Hormonal Growth Promotants (HGPs) — The ins and outs of implants

Hormonal Growth Promotants (HGPs) are implants that contain naturally occurring hormones to promote growth in cattle.  There are two types of implants available, compressed pellets or impregnated silicone and they both are inserted under the skin on the back of the ear.

The main types of HGPs used in Australia contain either female (oestrogens) or male (androgens) sex hormones.

• OESTROGEN (Oestradiol-17 β) is found in Compudose 100, 200 and 400 (silicone implants with a release period of up to 400 days)
• TRENBOLONE ACETATE (TBA – synthetic androgen) is found in Revalor and Component (compressed pellets with release periods of 60-120 days) and is in combination with Oestradiol.
• Implants may also contain a combination of the following: Oestradiol benzoate, testosterone propionate, progesterone or zeranol (synthetic testosterone).  Tylosin tartrate may also be included as a local antibacterial agent.

A list of HGP products registered for use in Australia and the hormone combinations they use, can be found HERE.

These hormones influence the relative rates of fat and protein deposition and causes differential growth rates of different muscles.  These impact carcass traits and quality.  At any given body weight, HGP treated cattle are leaner by five to eight percent. This is because under the influence of the implant, the body builds and deposits protein tissue at the expense of fat production.

Extended, or whole of life implant programs have been developed to keep cattle growing faster under seasonal patterns of pasture growth. The choice of HGP program needs to be determined by how long there will be good quality feed available, which breeds of cattle are being fattened, the market they are being prepared for and how often they are mustered.

When deciding whether to use HGPs, consider the following:

• The cost of both implants and the labour needed to insert them.
• Increase in feed intake. This is caused by the animals being larger/heavier, not by the HGPs themselves.
• Reduced market options. International markets such as the EU, Russia and China do not accept beef that has been treated with HGPs.  Domestically, Coles do not accept implanted cattle.
• What breeds are being implanted? Both early and late maturing breeds respond to HGPs, however they will respond at different rates and will result in different carcass composition. Early maturing breeds (Angus, Poll Hereford) may not respond as much as late maturing breeds (Simmental, Brahman).  At any given liveweight, late maturing types are in a higher growth phase and therefore have a higher base rate to increase from.
• What markets are you aiming for? Different markets have different specifications. Will HGP use help you reach those markets faster? Or will they push you out of required range of specs (carcass composition, age etc)?
• Will you have adequate feed supply and quality during the period of implantation? Cattle will only benefit from HGPs if the pasture/feed allows for weight gain.  In periods of poor nutrition, there will be no benefit.
• HGPs may cause minor changes to animals’ behaviour and appearance. Warnings on labels of HGP products include: prolapse of prepuce, rectum or vagina, increased bulling activity, sunken loins and udder development.

A logical way to develop a potential HGP strategy is to work backwards from the sale of the desired product.

Some general principles apply in the use and design of HGP programs:

• The more frequently animals are re-implanted, the higher the overall weight gain.
• Once a program has begun, it should continue up until slaughter for best results.
• Long duration implants (such as Compudose 400) allow for seasonal changes in pasture condition and are particularly beneficial in Northern Australia to shorten turnoff age.
• Short duration implants (such as Component 100) require high levels of nutrition for the whole period to be effective.

There are six steps to fulfil your legal responsibilities when using HGPs.  Farmers, graziers, lot feeders and livestock agents must follow these steps to help protect Australia’s market access.

1. Have a registered PIC

To purchase HGPs from an authorised seller, you must have a Property Identification Code (PIC).

2. At the time of purchase, complete a HGP purchaser declaration form and provide it to the supplier

Your supplier should have copies of this form, or you can access it here from the APVMA website. This form includes details about you, the HGP supplier, which HGP products will be implanted into which cattle, and the details of the property where the cattle will be implanted.

3. Use HGP products according to the label directions

Approved guidelines for the use of HGP products are prominent on the label. Follow these guidelines which include information on dosage, application, withholding periods and more.

4. Identify HGP-treated cattle with a triangular ear punch mark

The ear punch mark is an equal sided triangle with sides of 20mm; applied to leave a space on all sides within the margin of the right ear. If an animal has previously been treated with HGPs and has been ear punched with the prescribed mark, there is no requirement to add another mark.

Only the approved ear punch available from authorised retailers of HGPs may be used.

5. Keep a record each time an animal is treated with HGPs

This includes:

• Date of treatment, location and number of livestock treated
• Details of the product used (including trade name, batch number and dose).

Keeping records are requirements of the Livestock Production Assurance (LPA) program. These records can be either electronic or hard copy.

6. Declare animals treated with HGPs on the National Vendor Declaration (NVD) form