Meat quality and the calpain system of feedlot steers following a single generation of divergent selection for residual feed intake

• DOI: 10.1071/ea00024
• Publication Date: 2002-09-15T21:15:52Z
• Authors: M. B. McDonagh; R. M. Herd; E. C. Richardson; V. H. Oddy; J. A. Archer; P. F. Arthur
• Keywords: Marbled meat; Feedlot; Residual feed intake; Intramuscular fat; Shorthorn; Beef Cattle; Meat tenderness; Rump

Residual feed intake (RFI) is calculated as the difference between an animal’s actual and its expected based on size growth over a specified test period. Following single generation of divergent selection for postweaning RFI, Angus steers × Hereford, Angus×Poll Hereford Shorthorn crossbred born in 1996 1997 were fed feedlot. Cohorts slaughtered at same age had attained similar (P>0.05) final liveweights: 467 kg selected low RFI (high efficiency; HE, n = 91) 459 high (low LE, 98). The HE LE (P>0.05) carcass weight (247 244 kg), dressing percentage (53.1 53.2%) eye-muscle area (58.9 60.3 cm 2 ). slightly less subcutaneous fat rib than (9.2 v. 10.1 mm, P<0.05), there was trend towards rump (11.5 12.1 P 0.10). For meat samples taken from M. longissimus dorsi (LD) no differences content intramuscular (5.4 5.3% fresh weight), marbling scores, colour colour. There also shear force compression values LD aged 1 day (4.6 4.6 force, 1.45 1.44 compression), or 14 days (3.8 3.5 kg, 1.36 1.32 kg). Myofibril fragmentation index (MFI) measures breakdown these structural elements which occurs initial step process protein degradation tenderisation. MFI lower (i.e. fragmentation; P<0.05) steers, both (67.7 72.5 units) (87.8 91.1 units). rate decline post slaughter lines steers. activity m-calpain µ-calpain immediately after (HE steers: 1.9 2.3 units, 1.8 2.1 level calpastatin 13% higher (5.2 units respectively, P<0.05). Rate myofibril positively correlated (P<0.01) with ratios µ-calpain to calpastatin, but not (P>0.10) levels either calpain calpastatin. A produced that may, on-going negatively affect tenderness.