A variety of grasses from the genus Sorghum: Sorghum vulgare (sorghum, Sorghum bicolor, broom-corn, guinea corn, milo, schrock); S. vulgare var. sudanese (Sudan grass, Indian corn). Related wild species: S. halpense (Johnson grass, Aleppo grass).
A member of the plant family GRAMINEAE. Valuable plants cultivated as crops in the same manner as barley and oats. With the exception of Aleppo grass, sorghum is used as fodder (green chop or ensilage), and grain sorghum used for feeding horses, cattle and poultry.
The flowers of the plant are terminal inflorescences which develop into large heads of glossy small, round grain.


[affected.gif] Animals most affected
Cattle, (sheep, goats).


[etiology.gif] Etiology
Massive ingestion of sorgho or Sudan grass (a variety of sorghum) as fodder sorghum, or sprouting green sorghum or of regrowth of the grass after harvesting.


[toxic.gif] Toxicity
Contains a cyanogenetic heteroside, durrhine (which yields HCN on hydrolysis). The levels of durrhine are high in the young plant, but diminish as the plant matures. The leaves contain more durrhine than the stems. Drought, strong sun, nitrate fertilizers all increase the levels of HCN in Sorghum species.

Oral doses:
LD cattle 1 kg leaves/500 kg body weight.


[clinical.gif] Clinical features Ingestion of large amounts
Onset of clinical signs can be immediate if large amounts are ingested:

Ingestion of a moderate quantity

Ingestion of a small quantity
If the amount ingested is relatively small, recovery occurs within several hours, without sequelae.


[lesions.gif] Lesions


[treatm~1.gif] Treatment
Often of little value as the onset of clinical effects is so rapid; the efficacy of the treatment is also debatable. The following may be tried:



[labinv~1.gif] Laboratory investigations
Stomach contents:

Recommendations
ensure animals graze only old sorghum, avoid new growth or recently harvested sorghum fields;
use a medium-strength nitrate fertilizer and apply a manure which has a high phosphate level.


[case.gif]
Case summaries
A colleague of the author made an interesting case observation which illustrates the most common features of sorghum poisoning. A farmer had been growing sorghum for over 20 years. The area was grazed by cattle but access to the crop was restricted by an electric fence. The weather conditions were characteristic for July, with severe drought. The following month there were several storms which encouraged regrowth of the crop.
The farmer, hoping to avoid significant losses from this land, harvested the sorghum with a silage-maker and fed his animals with all the newly harvested crop that evening. On the morning of the next day a 4-year-old cow was found dead and a second 12-year-old cow presented with a staggering gait, wheezing and an atonic rumen. The cow recovered after symptomatic treatment.
In this particular case the new shoots of sorghum, rich in cyanogenetic heterosides, had been pulverized by the silage-maker, liberating and dispersing the hydrocyanic acid within the crop. The affected animal showed no further ill effects after its recovery. This is a characteristic of sorghum poisoning.