Breeders wishing to build a strain of rollers possessing family type uniformity can only achieve this by using an inbreeding system of one form or another. The heritable makeup of each adult bird is unalterable but by skillfully matching, the breeder can only hope that the mating will nick and advance the quality of his strain. The breeder skill in this will be evident in the quality of the young he rear.
The method known as inbreeding is the system of mating together closely related birds, combined with selection, to enhance what breeders consider desirable qualities and eliminate those thought less desirable. With inbreeding, the breeder hopes to preserve the genetic line of descent and relating within a family group of rollers, the genetic influences that produces stock close to the Ideal.
Inbreeding is the inter-mating of very closely related rollers such as father to daughter, mother to son, brother to sister, half brother to half sister, grandfather to granddaughter, and grandson to grandmother. These are the mating, often referred to as pairing down the line. The objective of their use is to achieve genetic similarity within the strain. Selection and inbreeding combined with culling of the birds below the required standard will, in time, achieve uniformity. Bear in mind, no one should ever become involved in any form of close inbreeding, unless the stock of rollers used is of the best quality, in character features and performance, type and vigor; otherwise, the outcome can be disastrous.
The breeder must keep detailed stock records and refer to them frequently to enable the breeder to become totally aware of the background of all his birds in the stud which is intended to be used for breeding. Remember that each roller does not inherit factors solely from its parents. Rather, each is more an aggregate of its ancestry. Therefore, if the breeder wants to have proper control of his inbreeding program, he must be able to check back at least three years or more into each bird’s past.
While taking breeding records, take notes of all happenings, with details of infertile eggs, dead in shell, clutch sizes, chick hatchlings and chick mortality. Also include information on aggression towards chicks in the nest or when fledged and note any serious plucking behavior. With an inbreeding system it is essential to be able to know the complete history of all birds used for breeding. Details of any health failings should be recorded. By doing so, the breeder can keep a check on and trance any recurring health or type weaknesses.
No one should rely on memory alone, many things happen in the course of the year making it very easy to overlook valuable details. The aim and the goal of any pairing is to produce young as good as the better parent, superior if possible, and promote the performance quality and the type uniformity of the strain. By careful selection and elimination, the breeder, seek to retain within his stud the genes responsible for the qualities that he desire, and to eliminate those genes which influence type qualities and performance in a negative way.
The purpose of inbreeding is to preserve the genetic permutation which has produced the qualities evident in the parent stock. It also seeks to reveal any non visible type or performance failings, which once apparent, the breeder can set about eliminating from his strain. The outcome is the evolving of a strain, which has genetic similarity for quality that is uniform and transmittable from generation to generation. Such a strain will be free from effects of variance which comes with variety of ancestry.
The adherence to this policy will enable the breeder to fix his personal interpretation of his variety’s type standard and uniformity through out his strain and will allow him to establish a group of birds that will breed true for these characteristics.
Inbreeding brings the recessive type and performance features to the surface much quicker than would occur in outbreeding. Therefore, in the early years, the breeder must be prepared to cull a fair number of the progeny each year. The breeder should never give into the temptation to retain birds that do not come up to the required standard in performance and type. The best and least expensive way of making a start is to use one superior cock mated to two or three hens of good type and performance qualities. The aim should be, in the first season, to mate this superior cock with as many hens as possible.
The cock should not at this stage be used as a rearer; rather his task is filling as many eggs as possible. The following diagram will illustrate the inbreeding process and techniques for the first season:
This diagram is for starting the strain. It is based on the use of one outstanding cock mated to three good hens. The cock is given the symbol ‘F’ and his three mates are known as A, B, C. From the diagram above, each young bird inherits half of its genetic makeup from each parent. Therefore, all the young have 50% of the foundation cock’s blood.
At the end of the first breeding season, make careful study of all the young hens produced from mating the foundation cock to his three mates. Select the best three hens from those bred. This can consist of the best one from each mating or all three from one mating. Choose only the best three, but if others are worthy of retaining, by all means, hold on to some more as spares in case anything goes wrong with the first selection. These three daughters then are mated back to their father the following season.
The purpose of inbreeding is to fix the good qualities of the foundation cock bird into the strain. This can only be made possible by achieving genetic similarity. The best and quickest way of achieving this by mating directly back to the foundation cock. The following diagram illustrates the back pairing:
As you can see from the above illustration, this back mating increases the foundation cock’s influence considerably for these young. Now, they derive 75% of their blood from the foundation cock. His genetic characteristics now the majority influence and will remain unalterably so providing no new birds brought in. By continued back pairing, the breeder can increase further the foundation cock influence if he desire.
If the young from the above mating are paired back to him, the resulting progeny will derive 7/8ths of their inheritance from the foundation cock. Now you ask, what happens to the original hens A, B, C that first mated to the foundation cock? If space exists and the hens are of good quality, they would become the founding of additional lines, by mating the best of the young sons back to their mothers.
This could give the breeder alternative lines to develop, all of which would have the original foundation cock as a common ancestor, and may provide useful outcross material later. The female line at this stage is being used mainly to carry the superior cock’s factors on to future generations. Looking back at the stud’s breeding records will bring to notice that some pairs reared more than others. There will also be those that laid the odd one or two egg clutch. However, in taking the average, the breeder has to include the non producers or clutches too.
Therefore, the breeder has to set his expectations of the average number he would like to rear, and then select birds which have shown themselves capable of achieving these results. It all comes down to striking a balance between quality and quantity. There is no value in a breeder producing large number of inferior birds nor in producing just a few quality birds, too few to maintaining the strain.
A foundation hen can be used also, but it is very much slower process and she may not accept more than one mate in a season. So, it has severe limitations. With a hen as the foundation bird, the breeder would pair the best sons back to her the following season. The method is still the same, as is the aim that of building the stud on a single line of descent of an outstanding foundation bird. To achieve this, the breeder must back pair until the strain is in excess of 50% or more directly derived from the hen.
If the breeder prefers to use pairs from the beginning, he can use three cocks and three hens. The breeder would then develop three family lines using the same back pairing and inter-mating system discussed earlier. Breeders with limited space would most likely be better served using the one cock and three hens system for the first two seasons. The breeder can then revert to the pair system for the bulk of his pairings fom the third season onwards because from this stage on, the foundation bird’s factors will have majority influence, no matter how the matings are arranged.
In conclusion, in time and step by step, with careful selection and elimination, inbreeding offers the breeder a system of establishing a strain of rollers that are genetically similar, which will breed true. With rollers of similar gene combinations, like does tend to breed like, so the breeder will have founded a strain that can be expected to breed consistently, a uniform type and performance of birds.
The breeder success will depend upon selecting the most suitable foundation cock. The foundation cock must possess all the required features and be devoid of major faults. Also of importance will be the ability of the breeder to fix in his mind the Standard of Excellence in the performance of rollers.