The effect of nitrogen source and concentration on in vitro gas production using rumen micro-organisms

The effects of nitrogen (N) on an in vitro gas production method were investigated by fermenting two N-deficient substrates (glucose or barley straw) in media with different concentrations of N (from 0 to 165 mg l−1) from two N sources (ammonium sulphate or urea). The response of the in vitro gas production system to N supplementation was broadly consistent with earlier in vitro work, indicating that a minimum of about 80 mg l−1 N was required to achieve the maximum degradation of carbohydrate by rumen microbes. The effect of N appeared to be mainly, if not entirely, on the rate of degradation rather than its extent. The in vitro gas production method appeared to be suitable for investigating interactions between feeds.