The relationship between egg production, reproductive hormones, and the GDF9 gene in three different chicken strains

Abstract

Egg production is the most important commercial attribute of layer hens since it has a direct impact on the efficiency of the poultry industry. This research aimed to study the age at first egg (AFE), egg number (EN), egg quality, and some plasma hormones within the period from the start of laying eggs until day 90 of production in three strains of laying hens (Lohman Brown (LB), Golden Sabahia (GS)) and White Leghorn (WL) as the reference breed for egg production. In addition, a time series expression profile of growth differentiation factor 9 (GDF9) gene was investigated to get a better understanding of the genetic basis of egg production. The LB laying hens recorded the highest improved estimates of egg production and egg quality traits. Further, GDF9 was highly expressed in LB tissues (magnum and isthmus) compared to WL except in the uterus. These results suggest that there is a direct relationship between number of eggs produced, quality of eggs and the expression level of the GDF9 gene in the LB strains. Besides, the LB strain is superior with candidate productive traits, therefore they can be used as proven ancestors to improve laying hens.