| More

The effect of thiamizole in thyroid and ovarian activity of Karagouniko breed ewes

Views: 323 Downloads: 257


The objectives of the present study were to investigate the feasibility to extent the breeding season after pharmacological thyroid gland suppression in Karagouniko ewes. During the first experimental phase, we studied the circannual variation in thyroxin and triiodiothyronin concentration in 10 ewes. During the next year, on the basis of the results obtained from the first phase, thiamazole was administered in 10 of 20 ewes. Sample analysis from the first experiment showed that T3 and T4 fluctuate throughout the year, but at the period of increasing daylight their concentrations were higher in comparison to those of the periods of decreasing daylight. A clear and abrupt increase in both T3 and T4 was observed during the end of spring. In the second experiment we attempted to eliminate this increase by thiamazole administration. Thiamazole suppressed T3 and T4 increase, but estrous cycle characteristics (ovarian structures, progesterone concentration) and mainly the duration of the breeding season did not differ between the two groups. We infer that stronger and possibly longer thyroid gland suppression is required in order an extension of the breeding season to be achieved.


thyroxine; progesterone; thiamazole; ewe

Full Text:



Calza L, Aloe L, Giardinos L (1997). Thyroid gland induced plasticity in the adult rat brain. Brain Res Bull., 44,549-557

Chandrasekhar Y., D'Occhio M.J., Holland M.K., Setchell B.P. (1985). Activity of the hypothalamo-pituitary axis and testicular development in prepubertal ram lambs with induced hypothyroidism or hyperthyroidism. Endocrinology. 117:1645-1651.

Dahl GE, Evans NP, Moenter SM, Karsch FJ (1994). The thyroid gland is required for reproductive neuroendocrine responses to photoperiod in the ewe. Endocrinology 135,10-15.

Dahl GE, Evans NP, Thrun LA and Karsch FJ (1995). Thyroxin is permissive to seasonal transition in reproductive neuroendocrine activity in the ewe. Biol Reprod 52,690-696.

Follet B.K. & Nochols T.J. (1984). Influence of thyroidectomy and thyroxin replacement on photoperiodically controlled reproduction in quail. J Endocrinology 107:211-221.

Follett B.K., Potts C. (1990). Hypothyroidism affects reproductive refractoriness and the seasonal oestrous period in Welsh Mountain ewes. Journal of Endocrinology 127: 103-109.

Gifford CA., Duffey J.L., Knight R.L, Hallford D.M. (2007). Serum thyroid hormones and performance of offspring in ewes receiving propylthiouracil with or without melatonin. Animal Reproduction Science 100,32-43.

Goldsmith BK, Nocholls TJ (1984). Thyroidectomy prevents the development of photorefractoriness and the associated rise in plasma prolactin in starlings. Gen Comp Endocrinol 54:256-263.

Hernandez J.A., Hallford D.M., Wells N.H., (2003). Ovarian cyclicity in thyroid-suppressed ewes treated with propylthiouracil immediately before onset of seasonal anestrus. J Anim. Sci. 81: 29-34.

Jallegeas M, Assenmacher I (1979). Further evidence for reciprocal interactions between the annual sexual and thyroid cycles in peking ducks and teal Gen Comp Enndoc. 36: 201-210.

Karsch FJ, Dahl GE, Hachigian TM Thurn LA (1995). Involvement of thyroid hormones in seasonal reproduction. J Rep Fert (sup) 49:409-422

Lehman ΜΝ, Goodman RL, Karsch FJ, Jackson GL, Berriman SJ, and Jansen HT (1997). The GnRH system of seasonal breeders: anatomy and plasticity. Brain Res. Bull. 44(4): 445-457

Menegatos I, Kalogiannis D, Lainas T, Nikokiris P, Deligiannis K, Nikolaou E, (1994). Annual concentration of thyroxin in ewes of the Greek breeds Karagouniko and Epirus. Annals of Greek Veterinary Society, 45(1): 20-24.

McNabb FMA, 1992. Thyroid hormones. Prentice hall Englewood Cliffs

Moenter SM, Woodfill CJ & Karsch FJ (1991). Role of the thyroid gland in seasonal reproduction: thyroidectomy blocks seasonal suppression of reproductive neuroendocrine activity in ewes Endocrinology 1337-1344.

Oppenheimer JR, Schwartz HL (1997). Molecular basis of thyroid hormone dependent brain development. Endoc Rev 18,462-475.

Saleh D.M., Barrell G.K., Bailey C.I., Frampton C.M.A.(1998). Effects of exogenous triiodothyronine (T3) and a goitrogen, methylthiouracil (MTU), on thyroid gland function in sheep. Small Ruminant Research 30, 49-56.

Shi ZD, Barrel GK (1992). Thyroid hormones are required for the expression of seasonal changes in red deer stags. Rerod. Fertil Dev 6:187-192

Thrun LA, Dahl GE, Evans NP Karsch FJ (1998). Effect of thyreoidectomy on maintenance of seasonal reproductive suppression in the ewe. Biol Reprod 56,1035-1040.

Thrun LA, Dahl GE, Evans NP, Karsch FJ (1996). Time-course of thyroid hormone involvement in the development of anestrus in the ewe. Biol Reprod 55,833-7.

Viguie C, Battaglia DF, Krasa HB, Thrun LA, Karsch FJ, (1999). Thyroid hormones act primarily within the brain to promote the seasonal inhibition of luteinizing hormone secretion in the ewe. Endocrinology 140,1111-7.

Webster JR, Moenter SM, Barrell GK, Lehman MN, Karsch FJ (1991). Role of the thyroid gland in seasonal reproduction. Thyreoidectomy blocks seasonal suppression of gonadotropin - releasing hormone secretion in sheep. Endocrinology 129 1635- 1643.


  • There are currently no refbacks.

Copyright (c) 2018 D. Kantas (Δ.Καντάς, E. Ntovolou (Ντόβολου Ε.), T. Tsiligianni (Θ. Τσιλιγιάννη), E. Valasi (Ε. Βαλάση), P. Goulas (Π. Γούλας)

Creative Commons License
This work is licensed under a Creative Commons Attribution-NonCommercial 4.0 International License.