title: Ovum formation and multiple ovulation in lines of white Plymouth Rocks and their crosses.
abstract: The production of double-yolked eggs and the duration of the rapid growth phase of yolks were measured in parental lines of White Plymouth Rock pullets and their crosses over 30 d, commencing with the day of first egg. Significant differences were found between mating combinations in the incidence of multiple-yolked eggs, but not in the period of rapid yolk growth. Heterosis and recombination effects for multiple ovulation were respectively -9% and -66% of the mean, while the corresponding values for the period required for rapid yolk growth were -1% and -5%. Three double-yolked eggs were observed containing yolks which differed by 3 d in their periods of rapid growth. Hypotheses are were presented for the origin of double-yolked eggs.
mesh_terms: D000818:Animals; D002645:Chickens / Q000502:physiology*; D003433:Crosses, Genetic; D004530:Egg Yolk; D004531:Eggs; D005260:Female; D010060:Ovulation