Mouldy Feed Can cut performance and may permanently damage cattle.

Take Home Messages

Any mouldy feed has the potential to damage performance and cattle
Some toxins are carried through to milk - the EC demands exacting standards
Whilst mouldy feeds are frequently fed the recommendation is donít
Adopt a least risk strategy to reduce potential field and storage toxins.

Effect of level of spoiled maize silage on dry matter intake and nutrient digestibility

Dr. Keith Bolson of North Carolina summarized the effect of feeding spoiled silage from the top of maize silage clamps.   The top three feet of maize silage in a bunker was allowed to spoil and fed to steers fitted with rumen cannulas.

Four diets were fed

100% normal silage
75% normal + 25% spoiled silage
50% normal + 50% spoiled silage
25% normal + 75% spoiled silage 

Feed results are summarized in Table 1.

Table 1.  Effect of level of spoiled silage on dry matter intake and nutrient D Value



25% Spoiled

50% Spoiled

75% Spoiled

DM intake (kg/day)





Organic matter D (%)





Crude protein D (%)





Fibre (NDF) D (%)





  The addition of spoilage had large negative effects with the first 25 percent having the greatest impact.  When rumen contents were removed, spoiled silage had destroyed the forage mat in the rumen.   The impact was greater than expected and damaged forage digestion; rate of passage, and performance; especially in high producing dairy cows.

In the US it is not uncommon to find maize clamps unsheeted. What will deliver the same thing in the UK is

risks begin in clamp, at the face, or in the feed passage in over 32% DM maize,
poor consolidation of clamp & shoulder management
low feed out rate -to wide a clamp - 1ft per day in summer

Strategies to minimize storage moulding in any feed include:

improved feed storage conditions - optimal moisture and limiting exposure to moulds
adding mould inhibitors - propionic acid or salts of propionic acid, Urea, Caustic Soda
adding compounds that tie up mycotoxins - sodium bentonite, commercial clay products, activated charcoal, and complex oligosaccharides
monitor feed storage conditions and feed quality
low levels of mycotoxins may be a marker of a feed storage and handling problem but the cost of analysis is prohibitive - £100+

The most damaging of mycotoxins are

         Aflatoxin & Ochretoxin - these are storage toxins from moulding of grains / straights in damp warm conditions - they can be carcinogenic or permanently damage the liver.  Ammonia and possibly urea treatment can denature Aflatoxin.  Ochretoxin shows up in milk - there are strict EC standards for Ochretoxin and Aflatoxin.

         DON - or Vomitoxin - a field toxin from fusarium (head blight - head scab) in wheat can give rise to digestive upsets particularly in the young ruminant and mono gastric.  DON has not shown up in milk.  There are lots of other causes of digestive upsets - (Lack of effective fibre, excessive grains, disease) but if these are ruled out through careful feed / diet management then DON or some other mould should not be discounted.

         There are other mycotoxins from fusarium that can effect fertility


What's the position in the UK? 

Storage Toxins:

Nationally a survey showed storage mycotoxins are at low levels in well dried and cooled grain held in damp proofed non-leaking stores. However, we all recognise that dairy farmers for the most part are not arable farmers. 

         The old covered silage pit converted to grain store next to the new silage pit generally runs wet, roofs leak, space boarding lets in horizontal rain and when the door is left open the dog / cat or starlings crap all over.

         For long term storage dry cereals need to be cool - under 10C AND

o        17-18% moisture with low volume ventilation max 6 months

o        15% Max moisture for all year - particularly summer.

         Inappropriate moisture content / application rate / sheeting for any crimped, caustic, urea  innoculant or propcorn treated grain has the potential to deliver a potentially nasty mould. 

         Aim for a feed out rate of 1ft per day for damp treated products other than caustic grain.  This means long narrow mini bunkers.  Any fermented product is going to be attractive to vermin - much less so caustic or urea treated whole grains.


Field Toxins - Fusarium. spp

  Again national surveys have shown toxins to be at moderate levels BUT in the South West Fusarium is rampant and is encouraged by moist conditions from flowering onwards in Wheat & Triticale.

The Maize Wheat Maize Wheat rotation has but one weakness - fusarium.  A spray with Amistar and Caramba when the wheat head has just fully emerged from the stem is essential.

Where there is sufficient acreage to more than fulfil starch and fibre requirements then pulses and linseed ( Not OS Rape)  should be considered.

The following rotations are recommended  to minimise fusarium

No Grass With Maize:

WWheat Maize Spring Beans WWheat Maize WLupins
WWheat Maize Spring Beans WWheat Maize SLinseed

No Grass Without Maize

WWheat WBarley Spring Beans WWheat WBarley WLupins
WWheat WBarley Spring Beans WWheat WBarley SLinseed


Conventional wisdom would discourage these rotations for sclerotinia disease, which attacks most crops.  Conventional advice is to grow no legume within 5 years of another.  If sclerotinia does become established - then seed yield can be savaged - then will be time to widen the gap.