+ Site Statistics
+ Search Articles
+ PDF Full Text Service
How our service works
Request PDF Full Text
+ Follow Us
Follow on Facebook
Follow on Twitter
Follow on LinkedIn
+ Subscribe to Site Feeds
Most Shared
PDF Full Text
+ Translate
+ Recently Requested

Seasonal variations in prolactin, growth hormone and thyroid hormones and the prolactin surge at ovulation do not affect litter size of ewes during pregnancy in the oestrous or the anoestrous season



Seasonal variations in prolactin, growth hormone and thyroid hormones and the prolactin surge at ovulation do not affect litter size of ewes during pregnancy in the oestrous or the anoestrous season



Journal of Reproduction and Fertility 90(1): 47-53



Injection of bromocriptine from 5 days before until 5 days after mating clearly suppressed the periovulatory prolactin surge in ewes in the anoestrous and oestrous season but did not change the litter size significantly. Progesterone, GH, TSH or thyroid hormone concentrations were not influenced by the bromocriptine treatment. The progesterone concentrations were lower during the first weeks after mating in the anoestrous season compared to the oestrous season, while there was no difference between pregnant and non-pregnant ewes. During later gestation this seasonal differences was only observed in the non-pregnant ewes. At the same time there was a clear differences between pregnancy and non-pregnancy in both seasons. The prolactin, GH and thyroid hormone values also varied significantly during gestation. Since these patterns are identical in pregnant and non-pregnant ewes, the fluctuations are due to environmental factors and not to pregnancy or altered progesterone concentrations. In the anoestroupus season prolactin, GH, T4 and T3 levels were higher than in the breeding season, while rT3 showed the opposite pattern. The TSH concentration did not differ between the two seasons. These results suggest that seasonal variations in prolactin, GH and thyroid hormones or the periovulatory prolactin surge dod not affect litter size of ewes during pregnancy in the oesterous or the anoestrous season.

Please choose payment method:






(PDF emailed within 0-6 h: $19.90)

Accession: 001940940

Download citation: RISBibTeXText

PMID: 2231554

DOI: 10.1530/jrf.0.0900047


Related references

Effect of TRH on the secretion of prolactin in ewes at various stages of pregnancy and in non-pregnant ewes during the breeding season and seasonal anoestrus. Journal of Reproduction and Fertility 61(1): 149-155, 1981

Effect of thyrotropin releasing on the secretion of prolactin in ewes at various stages of pregnancy and nonpregnant ewes during the breeding season and seasonal anestrus. Journal of Reproduction and Fertility 61(1): 149-156, 1981

Prolactin in Finnish dairy cattle. 1. Long-term and daily variations of blood prolactin in heifers and lactating cows and effect of TRH-injection on prolactin and thyroid hormone levels. Annales Agriculturae Fenniae 30(1): 41-55, 1991

On the out-seasonal production of lambs. II. Further experiments on the hormonal induction of fertility in the anoestrous ewes, and changes of oestrogen concentrations in the blood plasma of thus treated ewes, compared with those of oestrous cycle in breeding season. Tohoku J. agric. Res 13: 119-134, 1962

Variations in plasma prolactin, thyroid hormones, gonadal steroids and growth hormone in turkeys during the induction of egg laying and moult by different photoperiods. British Poultry Science 20(2): 143-148, 1979

Diurnal and seasonal variations in cortisol, prolactin, TSH and thyroid hormones in women with and without seasonal affective disorder. Journal of Interdisciplinary Cycle Research 24(3): 185-196, 1993

Prolactin Short-Loop Feedback and Prolactin Inhibition of Luteinizing Hormone Secretion during the Breeding Season and Seasonal Anoestrus in the Ewe. Neuroendocrinology 54(3): 279-285, 2008

Prolactin short-loop feedback and prolactin inhibition of luteinizing hormone secretion during the breeding season and seasonal anoestrus in the ewe. Neuroendocrinology 54(3): 279-285, 1991

Seasonal effects of antihistamine on mean serum concentrations of luteinizing hormone, growth hormone and prolactin in ovariectomized ewes. Animal Reproduction Science 37(1): 15-24, 1994

Effect of chronic thyroid hormone treatment on cycling, ovulation, serum reproductive hormones and ovarian LH and prolactin receptors in rats. Endocrine 3(2): 121-127, 1995

Dopaminergic-like activity in toxic fescue alters prolactin but not growth hormone or thyroid stimulating hormone in ewes. Domestic Animal Endocrinology 4(4): 259-269, 1987

Prolactin release during the estradiol-induced LH surge in ewes: modulation by progesterone but no evidence for prolactin-releasing peptide involvement. Journal of Endocrinology 177(3): 453-460, 2003

The roles of prolactin, growth hormone, insulin-like growth factor-I, and thyroid hormones in lymphocyte development and function: insights from genetic models of hormone and hormone receptor deficiency. Endocrine Reviews 21(3): 292-312, 2000

Effect of suppression of plasma prolactin on ovulation, plasma gonadotrophins and corpus luteum function in LH-RH-treated anoestrous ewes. Journal of Reproduction and Fertility 56(2): 601-609, 1979

The effect of exposure to oestrous ewes on rams' sexual behaviour, plasma testosterone concentration and ability to stimulate ovulation in seasonally anoestrous ewes. Applied Animal Behaviour Science 67(4): 293-305, 2000