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Fecha Publicación: 2011-12-16
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Uribe Velásquez, L. F. ., Lenz Souza, M. I. ., & Correa Orozco, A. . (2011). Efecto de altas concentraciones de progesterona durante la fase luteal temprana sobre la secreción de LH y estradiol en ovejas. Revista Veterinaria Y Zootecnia (On Line), 5(2), 44–54. Recuperado a partir de https://revistasojs.ucaldas.edu.co/index.php/vetzootec/article/view/4455
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RESUMEN: Se evaluaron los efectos de la progesterona (P4 ) sobre la endocrinología reproductiva en hembras ovinas. Las ovejas fueron sincronizadas con rostaglandina-PGF2α (PG) y distribuidas aleatoriamente en dos grupos (n = 7/grupo): grupo-control y grupo tratado con progesterona (CIDR) después de la ovulación (día cero). Desde el día anterior a la aplicación de PG hasta el día 10 después de la ovulación, se realizó monitoreo ecográfico. Diariamente fueron colectadas muestras de sangre para la determinación de las concentraciones plasmáticas de P4 y estradiol (E2 ). Para el perfil de los pulsos de la hormona luteinizante (LH), las colectas de sangre se realizaron a intervalos de 30 minutos por un período de ocho horas, en los días uno y seis. Las concentraciones de las hormonas fueron determinadas por radioinmunoanálisis. La frecuencia de los pulsos de LH difirió en el primer día del ciclo (P<0,01), con valores de 2,55±0,09 pulsos/8 horas en el grupo-control y de 1,49±0,11 pulsos/8 horas en el grupo tratado. En el sexto día, el grupocontrol presentó significativamente (P<0,05) mayor número de pulsos (2,20±0,09 pulsos/8 horas) que el grupo tratado (1,22±0,11 pulsos/8 horas). Las medias de las concentraciones plasmáticas de P4 difirieron entre los grupos (P<0,001), durante la administración de P4 , en el primer y sexto día del ciclo estral. Además, hubo diferencia significativa (P<0,0001) en las concentraciones de E2 entre los grupos durante la administración de P4 . Estos datos sugieren que la progesterona exógena reduce los pulsos de LH.
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Ali, A.; Hayder, M.; Saifelnaser, E.O.H. Ultrasonographic and endocrine evaluation of three regimes for oestrus and ovulation synchronization for sheep in the subtropics. Reproduction in Domestic Animals, v.44, p.873-878, 2009.
Badinga, L.; Driancourt, M.A.; Savio, J.D. et al. Endocrine and ovarian response associated with the first-wave dominant follicle in cattle. Biology of Reproduction, v.47, p.871-883, 1992.
Campbell, B.K.; Mann, G.E.; McNeilly, A.S. et al. The pattern of ovarian inhibin, estradiol, and androstenedione secretion during the estrous cycle of the ewe. Endocrinology, v.127, p.227- 235, 1990a.
Campbell, B.K.; Mann, G.E.; McNeilly, A.S. et al. Pulsatile secretion of inhibin, oestradiol and androstenedione by the ovary of the sheep during the oestrus cycle. Journal of Endocrinology, v.126, p.385-393, 1990b.
Currie, W.D.; Medhamurthy, R.J.; Cook, S.J. et al. Seasonal fluctuation in diurnal rhythms of luteinizing hormone secretion in ewes during the mid-luteal phase of the oestrus cycle. Journal of Reproduction and Fertility, v.97, p.71-74, 1993.
Custer, E.E.; Beal, W.E.; Wilson, S.J. et al. Effect of melengestrol acetate (MGA) or progesteronereleasing intravaginal device (PRID) on follicular development, concentrations of estradiol-17β and progesterone, and luteinizing hormone release during an artificially lengthened bovine estrous cycle. Journal of Animal Science, v.72, p.1282-1289, 1994.
Downing, J.A.; Joss, J.; Scaramuzzi, R.J. Ovulation rate and the concentrations of LH, FSH, GH, prolactin and insulin in ewes infused with tryptophan, tyrosine or tyrosine plus phenyalanine during the luteal phase of the oestrus cycle. Animal Reproduction Science, v.45, p.283-297, 1997.
Fernández-Moro, D.; Veiga-López, A.; Ariznavarreta, C. et al. Preovulatory follicle development in goats following oestrous synchronization with progestagens or prostaglandins. Reproduction in Domestic Animals, v.43, p.9-14, 2008.
Forsberg, M.; Tagle, R.; Madej, A. et al. Radioimmunoassay of bovine, ovine and porcine luteinizing hormone with a monoclonal antibody and a human tracer. Acta Veterinaria Scandinavica, v.34, p.255-262, 1993.
González-Bulnes, A.; Veiga-López, A.; García, P. et al. Effects of progestagens and prostaglandin analogues on ovarian function and embryo viability in sheep. Theriogenology, v.63, p.2523-2534, 2005.
González-Reyna, A.; Valencia, M.J.; Foote, W.C. et al. Hair sheep in México: reproduction in the Pelibuey sheep. Animal Breeding Abstracts, v.59, p.509-524, 1991.
Goodman, R.L.; Bittman, E.L.; Foster, D.L. et al. The endocrine basis of the synergistic suppression of luteinizing hormone by estradiol and progesterone. Endocrinology, v.109, p.1414- 1417, 1981.
Goodman, R.L.; Bittman, E.L.; Foster, D.L. et al. Alterations in the control of luteinizing hormone pulse frequency underline the seasonal variation in estradiol negative feedback in the ewe. Biology of Reproduction, v.27, p.580-589, 1982.
Goodman, R.L.; Karsch, F.J. Pulsatile secretion of luteinizing hormone: Differential suppression by ovarian steroids. Endocrinology, v.107, p.1286-1290, 1980.
Hamra, A.H.; Massri, Y.G.; Marcek, J.M. et al. Plasma progesterone levels in ewes treated with progesterone-controlled drug-release dispenser, implants and sponges. Animal Reproduction Science, v.11, p.187-194, 1986.
Haresign, W.; Cooper, A.C.; Khalid, M. et al. Patterns of gonadotropin secretion in cyclic Finn ewes selected for low and again high ovulation rate. Animal Science, v.61, p.251-257, 1995.
Johnson, S.K.; Dailey, R.A.; Inskeep, E.K. et al. Effect of peripheral concentrations of progesterone on follicular growth and fertility in ewes. Domestic Animal Endocrinology, v.13, p.69- 79, 1996.
Joseph, I.B.J.K.; Rawlings, N.C. Infusion of estradiol during the luteal phase of the estrous cycle in the ewe completely eliminates LH pulses. Canadian Journal of Animal Science, v.70, p.1147-1150, 1990.
Kaneko, H.; Terada, T.; Taya, T. et al. Ovarian follicular dynamics and concentrations of oestradiol-17β, progesterone, luteinizing hormone and follicle stimulating hormone during the periovulatory phase of the oestrus cycle in the cow. Reproduction, Fertility and Development, v.3, p.529-535, 1991.
Kim, S.; Tanaka, T.; Kamomae, H. Different Effects of Subnormal Levels of Progesterone on the Pulsatile and Surge Mode Secretion of Luteinizing Hormone in variectomized Goats. Biology of Reproduction, v.69, p.141- 145, 2003.
Kinder, J.E.; García-Winder, M.; Imakawa, K. et al.Circulating concentrations of 17beta-estradiol influence pattern of LH in circulation of cows. Domestic Animal Endocrinology, v.8, p.463- 470, 1991.
Kinder, J.E.; Kojima, F.N.; Bergfeld, E.G.M. et al. Progestin and estrogen regulation of pulsatile LH release and development of persistent ovarian follicles in cattle. Journal of Animal Science, v.74, p.1424-1440, 1996.
Kojima, F.N.; Bergfeld, E.G.M.; Wehrman, M.E. et al. Frequency of luteinizing hormone pulses in cattle influences duration of persistence of dominant ovarian follicles, follicular fluid concentrations of steroids, and activity of insulin-like growth factor binding proteins. Animal Reproduction Science, v.77, p.187- 211, 2003.
Latour, D.; Littell, R. Advanced general linear models with an emphasis on mixed models. Version 6.12. Cary: SAS Institute, 1996. 268p. Leyva, V.; Buckrell, B.C.; Walton, J.S. Regulation of follicular and ovulation in ewes by exogenous progestagen. Theriogenology, v.50, p.395- 416, 1998.
Martin, G.B. Factors affecting the secretion of luteinizing hormone in the ewe. Biological Reviews, v.59, p.1-87, 1984.
Menchaca, A.; Miller, V.; Salveraglio, V. et al. Endocrine, luteal and follicular responses after the use of the Short-Term Protocol to synchronize ovulation in goats. Animal Reproduction Science, v.102, p.76-87, 2007.
Menchaca, A.; Rubianes, E. Relation between progesterone concentrations during the early luteal phase and follicular dynamics in goats. Theriogenology, v.57, p.1411-1419, 2002.
Mihm, M.; Diskin, M.G.; Roche, J.F. Regulation of follicle wave growth in cattle. Reproduction in Domestic Animals, v.31, p.531-538, 1996.
Montgomery, G.W.; Martin, G.B.; Pelletier, J. Changes in pulsatile LH secretion after ovariectomy in Ile-de-France in two seasons. Journal of Reproduction and Fertility, v.73, p.173-183, 1993.
Nett, T.M.; Turzillo, A.M.; Baratta, M. et al. Pituitary effects of steroid hormones on secretion of follicle-stimulating hormone and luteinizing hormone. Domestic Animal Endocrinology, v.23, p.33-42, 2002.
Norris, T.A.; Weesner, G.D.; Shelton, J.M. Biological activity of LH during the peripartum period and the estrous cycle of the ewe. Domestic Animal Endocrinology, v.61, p.25-33, 1989.
Oyedipe, E.O.; Pathiraja, N.; Gyang, E.O. et al. Effect of dose of pregnant mare serum gonadotrophin on estrus parameters, ovulation rate and peripheral progesterone concentrations in Yankasa ewes. Animal Reproduction Science, v.20, p. 255-264, 1989.
Price, C.A. Secreção pulsátil de LH alterada durante a superovulação em bovinos. Arquivos da Faculdade de Veterinária, v.27, p.35-53, 1999.
Ravindra, J.P.; Rawlings, N.C.; Evans, A.C.O. et al. Ultrasonographic study of ovarian follicular dynamics in ewes during the estrous cycle. Journal of Reproduction and Fertility, v.101, p.501-509, 1994.
Rhodes, F.M.; Chagas, L.M.; Clark, B.A. et al. Effect of dietary intake on steroid feedback on release of luteinizing hormone in ovariectomized cows. Reproduction, Fertility and Development, v.15, p.11-17, 2003.
Richter, T.A.; Robinson, J.E.; Evans, N.P. Progesterone blocks the estradiol-stimulated luteinizing hormone surge by disrupting activation in response to a stimulatory estradiol signal in the ewe. Biology of Reproduction, v.67, p.119- 125, 2002.
Rubianes, E.; Castro, T.; Carbajal, B. Effect of high progesterone levels during the growing phase of the dominant follicle of wave 1 in ultrasonically monitored ewes. Canadian Journal of Animal Science, v.76, p.1-3, 1996.
Sánchez, T.; Wehrman, M.E.; Kojima, F.N. et al. Dosage of the synthetic progestin, norgestomet, influences luteinizing hormone pulse frequency and endogenous secretion of 17-β-estradiol in heifers. Biology of Reproduction, v.52, p.464- 469, 1995.
Scaramuzzi, R.J.; Adams, N.R.; Baird, D.T. et al. A model for follicle selection and the determination of ovulation rate in the ewe. Reproduction, Fertility and Development, v.5, p.459-478, 1993.
Schrick, F.N.; Surface, R.A.; Pritchard, J.Y. et al. Ovarian structures during the estrous cycle and early pregnancy in ewes. Biology of Reproduction, v.49, p.1133-1140, 1993.
Seekallu, S.V.; Toosi, B.M.; Rawlings, N.C. LH pulse frequency and the emergence and growth of ovarian antral follicular waves in the ewe during the luteal phase of the estrous cycle. Reproductive Biology and Endocrinology, v.7, p.78-93, 2009.
Skinner, D.C.; Harris, T.G.; Evans, N.P. Duration and amplitude of the luteal phase progesterone increment times the estradiol-induced luteinizing hormone surge in ewes. Biology of Reproduction, v.63, p.1135-1142, 2000.
Smith, J.F.; Briggs, R.M.; Parr, J. et al. Seasonal changes in LH profiles of ewes selected for and against an early lambing date. In: Conference of New Zealand Society of Animal Production, 55, 1995, Otago. Proceedings... Otago: New Zealand Society of Animal Production, 1995. p.224-227.
Souza, C.J.H.; Campbell, B.K.; Baird, D.T. Follicular dynamics and ovarian steroid in sheep during anoestrus. Journal of Reproduction and Fertility, v.108, p.101-106, 1996.
Thomas, G.B.; Martin, G.B.; Ford, J.R. et al. Secretion of LH, FSH and oestradiol-17β during the follicular phase of the oestrus cycle in the ewe. Australian Journal of Biological Sciences, v.41, p.303-308, 1988.
Tsonis, C.G.; Carson, R.S.; Findlay, J.K. Relationships between aromatase activity, follicular fluid oestradiol-17β and testosterone concentrations, and diameter and atresia of individual ovine follicles. Journal of Reproduction and Fertility, v.72, p.153-163, 1984.
Tsukamura, H. Neuroendocrine mechanism regulating luteinizing hormone secretion during periovulatory period: Negative and positive feedback actions of estrogen in the brain. Journal of Reproduction and Development, v.44, p.j81-j90, 1998.
Uribe-Velásquez, L.F.; Souza, M.I.L.; Loaiza, A.M. Efecto de la sincronización del estro con prostaglandina-F2α vs CIDR + 500 UI de eCG en ovejas Bergamacia durante el inicio de la fase luteal. Revista Científica, FCV-LUZ, v.18, n.4, p.368-373, 2008.
Wherman, M.E.; Roberson, M.S.; Cupp, A.S. et al. Increasing exogenous progesterone during synchronization of estrus decreases endogenous 17β-estradiol and increases conception in cows. Biology of Reproduction, v.49, p.214- 220, 1993.
Badinga, L.; Driancourt, M.A.; Savio, J.D. et al. Endocrine and ovarian response associated with the first-wave dominant follicle in cattle. Biology of Reproduction, v.47, p.871-883, 1992.
Campbell, B.K.; Mann, G.E.; McNeilly, A.S. et al. The pattern of ovarian inhibin, estradiol, and androstenedione secretion during the estrous cycle of the ewe. Endocrinology, v.127, p.227- 235, 1990a.
Campbell, B.K.; Mann, G.E.; McNeilly, A.S. et al. Pulsatile secretion of inhibin, oestradiol and androstenedione by the ovary of the sheep during the oestrus cycle. Journal of Endocrinology, v.126, p.385-393, 1990b.
Currie, W.D.; Medhamurthy, R.J.; Cook, S.J. et al. Seasonal fluctuation in diurnal rhythms of luteinizing hormone secretion in ewes during the mid-luteal phase of the oestrus cycle. Journal of Reproduction and Fertility, v.97, p.71-74, 1993.
Custer, E.E.; Beal, W.E.; Wilson, S.J. et al. Effect of melengestrol acetate (MGA) or progesteronereleasing intravaginal device (PRID) on follicular development, concentrations of estradiol-17β and progesterone, and luteinizing hormone release during an artificially lengthened bovine estrous cycle. Journal of Animal Science, v.72, p.1282-1289, 1994.
Downing, J.A.; Joss, J.; Scaramuzzi, R.J. Ovulation rate and the concentrations of LH, FSH, GH, prolactin and insulin in ewes infused with tryptophan, tyrosine or tyrosine plus phenyalanine during the luteal phase of the oestrus cycle. Animal Reproduction Science, v.45, p.283-297, 1997.
Fernández-Moro, D.; Veiga-López, A.; Ariznavarreta, C. et al. Preovulatory follicle development in goats following oestrous synchronization with progestagens or prostaglandins. Reproduction in Domestic Animals, v.43, p.9-14, 2008.
Forsberg, M.; Tagle, R.; Madej, A. et al. Radioimmunoassay of bovine, ovine and porcine luteinizing hormone with a monoclonal antibody and a human tracer. Acta Veterinaria Scandinavica, v.34, p.255-262, 1993.
González-Bulnes, A.; Veiga-López, A.; García, P. et al. Effects of progestagens and prostaglandin analogues on ovarian function and embryo viability in sheep. Theriogenology, v.63, p.2523-2534, 2005.
González-Reyna, A.; Valencia, M.J.; Foote, W.C. et al. Hair sheep in México: reproduction in the Pelibuey sheep. Animal Breeding Abstracts, v.59, p.509-524, 1991.
Goodman, R.L.; Bittman, E.L.; Foster, D.L. et al. The endocrine basis of the synergistic suppression of luteinizing hormone by estradiol and progesterone. Endocrinology, v.109, p.1414- 1417, 1981.
Goodman, R.L.; Bittman, E.L.; Foster, D.L. et al. Alterations in the control of luteinizing hormone pulse frequency underline the seasonal variation in estradiol negative feedback in the ewe. Biology of Reproduction, v.27, p.580-589, 1982.
Goodman, R.L.; Karsch, F.J. Pulsatile secretion of luteinizing hormone: Differential suppression by ovarian steroids. Endocrinology, v.107, p.1286-1290, 1980.
Hamra, A.H.; Massri, Y.G.; Marcek, J.M. et al. Plasma progesterone levels in ewes treated with progesterone-controlled drug-release dispenser, implants and sponges. Animal Reproduction Science, v.11, p.187-194, 1986.
Haresign, W.; Cooper, A.C.; Khalid, M. et al. Patterns of gonadotropin secretion in cyclic Finn ewes selected for low and again high ovulation rate. Animal Science, v.61, p.251-257, 1995.
Johnson, S.K.; Dailey, R.A.; Inskeep, E.K. et al. Effect of peripheral concentrations of progesterone on follicular growth and fertility in ewes. Domestic Animal Endocrinology, v.13, p.69- 79, 1996.
Joseph, I.B.J.K.; Rawlings, N.C. Infusion of estradiol during the luteal phase of the estrous cycle in the ewe completely eliminates LH pulses. Canadian Journal of Animal Science, v.70, p.1147-1150, 1990.
Kaneko, H.; Terada, T.; Taya, T. et al. Ovarian follicular dynamics and concentrations of oestradiol-17β, progesterone, luteinizing hormone and follicle stimulating hormone during the periovulatory phase of the oestrus cycle in the cow. Reproduction, Fertility and Development, v.3, p.529-535, 1991.
Kim, S.; Tanaka, T.; Kamomae, H. Different Effects of Subnormal Levels of Progesterone on the Pulsatile and Surge Mode Secretion of Luteinizing Hormone in variectomized Goats. Biology of Reproduction, v.69, p.141- 145, 2003.
Kinder, J.E.; García-Winder, M.; Imakawa, K. et al.Circulating concentrations of 17beta-estradiol influence pattern of LH in circulation of cows. Domestic Animal Endocrinology, v.8, p.463- 470, 1991.
Kinder, J.E.; Kojima, F.N.; Bergfeld, E.G.M. et al. Progestin and estrogen regulation of pulsatile LH release and development of persistent ovarian follicles in cattle. Journal of Animal Science, v.74, p.1424-1440, 1996.
Kojima, F.N.; Bergfeld, E.G.M.; Wehrman, M.E. et al. Frequency of luteinizing hormone pulses in cattle influences duration of persistence of dominant ovarian follicles, follicular fluid concentrations of steroids, and activity of insulin-like growth factor binding proteins. Animal Reproduction Science, v.77, p.187- 211, 2003.
Latour, D.; Littell, R. Advanced general linear models with an emphasis on mixed models. Version 6.12. Cary: SAS Institute, 1996. 268p. Leyva, V.; Buckrell, B.C.; Walton, J.S. Regulation of follicular and ovulation in ewes by exogenous progestagen. Theriogenology, v.50, p.395- 416, 1998.
Martin, G.B. Factors affecting the secretion of luteinizing hormone in the ewe. Biological Reviews, v.59, p.1-87, 1984.
Menchaca, A.; Miller, V.; Salveraglio, V. et al. Endocrine, luteal and follicular responses after the use of the Short-Term Protocol to synchronize ovulation in goats. Animal Reproduction Science, v.102, p.76-87, 2007.
Menchaca, A.; Rubianes, E. Relation between progesterone concentrations during the early luteal phase and follicular dynamics in goats. Theriogenology, v.57, p.1411-1419, 2002.
Mihm, M.; Diskin, M.G.; Roche, J.F. Regulation of follicle wave growth in cattle. Reproduction in Domestic Animals, v.31, p.531-538, 1996.
Montgomery, G.W.; Martin, G.B.; Pelletier, J. Changes in pulsatile LH secretion after ovariectomy in Ile-de-France in two seasons. Journal of Reproduction and Fertility, v.73, p.173-183, 1993.
Nett, T.M.; Turzillo, A.M.; Baratta, M. et al. Pituitary effects of steroid hormones on secretion of follicle-stimulating hormone and luteinizing hormone. Domestic Animal Endocrinology, v.23, p.33-42, 2002.
Norris, T.A.; Weesner, G.D.; Shelton, J.M. Biological activity of LH during the peripartum period and the estrous cycle of the ewe. Domestic Animal Endocrinology, v.61, p.25-33, 1989.
Oyedipe, E.O.; Pathiraja, N.; Gyang, E.O. et al. Effect of dose of pregnant mare serum gonadotrophin on estrus parameters, ovulation rate and peripheral progesterone concentrations in Yankasa ewes. Animal Reproduction Science, v.20, p. 255-264, 1989.
Price, C.A. Secreção pulsátil de LH alterada durante a superovulação em bovinos. Arquivos da Faculdade de Veterinária, v.27, p.35-53, 1999.
Ravindra, J.P.; Rawlings, N.C.; Evans, A.C.O. et al. Ultrasonographic study of ovarian follicular dynamics in ewes during the estrous cycle. Journal of Reproduction and Fertility, v.101, p.501-509, 1994.
Rhodes, F.M.; Chagas, L.M.; Clark, B.A. et al. Effect of dietary intake on steroid feedback on release of luteinizing hormone in ovariectomized cows. Reproduction, Fertility and Development, v.15, p.11-17, 2003.
Richter, T.A.; Robinson, J.E.; Evans, N.P. Progesterone blocks the estradiol-stimulated luteinizing hormone surge by disrupting activation in response to a stimulatory estradiol signal in the ewe. Biology of Reproduction, v.67, p.119- 125, 2002.
Rubianes, E.; Castro, T.; Carbajal, B. Effect of high progesterone levels during the growing phase of the dominant follicle of wave 1 in ultrasonically monitored ewes. Canadian Journal of Animal Science, v.76, p.1-3, 1996.
Sánchez, T.; Wehrman, M.E.; Kojima, F.N. et al. Dosage of the synthetic progestin, norgestomet, influences luteinizing hormone pulse frequency and endogenous secretion of 17-β-estradiol in heifers. Biology of Reproduction, v.52, p.464- 469, 1995.
Scaramuzzi, R.J.; Adams, N.R.; Baird, D.T. et al. A model for follicle selection and the determination of ovulation rate in the ewe. Reproduction, Fertility and Development, v.5, p.459-478, 1993.
Schrick, F.N.; Surface, R.A.; Pritchard, J.Y. et al. Ovarian structures during the estrous cycle and early pregnancy in ewes. Biology of Reproduction, v.49, p.1133-1140, 1993.
Seekallu, S.V.; Toosi, B.M.; Rawlings, N.C. LH pulse frequency and the emergence and growth of ovarian antral follicular waves in the ewe during the luteal phase of the estrous cycle. Reproductive Biology and Endocrinology, v.7, p.78-93, 2009.
Skinner, D.C.; Harris, T.G.; Evans, N.P. Duration and amplitude of the luteal phase progesterone increment times the estradiol-induced luteinizing hormone surge in ewes. Biology of Reproduction, v.63, p.1135-1142, 2000.
Smith, J.F.; Briggs, R.M.; Parr, J. et al. Seasonal changes in LH profiles of ewes selected for and against an early lambing date. In: Conference of New Zealand Society of Animal Production, 55, 1995, Otago. Proceedings... Otago: New Zealand Society of Animal Production, 1995. p.224-227.
Souza, C.J.H.; Campbell, B.K.; Baird, D.T. Follicular dynamics and ovarian steroid in sheep during anoestrus. Journal of Reproduction and Fertility, v.108, p.101-106, 1996.
Thomas, G.B.; Martin, G.B.; Ford, J.R. et al. Secretion of LH, FSH and oestradiol-17β during the follicular phase of the oestrus cycle in the ewe. Australian Journal of Biological Sciences, v.41, p.303-308, 1988.
Tsonis, C.G.; Carson, R.S.; Findlay, J.K. Relationships between aromatase activity, follicular fluid oestradiol-17β and testosterone concentrations, and diameter and atresia of individual ovine follicles. Journal of Reproduction and Fertility, v.72, p.153-163, 1984.
Tsukamura, H. Neuroendocrine mechanism regulating luteinizing hormone secretion during periovulatory period: Negative and positive feedback actions of estrogen in the brain. Journal of Reproduction and Development, v.44, p.j81-j90, 1998.
Uribe-Velásquez, L.F.; Souza, M.I.L.; Loaiza, A.M. Efecto de la sincronización del estro con prostaglandina-F2α vs CIDR + 500 UI de eCG en ovejas Bergamacia durante el inicio de la fase luteal. Revista Científica, FCV-LUZ, v.18, n.4, p.368-373, 2008.
Wherman, M.E.; Roberson, M.S.; Cupp, A.S. et al. Increasing exogenous progesterone during synchronization of estrus decreases endogenous 17β-estradiol and increases conception in cows. Biology of Reproduction, v.49, p.214- 220, 1993.
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