CASE NOTES
Kikuyu Poisoning
Digby Rayward, District Veterinarian, Maitland RLPB
Posted Flock & Herd February 2011
History
Kikuyu is an imported grass species from South Africa. Poisonings have been recorded in South Africa, New Zealand and Australia.
Kikuyu poisoning occurs infrequently, considering the amount of kikuyu grown for pasture feed. The combination of circumstances that results in kikuyu poisoning is fortunately rare and little understood. When outbreaks occur they are limited to small numbers of paddocks or grazing management systems.
Clinical cases were first recognised in NSW in about 1980. I have seen clinical cases from one animal up to about 70 cases at Tea Gardens with AMP cattle.
The last outbreaks in the Maitland area were in February 2003 where 18 cows and a bull died after strip grazing a lush stand of kikuyu, and losses were also seen at Kulnura in April 2003, where 10 hereford cattle died. The calves at foot don't seem to be as badly affected as the adults.
The combination of events that creates a toxic feed have been variable, but are usually associated with a fertilised paddock, and rapidly growing kikuyu often following a dry period with some good rain.
There have been some claims that it is associated with army worms, but my judgement is that the army worms are incidental to the mortalities, as deaths have been seen with no army worms present.
It has been thought that a fungus may be involved, and at our last outbreak, samples were sent to the USA via Chris Burke. All samples were negative for mycotoxins and no endophytes were seen. Check with Chris for more details on this testing.
My gut feeling is that the toxin is in the grass itself. It is not uncommon to see cattle leave a patch of kikuyu ungrazed. This grass may or may not have a slightly different colour about it, but I think the cattle know that there is something different with this grass. It may become palatable after a few days.
I assume that deaths occur when cattle eat this affected grass, either because there is no other non affected grass available or they are forced onto the affected area via strip grazing.
Clinical Signs
Ataxia, clear drools of saliva hang from the mouth, recumbency and death. Ruminal stasis is shown in all cases, and signs of abdominal pain are frequently seen. Affected animals may also show sham drinking, and in rare cases the animals may charge. When the animals eventually go down they are often found in sternal recumbency with the nose pointing into the ground.
GROSS PATHOLOGY
The most obvious finding is the rumen distended with an abnormal amount of fluid. The ruminal contents are obviously very green and watery. Eyes can be sunken showing severe dehydration.There are no other obvious post-mortem signs.
LABORATORY RESULTS
Findings seem to be centered on the rumen and omasum. Severe acute segmental necrotic rumenitis is reported on histopathology along with omasitis.
These findings can also be found with lactic acidosis and superphosphate poisoning. These need to be eliminated in the clinical assessment of the case. That is if pH > 5.8, not lactic acidosis. I have never seen superphosphate poisoning.
If ruminal fluid is examined from an ill animal, there will be no protozoa seen.
TREATMENT OPTIONS
If the animals have not ingested a lot of toxin, they may survive by themselves in spite of any treatment.
However, drenching with epson salts, litres of vegetable oils, walking the animals, fluid therapy have all been tried with limited results.
The bold may even try a rumenotomy, evacuate contents, replace with chaff and ruminal fluid. (Good luck!)
CONTROL OPTIONS
If cattle are reluctant to eat any kikuyu, don't force them onto it. Give them a bigger paddock to graze, or move them onto a different feed source altogether. The affected kikuyu seems to self cure after about a week or so.