Transfer of urea from the blood to the rumen of sheep

Abstract

1. The rate of transfer of plasma urea-nitrogen to rumen ammonia was measured by infusion of 15 NH 4 Cl and [ 15 N]urea into sheep given brome grass ( Bromus inermis ) or lucerne ( Medicago sativa ) pellets. Urea was infused into the rumen or abomasum of two sheep given brome grass in order to increase the concentration of rumen ammonia. 2. From 6.2 to 9.8 g/d of plasma urea-N were transferred to the rumen of sheep given brome grass pellets and a measurement of 1.3 g nitrogen/d was obtained for a sheep given lucerne pellets. When urea was infused into the rumen of sheep given brome grass pellets the transfer was only 2.8–3.7 g N/d.3. There was a significant negative correlation between the rate of transfer of plasma urea-N to the rumen and the concentration of rumen ammonia.