Hagerdoorn System of Poultry Breeding

New Zealand Journal of Agriculture, Volume 85, Issue 2, 15 August 1952, Page 107

Hagerdoorn System of Poultry Breeding

OF the many different breeding systems for the up-grading of poultry flocks perhaps none causes more controversy than that advocated by the Dutch geneticist Dr. A. L. Hagerdoorn., In this article J. H. Jones, Poultry Instructor, Department of Agriculture, Christchurch, outlines the system and comments on its advantages and disadvantages to the breeder. SUCCESS in poultry breeding does not come through wishful thinking. To build up and maintain a successful strain there must be some definite plan which takes into. consideration the laws of nature and makes use of what scientists have discovered in the field of genetics. A haphazard system of selection of birds that handle well and of hoping for the best will lead to stagnation; further improvement will cease and flocks will remain on that level of mediocrity until a definite system of up-grading is launched. These are the sentiments of Dr. Hagerdoorn, who proposes a system of breeding which he considers suitable for the practical poultry- breeder who has neither the time nor the inclination for progeny testing with trapnests. The system is a variation of that known as line breeding, in which the mating , is not as close as with in-breeding but the principles are similar. The mating is restricted to one line of descent to discourage variability and to try to fix desirable characters within a strain by the repeated introduction of the characteristics of an exceptional individual or individuals, and by prevention of the introduction of other factors which are likely to prove dominant to them. Line breeding is less risky than in-breeding; beneficial or harmful effects are less marked. Very closely in-bred stock tends to lose vigour and precocity and may become undersized and lacking in vitality. The impurity which indi-

vidual selection will leave in a breed s the cause of these troubles, which become very apparent on in-breeding, th ? inferior quality of the in-breds being directly due to the impurities i n “ genetical make-up of the Parents. The only way out of this difficulty is group selection or progeny testing. Prgeny Tes+ng of Male Bird rr 99eny lesTing ot Male Dira In a good flock of birds some are homozygous (pure bred) and others heterozygous (impure bred) for the desirable qualities which they display, The only way to discover whether a bird has the ability to pass on her good qualities to her progeny is to observe the performance .of that progeny. In poultry breeding this is difficult, as each hen has only a small number of

offspring and these are generally from one father. Further, it is necessary in testing the performance of a female’s progeny to trap-nest her and record each chick to her, and this entails a great deal of work both in the trapping and the recording. A very much simpler method, Dr. Hagerdoorn contends, is to progeny test the male. . _ Dr. Hagerdoorn’s system consists of using as many males in the breeding pens as there are laying houses for pullets. The chickens are toe marked or punched to each breeding pen and are housed in such a way that in each pullet house there are only daughters of the same father; some of the cockerel chicks are kept in reserve from each breeding pen. It is then easy to keep a record of the performance of each batch of chicks. ► The chief factors to record are chick mortality and the number of culls removed. When the pullets begin laying there should be noted the number of unthrifty pullets culled, the number and weight, of eggs produced, the quality of shells, the persistency of laying (that is, which birds lay longest during the summer before they moult), and the value of the food consumed by the house. The group which is selected at the end of the pullet laying season for breeding stock is that which shows, with its parent stock, the highest number of good points. Important Initial Points , ' When the selection is being made vigour and efficient reproductive ability must be considered as of more importance at the outset than high egg-producing qualities, and the mistake should not be made of preferring birds which have a high egg record to those which have produced the highest number of healthy chicks and whose mortality has been lowest. This is a point where the use of the trapnest is apt to lead one astray, as it is hard to resist the temptation to include in a breeding pen a bird which has a wonderful record, even if she handles indifferently. .

The group which is chosen is promoted to the breeding pens and mated with their own half-brothers (which

will be full-brothers to a small minority). This system is continuously repeated in subsequent years, so that in every nucleus there is a comparison of a few houses full of pullets.

A combination of group selection and in-breeding has been used in the development of the present strains of agricultural seeds, and a similar system could apply with poultry. Any scheme of purifying and improving a breed entails some in-breeding. Combined with a system of selection for individual high production such a scheme would be very unsafe. The nucleus system should take care of this risk, for any group showing any deterioration due to the fixing of any fault by in-breeding is automatically rejected. A male that has some inherent weakness will have no chance of being kept on. Dr. Hagerdoorn emphasises that a poultry breeder wanting to improve his stock will have to cease the popular method of trap-nesting. A much safer way is to compare large groups of pullets, each group consisting entirely of the daughters of one sire. t Adaptability of Scheme The scheme may be adapted to whatever equipment the breeder has available. He may use six small pens and six large laying houses in which to house the progeny, or he may, of necessity, split up the pullets, into smaller groups to fit into the available .accommodation. For the selection of -the breeding pens with which to begin, Dr. Hagerdoorn suggests that the distribution should be as even as possible. '.Naturally no poor birds should be included, but care should be taken not to have all the best in one pen. Arrangements should be made for as many chicks as possible to be hatched at the same time, and they should be marked at hatching for identification to their sire. The chicks should be

raised in mixed lots as far as possible, and a record made for each male sire who has headed the breeding pen. If

mortality is too high in any one lot, the birds should be sold. The pullets should be culled in autumn and a note made of the number discarded from each sire. They should then be housed in their six groups in laying houses. Ultimately at least six half-brothers of the best pen will be needed, and it is best to reserve at least 10 cockerels from each group. When, after a few months, the records begin to show a difference, some of the cockerels which will obviously not be needed may be sold. The final selection having been made, the pullets of the best laying house are split up to use in the breeding pens in their second year. If the father is still alive, he might be used to head one of the pens. Dr. Hagerdoorn admits that the system involves keeping a large number of young males through the winter, and says that if anyone is very much afraid of inbreeding, there is no great harm in using the sons of a very good pen on the daughters of the very best pen, but he does not advocate this. He says that a breeder may wish after a

year or two to start two separate lines, which he can cross together and the progeny of which he can sell.

Different Opinions of Breeders It is probable that Dr. Hagerdoorn’s system could be used with profit by poultry breeders in this country as a sound basis on which to work their selection, but successful breeders advocate occasional out-breeding, and it is as well to remember this fact. In bringing in fresh blood to a closed flock it is advisable to use birds which have been bred successfully with one’s own stock on a customer’s farm. Also there is surely no reason why the birds of the tested breeding pens, having proved successful as yearlings, should not be bred from for a second season (in their third year), and it might be wise to retain the best parent pen each year as an insurance policy. Dr. Hagerdoorn does not take into consideration body type or conformation to breed standards, and definitely states that in his opinion these factors should not be taken into account, as they are liable to complicate the issue unnecessarily. On these points much controversy arises with the established breeders, in whose opinion body type and conformation to breed have a definite bearing on the quality of the bird, and it would be wise not to ignore their opinion, founded on long experience. Dr. Hagerdoorn’s attitude may be explained by the fact that much of his experience in practice has been with ducks rather than with hens. Another important matter affecting egg production is broodiness, which may become a serious handicap in heavy breeds. There are thus a large number of factors to be dealt with when a selection of the best pen is being made, and it might be difficult to make a decision. It might then be advisable to run two strains. Poultry breeding never has been easy, and will always be an art as much as a science.

Australian Seed Potatoes

(?EED potatoes are in short supply this year and potato growers may be tempted to use for seed some of the potatoes imported from Australia for table purposes.. This practice cannot be encouraged, as there is a slight risk of introducing some disease not present in New Zealand. That risk does not occur with the potatoes imported specifically for seed purposes, as extra caution has been taken in selecting the supplies.