posted July 05, 2000 04:38 PM            

By Greg Sawyer, Research Officer and Roy Casey, Veterinary Officer, Animal
Industries, Bunbury

Summary

Hormone growth promotants (HGPs) are used to increase cattle livewirght
economically. Market effects of a ban on HGPs by the European Community are
described. Techniques for effective use with calves, yearling steers, non-breeding
bulls and heifers are given.

Hormone growth promotants, HGPs, are used for about 45 per cent of Australia's
cattle to increase their liveweight by 10 per cent to 15 per cent.

The effects of treatment, which alter the nutrient partitioning in animals, include
increases in growth hormone secretion, nitrogen retention in the muscles and intake
and efficiency of feed conversion.

HGPs are more effective on cattle that are growing well on good pasture or in a
feedlot.

For between $2 and $6 per head a farmer with good pasture can increase his
income by about $30 per head.

European Community ban on growth
promotants

The use of HGPs in all domestic and imported beef products was banned by the
EC from January 1, 1988. In an effort to protect this valuable and important
market, especially for offal, the Australian beef industry introduced an HGP
assurance program to ensure beef sold to the EC is guaranteed HGP free.

Since March 1993 all producers, when buying HGPs, have to sign a declaration
giving their property tail tag number, buy only from registered retailers and ear
punch and keep records of treated animals. This program (see Farmnote No. 20/94
'Requirements for the use of hormonal growth promotants in beef cattle' Agdex
420/684 or Document No. 23277) is subject to audit. The purchaser declaration
forms must be kept for two years.

Cattle not treated with HGPs and intended for EC markets are catered for under a
different system developed in co-operation with the Cattle Council of Australia.

This program entails completing and signing a declaration form and identifying
cattle with tail tags depending on whether sales are property to property, direct to
abattoir, CALM or saleyards.

However, declarations are not required for domestic sales or export markets that
accept treated cattle.

Plan well ahead and be aware of declarations and procedures needed regarding the
HGP status of cattle, before they are marketed.

Consumer safety

The EC ban was introduced for economic and political reasons, and not because
HGPs pose a hazard to consumer health. Three steroids that are used in growth
promotants are present naturally in humans and entire animals in concentrations
thousands of times higher than a person can eat in the meat of treated animals. The
amount of hormone ingested from correctly implanted animals is negligible.

Humans have been consuming meat and animal products from either lactating,
pregnant or entire animals for thousands of years without apparent side effects and
no scientific evidence exists that suggests eating meat from HGP treated animals,
administered as directed by the manufacturer, will cause any harm.

All of the implants available have undergone extensive toxicological investigation to
satisfy registration requirements. Implants are also placed in the ear, a non-edible
part of the carcass which is discarded, which provides a further safety measure.

Growth promotants

HGPs available include:

Ralgro� - registered for use in steers, claimed to be effective for 70 to 100
days. It costs between $1.90 and $2 per implant. No withholding period.
Compudose 200� and 400� - registered for steers and claimed to be
effective for 200 and 400 days respectively. Compudose 200� costs about
$3.60 and Compudose 400� costs about $6 per implant. No withholding
period.
Synovex� - registered for steers and claimed to be effective for 90 to 100
days. It costs about $2.10 per implant. No withholding period.
Synovex H� - registered for females, claimed to be effective for 90 to 100
days. It costs about $2.10 per implant. No withholding period.
Synovex C� - designed for male and female calves. It costs about $1.40 per
implant. No withholding period.
Revalor� - registered for steers and claimed to be effective for 150 days. It
costs about $4.50 per implant. Revalor� has a 60 day withholding period.

Using growth promotants effectively

Cattle that are growing quickly gaining at least 1 kg per day, such as steers, on
good quality feed or feedlot, will respond better than those on poorer nutrition. Little
response has been reported when animals are only fed enough to support growth of
less than 0.5 kg per day.

Combining growth promotants and a dietary supplement to modify rumen
fermentation for example, Monesin�, Avoparcin� increases feed conversion
efficiency even more.

Increasing the number of implants does not improve the response and repeating the
dose has not shown any consistent additional benefit.

The few comparative trials done in Australia have not shown any consistent
difference in performance between the different growth promotants.

For most producers, the choice of HGP will depend on the likely response rate, cost
and ease of application using their cattle handling facilities. These questions can be
answered by the stockists of hormonal growth promotants

When treating cattle, ensure the timing of the implantation takes into account the
annual cycle of pasture growth, feed availability and the intended date of slaughter.

Using promotants on different cattle groups

Suckling calves

Timing is critical when treating suckling calves with growth promotants. They
should be growing at least 0.6 kg per day before worthwhile responses can be
anticipated.

Synovex C� is specifically registered for calves, but all the growth promotants
have been used successfully. Growth rates to weaning may be improved by
implanting calves at four to five months rather than at one to two months. Calves
not intended for breeding may benefit most from a longer acting promotant such as
Compudose 200� or Compudose 400�, especially dairy breeds.

Do not implant female animals intended as breeders with products other than
Synovex C�.

Yearling steers

Yearling steers are the most responsive type of cattle if they are grazing on good
quality pasture or are fed in a feedlot. Weight gains are usually increased by 10 per
cent to 15 per cent from one implant.

Non-breeding bulls

Compudose� and Synovex� have reduced mounting and aggressive behaviour and
increased liveweight gain and carcass weight by up to 15 per cent in young bulls
destined for slaughter.

Warning: Do not use these products on bulls intended as sires.

Heifers

Growth promotants cannot be recommended for breeding heifers without
qualification. Repeated implantations before weaning usually delays puberty and
reduces conception rates. Even Synovex H�, which is registered for heifers
although not those intended for breeding, has delayed conceptions in some reported
cases. Successive implantation of growth promotants will seriously compromise
fertility in breeding heifers.

In heifers fattened for slaughter, 10 per cent to 15 per cent higher rates of gain
have been recorded after treatment with growth promotants.

Implantation technique

The recommended location for implants other than Ralgro� is under the skin in the
centre third of the back of the ear. Implant Ralgro� in the muscle at the base of
the ear. It is an offence to implant cattle at any other site.

Common errors made in implanting promotants are:

crushing the implant, which releases the active ingredient too quickly,
reduces its lifespan and may increase the side effects;
inserting the implant into the cartilage where there is minimal blood supply,
hence no absorption of the active ingredient;
inadequate or poor hygiene, which results in infection at the site of the
implant and some loss of implants. Needles must be dry on the inside, so
wipe the inside of needles to disinfect them.

Side effects

The incidence of side effects has been low and does not negate the economic
benefits of using growth promotants, particularly in steers.

Warning: Do not use growth promotants in females intended for breeding close to
the time of implantation.

Side effects can include:

increased incidence of raised tail-head settings in steers, which is usually
only temporary;
increased mounting and bulling behaviour, again usually temporary;
some mammary development and enlargement of teats;
digging up areas in paddocks, pawing the ground, roaring, leading the mob
and bull-like behaviour in steers, which is usually temporary;
delayed conception and lowered conception rates, raised tail-head settings,
increased mounting and bulling behaviour and mammary development in
females.

Effects on carcass and meat quality

In short, growth promotant implants do not significantly affect the carcass or meat
quality. In some studies the levels of lean meat, protein, have increased and the
amount of fat decreased in selected portions of the carcass. From the consumer's
point of view this would appear to be a healthy trend.

None of the growth promotants being used affect the most important eating quality
measure - tenderness. Other quality characteristics including juiciness, flavour and
colour were also unchanged in growth promotant studies.