and leg muscle (LM) weight, cathepsin B and L activities, DNA, RNA, and protein concentration, and BM shear force value (SFV) were measured in both trials. Thigh muscle (TM) SFV were measured in Trial 2 only. Fiber size of BM was measured (five birds per treatment) at d 2, 6, 10, and 14. In Trial 1, BM weight and SFV were lower in CIM-fed birds at 6 h (P < ,051. In Trial 2 BM SFV were higher at d 8 (P = ,061 and d 10 (P c .05) in CIM-fed chickens. The SFV of CIM-fed chickens were higher at d 4, 8, lo, 12, and 14 (P < .051. The BM of CIM-fed chickens had a higher protein:DNA ratio (P < .05) at d 6 through 14, whereas LM of CIM-fed chickens had a higher protein:DNA ratio at d 8, 10, and 14. Fiber size of the BM in CIM-fed chickens tended to be larger at d 10 (P = .13) and at d 14 (P = ,17). Total BM weight and BM as a percentage of final body weight (FBW) was higher at d 10 and 14 (P < .01) in CIM-fed chickens. Total LM weight and LM as a percentage of FBW was higher at d 14 (P < .01) in CIM-fed chickens. In the BM of CIM-fed chickens, protein:DNA ratio increased by d 6, SFV by d 8, muscle fiber size by d 10, and BM weight and BM as a percentage of FBW by d 10. The TM or LM of CIM-fed chickens showed increases in SFV by d 4, protein:DNA ratio by d 8, and LM weight and LM as a percentage of FBW by d 14. Response times to treatment with CIM differed for the various traits measured (i.e., meat tenderness, muscle composition, fiber size, or carcass characteristics).