SYSTEMS OF BREEDING POULTRY

New Zealand Journal of Agriculture, Volume 79, Issue 3, 15 September 1949, Page 205

SYSTEMS OF BREEDING POULTRY

farmers interested in breeding frequently seek an explanation of the systems of breeding applied to poultry. These systems are described and evaluated in simple terms in this article, one of a series on breeding poultry by F. C. Bobby, Superintendent of the Poultry Industry, Department of Agriculture, Wellington. Following articles will discuss breeding programmes for egg production and describe the progeny testing of poultry.

FOUR systems of breeding are commonly used/ in poultry-farming—-in-breeding, line breeding, out-cross-ing, and cross-breeding. Sn-breeding The mating together of related birds -for example, a brother and sister or a sire and his daughters— known as in-breeding. The closest form is between a full brother and a full sister. The effect of in-breeding is to intensify the characters in the birds matedthat is, to “fix” these characters — it is just as easy to fix undesirable characters as desirable ones. Therefore in-breeding, particularly between closely-related birds, must be used with care in a breeding programme, and should not be used even -on a limited scale unless accompanied by rigid selection. Birds showing weakness or other undesirable characters must be eliminated by culling. Close in-breeding in poultry leads to reduced, hatchability of eggs and increased mortality among chicks during the rearing period.

Thus in-breeding may be used to fix or intensify desirable characters in "breeding birds, thereby reducing the variations within the flock, whether measured in external characteristics or fecundity. Rigid culling against undesirable characters is essential, and the extent to which close inbreeding can be practised is limited, if •deterioration of the constitution of the stock is to be avoided.

Line Breeding

A form of in-breeding, line breeding is the repeated use of one bird in a mating programme for as many years as it is fit for the purpose. By this special form of in-breeding it is possible to intensify the inherent characters of a foundation male in a large number of progeny during a limited number of years. The success of this method depends largely on the selection of a high-quality male carrying as many desirable characters as possible and one which will transmit these characters satisfactorily. The necessity for finding a male with the ability to transmit desirable characters cannot be emphasised too strongly.

Out-crossing In breeding practice out-crossing is the opposite to in-breeding. It is the mating of birds of one breed which have no known relationship to one another. Results from out-cross matings are . more difficult to predict, and such matings may well lead to increased variation among the birds. Undesirable characters not apparent or recessive in the breeding stock may appear in the progeny. However, in many instances outcrossing tends to increase vigour. The bringing together of two unrelated lines of blood may result in increased hatchability, viability of chicks, egg production, and improved constitutions in the stock generally. Knowledge of the two blood lines should be available before an out-cross is made unless the mating is to be a completely hit-or-miss affair. Cross-breeding The mating of birds of two different breeds is called cross-breeding. Bringing together unrelated birds differing widely in their genetical make-up leads to a measurable general superiority over the parent stock, usually referred to as “hybrid vigour.” Such vigour often appears in the form of improved constitution, shown in a greater proportion of chicks reared and reduced wastage among mature birds compared with the parent stock

on either side of the mating. Crossbreeding may also result in increased egg production and rate of growth during the first 2 to 3 months of life. To obtain these possible benefits it is essential that sound and desirable stock be used on both sides of a crossbred mating. Though less attention to breed characteristics and type may be necessary where first crosses are bred for egg production, there must be no relaxation regarding the constitutions and health of birds used on either side of a cross-bred mating. All too often poultry producers consider that birds of poor general quality are good enough for a cross-mating; that policy is short-sighted and uneconomic. Progeny from cross-breeding should not be used for breeding because such birds are likely to vary extensively in type, colour, and economic value. Therefore, a poultry producer who wishes to use cross-breds for egg production or for sale must maintain two breeds on the farm or buy in male birds for one side of the mating. To some producers the maintenance of two breeds is a disadvantage. In New Zealand White Leghorns and Black Orpingtons (or Australorps) are used extensively for cross-breed-ing. Cross-matings made either way are satisfactory, . though the use of a White Leghorn male on Black Orpington females is recommended.