Benefits of castration alternative presented at global pig-health event

Two world-renowned experts discussed the economic and welfare benefits of using a novel castration alternative at the 2016 International Pig Veterinary Society conference in Dublin.

Cutting castration in favor of a novel alternative can significantly boost pig performance and meat quality, while also reducing welfare and behavioral concerns, experts say.

Boar taint is an unpleasant odor that can develop when cooking meat from sexually mature male pigs. To prevent boar taint, male pigs have traditionally been physically castrated (PC), but consumer-driven concerns in some markets about animal welfare have prompted some producers to seek alternative methods.

One alternative, sometimes referred to as immunocastration or boar-taint vaccination, involves administering an immunological (vaccine-like) product that stimulates pigs’ immune systems to temporarily block testicular function and inhibit accumulation of androstenone and skatole, the naturally occurring compounds that cause boar taint. A first dose is given around 9 weeks of age to prime the pig’s immune system, followed by a second dose during the finishing period, typically 4 to 6 weeks before the pigs go to market, although the period can be varied depending on the type of carcass composition desired.

Improved productivity

Speaking at a symposium sponsored by Zoetis at the 2016 International Pig Veterinary Society meeting in Dublin, Steve Pollmann, PhD, of DSP Consulting LLC, said this approach has tremendous potential to improve productivity.

Having worked with a major pork producer that was one of the early testers of the immunological product, he estimates its net value to be worth $5.00 to $6.50 per head ($1=£0.75=€0.90).

In one of the first production trials, intact male pigs that were treated with the product showed an improvement of 37 points (14%) in feed-conversion ratio (FCR) measured over a 151-day period compared to castrates. Compared with other interventions, such a large difference is rare, Pollmann said.

Optimizing nutrition

In the first 12 trials, use of the immunological product resulted in average improvements of 4.3% in daily gain and 8.4% in FCR compared to PC pigs fed the same diet and feed program, Pollmann reported.

When the data were examined week by week, different growth patterns emerged. After around 10 weeks of age, the FCR of the PC pigs increased faster than the treated, intact males, which continued to grow more efficiently until after the second dose of vaccine. There was a similar pattern for feed intake, with PC males eating more than entire males from 10 weeks of age. After the second dose of the product, which triggers the suppression of testicular function, the treated pigs also increased their feed intake and quickly overtook the PC pigs.

The treated pigs grow faster and more efficiently, but they perform even better when they are fed diets that meet their unique nutritional needs, Pollmann said.

Research in the US showed that up to the time of the second injection, when they are still growing as normal, intact boars, the treated pigs eat less than PC pigs but have the potential to grow faster and more efficiently, so they require more nutrient-dense feeds. When treated boars consume the same diets as PC pigs, growth is held back by the restriction of vital nutrients.

Studies show that prior to receiving the second dose, treated pigs need between 25% and 28% higher levels of the amino acid lysine for optimal growth. For phosphorus — a mineral required for healthy bone and muscle growth — treated boars need 11% more than PC pigs.

In university trials in which the treated, intact boars were fed diets that matched their needs, they outperformed PC pigs by an average 10.6% in average daily weight gain (ADG) and 13.3% in FCR.

Improved carcass yield

A meta-analysis of a series of US trials with more than 800 pigs showed the cutting yield of treated, intact pigs to be on average 1.23 units higher than that of their PC counterparts, Pollmann said. The carcasses gave significantly higher yields of the Boston butt and picnic cuts and numerically more loin and spareribs. There was potential for a slight reduction in belly value, especially in light carcasses. There were no differences in eating quality.

Summing up the benefits of the castration alternative, Pollmann highlighted the improvements in FCR (10-12%) and ADG (3.5-4.5%), while pre-weaning mortality was 1-2% lower. Under US conditions the total value to the production operation was estimated to be worth $3.00 to $4.00. The heavier carcass and higher yield of valuable cuts he estimated to be worth a further $2.00 to $2.50 per head.

Welfare benefits

Developed to reduce boar taint, the immunological product also has pig-welfare benefits, according to John Mackinnon, a veterinarian with the Pig Health & Production Consultancy in association with Oakwood Veterinary Group in the UK.

Speaking at the same event, he explained that one of the UK Farm Animal Welfare Council’s “Five Freedoms” is freedom from pain, injury and disease.

A first and obvious advantage of the vaccination is an end to the need for physical castration, which Mackinnon says is stressful and painful to the animal both during and after the procedure and has been shown to increase risk of infections.

Results of four different studies show that physical castration also increases the mortality of male piglets up to weaning compared with intact male pigs.

It has also been noted that in treated pigs, the socio-sexual behavior associated with sexually mature, intact boars is suppressed. After the second dose, treated pigs appear calmer; are less likely to ride, mount and engage in aggressive behavior; and have fewer injuries and body lesions than untreated, intact males. Sexual activity, which creates a risk of pregnancy if intact boars and gilts are raised together to heavy weights, is also virtually eliminated following treatment of the males with the immunological product.

Recent work from Australia demonstrates that treated, intact boars spend less time riding, fighting, pushing, head-butting and indulging in tail-directed behavior than untreated entire boars. In another study, the treated boars behaved more like castrates, spending more time feeding and less time engaging in aggressive behavior than entire males.