SELECTION OF HATCHING EGGS.

Star (Christchurch), Issue 18786, 15 June 1929, Page 26 (Supplement)

SELECTION OF HATCHING EGGS.

(By

DR B. F. KAUFF.)

No matter which way you hold the egg, the yolk will always come around on top. There is a tendency for the yolk, which is nearly centrally located when the egg is laid, to gradually come to the surface. Experiments in these laboratories to determine just how long a time will be required for the yolk membranes to come in contact with the shell membranes and stick so as to make it impossible to hatch is considerably more than three weeks. Sow liong Can Eggs Be Held? Eggs for hatching should not be saved for longer than three weeks, and better not over two weeks. Experiments have shown that deterioration in liatchability begins at about the third week, and is at the rate of about 4 per cent a day. It is advisable to set eggs just as soon after they are laid as possible. The Porous Shell and Evaporation. The eggs when laid contain 65 per cent moisture. The egg shell possesses fine pores through which evaporation of the liquid within gradually goes on. The rate of evaporation depends upon the temperature, dryness of the surrounding atmosphere and the rate of travel of the air. This fact can be taken advantage of in testing any eggs purchased for hatching purposes by candling the eggs. The air cell at the large end of the egg is normally about the size of a dime, and a shrinkage to a marked degree can easily be observed by the reflected light, through the egg in candling and the staleness or freshness observed. Should Not Wash Eggs. It is best not to wash eggs for hatching purposes. The egg has deposited on it a varnish coat which protects it from the weather. Washing will have a tendency to remove the bloom, and U is believed enlarges the pores of the shell and increases the possible evaporation to the detriment of the embryo. Poor hatches can be looked for. Pertility to Expect. Tests show that under ordinary conditions we should obtain from our large breeds a fertility of 80 to 90 per cent, with an average of about 85 per cent, and with the smaller breeds, as the Leghorns. 90 to 98 per cent, with an average of about 94 per cent. Of these fertile eggs about SO tq 90 per cent are capable of hatching. Fertility rapidly declines after the removal of the cocks. It is not advisable to save eggs for hatching after the males have been removed from the flock five days. If the hens being mated have been running with mongrel cocks all male germs should be out of the hens' oviducts by the eighteenth day, so that in the new mating eggs for hatching may be saved after the twenty-first day. This 'test showed that the fertility of the eggs from small and large lots will reach a level of fertility of at least 80 per cent by the sixth day after hens are mated. Prom these tests it appears that eighteen days will be ample time to elapse after mating hens previously mated before saving eggs. (Concluded.)