Dairy herds facing 'perfect storm' of mycotoxin risk this winter

With the maize harvest delayed across much of the country this autumn, the threat from mycotoxins could be even higher than usual, warns Dr Derek McIlmoyle, AB Vista’s Technical Director for GB & Ireland.

Combined with increased risk of sub-acute ruminal acidosis (SARA) from low dry matter, acidic grass silages and increased feeding of cheap cereals, it means that dairy herds could be facing a ‘perfect storm’ of mycotoxin risk this winter.

“SARA significantly increases the threat posed by mycotoxins by reducing rumen microbes’ ability to deactivate certain mycotoxins and easing mycotoxin passage into the blood by damaging the rumen wall,” states Dr McIlmoyle.

“Maize silages are highly susceptible to mycotoxin contamination, particularly from the Fusarium moulds that grow on the crop pre-harvest. With harvest delayed this year, there’s been a much greater opportunity for mould growth and mycotoxin production.”

A 2014-15 survey across the south west of England found that even in a ‘normal’ year, 90% of maize samples tested positive for mycotoxins, with 90% of those samples containing the extremely damaging deoxynivalenol (DON) and 54% contaminated with zearalenone (ZON).

According to Dr McIlmoyle, the impact on the cow can be substantial, including reduced milk yield and quality, falling body condition, poor fertility and an increase in health issues like lameness and mastitis.

“If a problem is suspected, it’s often more cost-effective to simply feed a ruminant-specific mycotoxin de-activator and monitor the response, rather than go to the expense of testing forage samples.

“A 2-3 litre/cow/day improvement within 3-4 weeks of adding a de-activator like Ultrasorb is indicative that the mycotoxin load was hurting performance.”