Abnormal Turkey Eggs

                                                                Dr. Karl Nestor

    Turkey eggs are normally developed in a very orderly process. The yolk (ovum) is released into the body cavity from the ovary and the upper end of the oviduct (the infundibulum) picks up the yolk and the rest of the egg is added as the egg moves down the oviduct. The white or albumen is added in the magnum portion of the oviduct. The shell membranes are added in the isthmus, and the shell is placed on the egg in the uterus. Spots and shell color are also added to the egg in the uterus.
    In the wild, turkey hens lay a clutch of eggs and then incubate them by setting on them for 28 days. The size of the clutch is usually the number of eggs that the hen can cover completely when setting on them. Near the end of the time for the wild turkey hen to lay a clutch, hormonal changes in the body of the bird occur so that egg laying ceases and the hen develops the desire to incubate the eggs. When turkeys are produced for commercial production, it is desirable that the hens lay as many eggs as possible and that they not develop a desire to nest or go broody. There are some turkey strains available that are very good egg producers and exhibit little or no desire to go broody.
    Selection for increased growth rate in turkeys disrupts the normal egg formation resulting in a decrease in the total number of settable eggs produced. Actually, selection for increased body weight does not change the desire to incubate the turkey eggs but rather causes disruptions in the egg formation process. In an ovary from a turkey hen that produces a large number of eggs, the development of the ova or yolks is a very orderly process. The yolks have a hierarchy in development in which they have many yolks developing at a time but the yolks are of different sizes. Selection for increased growth rate changes this hierarchy so that multiple yolks develop at the same time. The oviduct is geared to handle only one yolk per day so that the multiple yolks produced by growth-type hens are lost in the egg formation process. Actually, growth-selected hens produce more yolks in their ovaries that egg-selected hens.The extra yolks produced in growth-selected hens can be lost by several methods. First of all, the extra yolks may not be picked up by the oviduct and these yolks are reabsorbed. If too many yolks are reabsorbed, health problems can develop. A second method in which the growth-selected hens lose yolks is through the production of shell-less eggs. These are eggs in which all of the egg is formed except the shell and these eggs are usually broken soon after they are laid. If the oviduct picks up two yolks at one time, double-yolked eggs can be laid. These eggs will not hatch. Another abnormality that is possible is the development of two eggs at the same time in the oviduct. Because the oviduct is not capable of developing two normal eggs at one time, both of the eggs are abnormal. Usually one of the eggs is held longer than normal in the oviduct and too much calcium is added to the shell resulting in an “extra-calcified” egg. There are various variations of extra-calcified eggs. Some are just chalky and some have ridges of extra calcium. The pores of these eggs are filled with calcium and the eggs do not hatch or hatch very poorly. Sometimes the second egg of pair of eggs moving through the oviduct touches the first egg and the side of the second egg is compressed resulting in a “slab-sided” egg. The shell on the slab side is usually very thin and slab-sided eggs do not hatch.
    The egg production rate of growth-selected turkey hens can be improved by certain management practices. One of these that has been somewhat successful is restricting the growth rate of the hens by reduction of the feed intake. This can be done by several methods including feeding a measured amount of feed that is less than that required for maximum growth. A second method is to feed the birds for a limited amount of time so that they can not consume enough feed for maximum growth.