Changes in the liver fat of the pregnant sheep at different levels of nutrition and during starvation.

The importance of a study of the ovine fatty liver arises from the frequent reports of this condition in cases of pregnancy toxaemia occurring in the field or induced experimentally (Roderick & Harshfield, 1932 ; Frazer, Godden, Snook & Thomson, 1938-9, 1939-40; Groenewald, Graf, Bekker, Malan & Clark, 1941 ; Underwood, curnow & Shier, 1943). According to Best & Ridout (1933, 1936), Best (1934), Best & Channon (1935), Best & Huntsman (1934-5), Best, Mawson, NIcHenry & Ridout (1936) and Channon & Wilkinson (1934), excessive fat accumulates in the liver of experimental animals, principally rats, under a variety of circumstances, e.g. when the diet is rich in fat, when cholesterol is given, after pancreatectomy and following injection of anterior-pituitary extracts. In the pregnant animal, knowledge is uncertain about liver-fat changes, although it is of interest that Marshall (1922) quotes Mottram as finding an increasing ‘physiological’ infiltration of liver fat in woman during normal pregnancy. There are conflicting reports from the few instances of similar studies on animals. Coope & Mottram (1914) showed appreciable increases of liver fat in cats and rabbits, but Maclean (quoted by Best & Ridout, 1933) could not confirm this observation with rabbits. For the pregnant ewe, whether normal or suffering from pregnancy toxaemia, reports of fatty liver appear to have implied an infiltrated state, although there have been unsubstantiated claims that the presence of large quantities of fat renders the normal functioning of the liver cell impossible. There appears to be no certain evidence for considering this state of the ewe’s liver to be a pathological one, although no attempts have been made to reverse the movement of fat into the liver of this species. Snook (1g39-40), reported 5-7% total fat for the liver of the normal pregnant ewe, claiming that fatty infiltration is not usual in normal gestation, but that it is a feature of pregnancy toxaemia. Dryerre & Robertson (1940-I), on the other hand, demonstrated a rise from 7 to nearly 12% total fat between the 2nd and 4th months of gestation in healthy ewes, and considered that pregnancy toxaemia accounted for only a slight increase in fat beyond this upper level, although they pointed out that they had examined only a few cases of the disease. It is significant that some of the same material used by Dryerre & Robertson as the basis of their researches was also examined by Snook. Wallace (1948) found that there was little rise in the liver fat of ewes that were well nourished at the 14th day of pregnancy, even though low levels occurred at the 91st day. A considerable increase in liver fat occurred, however, when the quantity of