Effect of age at castration on animal performance, muscle characteristics and meat quality traits in 26-month-old Charolais steers.

摘要

Effects of castration age were investigated on performance, muscle properties and quality of beef from Charolais steers (cattle, n = 38). The steers were castrated at 2 or 10 months of age and 2 consecutive trials were performed. The animals were either reared at pasture during the summer or with high quality hay in a barn during the winter, and were slaughtered at 26 months of age and a carcass wt. of 402 kg. Tenderness, juiciness and flavour of rectus abdominis (RA) and triceps brachii (TB) meatwere evaluated after 14 days of ageing. Physicochemical properties were determined, including collagen contents and solubility, levels of intramuscular fat, mu-calpain and 27 K proteasome sub-unit, myosin heavy chain isoform (I, IIa and IIx) proportions,metabolic enzyme activities (isocitrate and lactate dehydrogenase, cytochrome-c oxydase) and fibre area and type (SO, FOG and FG). FOG fibres of 10-month castrated steers had a larger area in rectus abdominis samples (3801 vs 2983 mum2), but areas of the other fibre types were not affected by castration age. Proportions of FOG fibres in 10-month castrated steers were higher (8.5 vs 8.1 and 22.2 vs 16.7% respectively for RA and TB muscles), whereas proportions of FG fibres were lower (52.2 vs 55.8 and 50.1 vs 54.9% respectively for RA and TB muscles). Castration age had no impact on myosin heavy chain proportions, oxidative and glycolytic metabolism or intramuscular fat content. Delayed castration caused increases in collagen content (P = 0.04), but did not affect collagen solubility (P = 0.73). Levels of mu-calpain and the 27 K proteasome sub-unit were significantly lower for 10-month than for 2-month castrated steers. Meat from both muscle types in each treatment group demonstrated similar tenderness, juiciness and flavour.