Thyroid Hormone Response to Thyrotropin Releasing Hormone After Cold Treatment During Pre- and Postnatal Development in the Domestic Fowl

Abstract

The purpose of the present study was to compare the effect of periodic cooling during the establishment of a functional pituitary-thyroid axis at days 11-14 of incubation and at other developmental stages, on the subsequent thyroid hormone response to thyrotropin releasing hormone (TRH). In the first and second experiment chick embryos were cooled for 6 hr/day to 30 degrees C from day 11 till 14 and from day 15 till 18 respectively, whereas control groups were incubated throughout at 37.8 degrees C. In both experiments the thyroxine (T4) response upon TRH in 19 day-old embryos was higher in the previously cold treated embryos, according to the percentages of increase. However, the higher T4 response in the cold treated animals disappeared in 1 or 7 day-old chicks hatched from the 2nd experiment, but remained present in chicks of the same ages in the 1st experiment. In a third experiment the T4 response to TRH injection immediately and 3 and 8 days after a temperature treatment (25 degrees C or 12 degrees C) for one week on four weeks old broiler chickens was found to be similar in both temperature groups. In all experiments there was a concomitant triiodothyronine (T3) increase after TRH injection, but differences between experimental groups were observed at days 15 and 19 of incubation and immediately after the postnatal temperature treatment. As an overall conclusion the results indicate that cold treatment only during the establishment of the hypothalamo-hypophysial control of thyroid function can have a long lasting effect by enhancing the T4 response to TRH injection.

Early experiences matter: a review of the effects of prenatal environment on offspring characteristics in poultry

“…Periodic exposure to cold temperatures (30 min on d 18 and 2 30-min sessions on d 19 of incubation) was also beneficial, resulting in chicks hatching with higher BW than those not exposed to cold stress (Shinder et al., 2009 ). Embryos that were cooled for 6 h/d from d 15 to 18 also had enhanced thyroxine response to the thyrotrophin releasing hormone, which may help the chick cope with later stressors (Decuypere et al., 1988 ). However longer exposure to relative extremes of temperature (e.g.…”

Brood size constrains the development of endothermy in blue tits

“…Thyrotropin releasing hormone (TRH) is produced in the hypothalamus and stimulates production of thyroid stimulating hormone (TSH) in the pituitary gland, which, in turn, leads to increased synthesis and release of thyroid hormones (Debonne et al, 2008). These thyroid hormones (T3 and T4) have been shown to induce thermoregulatory abilities in chicks of domestic fowl (Gallus g. domesticus; Debonne et al, 2008) and TRH also seems to have a direct effect on T b in neonatal chicks (Takahashi et al, 2005; but see Decuypere et al, 1988). However, the hypothalamus-pituitarythyroid (HPT) axis in altricial nestlings does not become fully functional until sometime during the first week after hatching (Debonne et al, 2008).…”

Dosed Exposure to Low Temperature as a Breeding Background in The Selection of Gene Pool Breeds of Chickens for Viral Vaccines Production

“…The ability to adapt and maintain productivity over a wide temperature range is an important, economically significant trait. When solving the problem of thermal resistance of birds, two approaches are considered: the first one is based on the study of epigenetic adaptation [13 -16], and the second approach is selectivegenetic [3,17]. The possibility of selection for resistance to extreme ambient temperatures has been confirmed [5,18,19].…”