1Institute of Subtropical Agriculture Chinese Academy of Sciences Changsha 410125.
2Graduate University of Chinese Academy of Sciences Beijing 100039.
3Centre of Experimental Animal Xinjiang Medical University Urumchi 830054.
4Department of Animal Sciences Xinjiang Agricultural University Urumchi 830052 Peoples Republic of China.
*For correspondence: Tel: 86 731 4619702; Fax: 86 731 4612685; E-mail: zltan@isa.ac.cn
Two experiments were conducted to determine the effects of method and level of urea supplementation on feed intake, N efficiency, site of digestion and ruminal fermentation in sheep fed a maize stover-based diet. Treatments included an un-supplemented control, two urea supplementation levels and two urea supplementation methods. Feed intakes were not affected (P>0.05) by method or level of supplementation. Total N intake increased (P<0.001) with urea supplementation. N digestibility (P<0.001) and retained N (P<0.05) increased with urea supplementation. It also influenced ruminal DM, OM, ADF and N disappearances. Urea supplementation method or level did not affect rumen pH, however, it influenced rumen NH3-N concentration. The results suggested that ruminants mainly consuming low protein feeds efficiently used urea as N source. However, spraying higher levels of urea were not beneficial.
Urea supplementation, nitrogen utilization, ruminal fermentation, sheep
