Endocrine Changes in the Incubating and Brooding Turkey Hen1 1

Abstract

Turkey hens were allowed to incubate eggs and to hatch and rear young. Plasma prolactin (Prl) levels increased prior to the start of continuous incubation and rose sharply as incubation progressed to reach a peak of 1178.2 +/- 221.8 ng/ml (mean +/- SEM) just before hatching. Prl levels then fell precipitously before the hens left the nest, and returned to preincubation levels (36.8 +/- 3.4 ng/ml) by the time the poults were 2 weeks old. These results show that the high plasma concentrations of Prl found during incubation are not initiated or maintained only by the stimulus of nesting. We suggest that the decline in Prl levels at the end of incubation could be related to the pipping and hatching of eggs, and the consequent shift to maternal behavior. Plasma growth hormone (GH) levels were significantly increased in hens which were brooding poults, but not in hens incubating eggs. An elevenfold, 1-day increase in plasma GH was observed immediately after the hens left the nests. Mean plasma GH levels rose from 12.0 +/- 4.7 ng/ml on the day that the hens left the nests to 133.0 +/- 32.0 ng/ml on the following day, and then declined to 23.1 +/- 9.6 ng/ml after an additional day. There were no significant changes in plasma thyroxine levels during laying, incubation and brooding. Plasma glucose concentration was significantly depressed during incubation.

GH as a co-gonadotropin: the relevance of correlative changes in GH secretion and reproductive state

“…These relationships are also seen in domesticated species. For instance, the onset of lay in chickens and turkeys is preceded by a rise in the circulating GH concentration which is sustained during the laying cycle (Scanes et al 1979, Williams et al 1986), declines during incubation (Harvey et al 1979, Sharp et al 1979 and increases with the brooding of young (Wentworth et al 1983). These changes reflect differences in the numbers of pituitary somatotrophs (Ramesh et al 1995(Ramesh et al , 1996 and the abundance of pituitary GH mRNA (Karatzas et al 1997).…”

Effect of anti-prolactin drug and peppermint on broodiness, laying performance and egg quality in indigenous hens

“…During incubation, PRL mRNA reaches its highest level (Talbot et al, 1991;Karatzas et al, 1997) which infers that PRL is important in the maintenance of broodiness. Still it is not fully elucidated that a change in the concentration of prolactin is responsible for timing of oviposition in domestic hen (Wentworth et al, 1983) or due to longer intervals of LH surges. Also prolactic plays a role in the development of broodiness in poultry with reference to turkey and bantam hens (Sharp et al, 1988) nothing is reported in this breed.…”

Dopamine and prolactin involvement in the maternal care of chicks in the native Thai hen (Gallus domesticus)

“…The estimated effect sizes (d) and P values for the comparisons of plasma PRL levels and the number of TH-ir neurons in each hypothalamic nucleus of rearing (R) and non-rearing (NR) hens at different days during the observed rearing period (n = 6/group). decline sharply (Opel and Proudman, 1989), and the hen leaves the nest and begins to display rearing behavior toward its new offspring (Wentworth et al, 1983). Indeed, species-dependent, sharp declines (bantams, Sharp et al, 1988;bar-headed geese, Dittami, 1981;common eiders, Criscuolo et al, 2002;domestic ducks, Hall, 1987; Japanese bantams, Zadworny et al, 1988;mallard ducks, Goldsmith and Williams, 1980;swans, Goldsmith, 1982; native Thai chickens, Chaiyachet et al, 2013b;and turkeys, Wentworth et al, 1983) or slow decreases (spotted sandpipers, Oring et al, 1986;Wilson's phalaropes, Oring et al, 1988;and red-necked phalaropes, Gratto-Trevor et al, 1990) in circulating PRL concentrations in hens after chick hatching have been reported (Schradin and Anzenberger, 1999).…”