Why your dairy cow is eating discarded plastic

Cows eating garbage.

Dear Dr Othieno

I have four dairy crosses which I sometimes let loose to graze in my compound although they are mostly under zero grazing. One cow has started chewing on pieces of clothes and polythene waste and rags. I have also observed it licking tree backs, timber and even walls. What could be the problem and what’s the remedy?



Dear Cheruiyot,

Animals, like human beings, have behavioural patterns, while some are normal, others are not. It is upon the farmer to decipher which is normal or abnormal behaviour. 

Licking inanimate objects is called pica or deprived behaviour. It is a strong desire to eat things that don’t have any nutritional value and aren’t feeds.

An animal suffering from this behaviour will lick walls, chew wood, eat rags or clothes, polythene, tree backs or anything in its environment. Some will eat soil, bones or their dung or drink urine. 

Causes of Pica

Although the cause of this condition is not explicitly known, it is thought to be imbalances in mineral salts especially calcium, sodium and phosphorus. This may explain the animal “looking” for the minerals or trying to quench the graving.

Pica has also been thought to be caused by nervous problems, liver diseases or toxicity (lead) poisoning or metabolic diseases or low roughage diets. Some researchers have also attributed pica to boredom, especially in calves.

Clinical Signs

The main clinical sign is an animal eating things that aren’t of any nutritive value listed above. The others will manifest as secondary and include indigestion, loss of body condition due to the ingestion of objects that have no nutritive value.

Polythene bags are indigestible and normally lodge in the rumen occupying a lot of space hence reducing the digestive capacity of the cow, this translates to reduced production and loss of body conditions.


If the cause is attributed to mineral deficiency supplementation can be done, sometimes the deficiency can trace back to the soil on which the pastures are grown.

Where low roughage is the cause, hay should be provided.  The animal should not be grazed in areas with pieces of clothes or polythene papers.

[Dr Othieno was the Vet of the Year Award (VOYA) winner in 2006 and works with the Kenya Tsetse and Trypanosomiasis Eradication Council  - KENTTEC. He can be reached on [email protected]]

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