Mycotoxins in feed and how to spot them
Pakistan’s climate is close to ideal for aflatoxin. You will not see it, smell it or taste it — you will see it in performance that makes no sense.
Awaiting veterinary review. This guide is written from published industry practice and has not yet been checked by our domain advisor. Confirm anything clinical with your own veterinarian before acting on it.
Mycotoxins are produced by moulds growing on grain — before harvest, during drying, or in storage. They are invisible, tasteless and heat-stable, which means you cannot see them, the birds will eat the feed anyway, and pelleting does not destroy them.
Why Pakistan is high risk
Maize is harvested twice a year and much of it is stored in the open. A wet monsoon on top of grain that is not properly dried is close to ideal for mould growth.
The 2025 season is a case in point: flooding damaged corn harvested in May and June, with feed mills estimating a large share of the crop lost in open-air storage. Grain that is salvaged from those conditions is exactly the grain most likely to carry toxin.
What they do
Different toxins do different things, but the shared effects are:
- Reduced feed intake and slower growth
- Poorer nutrient absorption — FCRFeed conversion ratio — kilograms of feed to put on a kilogram of live weight. The single most useful number in broiler production, because feed is 60–75% of what the bird cost.Glossary → worsens
- Immunosuppression — vaccines take less well, disease hits harder
- Organ damage, particularly liver and kidney
- In layers, drops in production and shell quality
Aflatoxin and ochratoxin are the ones most often named. Mould growth visible in feed is a warning sign, but absence of visible mould does not mean absence of toxin — the mould can die and leave the toxin behind.
The pattern that gives it away
Suspect mycotoxins when a change of feed lot lines up with a step change in performance that nothing else explains.
That is the signature: not a gradual drift, but a flock that was doing fine and then was not, with the timing matching a delivery. It is also why recording feed lot numbers against daily performance is worth the two minutes.
Other clues: birds off feed without respiratory or gut signs, vaccination responses that fail across a whole flock, and pale or enlarged livers found at post-mortem.
What you can actually do
Buy on analysis where you can. A mill that will share a toxin analysis is selling a different product from one that quotes only a price.
Store properly. Dry, ventilated, off the floor, and turned over rather than left sitting through a monsoon. Most of the problem starts in storage, not in the field.
Watch rice polish in particular. It is high in oil and goes rancid in storage — buy fresh, use quickly, especially in summer. De-oiled rice bran keeps far better for exactly that reason.
Toxin binders. Widely used, and they work by reducing absorption in the gut. Two honest caveats: a binder does not remove toxin from the feed, and different binders work on different toxins. They are damage limitation, not a licence to buy suspect grain.
What it is not
Mycotoxins get blamed for a lot of unexplained performance, and sometimes correctly. But before settling on it, rule out the cheaper explanations: water quality, feeder height, stocking density and subclinical coccidiosis all produce a similar picture and are easier to fix.