Hormonal growth promotant use in the Australian beef industry
R. A. HunterCSIRO Livestock Industries, Queensland Bioscience Precinct, 306 Carmody Road, St Lucia, Qld 4067, Australia. Email: bob.hunter@csiro.au
Animal Production Science 50(7) 637-659 https://doi.org/10.1071/AN09120
Submitted: 14 September 2009 Accepted: 22 April 2010 Published: 30 July 2010
Abstract
This review focuses on the science that underpins the use of hormonal growth promotants by Australian beef producers. Their effect on increased liveweight gain is reliable and they are used in the grass-fed industry to produce heavier carcasses suitable for the liveweight and age specifications on high value markets. With implants containing only oestradiol, the growth rate response varies between 0.05 and 0.1 kg/day, dependent on the digestible energy intake and the duration of the implant’s functional life for which the animal is in positive energy balance. Combination implants containing both oestradiol and trenbolone acetate promote greater responses in liveweight gain, which can be as high as 0.2 kg/day on good quality pasture. Although there is also accelerated liveweight gain on energy-dense feedlot diets, the main commercial benefit is reduced feed costs associated with improvements in feed conversion efficiency. An example given demonstrates that finishing an implanted steer from 400 to 650 kg reduces feed consumed by ~4%.
Androgenic hormones (testosterone and trenbolone acetate) directly reduce fat content of the carcass. Oestradiol treatment increases mature body size so at any intermediate bodyweight the animal is less mature and likely to have less fat in the carcass. Hormonal treatment has a negative influence on the tenderness and eating quality of beef, the effect being more pronounced with combination implants than with oestradiol alone. Aging for up to 28 days of those muscles that age extensively helps to overcome the detrimental hormonal growth promotant effect.
Acknowledgements
This investigation was funded by MLA as a commissioned review. I am grateful to MLA for the permission and the encouragement to publish the review in a scientific journal.
In the preparation of this review, all Australian companies that market HGP in cattle were contacted and invited to contribute information about their products and any other information relevant to the objectives of the investigation. I am indebted to Elanco Animal Health through Mr Jon Hunt and Virbac (Australia) through Mr Craige Allan and Dr Jane Parker for generously allowing me access to company resource material, some of it confidential. The confidential information does not appear in the review but was valuable as background information.
I am also grateful to Professor David Pethick, Dr Ray Watson and Mr Rod Polkinghorne for providing draft papers on meat eating quality that at the time of writing the first draft were unpublished. Mr Cameron Dart and Professor David Pethick kindly met with me and provided an excellent briefing on the MSA Grading System.
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