Vet on Call: Human food that’s poison to cattle

Kaloki’s question was, “Are tomato stalks good for cows or was it another problem that killed my cow because the animal was very healthy before eating the stalks?” Before responding to his question, let us have a mental recall of the smell of tomato plants.

The bad tomato smell is part of the weaponry the plant employs to prevent itself from being eaten by animals. For sure, cows do not readily eat tomato plants. To add on to the smell, the tomato plant packs in a natural toxin called solanine and nitrate. Solanine is in the group of natural poisons known as steroidal glycoalkaloids.

The tomato plant belongs to a family of plants called the solanaceae or night shade. Other members of the family grown as food crops include the Irish potato, eggplant, bell pepper and capsicum. Most members of this family are known to contain the toxin solanine in the leaves, stem, tubers and green fruits but the solanine content in the fruit reduces to below toxic levels by the time the fruit ripens. Solanine is a bitter chemical and that is why green tomatoes are bitter.

The Irish potato, commonly grown for human food, has low levels of solanine in the tuber except when it has been exposed to a lot of sunlight and it turns green. Green potatoes should not be eaten as they are bitter and poisonous.

What most people forget is that humans normally will not eat the same part of the plant as animals. Further, human food is mostly cooked and this denatures most of the chemicals thereby detoxifying the food. Just as in people, ripe tomatoes are safe for cattle.

Other plants we grow as food for humans but may poison cattle include cabbage or any plant in the brassica family, onions, amaranthus and beans. Unfortunately, some of the plants like amaranthus, brassica and beans are also appetising to cattle and cows can consume them in large quantities.

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