Seasonal effect on rumen function in sheep on range in the Accra Plains of Ghana

This study aimed at investigating the effect of the seasonal decline in quality and availability of feed on rumen function in sheep grazing without supplementation. Effects of season on rumen pH, ammonia nitrogen concentration and rumen degradation of urea-treated rice straw in grazing sheep were determined. Four fistulated Djallonké sheep were added to a group of grazing sheep and used for this study. Rumen contents were sampled for pH and ammonia in the rainy season and in the dry season. Ammoniated rice straw was incubated in the rumen to determine its degradation characteristics. Rumen pH was higher (p?p?>?0.05) in the two seasons. In sacco dry matter degradation parameters of urea-ammoniated rice straw showed seasonal differences in the soluble (a) and the insoluble but degradable (b) fractions as well as lag time before the start of degradation. It was concluded that despite higher pH in the dry season and similar ammonia nitrogen concentration in the two seasons, rumen degradability of dry matter of urea-treated rice straw in sheep was higher in the rainy season than that in the dry season.     

Reducing Ammonia Volatilization and Improving Nitrogen use Efficiency of Rice at Different Depths of Urea Supergranule Application

An experiment was conducted to determine the depth of urea supergranule (USG) application that reduces ammonia (NH₃) volatilization and improves nitrogen use efficiency of rice. Canne, Voudou, Akuse, and Bumbi series were used. Treatments involved surface application of prilled urea (PU), USG applied at 0, 4, 8, 12 and 16 cm depths and a control. Rice variety IR-841 was grown up to maturity. Closed chamber device was used to trap NH₃. Results indicated that the highest mean NH₃ loss occurred in Bumbi series (13.67%) while the lowest was Canne series (8.16%). USG applied at 0 cm resulted in the highest NH₃ loss (37.2%). NH₃ volatilization decreased with increasing depth of USG application. The highest grain yields were obtained when USG was applied at 4 and 8 cm. In Canne series, the highest agronomic use efficiency (AE) of N (57 g g^?1) was obtained with USG applied either at 8 or 12 cm while the highest recovery efficiency (RE) (84%) occurred at 8 cm. In Akuse series, the highest AE (55 g g^?1) and RE (78%) were obtained when USG was placed at 8 cm. In Voudou and Bumbi series, the highest AE (45 and 48 g g^?1 respectively) and RE (64%) were obtained with USG deep placed at 4 cm. The results therefore suggested different specific depths of USG application to reduce ammonia loss and improve nitrogen use efficiency.