In view of the potential value of rice straw as a crop by-product suitable for feeding ruminants in Malaysia, a programme of research was initiated to determine its value and usefulness in the diet. Paper one in this series reports the results of three digestibility experiments using sheep, to determine the optimal level of rice straw utilization. Indigenous sheep each weighing about 22-24 kg. live weight were used.
Seven rice straw varieties were examined: Bahagia, Malinja, Mashuri, Mat Chandu, Murni, Ria and Sri Malaysia 1, but only the Bahagia variety was used in the trials reported. The crude protein content of these straws ranged from 3.3 to 4.5% and crude fibre from 28.3 to 33.6%. Ria recorded the highest nitrogen-free extract, gross energy, calcium and potassium contents.
It was demonstrated that in diets varying in rice straw levels up to 60% with molasses-urea with or without copra cake, that there were significant (P<0.05) treatment differences. the apparent digestibility coefficient of dry matter was highest for the 20% rice straw level (70.5 to 74.0%) but no differences existed between a 20 and 30% level of rice straw inclusion. it is suggested that 30% is the optimal level of dietary rice straw inclusion in the context of increasing its utilization.
the addition of urea significantly (p<0.05) increased the digestibility of crude fibre in the diet and also the intake of rice straw by up to 48.8%. this increased intake decreased with increasing level of rice straw inclusion. the presence of molasses tended to increase the digestibility of crude protein suggesting increased efficiency of nitrogen utilization. the potential role of urea in relation to the beneficial effects and the importance of these findings to encourage increased utilization of abundantly available rice straw (2.5 tonne/a) in malaysia is discussed.