Nutrition-progesterone interactions during early pregnancy in sheep [ewes]
1992
Parr, R.A. (Victorian Dept. of Agriculture, Werribee (Australia). Inst. of Animal Science)
Ewes fed twice maintenance (2M) rations after joining had a pregnancy rate of 48 percent. Ewes fed 2M rations and given exogenous progesterone between 8 and 14 days after mating had a pregnancy rate of 76 percent. Ewes fed rations calculated to maintain live weight or fed restricted rations during this same time had pregnancy rates ranging from 60 to 68 percent, with no beneficial effect of progesterone supplement. Concentrations of peripheral plasma progesterone on day 12 after mating were inversely related to the level of feed intake. Injection of epostane, an inhibitor of the enzyme 3beta-hydroxysteroid dehydrogenase, caused 'windows' of progesterone reduction for 48-h periods over days 9-13 after mating. Blood flow rates in the portal vein of ewes were directly related to the level of feed intake. This, together with the fact that the liver and gut were efficient in the removal of 96 percent of the progesterone entering this region in the blood, indicated that changes in the rate of blood flow were the most likely explanation for the inverse relationship demonstrated between feed intake and peripheral concentrations of plasma progesterone.
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