INTERACTIVE EFFECT OF FOOD-DEPRIVATION AND AGONISTIC BEHAVIOR ON BLOOD PARAMETERS AND MUSCLE GLYCOGEN IN PIGS

Agonistic behavior, neuroendocrine and plasma metabolite changes, and muscle glycogen content were studied in 16 fed and 16 24 h-fasted dome stic Large White pigs (100 +/- 5 kg) submitted to dyadic encounters (3 0 min) in a novel environment. Comparisons were made with correspondin g control pigs (eight fed and eight 24 h-fasted animals) kept under re sting conditions. At rest, fasting resulted in a significant decrease in plasma insulin, increase in plasma-free fatty acids, and decrease i n glycogen content in the predominantly red Semispinalis muscle. Faste d pigs displayed significantly more submissive acts than fed ones. In response to dyadic encounters, fed and fasted pigs showed similar rise in plasma levels of cortisol, catecholamines, and lactate, but stress -induced hyperglycemia was suppressed in food-deprived animals. Fastin g enhanced stress-induced glycogen depletion in the predominantly whit e Longissimus muscle but this effect was significant only in fast-twit ch glycolytic fibres (alpha W). In the Semispinalis of fasted pigs, ho wever, dyadic encounters did not induce further glycogen depletion. Th e present findings suggest that in response to dyadic encounters, fast ing-induced changes in glucose metabolism lead to a higher dependence on endogenous energy reserves, i.e., glycogen, in working muscles.