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.