Estimation of HCN content in sorghum under irrigated and stressed conditions

Premise of research: Sorghum (Sorghum bicolor (L.) Monech) is one of the most important fodder crops for ruminants and it is a dual purpose crop used as a food and fodder but one of the great limiting factor with the forage sorghum is that it is having an anti-nutritional factor cyanogenesis, which is extremely toxic to the animals when feeding on the livestock. Sorghum leaf and stem tissues produces dhurrin, during the early growth stages; after a drought or heat stress or after a cutting for fodder etc. The effect of cyanogenic (HCN-producing) glycoside dhurrin (β-D-glucopyrinosyloxy-(S)-p-hydroxy-mandelontrile) which lowers the nutritive value of sorghum fodder. Hence, there is a need to improve the forage quality and also identify the sorghum genotype which will produce the safe levels of HCN that would be used as a livestock for animal feeding. Therefore, this present was designed to study/predict the amount of HCN released in both the irrigated and stressed (drought) conditions in sorghum plants. Pivotal results: To identify the cyanogenesis and to predict the exact stage where cyanogenesis is maximum in sorghum fodder, 5 prominent sorghum genotypes viz. EJ24, SSG59-3, SPV-462, CSV-15, IS18845 are used for HCN estimation in multi-cut hybrid and single cult hybrids. The cyanogenesis of these genotypes was determined by estimating the HCN in the intervals of 15, 30, 45, 60 and 80 days after sowing of sorghum plants. The results of the cyanogenesis analysed after 45 days of sowing showed that the high levels of HCN released in all five genotypes of sorghum under stressed (drought) conditions when compared with the irrigated conditions.Conclusions: Based on the obtained results it was concluded that hydrogen cyanide (HCN) production was more severe in the plants grown under drought conditions when compared with plants grown under irrigated conditions. It was also noticed that forage sorghum genotypes exhibited greater cyanogenic toxicity especially if fed in early growth stages. Increased uptake of forage sorghum grown under irrigated conditions is required such that farmers are assured of cyanogen-safe fodder. From these studies it was recommended that sorghum crop cultivated especially under drought conditions should be strictly evaluated for HCN estimation before its use as fodder for livestock.