Focus on boar taint, part 2: Questions and answers

Any novel method, like vaccination against boar taint, is bound to generate lots of questions among those who may be considering using it. The following questions have been asked by vets, swine producers, buyers and processors from different EU states. The answers are provided by technical staff from the manufacturer Pfizer Animal Health.

Can I continue to castrate pigs and just use the vaccination to improve my feed conversion efficiency?
The vaccine Improvac is designed and registered for reducing boar taint and replaces physical castration, which is to the benefit of the pigs as it improves welfare, and of benefit to producers as it allows them to rear naturally more efficient entire male pigs. The beneficial effect on feed conversion that has been routinely observed in commercial trials is simply due to the naturally greater feed efficiency of boars compared to barrows. Other major benefits of using the vaccine are also linked to stopping castration rather than the use of the product itself, such as avoiding the infections, pre-weaning deaths and labour costs associated with castration procedures. Continuing to castrate along with using the vaccination would mean losing all the potential benefits, for the pigs and for the whole production chain.

What is the oldest age that pigs can be slaughtered using vaccination against boar taint?

The age of the pig is not a limitation for the use of vaccination. What matters is the time between the last dose received and the time of slaughter, which should be 4-6 weeks. The second dose must be given at least four weeks after the first vaccination. The veterinarian prescribing the product will easily evaluate with the producer the best protocol for vaccination, according to the farm management habits and the performance of the animals.

Vaccinating young pigs against boar taint has raised many practical questions among veterinarians.

Could vaccination be used in female pigs?

No – boar taint is primarily a problem in male pigs and for this reason the method has been developed, tested and is now registered for use in male pigs only.

Do vaccination injection sites need to be trimmed out?

The product should be given by subcutaneous injection just behind the ear, using a short needle designed to give 12 to 15 mm penetration. When used as directed it is well tolerated and there is no need to trim the injection site. As with all injectable products pigs should not be treated when they are wet or dirty, as this increases the risk of accidentally introducing infection and causing an abscess, which would require trimming.

What level of improvement in feed conversion can I expect to see if I use vaccination instead of castration?

The improvement in feed conversion rate demonstrated in studies is typically around 8-10% for the pigs vaccinated compared to those that have been castrated. Although this figure may vary from study to study, the pattern is consistent across countries, breeds and management systems. In fact, and logically, vaccinated boars show growth patterns and feed conversion rates similar to those of intact boars. Compared to barrows, vaccinated pigs use less feed to produce the same amount of meat. This not only improves efficiency but also reduces the environmental impact of pig production.

What effect does vaccination have on carcass composition?

Compared to castrated pigs the carcasses of vaccinated pigs will typically have more lean meat and less fat. However, this is not a direct effect of vaccinating. It results from the fact that vaccination is a replacement for physical castration, so its use allows male pigs to grow naturally for most of the fattening period, without the negative impact of castration on growth performance. The carcass composition of vaccinated pigs is more similar to that of entire male pigs than that of castrates. Meat quality parameters such as pH and drip loss, however, are similar to those found in castrates and females.

How will my abattoir and the abattoir workers react when they see animals or carcasses with testicles?

It is essential to tell your slaughterhouse about the use of the vaccine and to let the slaughterhouse managers know in advance that they will be receiving vaccinated animals, so that they can inform their operators. You may want to contact your veterinarian or a local company representative to know more about the local situation and to what extent a particular slaughterhouse is familiar with the method.

In general there is a visibly obvious reduction in testicle size and behaviour of vaccinated pigs compared to entire boars so there is no confusion. In practice, where the vaccine is being used on a large scale, abattoirs have encountered no problems receiving and processing vaccinated boars, not least because these animals are generally as calm and easy to handle as females or castrates.

What happens if one of the injections is missed?

As with many other vaccines, the first dose merely primes the immune system and it is only after the second injection that it shows the expected efficient reduction of boar taint. So, if one dose is missed by accident, the pig cannot be considered as correctly vaccinated and there will be a risk of boar taint. Fortunately, such pigs are likely to be spotted easily on the farm as they will show typical boar-like behaviour and develop the larger testicles typical of unvaccinated boars. Any pigs like this should be given another dose and not sent for slaughter for four weeks. It is recommended that all vaccinated pigs are routinely checked every week, starting two weeks after the second injection, to detect any pigs that might have been missed. Pigs should also be checked just prior to shipping for slaughter. It is very important to vaccinate carefully, making sure not to miss one boar. Every boar must receive two vaccinations for an effective reduction of boar taint.

Can vaccination be used on sick pigs?

No. Only healthy pigs should be vaccinated. Sick pigs should be treated and allowed to recover before being vaccinated.

Can injections be given at the same time as other treatments or injections, such as routine vaccinations?

This is a complex question as the possibility of an interaction between two medicines depends on what the medicines are. A decision to use any other medicine at the same time as the boar taint vaccine should be made on a case by case basis after consultation with the responsible veterinarian.

What do I do if a worker accidentally injects him or herself with the vaccine?

First of all you should wash the injury thoroughly with clean running water. Then, seek prompt medical advice and take the package leaflet with you. The person who has self-injected must not administer the product in the future. The attending medical adviser may contact the company if more information is needed. Remember that one of the risks following a self-injection is infection from a dirty needle. Exposure to the vaccine is not the only consideration.

Can anybody vaccinate pigs using this method?

The method is easy to use; however, the vaccine should only be administered using an injector with enhanced safety features and only by persons who have attended a training workshop. It should never be administered by pregnant women, or anyone who has already accidentally self-injected the product.

Can I just use one injection to make boars easier to handle?

No. A single injection simply ‘primes’ the pig’s immune system but has no effect on behaviour. Because of the way the vaccine works there is an incidental effect on behaviour after the second dose, which is an important indicator that the full vaccine course has been given, but the reason for using the product should be to reduce boar taint.

The injections cost more than castration, so why should I use it?

Castration may be less expensive to carry out but it costs money because of the mortality and setback it can cause, and because castrated animals do not grow as efficiently as intact boars. Vaccination not only avoids the losses due to the trauma of castration but also allows pigs to grow more like boars during much of the fattening period, with a superior feed conversion ratio and a leaner carcass. These benefits are likely to mean that the vaccine provides a better return on investment than physical castration in an individual farm.

Can vaccination be used in heavy pig production – for example 160 kg?

The method will work in pigs of any weight. However, the management approaches will need to be different in heavy pig production and work is in progress to see how to optimise the value of the vaccine in such systems. As always, producers should discuss the use of the product with their veterinarian.

We fatten a lot of boars already, is there a need for vaccination?

The risk of boar taint increases as male pigs mature, as does the risk of mounting and aggressive behaviour between boars housed together. As a result, those rearing entire boars typically send them to slaughter at a relatively young age, before the problems of taint and behaviour become too severe. The vaccine offers an alternative approach, allowing the production of better quality pork, both because of more reliable boar taint reduction and the ability to take pigs to a higher weight, which may also improve production profitability.

Source: Pig Progress Volume 25 nr 8