Four Toes On A Silkie

What are the odds that a roo with 4 toes/5 toes produces a 4-toe chick?

Should I use him?

Normally 4 toed silkies are culled. I don't think anyone has bred one due to the fact that they could end up with 4 toed chicks. But I am not a silkie breeding master!

found this:

By Tim Adkerson
These are the probabilities from possible crosses.

four toes silkie X five toes silkie( has two five toes genes or homozygous)= 100 % five toes offspring ( heterozygous or carry a recessive and dominant gene)

If you get any four toes offspring that means the parent is split ( heterozygous) for five toes; or in other words the parent has a dominant and recessive gene.

five toes offspring X five toes offspring = 25% homozygous five toes (two five toes genes), 50% heterozygous (split), and 25% four toes ( two recessive 4 toes genes)

The chicks that are split (heterozygous) can produce four toes offspring.

five toes offspring (heterozygous) X homozygous five toes parent = 50% homozygous and 50% heterozygous five toes offspring

If you keep track of which birds you mate and the number of toes the offspring have you can determine if your five toed birds are homozygous or heterozygous.

If you mate two five toed birds and some of the offspring are four toed, then both parents are heterozygous or both parents carry a recessive gene. MARK THE BIRDS AS HETEROZYGOUS.

You can also test mate your birds. Cross a five toes bird with a four toes bird: IF NO FOUR TOES SHOW UP THEN THE FIVE TOES IS HOMOZYGOUS FOR FIVE TOES. You will have to hatch more than a few eggs

also another article:
Two common faults, single combs and four toes are simple recessive traits. If one single comb chick hatches from a breeding pen, you can be certain that both parents carry the trait for a single comb. The single comb "gene" is recessive to the normal Silkie comb so two Silkies with correct combs can produce a single combed chick quite easily. If you have a pair produce a single combed chick, you need to decide whether to continue using the parents in your breeding program. You must weigh the problems of introducing the undesirable trait into your flock against your breeding goals. Sometimes it is acceptable to use Silkie with a "bad" trait if that Silkie has other excellent qualities. Knowing which Silkies carry the trait is the first step towards eliminating it. With single combs, I would like to point out that with careful inspection, it is very easy to see if a chick has a single comb the moment that it hatches.

Another annoying fault is the Silkie that hatches with less than the required five toes on each foot. Having only four toes is another recessive trait but be warned that it is not a simple recessive. The five toed trait is only incompletely dominant so the Silkie with four toes can actually carry the five toed trait. Confusing? Definitely! However, if one four-toed chick hatches from a breeding pen, you can be certain that both parents carry the trait for four toes - to a certain degree.

Again, this "gene" is basically recessive to the normal Silkie five-toed condition, a condition that has the scientific name of polydactyly. Polydactyly simply means "many toes" and frequently involves too many toes! (However, six and seven toed Silkies are an entirely different story for another article.) So, restating the obvious, two Silkies with the correct number of toes on each foot can produce a four-toed chick quite easily. As with single comb producers, if you have a pair that produces a four-toed chick, you need to decide whether to continue using the parents in your breeding program. Decide whether you want to introduce an undesirable trait. No Silkie is perfect in all ways. It might look nearly perfect but odds are that it will have some genetic flaw that you do not like.

I look at each chick that hatches, band it and mark down its down color, whether its comb is correct, how many toes it has on each foot, whether is has a vaulted knob on its skull, and whether it has good foot feathering. Some breeders are quite particular on the degree and quality of separation of the 4th toe from the 5th toe.