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Will Castration Become A Thing Of The Past?

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Trials with four million pigs failed to find any evidence of boar taint in 200,000 pigs using chemical or sensory tests.

Bernie Peet is president of Pork Chain Consulting Ltd. of Lacombe, Alberta, and editor of Western Hog Journal.

About this time last year, I wrote about the pressure that the procedure of castration is coming under in Europe and the potential to avoid it by using a vaccine. Now that vaccine – called Improvac in Europe and to be called Improvest when it arrives in North America – is licensed by its manufacturer Pfizer for use throughout Europe and should be available here before too long. It is early days yet to know what the uptake will be in Europe, but the published trial results suggest considerable benefits.

Improvac works by stimulating the pig’s immune system to produce antibodies which temporarily block the function of the testes, dramatically reducing the amount of testosterone and the boar taint-causing compound androstenone. The vaccine also reduces production of the other compound that causes boar taint, skatole. Two vaccinations are required, the first to “prime” the immune system and a second dose, given a few weeks later, stimulates production of the antibodies that block the function of the testes.

Most European countries castrate male pigs, but the U.K. and Ireland don’t. The benefits of using the vaccine differ in each case. Producers in the U.K. stopped castrating in the late 1970s, when trial work showed considerable improvements in feed efficiency and carcass quality, resulting in financial benefits that were too big to ignore.

However, despite slaughtering at lower carcass weights than other countries in Europe, which reduces the risk of boar taint, doubts still linger in the industry about the wisdom of producing entire males. A proportion of the population is sensitive to boar taint and one bad eating experience can put people off pork for life. For a long time, some commentators have pointed to the declining consumption of pork – around 20kg/capita/year one of the lowest in Europe – and attributed it to the impact of taint. Therefore the outcome of using the vaccine would be to eliminate boar taint and, hopefully, improve the attractiveness of pork to the consumer.


Another benefit would be that producers could increase the weight at which pigs are slaughtered, which would reduce production costs per kilo. In addition, recent trials have shown that even when compared with entire males rather than castrates, Improvac vaccinated boars grew faster. Average daily gain from the second Improvac vaccination up to the time of slaughter increased by 138 grams/day – from 1,115 to 1,253 – reducing the time to reach market weight.

The U.K. trials also showed improved carcass characteristics of vaccinated males, which had less carcass drip loss than both boars and females. Vaccinated males also had a loin eye area 2.5 per cent bigger than boars and a massive 15 per cent bigger than gilts. Backfat was intermediate between gilts and boars, but intramuscular fat was similar to females at around 2.5 per cent compared to 1.7 per cent for boars.

Potentially larger benefits await the majority of producers around the world who currently castrate. At long last they will be able to reap the efficiency benefits of boars without the disadvantages. In Brazil, a major exporter of pork and competitor with Canada, Improvac was approved in 2005, but the ministry of agriculture did not permit its use until 2007, after its efficacy had been demonstrated. Trials with four million pigs failed to find any evidence of boar taint in 200,000 pigs using chemical or sensory tests.

In one trial, vaccinated pigs grew nearly 100g/day faster than castrates and had a feed efficiency 0.23 better, while carcass lean meat yield per side was improved from 26.6 kg to 29.1 kg, or over nine per cent. Later commercial trials involving 3,600 pigs showed a one-kg increase in carcass weight, a threemm reduction in backfat, a threemm increase in loin depth and a three-kg increase in lean meat yield per carcass side.

Other published trials from Australia, Mexico, the U.S. and Switzerland suggest feed efficiency improvements of eight to 15 per cent, daily gain increases of up to 10 per cent (although several trials showed no improvement), reduced backfat and higher carcass lean content.


While the likely cost of Improvac in North America is not known, it is cited as up to $5/pig, which obviously has to be offset by the performance and carcass value improvements. A modelling exercise carried out by Dr. John Deen and his colleagues at the University of Minnesota concluded that Improvac offers a substantial return on investment, while cautioning that this will vary depending on circumstances. In the model, the increased cost of vaccinating rather than castrating (excluding vaccine cost) was $0.10, while higher mortality in castrated pigs added $0.30 to the cost of producing each pig. Feed savings for the vaccinated pigs added up to $1.70, assuming a nine per cent improvement in feed efficiency. However, the biggest benefit came from the $7/pig improvement in income per pig resulting from a seven per cent increase in carcass value and a 1.4 per cent increase in weight. Carcass value post-slaughter was estimated at $144 for physical castrates and $150 for Improvac pigs, giving an additional benefit of $6/pig to the processor as result of higher lean meat yield.

It is still not known when the vaccine will be licensed in Canada and the U.S., but it’s likely it will be in the next year. Assuming processors are convinced by the mass of evidence that shows boar taint is not present in vaccinated entire males, it seems likely that producers will embrace a product that not only liberates them from the unpleasant task of castration but also puts money in their pockets. Castration could soon be a thing of the past.

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