Critical limit of HCN in sorghum (dry wt. basis) is:
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To avoid HCN poisoning in cattle, do not harvest or graze sorghum until the plants are at least 50-60 cm tall or have reached the 50% flowering stage.
Silage making also reduces HCN to safe levels.
Step 1: Understanding the Concept:
Sorghum (*Sorghum bicolor*) is an important winter and summer fodder crop.
However, young, drought-stressed sorghum plants contain a cyanogenic glycoside called dhurrin, which breaks down into toxic hydrocyanic acid (HCN or prussic acid) when chewed by livestock. Step 2: Detailed Explanation:
HCN is a highly potent toxin that inhibits cellular respiration in animals, leading to rapid asphyxiation and death.
The concentration of HCN is highest in young sorghum plants (under 45 days old or less than 60 cm tall) and in plants subjected to drought or frost.
Toxicological studies have established safety limits for feeding sorghum fodder to livestock:
An HCN concentration below \( 200\text{ ppm} \) (parts per million) on a dry weight basis is considered safe for consumption.
If the HCN content exceeds the critical safety threshold of \( 200\text{ ppm} \), the forage is highly toxic and can cause prussic acid poisoning in cattle.
As the plant matures past 50 to 60 days, or when it reaches the flowering stage, the HCN concentration naturally drops to safe levels. Step 2: Final Answer:
The critical safety limit of HCN in sorghum is 200 ppm on a dry weight basis.
