ASSESSMENT OF PROGESTERONE, CORTISOL AND THYROXINE SERUM CONCENTRATIONS ON DIFFERENT PHASES OF ESTROUS CYCLE IN MARES
Keywords:
mares, estrous cycle, progesterone, cortisol, thyroxineAbstract
The aim of this study was to evaluate the variations on serum concentrations of cortisol,
thyroxine and progesterone during the different phases of estrous cycle in mares, once in this
specie there are some contradictory results concerning the concentration of these hormones on
different periods. It was used 3 groups containing 6 mares in each, selected according to the
phase of estrous cycle, determined by transrectal palpation and ultrasonographic exam of
reproductive tract. Group 1 corresponds to anestrous mares, group 2 to diestro, group 3 to
mares in estrous. It was performed blood collection daily, during followed 5 days to serum
cortisol, progesterone and thyroxine dosage. The technique utilized to hormonal analysis was
Radioimmunoassay with Coat-A-Count Kit (DPC- Diagnostic Products Corporation). We
found an inverse relationship between progesterone and thyroxine during diestrus and it was
observed higher concentration of cortisol levels during the estrous, however the occurence of ovulation was not prevented, suggesting the estrus is a stress factor for the animal, but in a
mild form, which not interfere in the physiology of estrous cycle.
References
Donadeu FX, Ginther OJ. Changes in concentrations of follicular fluid factors during follicle selection in mares. Biology Reproduction. 2002. April;66(4):1111-8.
Bottoms GD, Roesel OF, Raush FD, Akins EL. Circadian variation in plasma cortisol and corticosterone in pigs and mares. Am J Vet Res. 1972; 33: 785-790.
Wagenmaker ER, Breen KM, Oakley AE, Pierse BN, Tilbrook AJ, Turner AI, Karsch FJ. Cortisol interferes with the estradiol-induced surge of luteinizing hormone in the ewe. Biology Reproduction. 2009; 80: 458-463.
Ginther OJ, Utt MD, Beg MA. Follicle deviation and diurnal variation in circulating hormone concentration in mares. Animal Reproduction Science. 2007; 100: 197-203.
Nicholls TJ, Follett BK, Goldsmith AR, Pearson H. Possible homologies between photorefractoriness in sheep and birds: The effect of thyroidectomy on the length of the ewe’s breeding season. Reprod. Nutr. Dev. 1988. 28:375–385.
Lowe JE, Foote RH, Baldwin BH, Hillman RB, Kallfelz FA. Reproductive patterns in cyclic and pregnant thyroidectomized mares. J Reprod Fertill.1987; 35: 281-288.
Porter MB, Cleaver BD, Robinson G, Porter MR, Shearer L, Dahl GE, Sharp DC. A comparative study examining the role of the thyroid in seasonal reproduction in pony mares and ewes. Biol Reprod.1995;52: Suppl 1: 134.
Johson AL. Serum concentrations of prolactin, thyroxine and triiodothyronine relative to season and the estrous cycle in the mare. J Anim Sci.1986; 62: 1012-1020.
Fitzgerald BP, Davidson LA, Thyroxine concentrations are elevated in mares with continue to exhibit estrous cycle during the nonbreeding season. J Equine Vet Sci.1988; 18: 48-51.
Huszenicza G, Nagy P, Juhász J, Kóródi P, Reiczigel J, Guillaume D, Solti L. Relationship between thyroid function and seasonal reproductive activity in mares. J Reprod Fertill. 2000; 56: 163-172.
Donadeu FX, Watson ED. Seasonal changes in ovarian activity: lessons learnt from the horse. Anim Reprod Sci. 2007. Aug; 100(3-4):225-42
Berghold P, Möstl E, Aurich C. Effects of reproductive status and management on cortisol secretion and fertility of oestrous horse mares. Anim Reprod Sci.2007; 102: 276-285.
Downloads
Published
How to Cite
Issue
Section
License
Este obra está licenciado com uma Licença Creative Commons Atribuição-NãoComercial 4.0 Internacional.
