EFFECT OF COLD-ACCLIMATION ON OXIDATIVE CAPACITY AND RESPIRATORY PROPERTIES OF LIVER AND MUSCLE MITOCHONDRIA IN DUCKLINGS, CAIRINA-MOSCHATA

1. The effect of cold acclimation on the oxidative capacity of the skeletal muscle (gastrocnemius and pectoralis) and the liver of ducklings was investigated. 2. In cold-acchmated (CA) ducklings, the oxidative capacity of the liver was higher (+40%) than in ducklings reared at thermoneutrality (TN). In these animals an increase in state 4 respiration and a decrease in the respiratory control index (RCl) was also found. 3. The oxidative capacity of both pectoralis and gastrocnemius muscles also increased in CA animals. 4. In these muscles the oxidative capacity of the subsarcolemmal mitochondrial fraction of CA ducklings was higher (+96% in the gastrocnemius and +58% in the pectoralis) than the intermyofibrillar one (+51% in the gastrocnemius and +33% in the pectoralis). No variations were observed in either the RCl or the ADP/0 ratios. 5. These findings indicate that the energy expenditure needed for non-shivering thermogenesis (NST) in cold-acclimated ducklings can be met by the increase in the oxidative capacity of the skeletal muscle and the liver, each by different mechanisms; the gastrocnemius muscle would seem to play a prominent role.