9 March, 1908.] Sorghum Poisoning. 161 



SORGHUM POLSONmCI. 



S. S. Cameron, M.R.C.V.S., Chief Veterinary Officer. 



Numerous fatalities of both horses and cattle have been recorded as a 

 result of feeding too plentifully on plants of the sorghum family when in 

 a green state. In years past the trouble was attributed to the animals 

 being affected with hoven or tympanitis through the formation of gases bv 

 the fermentation of the excess of green food. Later on it was put forward 

 by authorities in India that the fatalities were due to the excess of saltpetre 

 (nitrate of potash) which is present in large quantities in the plant tissues 

 of young sorghums, especially during dry periods ; but the deaths occur 

 too suddenly, and saltpetre, even if it were not quickly excreted but 

 accumulated in large amount, is so slightly poisonous that the theory was 

 quickly abandoned as untenable. 



Recent investigations, particularlv those conducted by the Scientific 

 Department of the Imperial Institute in 1902* have however resulted in the 

 discovery of prussic acid and cyanide of potassium in the young sorghum 

 plants in the proportion of 0.2 per cent., and it is apparently capable of 

 proof that it is to the toxic effect of these poisons that the sudden and 

 rapid mortalities are due. The prussic acid is present in dangerous 

 amount only in certain stages of growth (from five weeks to seven weeks 

 usually) and disappears gradually shortly after the blos.soming stage, when 

 the ear begins to form ; and has completely disappeared when the seed is 

 ripe. It also disappears on drying shortly after being cut. Prussic 

 acid is a very volatile substance and it apparently quickly evaporates when 

 the plant cells are dying and therefore incapable of elaborating more of it. 



Its presence would appear to be in inverse ratio to the vigor of growth 

 of the plant. It is found in increased quantitv during dry seasons and is 

 almost absent in plants grown quickly on moist land. Stunted crops and 

 crops that have had uneven growth or a check during growth are most 

 likely to contain poisonous quantities of prussic acid. Second growth 

 is also more dangerous than first growth. Unfortunately it is just such 

 crops as are the most dangerous that a farmer is tempted to graze off, 

 arguing that a stunted crop or second growth is not worth the bother of 

 cutting. All varieties of the sorghum family are liable to contain the 

 poison — none are immune. When grown on land rich in nitrogenous 

 elements (e.g., when manured with nitrate of soda) the amount of poison 

 is increased and by experiment it has been shown that 4 lbs. of .sorghum 

 so grown contain sufficient prussic acid to poison an ordinary cow. 



Prevention. — To avoid poisoning accidents when feeding sorghums 

 it is advisable to adhere to the following rules: — - 



1. Never allow stock to have access to growing crops of sorghum, 

 millet, amber cane, Dhoura or Egyptian corn, Kaffir corn, or other plant of 

 the sorghum family. Apart from the danger of poisoning the practice 

 of grazing the crop is a wasteful one. 



2. Never feed newly cut sorghum at any stage nf its growth, but always 

 allow it to dry or " wilt" for one or two days. If the atmosphere is 

 dry and sunnv the danger will disappear more quickly. 



3. Never feed immature growth. Feed only in the green state crops 

 which have blossomed and are forming grain. 



* Proceedings of Royal Society, London, June, igoa. 

 925. K 



