Mouldy straw problems for both man and beast
Published 19/12/2012 | 06:00
Forage quality and quantities are among the primary issues for most farmers I encounter at this time. Grass silage is the most common form of forage and is in short supply and of reduced quality on a lot of farms.
Supplies of all other alternative forage options are also scarce and in some cases simply not available.
This has led people to use 'bulky' forages such as straw and, to a lesser extent, hay or very stemmy, late-cut silage.
A lot of straw was baled damp, potentially leading to problems with mould. Mould organisms are capable of causing diseases in animals and humans.
Feeding or bedding even slightly moulded straw, hay or any other forage may not always be intentional and in some cases is unavoidable.
The potential disease impact and reduced animal performance means the feeding of moulded forage should be avoided at all costs.
The majority of moulds produce mycotoxins. These are metabolites that have a toxic effect on an animal's metabolism.
At the very least, mycotoxins will cause reduced milk yields in cows, reduced performance in beef animals, abortions and, in extreme cases, death.
The main organisms that produce mycotoxins capable of causing problems are:
This organism has links with many clinical diseases. The time between consuming moulded forage and showing clinical signs of being affected can be as long as three to four weeks, so animals can still develop disease despite having no relatively recent access to mouldy feed.
Problems that can arise include infection of the brain, eye disease, abortion, pneumonia and neonatal septicaemia.
Diseases caused by fungi include placentitis and abortion, so particular care should be taken to prevent the feeding of spoiled feed that may appear on baled silage and poorly covered silage pits. Farmer's lung is a serious respiratory condition caused by fungal spores that affects humans and livestock.
This organism is a common cause of abortion and stillbirths in pregnant animals. It is very difficult to avoid as it is widespread in the environment and unfortunately rapidly multiplies in mouldy damp forages.
How do you know you have a problem?
The first signal of a possible mycotoxin issue would be an unexplained drop in performance. Reduced feed intake, sporadic scouring and increased episodes of disease can also occur.
With cows, there will be inconsistent milk yields and, further down the line, poorer fertility.
The use of mycotoxin binders can offset some of the effects. They mop up or absorb some of the mycotoxins in an animal's digestive tract, and are then excreted harmlessly from the animal before the mycotoxins are digested.
If the straw available is damp and not moulded it may pose some problems with palatability.
The addition of molasses, however, will aid palatability. Adding up to 1kg or 2kg of molasses for dry cows, while feeding large quantities of straw, will supply the necessary energy required for most suckler cows in late pregnancy.
Again, caution is urged when using molasses for dry cows as over-feeding may result in greater risk of milk fever.
If damp or moulded straw is used for bedding, the risk to livestock and humans can rise.
Simply rolling out bales in a well-ventilated bedded area ensures the risk to human health is lessened.
Straw chopper blowers are very effective when used to prepare bedding.
They will cut the quantity of straw needed and greatly reduce labour.
However, when mouldy straw is being used, chopper blowers will produce high levels of fungal spores in the atmosphere.
Where this is the case, make sure the windows and doors of the tractor are kept closed and nobody else is in the building. It may also be necessary to remove stock from the building and certainly never blow straw directly onto the animals.
The general approach with straw choppers is to bed daily with small quantities of straw.
With damp or potentially moulded straw, a better approach is to bed less frequently and give more straw per bedding to limit the total number of hours that animals are exposed to high levels of harmful spores in the air.
Gerry Giggins is an animal nutritionist. Contact him by email at: firstname.lastname@example.org
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