Breeding methods for cattle, pigs, and poultry in the United States : including inter-state co-operation project no. 253.

  • European Productivity Agency.
Date:
[1957]
Catalogue details

Licence: Attribution-NonCommercial-NoDerivatives 4.0 International (CC BY-NC-ND 4.0)

Credit: Breeding methods for cattle, pigs, and poultry in the United States : including inter-state co-operation project no. 253. Source: Wellcome Collection.

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    around twice the cost of a conventional pure or crossbred com¬ mercial chick and, if farmers are willing to buy hybrid chicks at all, they do not argue about this price differential which they regard as insignificant in comparison with the extra eggs they expect to get per bird. Recent improvements in the production of these chicks have aimed at securing a white egg and better interior egg quality ; but much improvement would still appear to be needed (not only with hybrids but with poultry stock generally throughout the United States) in respect of viability. Annual losses of 25 per cent or more could not be tolerated in most countries, and it seems curious that more efficient work has not been carried out in America against specific and non¬ specific disease. Signs are not lacking, however, that more attention is now being devoted to this important problem. Returning, however, to the present position of hybrids in the internal poultry economy of the United States, it may be noted that, while only 9 per cent of the total day-old pullet market is in this form, ' hybrids represent some 40 per cent of all pullet chicks sold in the Corn Belt (where most of the large producers are located). Of the possibilities for the future, we shall have more to say at a later stage. For the moment, we should like to quote Henry Wallace Jnr. (the pioneer of commercial hybrid chicks), who told us that he made no claim that his chicks were the best or that his system was bound to prevail over all others. What he does claim is that, by throwing out this challenge to the whole industry, he has done more than any other man to stimulate progress in poultry breeding. 120. Since, in the early days, it was the practice to combine inbred lines of one breed with inbred lines of another, so that two breeds appeared in a two-way, and as many as four breeds might be represented in a four-way cross, the idea has become prevalent that part at least of the success of those chicks is due to hybridization. Hence the word hybrid, as it is commonly employed in the United States and indeed in parts of Europe today to mean, or at least to include, a bird that has been pro¬ duced by incrossbreeding. The phenomenon of improved per¬ formance has thus come to be referred to as hybrid vigour. One should be on one' s guard against this unfortunate and mis¬ leading term. It suggests that the productive-gains achieved by the above process have been made by hybridization ; and it also suggests that similar gains can be made by merely mating any two different breeds or varieties together. Both suggestions are incorrect. In the first place, similar gains have been achieved by the process of strain-crossing, as stated already in this report, and the phenomenon is therefore not essentially one involving hybridization. If we admit the argument of gene complexes for utility characters, however, it would be agreed (we think) that favourable combinations are more likely to arise (though they could still not be predicted) when inbred strains of one breed are mated with inbred strains of a different breed, than when one and the same breed is involved. The same argument would apply with equal force to the manufacture of ordinary crossbreds (non-inbred) ; although it would be impos- 46