The effects of pregnancy of the passage of food through the digestive tract of sheep

Abstract

The rate of passage of food residues through the digestive tract of pregnant and non-pregnant Merino ewes was measured at four levels of feeding.

The passage of digesta became more rapid as the level of feeding was increased, or, the intake being constant, as pregnancy advanced. The mean retention time fell by 3 hr per 100 g increase of food intake, and by 1 to 1½ hr per 100 g increase of estimated weight of concepta at constant intake.

The digesta increased by about 150 g dry matter (depending on level of feeding) per 100 g increase of daily food intake and fell by about 150 g per 1000 g increase of estimated weight of concepta.

Two alternative explanations of the changes of rate of passage during pregnancy are discussed. While reduction of the quantity of digesta by the increasing bulk of the uterus would tend to curtail appetite, increase of the flow of digesta as a physiological side-effect of pregnancy would tend to enhance appetite. In either case, more rapid passage of digesta would depress the digestibility of some rations and so contribute to undernutrition in late pregnancy.