Prolactin and luteinizing hormone levels in female turkeys (Meleagris gallopavo) during a photoinduced reproductive cycle and broodiness

Serum levels of prolactin (PRL), luteinizing hormone (LH), progesterone and estradiol-17t1 were compared in female turkeys during various phases of their reproductive life cycle. Prolactin levels of broody turkeys were higher (2164 ± 127 ng/ml) than those of laying turkeys (468 ± 74 ng/ml), which were in turn higher than those of hens that had stopped laying (119 ± 18 ng/ml). Serum LH, progesterone, and estradiol-17� levels of laying hens were significantly higher than those of the other two groups. The levels of these hormones did not differ between broody hens and hens that had stopped laying, but were not broody (photorefractory hens). Serum prolactin levels of broody hens dropped markedly within a day of nest-deprivation and confinement to cages. Levels remained low while hens were in cages. When nests were again made available to broody hens that had been deprived of nests for 48 h, they resumed nesting within 5 mm, and serum prolactin levels then increased. In other experiments, it was found that a significant decline in serum prolactin occurred after 8, but not 4 h of nest-deprivation. After a 48 h period of cage confinement of hens, prolactin levels were seen to increase within 30 mm after hens were returned to their home pens. Levels continued to rise and had nearly reached pre-cage confinement levels by 12 h after resumption of nesting. BIOLOGY OF REPRODUCTION 23, 118-123 (1980)

Effect of Nest-Deprivation on Serum Prolactin Level in Nesting Female Turkeys

Two experiments were conducted to evaluate the effect of estradiol benzoate (EB), progesterone (P), ovine prolactin (oPrl), or their combinations on temporal patterns of serum luteinizing hormone (LH) and Prl and on nesting behavior in adult ovariectomized female turkeys. Levels of serum LH were initially reduced (p greater than 0.05) by the steroid treatments, while continuation of treatments induced surges of LH to levels comparable to pretreatment levels. Administration of steroid increased (p less than 0.05) levels of serum Prl, which persisted until termination of treatments. Administration of oPrl had no effect on levels of serum LH but blunted the steroid-induced release of Prl. Neither EB, P, nor oPrl treatments alone nor a combination of EB + P elicited nest occupation. Nest occupation was observed after administration of P only in turkeys pretreated with EB. Administration of oPrl maintained and advanced the P-induced nesting to persistent nesting behavior (incubation behavior). Once persistent nesting behavior was established, hormonal treatments were terminated, yet nesting behavior was maintained and serum samples showed increasing levels of Prl and decreasing levels of LH. It is suggested that incubation behavior in the female turkey is facilitated by the combined action of estradiol, P, and Prl.

Hormonal induction of incubation behavior in ovariectomized female turkeys (Meleagris gallopavo).

Intracranial perfusion of ovine prolactin (oPrl) via osmotic pump in laying turkey hens caused a sudden onset in incubation behavior, defined as an increase in nest visits. The hens also displayed a gradual decrease in egg laying during the time they were receiving oPrl, another indicator of the onset of incubation. Circulating immunoreactive turkey Prl levels fell during the perfusion period, even though the hens were displaying persistent nesting activity and reduced egg laying. No effects on serum LH were noted. Perfusion of oPrl during the first 14 days of photostimulation delayed the onset of egg laying by several days. No effects on serum Prl or serum LH were noted. It is suggested that incubation behavior is facilitated by central levels of Prl.

A. Bona Gallo

Papers

Isolation and characterization of luteinizing hormone and follicle-stimulating hormone from pituitary glands of the turkey (Meleagris gallopavo)