Aspects of ruminant intermediary metabolism in relation to ketosis.

Both the cow and the sheep are susceptible to ketosis. In the cow the clinical condition is termed primary spontaneous bovine ketosis and in the sheep, pregnancy toxaemia. Bovine ketosis occurs typically in the third to eighth week of lactation in mature heavily lactating diary cows. Pregnancy toxaemia occufs in late pregnancy in ewes bearing two or more lambs. Both conditions are associated with hyperketonaemia, hypoglycaemia and developing inappetence (loss of appetite). The susceptibility to ketosis of these two ruminant species is doubtless due in part to their reliance on gluconeogenesis for their glucose supply. A further factor is that these animals have been bred for high productivity (i.e. of milk and of offspring in cows and sheep respectively) and this inbred productivity may overtax an animal’s metabolic resources. Many of the biochemical characteristics of the spontaneous condition can be elicited by subjecting cows in early lactation on the one hand, and multifoetate ewes on the other, to food deprivation. Data from food-deprivation ketosis in both species will be included below. The present review will deal mainly with the cow, but data from the sheep will be included as necessary. Other reviews on ruminant ketosis have been written (Eergman, 1971 ; Baird et al., 1974a,b; Schultz, 1974).