Prohibited substances widely used on Australian horses

Some basic information on some common horse care products that that have "NOT TO BE USED on horses that may be slaughtered for human consumption" as their meat withholding period.

There is no system for tracing the use of these substances in Australian horses. Any horse owner can use these products on their horses, with no legal requirement to report their use to anyone. 

1. Phenylbutazone 
A non-steroidal anti-inflammatory drug (NSAID) given to horses suffering from a wide range of different injuries and illnesses. It is commonly administered in the form of an oral paste or powder, but may also be injected or applied externally.

This substance is very dangerous to humans, it is known to cause aplastic anemia when ingested. As such, the European Union has the following position on Phenylbutazone use in horses:
Any horse in the EU treated with phenylbutazone must be excluded from the food chain and be signed out of the food chain in the equine passport. (Link to source)
Australian horses given Phenylbutazone do not have the same strict standards applied. Anyone can give their horse this drug, and there is no legal requirement for its use to be reported to anyone. 

Phenylbutazone is known as "bute" to most Aussie horse owners, it is used by many in a very casual way, as if it is "ibuprofen for horses". In practice it has to be prescribed by a vet, however many horse owners keep some on hand "just in case". These days it is available as a paste in a 500mL tub, which is enough for 50 - 200 doses, depending on the size of the horse and the nature of the injury. After the horse for which it was prescribed has recovered from its ailment, there is usually plenty left over, to be used whenever the owner feels like it. It is also common practice for horse owners who have a good relationship with their vet to obtain bute for certain ailments, with no veterinary examination required. 

Phenylbutazone is also present in products such as Phenylzone, which is a cream applied externally to the injury site. 

2. Dermapred 
A commonly used green ointment, applied to wounds, skin conditions and burns. From the Ilium website:

An easy to apply anti-inflammatory, antibacterial agent active against a wide range of bacterial and mycotic infections. It is used for the treatment of acute and chronic eczema, infected wounds and burns, reduction of irritation and oedema, and as a post-operative dressing for dogs, cats and horses.
Please see the website for more information, including:

Withholding Period: Not to be used in horses intended for human consumption.

Precautions: Do not use in food producing species of animals.

Once again, this product must be prescribed by a vet, but lots of horse owners have some in their first aid kit from previous vet visits to their animals.Horses injure themselves regularly, but not always seriously enough to warrant spending over $100 on a vet bill. Horse owners will therefore quite commonly treat minor injuries with medications that are officially meant to be prescribed by a vet.

3. Insecticides 
There are a number of insecticides for horses which are "not to be used on horses that maybe slaughtered for human consumption."

One example is "Brute", a widely used "wipe on" insect repellent that is widely used on horses. No vet is required here, as this product is available for purchase over the counter, and indeed over the internet, at any store dealing in horse supplies. These products are very popular, as they only have to be applied about once a week, rather than every day, as is often the case with spray on products. 

The following link is for an online horse supplies store that stocks "Brute", where they have listed a lot of the information on the label of this product: for more information click here. 

As you can see from that link, the label clearly states:
Restraints:  Not to be used on horses that may be slaughtered for human consumption.

This is one of a number of insecticide products that, when used, render a horse unsuitable for entry into the food chain. 

4. Anabolic Steroids
Anabolic steroids may be given to horses to aid in processes such as muscle building, tissue repair and the healing of fractures. An example of one is Ilium Anadiol. More information on their website here. If you visit that site you will see a familiar phrase:
Withholding period:   Not to be used in horses that may be slaughtered for human consumption.
Another example is Ilium Stanabolic. More information here.

5. Anti-Fungal Cream
Horse owners will be familiar with the many types of fungal infections horses can get. They include greasy heel, ringworm and rain scald. One product that may be used to treat these sorts of infections is a cream called Fungafite. 

Withholding period: Not to be used in horses intended for human consumption

Once again this is an Ilium product, and more information can be found on their website here.

6. More...
The above are some of the more common products used in horses. There are many others, including:

More detail to be added in the future, as time allows.