Dear daktari, my father is a retiree and he is doing very well with dairy farming. It seems to be making him younger everyday as he labours to feed, milk and bond with his cows. I am home for the voting exercise and I noted something interesting. We are just harvesting our maize and I have noted that mzee is feeding the rotten ones to the cows. I know they could be containing aflatoxins which are not only harmful to the cows but also to consumers of the milk. Please advise. [Wilson Owuor, Migori County]
Thank you for the timely question since it is harvest time in most parts of Kenya. You are right in noting that rotten grains are harmful to animals and human beings alike. Your observation is a common trend among farmers. There is this attitude that any spoilt food is animal feed.
Rabbits, ducks, pigs, calves and chickens are susceptible to aflatoxin poisoning. The animal feeds most likely to be contaminated are maize, cottonseed, copra and groundnuts. Animals may often be fed crops considered unfit for human consumption because of mould, insect damage, etc. These feeds are at high risk of aflatoxin contamination. Aflatoxins cannot be detected by sight or smell in contaminated food or feed neither can they be eliminated by boiling, cooking, or processing.
When using plant-processing wastes or byproducts as livestock feed, it is sometimes viewed as an economical way of turning such waste into good use. But it sometimes can be harmful to animals and humans. When producing livestock for human consumption you should be cognizant that any material that has not been produced specifically for use as livestock feed can cause unacceptable chemical residues in animal products and end up harming human health.
What causes the rotting?
Rotting results from spoilage that is caused by poor storage, which results from entry of moisture into grain. Insects like weevils and rodents like rats can also cause rotting of stored grains and this favours the growth of moulds. The three common moulds that produce mycotoxins and grow on grains are Aspergillus species, Fusarium species and Penicillium species. They grow on grain in the field, in stores or in the feeding trough.
The rotting is normally caused by microorganisms notably fungi that result in growth of mould. When these microorganisms grow they produce toxins called mycotoxins. These toxins when consumed by livestock will be passed to man through milk, eggs or meat and can cause cancer. To avoid rotting, only store properly dried grains. Make your grain storage free from pest attack and well aerated. When an animal feeds on rotten grains, they will become sick (Mycoses) and when the toxins are ingested they cause fatal diseases (Mycotoxicoses). This also applies to human beings. In addition to these, animals and human beings can also ingest these mycotoxins through their noses when in an environment with mould spores. Simple masking can help protect human beings from this. Breathing in such spores causes respiratory conditions. It also causes stress and the animal will have poor appetite and hence reduced production.
Aflatoxin is a common mycotoxin and its contamination is common in various food and feed ingredients. In dairy cows, chronic exposure to aflatoxins can reduce performance, impair liver function, compromise immune function, and increase susceptibility to diseases.
[Dr Othieno is a veterinary surgeon and the head of communications at the Food and Agriculture Organisation (FAO) Kenya. The views expressed here are not necessarily those of FAO]