THE EFFECT OF OVARIECTOMY ON CONCENTRATIONS OF PLASMA PROLACTIN AND LH AND PARENTAL BEHAVIOR IN THE DOMESTIC-FOWL

The role of ovarian hormones in the expression of parental behavior an d in the regulation of LH secretion was investigated in incubating com mercial meat-type hens. After ovariectomy, incubating hens continued t o incubate eggs normally and brooded day-old chicks given to replace e ggs, in a manner similar to sham-ovariectomized control hens. The conc entration of plasma LH increased significantly in incubating hens afte r ovariectomy while the concentration of plasma prolactin remained hig h. Plasma LH remained depressed in sham-ovariectomized incubating cont rol hens. The increase in plasma LH in incubating hens after ovariecto my (3.92 +/- 0.7 ng/ml) was less than that following the ovariectomy o f nonincubating, nonlaying hens (5.3 +/- 1.2 ng/ml). The two groups of hens differed in that plasma prolactin concentrations were high (527 +/- 7.4 ng/ml) in the incubating hens and low (70 +/- 9 ng/ml) in the nonincubating hens. Nest deprivation resulted in an increase in plasma LH in both ovariectomized and sham-ovariectomized incubating hens wit h a significantly larger increase occurring in the ovariectomized hens (8.5 +/- 1.41 ng/ml compared to 2.48 +/- 0.65 ng/ml). Nest deprivatio n resulted in a similar rapid decrease in plasma prolactin in both ova riectomized and sham-ovariectomized hens. Replacement of eggs with day -old chicks in ovariectomized or sham-ovariectomized incubating hens r esulted in a rapid decrease in plasma prolactin and after 6 days, in a n increase in plasma LH in the ovariectomized but not sham-operated he ns. It is concluded that once incubation behavior is established, ovar ian hormones are not required for its maintenance or the readiness to brood day-old chicks. Ovarian hormones do, however, suppress LH releas e during incubation while the high concentration of plasma prolactin s upplements this suppression. (C) 1996 Academic Press, Inc.