Physical activity, forced by steep pastures, affects muscle characteristics and meat quality of suckling beef calves

Abstract

SUMMARYOn steep slopes, grazing is associated with elevated physical activity. This is assumed to influence muscle metabolism, carcass and meat quality in beef cattle. However, there is a lack of experiments which allow distinguishing between physical activity and other factors of influence. In the present experiment, a setup was applied which excluded other factors as best as possible. Two groups of 12 Angus-sired suckling calves were each kept on high altitude pastures with either steep (whole area with about 40% inclination; S-calves) or with flat areas (0% inclination; F-calves). The two areas offered forage of similar nutritional quality. The calves, initially 18 ± 2·5 weeks old, were kept with their dams on the pastures for 11 weeks in a rotational grazing system. The calves were equipped with pedometers and rumination sensors to record physical activity and feeding behaviour, respectively. Slaughter took place on two dates immediately after the grazing period and carcass quality was assessed. Muscle fibre types were classified according to their contractile metabolism and post mortem (p.m.) protein degradation was quantified. The meat, aged for 21 days, was subjected to various physicochemical analyses and sensory evaluation. S-calves walked more steps and spent more time lying down than F-calves, whereas feeding behaviour was not affected by pasture inclination. The daily gains of S-calves were 10% lower compared with those of F-calves. Carcass characteristics were not influenced by pasture inclination. S-calves had a larger proportion of fast-twitch type IIX/B muscle fibres than F-calves. The opposite was observed for intermediate type IIA muscle fibres, whereas the proportion of slow-twitch type I muscle fibres was unaffected. Occasional differences were observed between S- and F-calves regarding indicators of p.m. proteolysis. In S-calves, compared with F-calves, meat from the longissimus thoracis muscle was juicier and showed a tendency to be of lighter colour, whereas meat from the biceps femoris muscle had a smaller shear force (24·5 v. 27·5 N in F-calves). In conclusion, 11 weeks’ exposure to environments forcing calves to exhibit different physical activities in a hypoxic environment was sufficient to cause adaptations in muscle metabolism and several, though small, differences in meat quality.