A Guide to the Recognition of Parthenogenesis in Incubated Turkey Eggs

Thomas F. Savage, Ph.D.

Professor and Head Advisor
Department of Animal Sciences
Oregon State University
Corvallis, OR 97331-6702
 
eMail:Thomas.Savage@oregonstate.edu
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Abstract. Embryonic parthenogenetic failures in turkey eggs can be assigned to one of four categories. Most commonly, parthenogenetic expression consists of unorganized embryonic tissues that may be closely aggregated (1cm. dia.), or extend over the entire surface of the yolk. The embryonic tissues may have a delicate and irregularly shaped appearance. The second category is that of embryonic tissues associated with a ruptured vitelline membrane resulting in the dispersion of the yolk's contents. Typically, the inner shell membrane of an egg with this parthenogenetic form is opaque rather than translucent. A third, less commonly observed form of parthenogenesis is embryonic tissue accompanied by dispersed aggregates of blood islets or an organized pattern resembling a 'blood ring'. The least frequently encounterd form of parthenogenetic expression is the embryo whose embryonic development is visibly delayed by two days when compared to a normal embryo of the same incubation period. Macroscopic differentiation between parthenogenetic and normal embryos can be achieved after 4 days of artificial incubation, but due to the variability in parthenogenetic expression, accuracy of detection is improved after 6 days of incubation.

Introduction

The phenomena of avian parthenogenesis is described as a process of cell division in an unfertilized egg that may result in the formation of embryonic tissues and in extreme situations a fully developed individual (Olsen,1975). The parthenogenetic process has been described in various avian species and appears to have potentially greater economic significance in turkeys than chickens. In most observations of avian parthenogenesis, the abortive expression of early embryonic development can be incorrectly identified as an early embryonic failure associated with the incubation process associated with fertilized eggs. The parthenogenetic tissues that develop in infertile eggs is diploid (Yao and Olsen, 1955; Sato and Kosin, 1960) which makes differentiation between normal and parthenogenetic embryos a difficult task.

The ability to macroscopically recognize embryonic failures attributable to parthenogenesis in fertilized eggs can result in improved reproductive efficiency. Since the first major period of early embryonic mortality in incubating turkey eggs occurs between the third and fifth days, a portion of this mortality may characterized by delayed blastoderm development. Olsen and Marsden (1950) described a line of turkeys having a high incidence of early embryo mortality and a concomittant low hatchability. The early embryonic mortality and poor hatchability (28%) may have been attributed to a high incidence of infertility and parthenogenesis. Without the proper diagnosis to determine the cause of an embryo's failure to develop, the poultry producer/hatchery person may direct their attention to the incubation process rather than the breeder's reproductive management and not improve hatchability as quickly as would be desired.
The scientific literature provides descriptions of studies influencing parthenogenesis in the turkey but lack illustrations and/or photographic images of the phenomenon that would allow the reader to more efficiently recognize the process. Therefore, the following guide was created to:

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