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Boar-taint vaccination associated with less male aggression in Australian study

Boar-taint vaccination improved the welfare of male pigs kept under commercial conditions by inhibiting sexual and aggressive behavior, according to new research from Australia.

Recording the behavior of male pigs daily between 16 weeks of age and slaughter, trained observers found male pigs were less likely to perform undesirable behaviors, such as riding, fighting, pushing and head butting, when they were given a vaccine against boar taint, which works by temporarily delaying puberty. These are the main conclusions of a scientific paper recently published in Australian Veterinary Journal by Dr. Branislav Karaconji, of Zoetis Australia Pty Ltd, and others.

Natural but aggressive actions perpetrated by male pigs can cause injuries to participating animals and disturb all those in the group. If these behaviors could be eliminated or greatly reduced, overall pig welfare would be improved, the researchers concluded.

“The main reason for this trial was to investigate the effects of boar-taint vaccination on animal-welfare improvement,” Karaconji told Voice of Sustainable Pork. “There is plenty of work done in Australia related to the effects of the vaccine on meat-quality improvements and animal growth, but no study has been done here before on its effects on animal welfare under Australian commercial farming conditions.

“This trial provides reliable additional information and a basis for ongoing discussions at different levels within the Australian pig industry on current market issues relating to farm-animal welfare…based on technical and scientific data rather than emotional and anecdotal aspects.”

Aggressive behavior and boar taint linked

Mounting, fighting and aggression are behaviors associated with the production of testosterone in male pigs as they mature. Also around sexual maturity in boars, there is an increase in the production of a steroid compound called androstenone, which, if it accumulates in the animal’s fat with skatole, can lead to the development of an unpleasant odor when the meat is cooked.

To avoid these behavioral and meat-quality issues, many countries allow surgical castration of male pigs. This is not widely practised in Australia, where instead, the animals are typically slaughtered at lighter weights — 95% of the country’s pigs are slaughtered at around 74-75 kg — when they are thought still to be immature.

However, as Karaconji reports in the paper, Australian pig producers report that boar taint in untreated male pigs can still be an issue, as can sexual and aggressive behavior among male pigs kept in the large groups, per usual commercial practice on farms in Australia.

Reduced aggression in vaccinated pigs

Researchers at Zoetis Australia and at a livestock veterinary service company, Dr. Barry Lloyd Pty Ltd, set out to study how administering the puberty-delaying boar-taint vaccine — sometimes referred to as immunocastration — affects the behavior of male pigs, compared to untreated, entire boars.

Over a 4-month period, uncastrated male pigs from four consecutive batches were assigned to one of two groups. One group was treated with the boar-taint vaccine (n = 433); the other group (n = 434) was untreated and served as the control.

To reflect the most commonly used commercial grower-finishing system in Australia, all the pigs from each treatment and period were kept in a single pen in a group of around 100 animals.

Pigs in the treated group were given two doses of the vaccine, as specified by the manufacturer, at 10 and 16 weeks of age. Otherwise, management of all the groups was the same until they were sent for slaughter at 22 weeks of age.

Starting 1 day after the second vaccination of the treated group, investigators observed and recorded the behavior of the pigs in each pen, making note of riding, fighting, pushing, head butting, ear manipulation, tail manipulation and bar biting.

The mean incidence of the various behaviors is shown in Figure 1. (Click on Figure to enlarge.)

Figure 1. Incidence of sexual and aggressive behaviors of male pigs, with or without boar-taint vaccination, over 15-minute observation periods.
Figure 1. Incidence of sexual and aggressive behaviors of male pigs, with or without boar-taint vaccination, over 15-minute observation periods.

The reduced incidence of riding, fighting, pushing and head butting in the boar-taint-vaccinated group is highly statistically significant (P < 0.01), and tail manipulation was also significantly lower (P < 0.05).

Treatment had no significant effects on ear manipulation or bar biting in this experiment.

Karaconji said the trial provides evidence of the benefits of boar-taint vaccination for animal well-being.

“Hopefully, these results will add another important dimension to pig welfare-management discussions and increase awareness of available solutions for animal welfare,” he said. “This trial, under Australian commercial farm conditions, provides a good base and reasons for the market players to re-visit their position in regard to farm-animal welfare, which in some segments of the market is scientifically unsupported.”

Commenting on the work in a recent issue of its Animal Welfare Science Update, the Royal Society for the Prevention of Cruelty to Animals (RSPCA) of Australia wrote: “The use of immunocastration tools allow Australian farmers to produce larger animals that remain free of boar taint while resolving the behavioral issues associated with keeping heavier male pigs until slaughter, improving their welfare.”

“I’m very glad that RSPCA has recognized the benefits of vaccination on animal welfare and supports its use on farms in the RSPCA-approved farm scheme,” Karaconji added.

 

Boar-taint vaccination associated with less male aggression in Australian study
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