| Abstrakt: |
In vivo and in vitro studies were conducted to investigate the effects of urea (U) substitutions on the utilization of feather meal (FM) and hair meal (HM) by ruminants. A rumen-fistulated steer fed grass hay ad libitum received 1.5 kg of protein concentrate (20% CP) twice daily, with soybean meal (SBM), U, FM, FM-U, HM or HM-U supplying the supplemental N. Rumen samples were obtained at hourly intervals for 8 h postfeeding for pH, ammonia nitrogen (NH4-N) and volatile fatty acid (VFA) determinations. Increases (P<.05) in NH4-N and total VFA were found when U was fed in combination with FM or HM vs FM or HM alone. Rumen NH4-N and VFA were lower (P<.05) with the FM and HM treatments than they were with the SBM control. In vitro batch trials were used to evaluate U when it replaced 0, 20, 30, 40, 50 and 100% of the FM or HM N and with a SBM control. Dry matter disappearance (DMD), NH4-N, VFA and ribonucleic acid (RNA) concentrations were lower (P<.01) with FM and HM than with SBM. Additions of U at all levels increased (P<.01) DMD, NH4-N, VFA and RNA over that observed with FM and HM alone. The 40% level of U substitution for FM or HM met or exceeded the results obtained with SBM for all measurements taken. |
