A piggy breeder who got most of her stock from me, wrote me about a red-eyed white baby who seemed blind. At my urging, she checked him out thoroughly and he is also deaf and missing teeth-- a typical "lethal" roan that occurrs in 25 percent of babies born to roan x roan breedings.

Because the roan gene is dominant and what you see is what you get-- if a pig is roaned, it carries the roan gene heterozygously, that is: Rn rn. If it is not a roan, it is rn rn, and lethals are dominany homozygous, or Rn Rn. What we call a lethal is a white pig who is usually blind, deaf, has missing or misaligned teeth, and may have internal problems as well. They rarely live to adulthood and are usually sterile anyway. Most roan breeders try to avoid breeding roan x roan for this reason, or euthanize these babies at birth. Because the roan gene is dominant, there can be no non-roan "carriers."

That said, it's not so simple. I had a dark-eyed white boar who, when bred to a roan sow, produced a lethal. A thorough physical check of the boar showed a couple black hairs-- he was a "silent" roan, or a roan with so few colored hairs that he appeared white.

The parents of the lethal I mentioned in the beginning are not roans either. The mother is a mostly-black brindle, out of two other brindles, "I" and "B". "I" 's maternal side has roans.

The father of the lethal is a -- suprise-- tortoiseshell and white, also sired by "B" and his dam is a self black out of no-roan lines. We'll set her aside.

Of the father's parents, "B" is a mostly black brindle who was sired by a line of TSWs. His mother is a patchy red roan. The father does have some intermingling of red and black hairs on his rump patch.

OK, go figure. The pigs' owner swears there's no one but this father who could have sired this litter. In fact he was the only boar she owned at the time. If this is true, he must be a genetic roan, right?

Insight invited!!