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Benefits of Improvac Explained

16 August 2012, at 11:34pm

UK - In connection with the launch of a report into the possible welfare implications of rearing entire male boars in London on 16 August, Nigel Lodge, MRCVS, National Veterinary Manager of Pfizer Animal Health, explains the mode of action of his company’s product, Improvac, as well as its economic, meat quality and welfare benefits.

How does Improvac work?

Improvac® creates a temporary immune response in the boar, producing antibodies which neutralise gonadotrophin releasing factor (GnRF), thus blocking the mechanism that controls testicular function.


Nigel Lodge, MRCVS
National Veterinary Manager of Pfizer Animal Health, UK

Economic benefits

The cost of Improvac is offset by reduced production costs, resulting from either (1) reduced feed costs (for those choosing to finish pigs five to seven days earlier) or (2) increased carcase value (for those choosing to finish pigs one week heavier).

The gain in performance with Improvac is clearly shown in a UK trial involving 434 pigs grown in indoor, naturally ventilated straw pens. The control group and the 210 pigs in the group vaccinated with Improvac were similar in terms of their genetics, feeding and management. The benefits were seen after the second vaccination with Improvac. The vaccinated pigs gained 40.4kg to finish at 114kg while, over the same period, the entire pigs gained 36.2kg to finish at 112kg. This represents a significantly higher average daily weight gain of 1.253kg in the vaccinated pigs compared with 1.115kg in the entire pigs. In addition, there were no significant differences in feed conversion rates between the vaccinated and non-vaccinated pigs.

Over the past three years, trials in a number of European countries have shown that Improvac enables faster growth in the later stages normally associated with castrated pigs.

“All producers are seeking to reduce their costs and using Improvac brings a significant benefit in the later stages of finishing,“ said Mr Lodge.

“The increased daily weight gain could allow producers to finish pigs up to a week earlier, potentially increasing profits and enabling increased use of facilities. This also means that in future, producers have the option of finishing pigs to heavier weights to meet specific demands of processors and retailers.

“Farmers are able to market a premium product with superior taste and texture of meat associated with castrated pigs,“ he added.

Potential for premium eating quality

The eating quality of pork loin steaks from entire lightweight boars and Improvac-treated boars was assessed in a study conducted by the University of Bristol.

A batch of 450 healthy, entire boars of similar genetic stock were housed in a naturally ventilated shed, in straw bedded pens. Pens of pigs were randomly allocated to two groups: a group treated with Improvac and an untreated control group. Pigs in the Improvac group were treated first at 10 weeks of age, then five weeks before slaughter at 20 weeks of age.

The trained taste panel at the University compared steaks from the two groups, cooked for three minutes at 72.5°C. Abnormal odour and taste were significantly reduced in the treated pigs.

“Studies in many countries have shown pork from treated animals to have equivalent sensory quality to that from female or physically castrated male pigs and superior to pork from lightweight male pigs,“ stated Mr Lodge. “Improvac allows farmers to grow bigger pigs with the increased intramuscular fat providing the potential for superior taste and texture.“

Pork quality is inevitably a balance between fat content (‘juiciness’), colour and drip loss (appearance). The European Food Standards Agency has reported that boars produce a higher proportion of dark, firm and dry meat, lower bacon yield, less favourable joint proportions, higher degree of unsaturation and higher water content.

Processors are also benefiting in several ways – through calmer pigs in transit and in the lairage at the abattoir, a reduction in drip loss on the line and greater assurance of quality and consistency.

Welfare benefits

With the UK system of rearing entire pigs, boar behaviour can become a problem during the later stages of finishing. The rising level of the male sex hormone, testosterone, leads to a number of behavioural changes, particularly aggression and mounting, which can lead to high levels of injury, lameness and generally poor welfare during this period.

A number of studies have clearly shown the ability of Improvac to reduce aggression and mounting in entire male pigs, which has led the Committee for Medicinal Products for Veterinary Use and the European Commission to approve the use of Improvac for reducing such behaviour.

“Using the vaccine means that boars are much less likely to injure each other during the later stages of production and in the lairage, so the risk of losses through bruising or other carcass damage is reduced. There is also a much lower risk of pregnant gilts being sent for slaughter,“ added Mr Lodge.

Further Reading

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