Aflatoxin Delivers Knock-out Punch to Calves

Molds – more specifically the mycotoxins they produce – can have a significant impact on dairy cattle performance, especially in young calves. That’s because rumen microorganisms in adult dairy cattle act to break down certain mycotoxins, making them less harmful to the animal. Young calves with undeveloped rumens don’t have that line of protection.

This is an especially interesting year for mycotoxins due to the summer’s drought. Most molds thrive in high levels of moisture. However, aflatoxin, produced by the Aspergillus mold, thrives in periods of excessive heat and drought. Because it is carcinogenic, aflatoxin is tightly regulated by the Food and Drug Administration. It has received a lot of attention this year as dairy plants test for the toxin to ensure milk with aflatoxin levels above 0.5 ppb is dumped and doesn’t enter the human food supply.

Aflatoxin isn’t just a major concern in lactating cows. The toxin can deliver a huge blow to a calf as it damages the liver and subsequently the young animal’s immune system.

Deb O’Connor, dairy technology manager with Prince Agri Products, Inc., reminds producers that damage to the calf’s immune system now will have lasting impacts throughout its life. With a weakened immune system, the animal will always face a bigger disease challenge. The animal’s body will have to invest more energy into fighting disease, which means it will have less energy for growth and maintenance. Poor immunity also affects the success of vaccination programs.

According to O’Connor, calf feeds should ideally be aflatoxin-free. If your grain does test positive for aflatoxin, you might be able to blend it with “clean” grain to reduce the concentration to below 20 ppb.

The key here is proper sampling. Aflatoxin levels will vary greatly from field-to-field and even plant-to-plant. Thus, a load of grain may contain “hot spots” of the toxin. To secure a representative sample, take several sub-samples from throughout the load and blend them into a composite sample.

If you are purchasing grain or calf starters, your supplier should be able to assure you that the grain is clean. O’Connor encourages producers to ask for proof of testing and sampling procedures when purchasing grain if aflatoxin contamination is a concern.

Although aflatoxin is in the spotlight now, it’s not the only mycotoxin that may be an issue this year. O’Connor said the 1988 drought brought on aflatoxin issues that were later followed by T-2 toxin. This toxin also affects calves’ immune systems, further impacting health and performance. O’Connor said she regularly checks in with diagnostic labs and, so far, none are reporting T-2 issues. That doesn’t mean they won’t appear later.

In years with more typical rainfall, other mycotoxins are a concern in calf feeds. Again, because young animals are more susceptible to their effects, mycotoxins like DON (vomitoxin) and zearalenone should be closely monitored and eliminated from calf diets.

O’Connor reminds producers they’re not just feeding calves, they’re feeding the next generation of the milking herd. Any stress that limits performance now will also limit the adult animal’s potential.

Work with your nutritionist to make sure diets are properly formulated with the right levels of energy, protein, vitamins and minerals. Review your management protocols and limit any stress the young calf might experience. Finally, remember that mycotoxins aren’t an issue in grain only. Hay and forages can also carry various mycotoxins. Always look at your total program to ensure calves receive the best feeds that promote optimal performance and limit potential problems.