FIGURE 18.—Twisted albumen of an egg that was turned always in the same direction during incubation.
EGG Hatchability Is Increased by Frequent Turning in Incubator
The hatchability of fertile eggs may be increased by frequent regular turning during the first 2 weeks of incubation, recent investigations indicate. Eggs in large incubators are usually turned mechanically, a half turn in one direction at one turning, then a half turn in the other direction at the next. Eggs in small incubators are usually turned by hand, the direction of successive turnings depending on the operator. The usual number of turnings a day is from 1 to 3. Recent data obtained at the United States Animal Husbandry Experiment Station at Beltsville, Md., indicate that eggs turned mechanically at 15-minute intervals, about a half turn in one direction at one turning and an equal distance in the opposite direction at the next turning, hatched 7 percent better than eggs turned 3 times a day by hand. Both lots of eggs were of the same general origin and were in the same incubator at the same time. Still another investigation indicated that eggs turned at least 8 times a day, at 3-hour intervals night and day, will hatch better than eggs turned less frequently.
The manner and frequency of turning the eggs in the experiments at Beltsville were patterned after the procedure followed by the setting hen. She turns her eggs once every 15 minutes, on the average, in one direction at one turning, back at another, not over and over in the same direction.
Eggs turned always in the same direction, at 15-minute intervals from the beginning of incubation, usually fail to hatch. In many cases, the thick strands of egg white at each end of the yolk, the chalazae, become twisted so tightly (fig. 18) that the yolk is ruptured during the first week of incubation. Even when the embryos live to the second week of incubation, the membranes through which they breathe and also obtain lime from the shell seldom adhere properly to the shell membrane.
Hatchability may be increased also by maintaining the proper position of the eggs in the incubator. The position of the egg partly determines the position of the chick in the egg at hatching time. Between the third and fifteenth days of incubation the operator should not allow the small end of the egg to be above the large end for a long period, because such a position is likely to result in the chick’s head being in the small end of the egg at hatching time. Such a chick has only about half as much chance of hatching as a chick in the normal hatching position with its head in the large end of the egg.
The turning and position of the eggs are most important during the first 2 weeks of incubation. The position of the chick within the egg is less affected by outside influences after the fifteenth day of incubation than before. Voluntary movements of the chick in response to gravity, mechanical shock, suffocation, or other cause probably result in some shift in position. Though it is certain that the effects of turning and egg position are relatively slight during the third week of incubation, the standard recommendation that eggs be kept in proper position and turned regularly to the eighteenth day of incubation should be followed until sufficient evidence is produced to indicate that even a slight improvement in hatchability may be obtained by some other method.