Liver histology of reindeer calves during the winter season

Seventeen reindeer calves were divided into three groups and liver biopsies were taken during the winter. Group 1 consisted of 6 animals allowed to graze freely under natural conditions, those in groups 2 (n = 5) and 3 (n = 6) were kept in pens and fed with lichens, the diet being designed to achieve a slight (group 2) or moderate (group 3) weight loss. Weight losses from November to April averaged 14.9%, 13.2% and 24.8% in the three groups respectively. The relative volumes of the different structures in the liver were determined by light microscopic morphometry. The mean size of the hepatocytes was slightly greater in March than in January in groups 1 and 2, and slightly smaller in group 3 (no statistical differences) and then decreased markedly. These changes could also be seen in the sinusoidal lumina. The decrease in the size of the hepatocytes may reflect a shortage of amino acids in the cells or it may be hormone-mediated. Unlike the situation in cows, there was no fatty accumulation in the hepatocytes. This may be a species adaptation to an annual period of starvation.