Compositional, organoleptic, metabolic enzyme activity and fibre characteristics of muscle from bulls with different growth paths to a common carcass weight

Abstract

The proximate composition, organoleptic quality, metabolic enzyme activity and fibre characteristics of longissimus thoracis muscle from suckler bulls assigned to three target indoor winter (from 9 to 13 months of age approximately) growth rates (average daily gain of 0.6, 1.0 and 1.5 kg; n = 14/group) were investigated. The feeding regimes to achieve the target average daily gains were 2, 4 and 6 kg of concentrate respectively, plus grass silage ad libitum. The duration of the winter feeding period was 123 days, after which bulls were turned out to pasture and grazed for 99 days before re-housing and finishing on concentrates ad libitum plus grass silage until they reached a liveweight to yield a target carcass weight of 380 kg. The average daily gain during the grazing period was higher (P < 0.001) for the 0.6 than for the 1.0 and 1.5 average daily-gain groups, which did not differ. Proximate composition, collagen content, metabolic enzyme activity and fibre-type distribution of the longissimus thoracis muscle were similar (P > 0.05) between the 0.6, 1.0 and 1.5 average daily-gain groups. Apart from tenderness, which was rated higher (P < 0.05) for the 0.6 group than for the 1.0 average daily-gain group, the sensory characteristics of the beef were not influenced by the different winter growth rates applied. Overall, restricting the growth rate during winter had little effect on subsequent beef appearance or eating quality.