Metabolic and physiological basis of cold acclimation in the piglet

Abstract

Cold-induced metabolic adaptations and their consequences on piglet growth are analysed in terms of regulatory mechanisms of thermogenesis. Zootechnical, biochemical, hormonal and bioenergetic aspects are successively presented. Acclimation to cold requires an increase in food intake and results in an enhanced heat production ; when piglets are pair-fed, their growth rates are reduced by cold exposure. Cold-induced modifications of body composition depend on dietary conditions. The key role of lipids and white adipose tissue (uptake, synthesis, storage and mobilization of fatty acids) suggested by zootechnical data, is demonstrated by enzyme activity measurements (lipoprotein lipase, lipogenesis, lipolysis) which suggest an increased rate of fatty acid turnover. The energetic role of carbohydrates is also of some importance. Catecholamines and thyroid hormones are the main regulatory effectors of thermogenesis in the cold. As brown adipose tissue is absent in swine, muscles seem to play a major role in utilization and oxidation of fatty acids released by white adipose tissue. In addition to shivering, some specific mechanisms of heat production which contribute efficiently to the regulation of body temperature, take place in muscles : loose-coupled mitochondria from rhomboïdeus muscle, Na⁺ /K⁺ -pump stimulation in intercostal muscle.