There comes a time for all strains when it becomes necessary to introduce an outcross. How long can a breeder continue without an introduction of new blood will depend on variety of things? Many of strains have been bred for more than thirty years without an outcross being brought in. Much will depend upon the inherent character of the foundation stock, and upon the breeder vigilance in selection and culling birds possessing any weaknesses.
There may also come a time when the breeder feels that his strain of rollers cannot be further improved from within. The breeder might come upon problems associated with performance, which can only be improved by the introduction of an outcross. In any of these events, the breeder will have to give thought to introducing a bird or birds possessing the qualities in which he feels his strain is lacking or losing ground.
For a successful, well-established inbred strain, an outcross should only be made as the last resort. Breeders with large studs are able to develop offshoot lines from the main inbred strain. They can develop these less closely related lines, which will have some common ancestry with their main bloodline.
Since the offshoot line is not as closely related as the inbred line and having developed from the same foundation stock, which has some genetic kinship, an outcross would be expected to be less disturbing in effect than a completely unrelated outcross. In contrast, breeders with smaller strain may likely have to purchase a new birds and bringing in an unrelated outcross.
The reason for bringing in an outcross is that the strain is lacking in a particular quality. The aim of the outcross is to implant the features that are sought after into the strain. For example, if it is mainly stamina and fertility the breeder wish to improve, then he could buy in some good type and vigorous hens, providing, he has excellent cocks in his strain. New hens will improve vigor and will employ the surplus cocks in the stock.
Outcross, must be followed by a period of inbreeding. The policy is the same where by selecting the most desirable young from the outcross to blend into the strain. Having established an inbred strain of good quality, the breeder should not breed out to the new bird and undo all the previous years’ hard work. First and foremost, the breeder needs to test mate the outcross and if the progeny shows the qualities which he require, then and only then, he should inbreed these young into his strain.
As mentioned above, the normal practice is for the breeder to breed the outcross into his strain, rather than breeding to the outcross. The breeder should only do so if founding a new line. The best and most suitable young from the outcross should be selected and test mated by pairing them with two or three of the breeder’s own birds.
If the results of these second season matings continue to his satisfaction and shows evidence that the outcross is in harmony with the genetic balance of the stud, then wider use can be made of the most suitable young.
Brother to sister or half-brother to half-sister matings are more likely to be employed when test mating an outcross. For this, the breeder will use the outcross bird and pair it with some of his own birds and the young resulting from the pairing would inter-mate in the following season. The following diagram will illustrate, by giving the outcross roller the letter ‘O’ and the established strain roller the letter ‘E’:
From the above illustration, all the young would have 50% of the blood or genetic makeup of each parent. The best of these young then be inter-mated and back paired to the breeder’s own rollers the following season. The following diagram illustrates the expectations of these parings:
It is possible that the factors could recombine to give a ‘1/2E 1/2E’ bird as you can see from the above illustration. This bird could be genetically similar to the strain with the improvement in the feature desired. The breeder should only retain and keep the best and carry them into his own strain.
However, the main reason of the outcross would be to back pair it to the main strain to implant its desired feature and regain the purity of the stud. The following diagram illustrates the back pairing of the best progeny of the original outcross ‘1/2O 1/2E’ to the established strain bird ‘E’:
As you can see, the young derives 75% of their factors from the established strain. In time, the breeder will have a wide range of generations and relationships within his stud. Some breeders take the outcross a step further before using it widely, either by inter-mating the outcross young or back pairing them to their established strain parent. Then they retain only the best from these matings for wider use.
In conclusion, to protect the strain line, type-improving outcrosses should be filtered through the ¼ and ½ bloodlines first. This will protect the strain line from hidden recessives or incompatibility with the outcross.
It would be devastating mistake to attempt type improvements by wide spread direct input of the new blood into the already established strain. Therefore, pair the outcross to ¼ - ½ blood line birds and inter-mate the best resulting young then pair back again to the ¼ - ½ line blood line birds. The best of the young from the second season matings can then be combined for carrying forward in the third season into the strain line.