The effect of aging on the ovarian follicular growth in laying hens

Two kinds of the fat-soluble dye, Sudan black and red, were intravenously injected on alternate days into layers aged from 5 to 23 months to study the growth pattern of the ovarian follicle in relation to aging. Results indicated: 1) the length of the rapid growth period showed a tendency to shorten during 5 to 11 months, then to lengthen from 15 to 23 months of age; 2) there was a continuous increase in follicular volume at ovulation with the progress of age; 3) the growth rate (degree of curvature of the growth line calculated in each follicle) was low at 5 months, increased from 8 to 11 months, and remained constant thereafter; 4) during the first year of age, the number of growing follicles in the ovary decreased gradually, whereas the total amount of daily yolk deposition increased. During the second year of age, both the number of growing follicles and total yolk deposition remained constant.