As a result of scientific experiments in the cross breeding of poultry, conducted some years ago at Cambridge University and latterly by hundreds of poultry-keepers chiefly in Great Britain, it has been ascertained that certain definite crosses can be made which will produce sex linked chicks; that is, chicks that can be quite clearly distinguished as cockerels or pullets at birth.
The possible crosses are usually divided into three classes as follows: (a) Self-coloured cocks crossed with barred hens. (b) Dark shanked cocks mated to light shanked hens, and (c) which is generally conceded to be the best and clearest form of sex-linked cross consists of mating what are termed “gold” cocks, which includes all breeds in which the ground colour of the chick’s down is some shade of buff of golden brown, such as Brown Leghorn, Rhode Island Red, Red Sussex Buff Orpington, etc. These gold cocks are mated to what are termed “silver” hens, which are not necessarily pure white hens, but include Black Plymouth Rock, Silver Wyandotte, Light Sussex and any breed in which the down of the chicks has a large percentage of cream colouring, not white.
Some Breeds Unsuited
There are many complications attached to sex-linked cross breeding, and whilst the choice of matings is very numerous, it should be realized that some breeds are totally unsuited and others doubtful for the production of sex-linked chickens.
Those who wish to go more deeply into the matter may be referred to Professor Punnett’s book “Heredity in Poultry” which gives a full list of all known sex-linked crosses and their results. This book is published by Macmillan & Co.
Only a few of the possible sex-linked crosses can be considered from a utility point of view, and to the breeder who is not biased in favour of any breed, the following which have been found to give excellent results can be recommended. (1) White or Black Leghorn cock mated to barred Rock hens. (2) Light Sussex cock mated to Barred Rock hens. (3) A Minorca cock mated to Barred Rock hens.
All of the above come under the class (a) and chicks from such matings are distinguishable by the cockerel chicks having a white patch on top of the head when hatched, and the pullet chicks having an absolutely black head at birth.
Generally speaking Class (B), the crossing of Dark Shanked Cocks with Light Shanked hens is not to be recommended because the distinction in the colour of the shanks of day old chicks is so fine as to need considerable experience before any certainty of accuracy can be depended upon. At the same time, the possibilities of this class mating cannot be overlooked since it is the only possible means of utilizing for six-linkage purposes the ever popular White Leghorn hen. White Leghorn hens mated to dark shanked cocks such as Hamburg, Langshan, Black Rock, Black Minorea, Black Orpington, Australorp, would produce day-old cockerels with light or yellow shanks, and day old pullets with dark shanks. In this connection, it is well to mention that although the White Wyandotte has a “silver” origin, it is not always to be depended upon for crossing with the “gold” cocks from sex-linkage, because White Leghorn blood has been introduced into the White Wyandotte breed by some breeders in the past to improve egg production, and there is always the possibility that the presence of a few Wyandottes carrying White Leghorn blood would vitiate the results from the whole flock, and since it would be almost impossible to detect the aberrant birds, it is advisable in order to obtain a sex-linked cross to make use of the dark shanked cocks in the same way as with the White Leghorn.
The La Bresse Cock which has dark shanks has been found to give excellent results mated to the White Leghorn or White Wyandotte hen.
In Class (c) the Rhode Island Red cock mated to the Light Sussex hen, the Brown Leghorn cock mated to Light Sussex hen, and the Red Sussex hen all produce day old cockerels that are silver or white coloured, and day old pullets that are golden or buff coloured.
Cross Only High Grade Stock
It should be thoroughly understood that these crosses must be made as written, for if the reverse mating, such as Light Sussex cock mated to Rhode Island hens were made, the chicks would be in no way sex-linked, and the sexes would be indistinguishable. Again in crossing these breeds for utility purposes, it is imperative that absolutely first class sock of high egg producing qualities on both sides be used.
The advantages to be gained from sex-linked breeding are self-evident. In the first place, the breeder can offer day old pullets for sale to the commercial egg farmer, who will be saved the trouble of brooding cockerels which do not interest him.
In England today, the demand for day-old sex-linked pullets is greater than the supply. It is safe to say that the average commercial egg farmer would be glad to pay double the price for guaranteed day-old pullets that he now pays for ordinary day old chicks. The breeder could then either sell the day old cockerels at a low price, or brood them in the new electric battery brooders, raising them from broilers.
Those who have had experience of the scientific cross breeding are unanimous in stating that hatchability is at least ten per cent better, mortality in chicks is at least ten per cent lower, growth of both sexes is much more rapid, and maturity of pullets is two to six weeks earlier, also mortality in adult stock is reduced to a minimum, and egg production is increased by at least ten per cent over what could be reasonably expected from pure progeny by either of the pure breds originally used in the cross mating.
A Successful Experiment
The following excerpt of a report on experiments conducted by “Poultry” England, should prove of interest to illustrate the value of sex-linked cross breeding – “We have tried several kinds of fowl for sex-linked crosses, but so far the most satisfactory result has been from Light Sussex hens mated to a Brown Leghorn cockerel. These birds had to pass the expert for standard, but were of no particular laying strain. They were of good weight and excellent vitality. The sex of the chicks was decidedly easy to distinguish since as day olds the cockerels were silvery white, and the pullets red brown. The cockerels realized top prices as broilers. Seventy-five per cent of the pullets started laying at eighteen weeks old, and the remainder quickly followed. At this time (18 weeks old) the pullets weighed 4-1/2 pounds each. Their eggs were saleable as extras from the commencement; and at six months of age the birds weighed 5-1/2 pounds each and were producing 2-1/2 ox eggs. In body formation they resembled heavy Leghorns, were uniform in colour having a buff body colour with black striped neck hackles, and made an attractive looking flock”.
At the National Laying Contest, England 1927-28, 133 cross bred pullets entered in a special first cross bred section, mostly by backyard or amateur poultry-keepers, and not by professional breeders put up an average of 206 eggs per bird in 48 weeks, which was ten eggs per bird more than the average for the whole contest. Not one cross bred pullet died or was sick.
Heavier Egg Production
During the first two winter months of the present English National contest, 156 cross bred pullets averaged 25.01 eggs per bird per month, which was considerably higher than the average for any pure bred bird.
A comparison between the above official average records and the average production obtained from pure bred flocks either in R.O.P or any Canadian Laying Contest will show that these cross bred pullets put up altogether heavier egg production than an official Canadian flock of pure breds.
The only argument against sex-linked cross breds is that they are not suitable for reproduction, which the writer ventures to suggest is sheer theoretical bunk based on the fact that cross breeding in the past has been haphazard in the hands of absolutely inexperienced poultry keepers. The theorists who put up this argument against cross breeding appear to have overlooked the fact that the very best of our modern pure breds originate at a comparatively recent date from a long series of cross breeding. The original Rhode Island Red, Orpington, Sussex and Barneveld are a result of many generations of cross breeding cross breds.
Even assuming that these cross bred pullets are unsuitable for breeding purposes, there is nothing lost, since of the vast number of pure bred chicks produced annually only a very small percentage are either intended or suitable for future breeders.
The Modern Method
The process of reproduction of pure bred stock today is something like this. The poultry breeder mates up two or three pens from which he produces his own future breeding stock, and he also mates one or more large flock pens from which he produces commercial chicks to be sold by the thousands to egg farmers all over the Continent, and which are destined to produce eggs from human consumption only, and not for hatching. The destiny of a chick for breeding is entirely different to that of a chick for egg production, and it should receive different and better treatment thoroughly its life.
What is to prevent a breeder from keeping two or three special pedigree pens of two different pure breds from which he would produce a certain number of pure bred pullets according to the size of his business. These pullets would be trapnested and the very best of them selected for the reproduction of more pure bred stock. The balance of the high egg record hens would be flock mated to high egg record pedigreed cockerels of the other pure bred, and from this pen day old sex-linked pullets could be produced from commercial egg production.