Pm. Hocking et Ha. Mccormack, DIFFERENTIAL SENSITIVITY OF OVARIAN FOLLICLES TO GONADOTROPIN STIMULATION IN BROILER AND LAYER LINES OF DOMESTIC-FOWL, Journal of Reproduction and Fertility, 105(1), 1995, pp. 49-55
Differences in the reproductive potential of female broiler parent and
layer fowl are related to differences in the recruitment of follicles
to the preovulatory hierarchy. Broiler and laying hens were fed ad li
bitum or a restricted diet during rearing and ad libitum after sexual
maturity. The sensitivity of thecal tissue, from ovarian follicles of
different sizes, from layer and broiler fowl to stimulation by pregnan
t mares' serum gonadotrophin (PMSG) was determined to test the hypothe
sis that differences in egg production are associated with changes in
the sensitivity of ovarian follicles to stimulation by gonadotrophin.
The activity of ornithine decarboxylase 0.5-4 h after injection of 200
iu PMSG kg body mass was assessed in thecal tissue from small white f
ollicles 2-3 and 5-6 mm in diameter and in the smallest preovulatory y
ellow follicle. Basal activity was similar in layers and broiler breed
ers. PMSG-stimulated ornithine decarboxylase activity in follicles of
5-6 mm diameter was greater in broiler breeders than in layers. There
was no difference between the lines in PMSG-stimulated ornithine decar
boxylase activity in follicles of 2-3 mm diameter or in small yellow f
ollicles. It was concluded that the low egg production and high preval
ence of eggs with defective shells in broiler parents compared with la
yers may be related to the increased sensitivity of follicles to endog
enous gonadotrophins at the critical stage of recruitment to the preov
ulatory hierarchy.