I just did a bit of reading and found this:
https://www.canadianpoultrymag.com/100th-anniversary/research/scientific-crossbreeding-12161
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.
https://www.canadianpoultrymag.com/100th-anniversary/research/scientific-crossbreeding-12161
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.
