Repletion of glycogen in muscle is preceded by repletion of glycogen in the liver of Merino hoggets

An experiment was conducted using 105 Merino hoggets to measure the change in tissue glycogen concentration over a 48-h period following an exercise regime. The exercise regime consisted of a 2-km run repeated four times with a 15-min break between each run. After exercise the hoggets were split into treatment groups and fed three different levels ( fasting, maintenance and three times maintenance) of the same ration. A subset of each group of hoggets was killed at -24, 0, 12, 24 and 48 h from the time of exercise and samples taken from the liver, skin, rumen, duodenum, colon, kidney, M. semimembranosus, M. semitendinosus, M. longissimus thoracis et lumborum, M. psoas major, M. triceps brachii and M. subscapularis. Exercise caused a reduction in glycogen concentration in the liver and all muscles but not in the kidney, skin, duodenum, or colon tissues. After exercise the most significant changes in glycogen concentration were in the liver, muscle and skin. Metabolisable energy intake influenced the change in the liver and muscle tissue but not in the skin. It was concluded that glycogen concentration increased in liver before muscle and that this effect may contribute to the slower rate of glycogen concentration in muscle for ruminants compared with monogastric animals. Skin may also compete with muscle for glucose during the repletion phase in Merino sheep but the exact nature of this effect remains uncertain.