Effects of ammonia bicarbonate treatment on kinetics of fiber digestion, nutrient digestibility and nitrogen utilization of rice straw by sheep

Abstract

Three sheep were used to study the effects of ammonia bicarbonate (AB) treatment on ruminal fiber digestion kinetics, nutrient digestibility and nitrogen (N) utilization of rice straw (RS). The results for RS and AB-treated RS (ABRS) were compared with those for hay which is commonly used in our region. The AB treatment significantly increased dry matter intake and nutrient digestibility of RS ( P < 0.05). The digestibility of nutrients of ABRS were higher than those of hay. Nitrogen retention was highest in animals fed ABRS ( P < 0.05), followed by hay and the lowest in RS. The AB treatment had little effect on the potential degradability of protein in the rumen, but the degradation rate of the slowly degraded fraction was greatly increased by treatment with AB. Effective protein degradability was 64.4%, 48.7% and 46.2% for ABRS, hay and RS, respectively. Higher N content and rumen degradation in ABRS resulted in a more synchronized supply of nutrients to the rumen microbes than in RS and hay. The RS and hay had similar potential extent of digestion (PED) and a similar rate of PED ( k d) of fibrous materials. The RS had a shorter discrete lag time of digestion than hay. The AB significantly increased the PED ( P < 0.05), k d ( P < 0.01) and rate of ruminal passage of digesta of RS, but had little effect on lag time. These results indicate that treatment of RS with AB can increase N content, improve ruminal fiber digestion and protein status in lambs, and in turn increase the intake and digestibility, suggesting that AB can be utilized as an effective source of ammonia for upgrading RS.