1 commentlast update:Jan 3, 2007

Some comments on immunocastration

Steven McOrist
Immunocastration is occasionally wheeled out as an acceptable alternative to physical or proper castration. Basically the product offers very little to the pig farmer or the pig industry and is in many ways less acceptable than physical castration.

Immunocastration is occasionally wheeled out as an acceptable alternative to physical or proper castration. Immunocastration products are commercially available in some markets and are now being promoted by a major global company. Having considerable experience with this product in the Australian market, can I offer some comments? Basically the product offers very little to the pig farmer or the pig industry and is in many ways less acceptable than physical castration.

1. The product is analogous to a killed vaccine targeting the testicles and their boar odour. However, its efficacy wears off quite quickly. It therefore requires deep consideration about timing of the two full and separate doses required per pig to achieve the intended aim of reducing testicle size at slaughter. Start vaccination too early and the testicles may 're-grow'. Start too late and the testicles won't have shrunk by slaughter time. So usually for a slaughter age of say 20 to 23 weeks, then the two doses need to be given at some points in the grower-finisher period, a few weeks apart. Anyone with knowledge of pig farming will realise that the prospect of catching and injecting individual male pigs twice at those times is no small venture and will require money, staff, and time and will inevitably enact costs and some likely losses in terms of animal welfare, production set-backs, pig and staff injuries, injection equipment breakages etc.

2. The product is not species specific and any injection into a human male will potentially lead to possible human infertility. Employed or family male staff may view self-injection either as an unacceptable risk or alternatively as a means to create vexatious legal proceedings against an employer.

3. Assuming the best conditions, the best staff and the best will in the world and a realistic vaccine efficacy of say 98%, one would assume that a best practice outcome would be, say, a 96% success rate of the proposed product in full usage on a well-run and organised farm. But if one thinks through the consequences of this, this means that four out of every 100 pigs on a slaughter line at the abattoir will still have large testicles. So what then? Are these presumably potential boar tainted pigs to be removed from the line? Again, anyone with any knowledge of the industry would know that that will not happen on the modern high speed line, without considerable difficulties. So in most cases these pigs would simply go through to processing and retail. What then? Do these four boar pigs then mean the whole expensive and dangerous on-farm exercise was a waste of time? How many boar pigs does it need to taint a mince or other mixed process?

4. The product is aimed at improving carcass quality and consumer acceptance, but is used and purchased by farmers. As indicated there are also even some potential costs for processors. Considerable negotiations are clearly necessary before any farmer-processor axis is going to consider the cost burdens of the product. Similarly, any processor-retailer axis would need considerable negotiations before the product gained any leverage.

5. In many consumers' eyes, this anti-testicle hormone vaccine product is lumped into the 'hormone' or growth promoter devil category. To turn it into a positive alternative to a very long standing and routine farm husbandry practice is a long stretch.

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    Roger Campbell

    A few days ago I read with interest the views of my colleague Professor Steven McOrist on immunocastration. Although he raised some excellent points I have to say that my personal experience using the commercial immunocastration vaccine in Australia has been more positive. Producers have found the product to be straightforward and profitable to use, and many of the potential difficulties mentioned have proved relatively easy to manage in practice. I think the value of the approach is illustrated by the fact that a significant proportion of the male pigs in Australia, traditionally a non-castrating, lightweight slaughter market like the UK, are now reared using this method.

    There are a number of specific points that I should also like to make:

    1) Far from being an expense Improvac (I assume this is the product referred to, as it is the only one commercially available) should improve profitability for the producer. For those currently castrating pigs surgically, carcasses from Improvac treated boars have higher % lean meat, better feed efficiency and sometimes higher growth compared to barrows. These effects result from the fact that the pigs are boars for most of their lives and benefit from the naturally superior production efficiency of intact males compared to castrates. In non-castrating markets the potential commercial benefit is from rearing pigs to a heavier weight without the risk of boar taint. This may or may not be an opportunity in markets such as Australia, the UK and parts of Spain that currently slaughter intact males at light weights. Nevertheless, many Australian producers have found it profitable.

    2) Published data on the vaccine show efficacy of over 99%, similar to that of surgical castration, which also fails to reach 100% because of occasional missed pigs and cryptorchids (where immunocastration is effective). It is clearly correct that with careless procedures the failure rate could be higher, but in a well managed unit, with appropriate quality control procedures to identify and re-treat any missed pigs (generally obvious from behaviour and testicle size), efficacy approaches 100% and is not an issue. Visual checks on the slaughter line should also identify any pigs that might have escaped proper treatment.

    3) Improvac needs to be injected two times, at least 4 weeks apart. The last injection should be given 4 to 5 weeks before slaughter. If plans change, pigs should still be reliably free of taint from 3 to 8 weeks following the last injection. Injecting pigs is, of course, an extra chore, but I would not call it a problem when the event is properly planned as part of the management cycle.

    In my experience, trained farm staff prefer injecting 75 kg pigs compared to 20 kg pigs, and the technique is easy to learn. Obviously, the secret is in having the right equipment and facilities, but with these in place the second Improvac injection is as manageable as many other farm procedures. Also, although surgical castration of male piglets is well established in most countries, it should not be forgotten that is a labour intensive and unpleasant task for farmers.

    4) I have not seen or heard of any stockpersons who have accidentally injected themselves, and we have used the product in Australia for over 7 years now. Nevertheless, self-injection must be considered a risk, as with several other veterinary products used in swine production (prostaglandin to mention one). At least in this case adverse effects are only likely after two self injections, with an appropriate interval between them. Safety vaccinators to deliver the product are available and the manufacturer advises training on vaccination technique. In my experience, self-injection with any product in the commercial swine farm is a fairly rare event and these precautions should make the likelihood of self injection with Improvac extremely small.

    5) Consumer acceptance has not been an issue in Australia. Taste panel studies have confirmed that pork from Improvac treated animals has high eating quality and the immunocastration approach itself has not been considered controversial from a food safety point of view. The product is not a hormone and this fact should be repeated clearly by all connected with the industry. Although the antigen raises antibodies against GnRF, the molecule itself is an incomplete analogue of GnRF conjugated to a larger protein, with no intrinsic hormonal activity. Also, of course, the vaccine is a replacement for surgical castration, which is itself an animal welfare and potential consumer issue.

    In conclusion, the successful use of immunocastration does require the introduction of new management procedures. These, however, are not excessively difficult or onerous. In my view the technology represents good science and is a profitable and animal welfare friendly option for producers, that deserves serious consideration.

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