Effect on digestibility and nitrogen content of barley straw of different ammonia treatments

The article discusses the effect on solubility in cellulolytic enzyme suspensions, digestibility in vitro and crude protein content (F × 6.25) of treating barley straw with various dosages of NH₃ (2.6–5.9%), at various temperatures (15–75°C) for various treatment times (1–14 days).An increase in any of the above factors resulted in an increased intensity of treatment, with an increase in temperature of 15°C being equal to an increased NH₃-dosage level of 1.5% or prolongation of the treatment time by a factor of 4.5Digestibility in vitro increased with increased intensity of treatment, until a maximum level was obtained. Beyond this point, an increase in NH₃-dosage, or especially in temperature, tended to decrease digestibility in vitro. Maximum digestibility could be obtained, for example, with 2.6% NH₃, 62°C and 4 days incubation, or 5.9% NH₃, 30°C and 3–7 days incubation.Likewise, both solubility in cellulolytic enzyme suspensions and crude protein content increased with increased intensity of treatment, up to a certain level. Thereafter, increased dosing with NH₃, higher temperatures or longer incubation times had little or no effect. However, maximum values were obtained with a greater intensity of treatment than the maximum digestibility in vitro, and no tendency towards decreased values was observed.Increased enzyme solubility, beyond that corresponding to maximum digestibility in vitro, was accompanied by an increased rate of fermentation and a decreased content of neutral detergent fibre.Treatment with heat (100°C) and pressure after incubation, to simulate pelleting before evaporation of surplus NH₃, was also investigated. Only after the lowest incubation temperatures, however, was there an obvious tendency towards increased digestibility. The enzyme solubility was, on the other hand, very obviously increased. Crude protein content was also slightly increased by the heat- and pressure-treatment.