Egg production is an important economic trait in the commercial poultry industry. Ovarian follicle development plays a pivotal role in regulation of laying hen performance and reproductive physiology.
The domestic fowl provides a unique model for the study of the mechanisms involved in follicular development. The single left ovary contains follicles of various sizes and developmental stages including quiescent primordial follicles, prehierarchical growing follicles and large yolk-filled follicles that have been recruited to the well-ordered pre-ovulatory hierarchy.
Growth from 3 to 5 mm takes 3 days, from 5 to 8 mm 2 days and from 8 mm to ovulation (40 mm) 6 days, with the total time for development from 1·5 mm to 40 mm being around 17 days . As follicles increase in size there is a progressive decrease in the number of follicles in that size class, with the ovary of the laying hen containing 50 follicles between 1 and 8 mm in diameter.
Regression of follicles in the ovary may because of low body wt, reduce feed intake, Regression of follicles in the ovary may because of low body wt, reduce feed intake, overcrowding, less feeding space etc results fowl cholera, Newcastle disease..,
Free yolk is seen in many cases of acute illness, injury, or forced molt. Regression of the ovary is frequently caused by:
- Low body weight, deliberate reduction of feed, overcrowding, or lack of feeder space.
- Infectious diseases known to cause regression of the ovary include:
- -Newcastle disease
- -fowl cholera
- -Pullorum disease
- -avian influenza
- It can also result from severe stress, which is often accompanied by feather molt, emaciation, and dehydration.