Effect of using different sources of nitrogen on digestibility and nitrogen balance in Mehraban male lambs

This study was conducted to compare effect of different nitrogen sources on the rate of release, nitrogen balance and nutrient digestibility in Mehraban male lambs. Digestibility parameters and nitrogen balance were measured in 15 Mehraban male lambs. The experiment lasted 21 days including 16 days of adaptation and five days for sample collection. Diets were isonitrogenous and isoenergetic. Diets were included concentrate, mineral and vitamin supplements plus: 1) wheat straw and soybean meal, 2) wheat straw and urea, 3) wheat straw and Optigen® (a commercial slow-release urea supplement) and 4) wheat straw and slow-release urea produced in laboratory. Before beginning the in vivo experiment, release rate of slow-release urea sources in water and also rumen disappearance was measured. Intake and digestibility of dry matter and organic matter did not affect by treatments, whereas the digestibility of NDF and ADF was significantly different in the treatments containing slow-release urea supplement in comparison of soybean meal treatment (P