The Genetics of Wattles - A Biology Lesson
I think any kunekune breeder would tell you that they love wattles. Not only are they adorable, they are one of those features that truly distinguish kunekunes from other breeds. I am no different, however wattles are low on my list of things that I look for when selecting breeding stock. Things like feet and leg structure, topline, teat lines, mothering ability, temperament are all things that rank higher to me than the dangly bits on their jowls. I worry that by trying to eliminate non-wattled kunekunes, that we will inadvertently eliminate other desirable traits. In fact, many breeders observe that the largest and fasting growing pigs in their litters are often the non-wattled piglets. So, let get into the genetics to determine which pigs will have wattles and which will not.
The first thing to know is that each gene is made up of two parts. Each part is called an allele, and one comes from your mother and one from your father. Together, these two inherited alleles make up a geneotype. There are two forms of an allele, a dominant form, which for our purposes we will denote as “W”, and a recessive from, which we will denote as “w”.
Having wattles in a kunekune is a heterozygous dominant trait. Putting it simply, if they have a “W” in their gene makeup, they will have wattles. It is dominant over the “w”. Only a pig that inherits a “w” from both parents will be without wattles.
So, a kunekune with a geneotype of “WW” will be wattled. A kunekune with a gene makeup of “Ww” will also be wattled, and a kunekune with a gene makeup of “ww” will be non-wattled.
The following diagrams will demonstrate what is called a Punnett Square – a simple way to look at what will happen if we breed different gene combinations, remembering that each parent will give one allele of their gene to their offspring. For the cases of breeding a non-wattled pig to a wattled one, it makes absolutely no difference in the results as to which parent was wattled.
If we cross two wattled parents of geneotypes, WW x WW = 100% of the offspring will be WW so wattled.
If we cross two wattled parents with geneotypes of WW x Ww = 75% of the offspring will be WW and 25% will be Ww so all will be wattled
If we cross two wattled parents of geneotypes Ww x Ww = 25% will be WW, 50% will be Ww and 25% will be ww, so 75% of the offspring will have wattles and 25% will not.
If we cross a wattled parent and a non-wattled parent of genotypes WW x ww = 100% will be Ww so all wattled. Isn't that amazing? You could cross a non-wattled sow to the right wattled boar and 100% of your offspring would be wattled!
If we cross a wattled parent and a non-wattled parent of geneotypes Ww x ww = 50% will be Ww so wattled, and 50% will be ww so non-wattled.
Here is possibly the most important one: ww x ww = 100% ww. If you cross two non-wattled pigs, 100% of the offspring will be non-wattled.
Of course, biology and genetics isn’t always clean. The above are statistical occurrences so over time and many litters, you would see these percentages but not necessarily in each and every individual litter. There is also no way of knowing, unless you extensively use trial and error breeding comparisons, whether your wattled pig has a “WW” or “Ww” gene makeup.
Similarly, sometimes wattles can fall off in-utero, or shortly after birth, and sometimes pigs are born with only 1 wattle. This gets a little more complicated and may point to other genetic factors/interactions that are much more complex.
So long story short, breeding two wattled pigs together will likely give you a combination of wattled and non-wattled offspring. Similarly, breeding a wattled and non-wattled pig will also give you a combination, but breeding two non-wattled pigs together will always result in non-wattled offspring.