REPEATABILITY OF EGG NUMBER AND EGG QUALITY TRAITS IN COMMERCIAL PULLETS

Abstract

Repeatability estimates of 0.09 for egg number to 30 weeks of age; 0.67, 0.53, 0.51 0.20 and 0.26 for egg weight (EW), shell thickness (ST), Haugh unit (HU), yolk index (YI) and shape index (SI), respectively, at 22 weeks of age; and 0.85, 0.78, 0.82, 0.49 and 0.62 for the same traits, respectively at 30 weeks of age were obtained in a flock of exotic commercial pullets reared in cages. The expected relative genetic gain per generation of selection for repeated records was inversely related to the magnitude of repeatability. Thus, as laying progressed, repeatability estimates became higher and expected genetic gain from using additional records decreased and fewer records were required to characterize the pullets for inherent transmitting ability. While 4 eggs per hen areconsidered adequate for 22 - week EW, ST and HU, 8 eggs are required for YI and ŞI. The considered numbers of eggs for corresponding traits at 30 weeks are 3 and 4, respectively. Measurements on 10 eggs per hen are required for egg number to 30 weeks.