By Francis Ndungu

Five cows died in a single morning last week in Murichu, Laikipia West, from a deadly combination of flowering oxalis and bees, with one farmer Simon Kimani having taken the risk of using another field, even after inventing a cheap and permanent solution to the problem on his own grazing land.

Veterinary officer Alex Maine confirmed the deaths were caused by cows ingesting bees feeding on oxalis flowers. “Oxalis effects on animals are exhibited by bloat on the rumen which is not seen immediately after the cattle consumes oxalis, unlike bees, [which] cause sudden death of animals either when ingested or stung,” said Alex. “Bees’ effects are more dangerous than oxalis effects. If care is not taken within one hour there is a high possibility of losing the animal.”

Farmer Simon Kimani lost three Friesian cows and his neighbours John Nguu and Joram Huria each lost one, with all five animals dying within minutes of being released to graze on fields dense with flowering oxalis.

Oxalis is a common plant in Laikipia’s grazing fields, spreading quickly after rainfall through deep rhizomes that can survive in soil for over five years. Its salt-like sap appeals to cattle, but the plant causes gas to build up in the rumen, leading to dangerous bloat.

But Simon and his neighbours believed they had mastered grazing cattle on oxalis, following a series of deaths some years back.

“Grazing my cattle very early in the morning before dew evaporated made my cows accumulate gases in their rumen and caused swelling in their left side of the rumen,” said Simon. After losing a cow to oxalis bloat, he was advised by his vet not to release his animals before 9am. “That rescued my cows from bloat issues,” he said. “The change in timing solved about 60 per cent of the problem.”

Simon also adopted a range of local remedies for oxalis bloat. “Making animals run when having bloat issues is an excellent method. Running helps in expansion of gases in the stomach, forcing it out through the mouth, anus, ear, and even the skin,” he said. For severe cases, he smears paraffin or engine oil around the cow’s nose and mouth. “After 30 minutes the bloat gases got out of the rumen.”

While these methods helped reduce losses, the weed has remained a constant risk. 

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The farmers have tried herbicides, but these meant withholding grazing. “I had to keep away my cattle out of the field for two weeks, which made my cattle grow weak since I could not be able sustain them with bought feeds.”

Yet, the risk was managed, except for a single deadly side effect when oxalis entered full bloom, drawing bees from nearby apiaries. Cattle ingesting the bees while feeding suffered fatal poisoning. “Unlike oxalis, bees kill very fast,” said Alex.

Simon had been using antihistamines to counter this after advice from his vet. “Antihistamine is not only for bee poison but for all poisonous insects which may have caused bites on cattle,” he said. But, last week, in a field full of flowering oxalis and bees, it was not enough – preventing exposure was the only sure protection.

Yet Simon had found a permanent solution in his own field by using engine oil, which he had previously used to drive bees away from underperforming hives, “I smeared 10 oxalises with old engine oil the first day while grazing. The plants looked shiny during the first three days and started wilting the fifth day. I also noted that bees did not extract nectar on the smeared plants.”

Encouraged, he treated the entire field. “After one month, all the oxalis dried up with no chance of germinating again,” he said. “The engine oil was absorbed up to root level and covered the rhizomes, squeezing out oxygen. The plants died completely.”

This unorthodox method also cleared the bees. “In the field, bee population was reduced as they did not like the smell. Cases of ingesting bees by animals were curbed instantly,” said Simon.

He now applies the oil carefully to avoid contaminating edible grass. “Where the oxalis had dominated, I applied the oil on the base of the plants and they dried up successfully.”

“This method of smearing used engine oil on the oxalis flowers is cheap, requires less skill, and is the fastest way of getting rid of the bloat problem and the bee risk,” he said.

But he has had no choice but to sometimes use untreated fields.  “We don’t have any other place to graze,” he said, despite advice from Alex to avoid grazing in fields with oxalis or near apiaries.

Yet the costs of the toxins are very real. “After I previously lost my cow as a result of oxalis effects, I used to get 15 litres of milk in a day but later became a milk buyer,” he said. 

“Now I share what I’ve learned with other farmers. This knowledge had saved my herd.”

To this end, he is now working harder still as he comes to term with the deaths of the five cattle last week in an untreated field.