Swine nutritionist Mark Bertram, PhD, of First Choice Livestock, Polk City, Iowa, says technology that removes the need to physically castrate boars has the potential to radically change US pig production for the better.

But maximising return on investment in the technology relies on producers thinking more strategically about the way they feed and market their hogs.

Licensed for use in growing pigs by the Food and Drug Administration, the technology involves administering a compound called GNRF (gonadotropin releasing factor) analogue-diphtheria toxoid conjugate, which uses the pig’s immune system to block the production of androstenone and skatole.

Androstenone and skatole are naturally occurring compounds that can create an unpleasant odour, known as boar taint, in pork from intact boars marketed at weights exceeding 200 pounds.

Administering the immunocastration product twice in a boar’s life not only alleviates boar taint but can also offer other benefits including improved feed efficiency, faster growth and improved survivability.

Yet despite the advantages, some obstacles remain. Packers in the US have been slow to accept immunocastrated pigs. From a performance standpoint, changes in nutrition also need to be made to capture immunocastrated pigs’ full economic potential.

“One of the barriers to adoption [for some producers] is that if nutritional programmes aren’t followed properly, there’s less adequate performance to cover the cost of production,” he explains.

When the product is first administered at about nine weeks, treated boars will deposit higher amounts of protein than physical castrates, even though their feed intake will be lower. After the second dose is given a minimum of four weeks later, at which point feed intake can increase by as much as 20 percent, the boars will begin to deposit more body fat.

Early adopters of the product initially found it challenging to balance live-performance and carcass-characteristic goals to maximise profits.

“Most early studies [fed] immunocastrates like physically castrated males, but the animals are physiologically different,” he says.

“Those early studies showed a three to five percent improvement in average daily gain and a three to seven percent improvement in feed conversion.

“We have since refined the nutritional requirements to achieve a five to seven percent improvement in average daily gain and [up to] 14 percent improvement in feed conversion.

“From an economic standpoint, it pays the bills handsomely when [immunocastrates] are fed correctly.”

Nutritional balancing act

The key to providing the correct nutrition, according to studies Bertram has carried out, is in the amino acid requirements of immunocastrates.

Immunocastrates need 20 percent to 25 percent more amino acids to help build lean muscle. Similarly, because 45 percent of the phosphorous in the diet is used to build muscle, during that same period phosphorous should go up 10 percent to 14 percent. These levels can be dropped back down to the level fed contemporary physical castrates between seven and ten days after the second injection.

“As [immunocastrates] make the transition and their feed intake increases, protein deposition will slow and they will deposit more fat.

“Obviously [these diets] cost more, so there’s a balancing act to getting the amino acid requirement right and getting the carcass quality you’re looking for.”

Because immunocastrates can reach market weights up to 21 days faster than gilts, producers’ pig-marketing skills may be challenged. However, Bertram says with some simple adaptations these can easily be overcome.

He noted that, in wean-to-finish production, it’s common to double-stock barns with twice as many pigs as they are designed for when they are loaded with newly weaned pigs. Then at seven to eight weeks of age, half the pigs are moved to a grower-finisher barn.

“These [barns] are cheaper to run as they generally don’t have quite as much infrastructure in terms of heating and ventilation,” Bertram says.

One option to optimise the profitability of immunocastration is to double-stock wean-to-finish barns at loading and then move the slower-growing gilts to the lower-cost, grower-finisher site at seven to eight weeks of age.

He explained that tying the lower-cost grow-finish building with the less expensive gilts makes some economic difference, and it helps simplify the flows. Producers can completely empty, clean and refill the wean-to-finish barns rather than having barns at 50 percent capacity while the gilts catch up.

Timing to market

Once nutrition is right, the second part of the puzzle involves adjusting the timing of marketing immunocastrated pigs to get the best results. Because immunocastrates grow much leaner than physical castrates, it’s important that the first market cut is not done sooner than four weeks after the second dose of the product so the immunocastrates can attain enough fat deposition for eating quality, the nutritionist explained.

However, he noted, it’s equally important that all the immunocastrates are marketed within seven weeks after the second product dose as the feed efficiency advantage begins to deteriorate quickly. Within four weeks after the second injection, the average daily gain advantage goes down by 0.3 percent and the feed conversion advantage declines by 1.5 percent.

Overall, though, Bertram believes these adjustments are manageable for producers and well worth the initial effort.

“We’re seeing more and more systems understanding the value of the technology and realising that the changes they need to make to their production and management aren’t as great as they thought,” Bertram says.

“If you look at some of the successful systems, the economic value they get through immunocastration far outweighs the adjustments they make.”