SCIENTIFIC BREEDING

Bay of Plenty Beacon, Volume 10, Issue 77, 24 January 1947, Page 3

SCIENTIFIC BREEDING

BEST TO BEST IS NOT ENOUGH ANIMAL RESEARCH The world-famed Dutch animalbreeding scientist, Dr. Hagedoorn, makes a plea for a change from the present method of selecting breeding animals on the basis of their outward appearance or records to selection based on the merits of their offspring. Writing in the “Farmer and Stockbreeder” (England), Dr. Hagedoorn says:— “We geneticists must try to adapt the results of our studies to the improvement of practical breeding methods, and the point in which we can help most just at present is in showing just why progeny testing helps to improve breeds. “It is evident that the fact that plain mass-selection will help breeders to make considerable progress has led to the idea that this same process of strict selection, breeding the best to the best, will continue to improve and purify the breed, so that in the end the average quality will continue to improve up to the ideal point where practically every beast born is perfect. Proportion of Duds “This, however, is not the - case. Up to a certain point improvement and purification is possible, but after that the situation is attained which we all know from bitter experiece, narpely, that in which there are enough excellent individuals in every generation to continue to breed with, but in which every generation also produces a variable proportion of duds. “And this, to my mind, is the point where we geneticists can be of very great help. Even if some of us make no claims of being good show judges, if we don’t pretend to be able to place half a dozen heifers correctly in a class, those of us who have been experimenting on plants and on the smaller animals and registering our results have a practical experience in these matters which no animal breeder on' a bigish scale can ever have.

“Let it suffice to say that after a good many generations of plain selecting a point is reached in which most animals are good, as individuals, but in which some of them will still produce disappointing offspring among the good ones.

“And this is caused by the fact that in many cases and many qualities an individual which is impure (heterozygous) for a desirable inherited factor, and will for that reason make some reproductive cells which are deficient in some important ingredient, cannot by simply examining its qualities be picked out from among the others who happen to be pure.

“Even our best breeds of cattle, of pigs, rabbits, poultry are still in such a state that a proportion of the very best individuals are impure in respect to valuable necessary genes. “One aspect of this is the very frequent production of aberrant foals, calves, chicks—animals with fatal lethal hereditary constitution. “The most obvious case is that of animals or birds that simply will not come up to the required standard of perfection, even if given the best of care.

“It would lead me much too far to give figures about the extremely slow rate at which the proportion of animals impure for important factors is gradually lowered by just weeding out the undesirable aberrant individuals as they are born. Where dominance is really complete, plain selection will make no apreciable effect on the proportion of undesirable recessives in each generation in a few dozen generations.

“This, by the way, is where the ‘eugenic movement,’ so much advertised in the U.S.A., in Germany and other countries with ‘sterilisation laws for human betterment’ breaks down as inefficient!

Progeny Testing

“From the foregoing it is plain that a very efficient way to break up this jam is to use some method of progeny testing. If we once know that one stallion has a higher proportion of valuable offspring than another, that one bull produces no dud heifers, whereas his brother has given a few, and that one boar gives piglets with hernia, blind guts or other wasters, whereas another one of the same family is free of such ‘mistakes,’ it is really a very simple step to take, to defer our judgment of a breeding male to the moment where we can actually judge his offspring.

“Now the difficulty with progeny testing lies in the fact that many animal breeders and associations of breeders and associations of breeders (herd books) seem to prefer the present state of things to what it could be made by a correct system of progeny testing.

“If, by means of artificial insemination on a large scale and the use of proven sires of well-tried breeding value for this, purpose, the public becomes educated up to demanding outstanding proven quality in bulls, the market for the tens of thousands of speculative good-look-ing yearling bulls is certain to fall off considerably. “The occurrence of a certain proportion of duds in every generation constitutes a great economic loss for agriculture, and this loss is certainly avoidable. The only thing required is a system of progeny testing, so that if we want to find out just how a cock or a bull is performing as a breeder, we must sample his progeny.”