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Boar Taint T'ain't Anything You Want

By Diane Wells



At nearly 7 months old, Billy Boy the Boar is honing in on sexual maturity and increasing the likelihood his meat will suffer from boar taint.
Photo by Diane Wells.

Over Thanksgiving, I found myself sitting across the table from a friend of a friend, listening to his account as a guest of a wedding reception gone sour. The reception started out as quite a regal affair, defined by over 200 guests, a yacht club and men in skipper-esque white dress pants. Off to the side, as the guests mingled in the sea breeze and sipped bubbly beverages, the chef tended an enormous roaster, one that cradled the reception meal's guest of honor, a slow-roasted pig. When the time came, the chef threw open the roaster's cover with a proud, dramatic flair, as if to say, "Voila!" But instead of oohs and ahs of admiration, he received wrinkling noses and a grimace or two as an intensely foul stench wafted through the reception area. The beautifully roasted pig suffered from boar taint, and there wasn't anything anyone could do about it. The only guest that ate tainted pork that day was the father of the bride, a man who had surely paid a hefty sum for the opportunity to do so.

Because I was in the midst of writing about boar taint, I feasted as much on this tale as I did from the loaded plate before me. Boar taint is not something anyone in his or her right mind would want. In fact, if you raise pigs for meat, it's something you do your best to avoid. Not because it affects the boar's health, but because it affects the quality of the meat. Cooked tainted meat can smell like the inner workings of a sewer, a bin of onions gone by or a musk ox on a windless, 90-degree day. Since our olfactory senses and taste buds are in cahoots with one another, it's not particularly appealing to the pallet, and the meat ends up being a downright waste of resources.

As a boar matures and closes in on nine months of age, his body produces several compounds. Two have been pinpointed as the main cause of boar taint: androstenone and skatole. Androstenone is a steroid that the boar's testes produce as he approaches sexual maturity. It concentrates in his salivary gland and acts as an olfactory signal to an estrous sow, informing her she might want to think about taking the mating stance. Any excess androstenone accumulates in the boar's fat. Meanwhile, skatole is produced in the boar's hindgut when the amino acid tryptophan is broken down. This bacterial byproduct is absorbed into the bloodstream and either metabolized in the liver and excreted or absorbed into the animal's fat.

Pork producers around the world largely avoid the issue of boar taint by castrating at a young age: roughly 95 percent of the world's male piglets are castrated when a few weeks old. This is not ideal for a few reasons. Castration can lead to infections and hernias, and cause the animal pain and stress. And with the testes out of commission, androgens and oestrogens, steroids that play an important role in metabolism and the development of lean tissue, are also out of commission. Castrated boars, or barrows, will consequently have a reduced feed conversion rate compared to intact boars and not be nearly as lean come slaughter time. Androgens and oestrogens also play an important role in liver metabolism, particularly the enzymes that eventually break down skatole. Lastly, castration is not a 100-percent guarantee that the meat will be taint-free skatole (remember the compound skatole is part of the tainted meat puzzle), and many specialty butchers around the world, particularly in Asian countries, will only handle pork from female pigs. (Interestingly, females also produce skatole in their hindgut and absorb it from the environment, and a small percentage of female pigs have tainted meat because of it.)

Castration is frowned upon or flat out banned in a good number of European countries, so the issue of boar taint is addressed by slaughtering males at a premature age. In the United Kingdom, slaughter weights for young males average 165 pounds. In the Netherlands, they can go as high 200 pounds. The consequence of such an approach is the late finishing stage and the rapid growth rates associated with it. It also does not completely avoid the issue of boar taint: it is estimated that, of the young, intact males slaughtered in the UK, one out of five have tainted meat.

The big question is: How does one reduce androstenone and skatole levels without having a negative effect on the pig's health and growth rate? The most promising, albeit long-term, solution appears to lie in the fact that androstenone and skatole production is moderately to highly heritable. There is no doubt about it; some breeds are more susceptible to boar taint. Durocs are recognized for having much higher androstenone levels than the Hampshire, Landrace and Yorkshire breeds. There can also be considerable variability within a breed, with some individuals accumulating significantly higher levels of androstenone in their fat. Researchers have identified numerous candidate genes that encode the precise enzymes that synthesize and degrade androstenone and skatole. This work is ongoing, but the goal is to develop DNA markers that would ultimately be used to breed lines of boar-taint-free pigs.

Other solutions include sexing semen for artificial insemination, so as to control the number of male piglets that even set foot on this planet to begin with, and administering a vaccine. Yes, a boar taint vaccine exists, its name is Improvac and Pfizer Animal Health produces it. In a nutshell, it shuts down testicular development.

Back at the small farm, aside from castrating and/or slaughtering at a young age, the animal's diet and the environment it is raised in can reduce the risk of boar taint. The cycling of cells lining the gut is what produces tryptophan. Fermentable carbohydrates (i.e., raw potato starch, sugar beet pulp and inulin) appear to reduce the amount of tryptophan produced by gut microflora, thereby reducing the amount of skatole produced. Cutting back on feed the night before slaughter can also reduce skatole levels. And, because pigs can absorb skatole from manure, those kept in a clean environment will have lower levels of the compound in their fat.

My thoughts keep returning to the chef, the man hired to feed that hungry, well-to-do crowd. Let's hope he's since managed to crack a smile or two over the now infamous tainted reception.

The author, a regular contributor to Farming, is a biologist who lives and farms in Vermont's Northeast Kingdom.

Patrick White is a freelance writer based in Middlesex, Vt. Over the past 10 years, he has covered a wide range of agricultural operations around the Northeast. He is always on the lookout for unusual stories and cutting-edge installations.