Hormonal growth promotants (HGPs)
Hormonal growth promotants are commonly used in northern pasture production systems to increase weight gain and reduce age of turnoff. The economical benefits of using HGPs are well researched.
What hormones are in HGPs?
The hormones used in HGPs are safe for the consumer. If there is residual hormone left in meat when consumed the hormones levels will be significantly lower than those levels found in other foods such as eggs, potatoes, and cabbage.
The action of hormones in HGPs is to cause increased anabolic activity which is associated with the accelerated growth response, and improved feed conversion efficiency. The active compounds in HGPs are synthetically produced derivatives of naturally occurring hormones. The hormones used include:
- Female hormones. Oestrogens (e.g. Compudose® 100, 200 and 400 contain Oestradiol-17β). Zeranol is also classed as an oestrogenic compound.
- Male Hormones. Androgens used are testosterone and trenbolone acetate (TBA).
The term ‘aggressive implants’ or ‘combination implants’ may be used to describe HGPs (e.g. Compudose®-G, Revalor®-G) which contain trenbolone acetate (TBA) and an oestrogenic compound and/or androgenic compound. The compounds act independently and result in an ‘additive effect’. These are commonly used in the finishing phase of growth.
There are two delivery systems: compressed pellets, and silicone rubber which has been impregnated. Most products are compressed pellet implants, except Compudose® 100, 200 and 400. The latter are silicone rubber implants.
Pay-out period or functional life
The functional life is the period of time for which the implant releases hormone. It should be noted that the period of growth response, during increased anabolic activity, is longer than the period during which hormone is released from the implant.
Silicone rubber HGP implants result in a pay-out of hormone at a slower rate and hence over a longer period of time and have a long period of anabolic activity. Scientific studies agree that the functional life of compressed pellet implants is in the vicinity of 60–120 days, and that anabolic activity is not stimulated beyond approximately Day 140 after implantation.
Following implantation, hormone concentrations in blood plasma show an initial peak in the first 1–3 days and then the levels slowly drop off over the pay-out period.
Basic principles of using HGPs
- The liveweight gain response to HGPs is determined by the quality of the diet cattle are consuming at the time. The greatest economic response occurs when cattle are gaining weight rapidly. For further detail on liveweight gain and carcase responses see: Hormonal growth promotants – growth and carcase responses.
- For the best growth response an implant program should be continued right through until slaughter once the program has commenced.
- A greater response in weight gain can be achieved if cattle are treated more frequently with a new implant, e.g. using four doses of 100 day rather than one dose of 400 day Compudose®. In extensive northern production systems the cost benefit in relation to extra handling and mustering has to be carefully considered.
- To maximize HGP response it is important to address other cattle health issues which may arise (e.g. parasite infestations).
- Cattle treated with HGPs are eligible for MSA grading. (The European Union market will not take HGP treated cattle).
- The back of the middle third of the ear is the correct implant insertion site. If the implant is inserted too close to the base of the ear there will be more rapid absorption of the active compounds and the implants are likely to pay-out at a more rapid rate. This may lead to a greater incidence of problems such as prolapsed pizzles with some products.
- Read the labels to ensure recommendations are followed. This includes safe ages at which the implants can be used. HGPs are not recommended for breeding females.
Hormone growth promotants (HGPs) in the NT
When Trisha Cowley, beef extension officer with the NT Department of Industry, Tourism and Trade, embarked on a two year Producer Demonstration Site (PDS) with a cattle station located about 300 km south of Katherine in the Northern Territory, the questions asked by local producers included:
- Are hormone growth promotants really cost-effective under NT growth rates, where the dry season often involves liveweight loss or maintenance during the first year post weaning?
- If so, what are the most profitable strategies?
- What are the hidden costs?
- When do implant losses occur?
Join Trisha as she answers these questions in this webinar recording. For your convenience, here are the webinar presentation slides. 51:57 minutes published 8 November 2012 by FutureBeefAu.
Legal requirements for hormone growth promotant users, Biosecurity Queensland →
This article has been written by Felicity Hamlyn-Hill, formerly Queensland Government.