Variations in plasma prolactin, thyroid hormones, gonadal steroids and growth hormone in turkeys during the induction of egg laying and moult by different photoperiods

Abstract

1. Concentrations of prolactin, growth hormone, testosterone, progesterone, thyroxine and triiodothyronine were measured in the blood plasma of female turkeys during successive periods of egg laying, a decline in lay, a moult induced by a short photoperiod (6 light: 18 dark) and a resumption of egg laying induced by a long photoperiod (16L:8D). 2. Concentrations of prolactin, growth hormone, testosterone and progesterone were higher in laying birds than in birds which were moulting or not laying. 3. The concentration of testosterone, but not of the other hormones studied, increased significantly during the period of profuse moult. 4. Concentrations of the thyroid hormones did not change with the varying physiological condition of the birds. However, the concentration of thyroxine was depressed by the long photoperiod.

Growth hormone production and role in the reproductive system of female chicken

“…Involvement of pituitary GH is, however, strongly suggested by the correlated elevation in blood plasma GH concentration in pullets at the onset of lay (Williams et al, 1986) and around the time of oviposition and ovulation in hens . Attenuation of GH secretion in chickens, turkey and bantam hens with the cessation of egg laying is also observed (Bedrak et al, 1981;Scanes et al, 1979;Sharp et al, 1979). Moreover, a role for pituitary GH in the function of the ovary is also supported by an increase in the number of small ovarian follicles after GH administration to laying hens (Williams et al, 1992).…”

Serum Concentrations of Prolactin, Luteinizing Hormone, Growth Hormone, Corticosterone, Progesterone, Testosterone and Oestradiol in Relation to Broodiness in Domestic Turkeys (Meleagris Gallopavo)

“…The serum concentrations of the pituitary hormones were measured by specific homologous radioimmunoassays for chicken LH (Follett, Scanes & Cunningham, 1972), prolactin (Scanes, Chadwick & Bolton, 1976) and GH (Harvey & Scanes, 1977). These have been used for previous physiological investigations in turkeys (Scanes, Sharp, Harvey, Godden, Chadwick & Newcomer, 1979). The standard and 125I-labelled tracer used in the LH assay were a preparation of chicken LH (fraction AE1) purified to minimize thyroidstimulating hormone activity , although the antiserum was the same as used by Follett et al (1972).…”

Acute Decrease in Vitellogenin Synthesis by deprivation of food and Water in Laying Hens.

“…This forced change recorvers to the normal state after 2 months. Many studies employed different conditions to induce forced molting (Cole-and Hutt, 1928;Schaffner, 1954;Tanabe et al, 1957;Harris and Schaffner, 1957;Nakazawa et al, 1968;Ringer, 1976;Scanes et al, 1979;Pethes et al, 1982) van Bohemen et al, 1981;Korsgaard et al, 1986), Xenopus (Wallace and Jared, 1969;Kato et al, 1986;Holland and Wangh, 1987). Thus, vitellogenin synthesis is largely coupled with egg production under the control of the endocrine system.…”