Abstract
This study was made to clarify the possibility of cultivation and use of Colombus grass (Sorghum almum Parodi.) in the warmer area of Japan. For this purpose, two cultivars of Colombus grass and three cultivars of Sudangrass (S. sudanense (Piper) Stamp) were compared from the aspect of HCN content, yielding ability, chemical composition and feeding values. The obtained results were as follows. 1) Total dry matter yields of J-Colombus and K-Colombus of Colombus grass were 224 and 250 kg/a, respectively and those of Piper, Hi-Sudan and Hay-Sudan of Sudangrass showed 185, 188 and 211 kg/a, respectively. These results suggested that Colombus grass had higher yielding ability than Sudangrass. 2) The HCN content in Colombus grass was higher than that in Sudangrass. Among cultivars of Colombus grass, J-Colombus showed higher HCN content than K-Colombus. On the other hand, among cultivars of Sudangrass, Hi-Sudan showed the highest HCN content and Hay-Sudan followed and Piper showed the extremely low potential. Considering from the safety limitation of HCN being below 500 ppm on dry matter basis and from the relationship between the dry matter and plant length, the plant length should be over 110 and 140 cm for K-Colombus and J-Colombus in cultivars of Colombus grass, respectively. 3) The experimental results of digestion trial from sheep showed that the crude fiber of Colombus grass was digested much easier than that of Sudangrass. The contents of digestive nutrients of both grasses were as follows : DCP and TDN contents in the first crop of K-Colombus were 9.5 and 59.6%, respectively, and those in the second crop were 4.6 and 58.3%, respectively. These contents in Hi-Sudan were 9.9 and 54.4% in the first crop, respectively and 6.7 and 54.9% in the second one, respectively. 4) The above results indicate that Colombus grass is superior to Sudangrass in yielding capacity and digestibility of crude fiber, but it is important to pay attention to the desirable mowing time then HCN content in shoots is below poisoning level. Since Colombus grass is wet tolerant, this grass is considered to be useful in the future for a new green fodder crop to the rotational paddy field in the warmer area of Japan.
