The regulation by nutrition of glycogen in the muscle of ruminants

This paper discusses recent work by the authors which has investigated the nutritional regulation of glycogen concentration in skeletal muscle of sheep and cattle. Several experiments are summarised which show a clear relationship between the level of glycogen in muscle and the intake of metabolisable energy. This translates into strong seasonal effects on muscle glycogen in pasture fed cattle. The clear message is that animals destined for slaughter should be on a high plane of nutrition as this will contribute to an increased muscle glycogen at slaughter and so help alleviate the problem of dark cutting meat. Short–term regulation of glycogen is more problematical since the rate of glycogen repletion in skeletal muscle is relatively slow and the scope for rapid dietary change in ruminants is constrained by the need to allow rumen adaptation to high starch/sugar diets. However the sudden introduction of a high energy diet (based on cereal grain) in the presence of a ‘rumen modifier’ to reduce ruminal acidosis can increase muscle glycogen concentration within one week of feeding. The ability to further modify glycogen level in skeletal muscle using carbohydrate and electrolyte products is discussed. In particular the possibility of using oral glycerol/propylene glycol as a meaning for increasing blood glucose and so glycogen synthesis is proposed. An experiment to examine the effectiveness of MgO as a means for reducing the stress response is also discussed.