Many of the most interesting genes in poultry are the result of a single gene mutation that is recessive to the “wild type”. Examples of this type of gene are Lavender and Recessive White. I will use lavender in this breeding plan, but it work exactly the same with other genes.
Create a line with the recessive color using a single parent bird
Imagine that you have a flock of Cream Legbars and you have an opportunity to get an Opal chick, but just one. If you pair that Opal with one or more of your Creams of the opposite sex, all the progeny will be heterozygous for the lavender gene. They will look exactly like the other creams, but keep the chicks separated, as they are you breeders for the next step.
Raise a flock of these “splits”, as they are often called, and allow them to interbreed with each other, but do not include any pure creams in this breeding pen. The resulting chicks (f2) will be approximately 25% Opals, and 50% Creams. I sell the Creams from this pen, but they can be useful for additional breeding if the new color is rare. Keep the Opal chicks and they will breed 100% true as Opal Legbars.
This process also works when you start with a breeding group of Opals. If you add some Cream pullets into the Opal breeding pen, the resulting Cream chicks are the same as the F1 chicks mentioned above. The principle reason you would do this is the somehow improve the Opal line by incorporating genes from the Creams. This works best if you have access to excellent creams. It also completely resets any inbreeding that might be happening over time.
Maintain a mixed flock that produces both colors
You can maintain a separate line of the dominant color (Cream, in the case of Legbars) and use them repeatedly as an outcross to keep the recessive line improving and genetically diverse. I do this, being careful to always keep a pen of pure Rees Creams, continually selecting them to keep excellent egg color and cresting. This line is used to outcross the Opals, continually improving them and making them more like those high quality Rees birds.
That strategy requires multiple, permanent pens to maintain the lines. If you aren’t ready to do that, you can achieve most of the benefits with a single pen. Setup the breeding pen with Opal cockerels and a mixture of Opal and Cream (or split) pullets. The chicks they produce are a mixture of Opals and Creams (these really are all splits). When you need to refresh your breeders, keep some Opal cockerels and some of the split creams. You may want to also keep some Opal pullets, but if you do, you will be hatching more than 50% Opals. The formula to deterimine how many Opal pullets to keep is straightforward. Since the split will give you about 50-50 Creams and Opals, adding Opals (which produce 100% Opal chicks) will adjust the percentages high than 50% for the chicks the pen produces. Let’s say you want 75% Opal chicks, now use equal numbers of splits and pure Opals.
You can continue this strategy of replacing your flock every few years with chicks from the pen for many years. Should you desire to do an outcross, just locate a breeder with an excellent line of Creams and buy some Cream pullet chicks to include in your next pen.
Conclusion – From a single, well managed breeding pen, you can produce chicks for sale in 2 colors, both recessive and dominant colors. This can be a great savings in time and you give up very little in terms of genetic potential, especially if you have other local breeders to exchange bloodlines with.