Abstract
For the purpose of investigating the efficient method of utilizing the ensiled NaOH-treated rice straw, two digestion and nitrogen balance trials were carried out, in which the four rations: ensiled NaOH 6%-treated rice straw ; ensiled NaOH 6%-treated rice straw and ryegrass hay (expt. 1) or ryegrass silage (expt. 2) mixed at the time of feeding to approximate 50:50 or 25:75, respectively, on a dry matter basis ; and ryegrass hay (expt. 1) or ryegrass silage (expt. 2) were fed to four goats in a 4×4 Latin square design. The digestibilities of dry matter, organic matter, NFE, crude fiber, NDF, ADF, hemicellulose and cellulose were significantly higher for the ensiled NaOH 6%-treated rice straw than both for the ryegrass hay and the ryegrass silage. The digestibilities of all the constituents actually determined for the 50:50 and 25:75 rations significantly higher than those calculated by the combining ratios assuming constant digestibilities of both the ensiled NaOH 6%-treated rice straw and the hay (or the grass silage) rations, namely combining NaOH 6%-treated rice straw with hay or grass silage resulted in associative effects on digestibility of verious constituents. The digestibilities of all the constituents for the ensiled NaOH 6%-treated rice straw portion in the 50:50 and 25:75 rations calculted by an indirect method assuming constant digestibility of hay or grass silage increased with increasing level of hay or grass silage in the rations. The TDN contents of ensiled NaOH 6%-treated rice straws mixed with ryegrass hay ware 57.2, 59.7 and 62.5% of dry matter for the 100:0, 50:50 and 25:75 rations, respectively, and those of them mixed with ryegrass silage were 57.4, 59.9 and 62.7% for the 100:0, 50:50 and 25:75 rations, respectively. Much more nitrogen were retained with the mixed rations of ensiled NaOH 6%-treated rice straw and ryegrass silage than with the ryegrass silage ration. From these results it was suggested that the ensiled NaOH-treated rice straw could be efficiently used in combining with other feeds, especially with grass silage for fully attaining potential digestibility in the NaOH-treated rice straw.
