Chemical treatment of rice husks/ Zulkhairinin Zabidin

Rice husks are of low biodegradability and its voluntary intake by ruminants is poor. There are 2 types of rice husks, which are whole husks and ground husks. Whole husks is a husks from milling process and ground husks is a husks was grind in the grinding machine which are their particle size had been reduced to be less than 1mm. The main objectives of this research are to determine chemical composition, digestibility and degradability of rice husks and to identify a method of upgrading the nutritional value of rice husks as a feed for ruminants. Rice husks obtained from a commercial rice miller were treated with 4% urea or 4% sodium hydroxide solution and untreated as a control. Untreated and chemically treated of rice husks was estimated and analysed for its chemical composition and in vitro digestibility (IVD). Dry matter degradability was estimated by incubating rice husks samples in a cellulase buffer solution for 3,6,12,24,48 and 72 hours at 38°C. Degradation characteristic were calculated from the exponential equation p=a +b(l-e"ct). p= degradation at time at time t(hours) and a, b and c are contants (%) representing the rapidly degradable fraction, slowly degradable fraction and degradation rate of b respectively. Data were statistically analysed on a SAS (Statistical Analysis System) package. Result showed the composition and digestibility of ground husks was approximately similar to whole husks. For ground husks after NaOH treatment, total ash (TA) was 23.2% and In Vitro Digestibility (IVD) was 48.5% but for control and urea treatments TA was 13% and IVD 16%. Differences were significant (PO.001). The control and urea treatments were approximately similar in neutral detergent fiber (NDF) 80% but NaOH treatment reduced NDF to 61%. For insoluble ash (IA), control and NaOH was 6.3% but urea reduced to 3%. Difference were significant (p<0.01) and for crude protein (CP), control and NaOH was 2.3% but urea increased to 5.0%. For whole husks, after NaOH treatment, total ash (TA) was 21.1% and In Vitro Digestibility (IVD) was 45.7% but for control and urea treatments TA was 13% and IVD 13%. Differences were significant (PO.001). The control and urea treatments were approximately similar in neutral detergent fiber (NDF) 82% but NaOH treatment reduced NDF to 63%. For insoluble ash (IA), control and NaOH was 7.6% but urea reduced to 6%. Difference were significant (p<0.01) and for crude protein (CP), control and NaOH was 2.3% but urea increased to 3.4%. In cellulase degradability the potentially degradable fraction (a + b) of the NaOH treatment was significantly higher than control and urea. For ground husks the mean value of a, b and c for control was approximately similar to urea, 2.5%, 2.3% and 0.058 per hour, respectively. These parameters were increased after NaOH treatment. Whole husks the mean value of a, b and c These parameters were also increased after NaOH treatment.