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Seasonal Variation in Live Weight, Testes Size, Testosterone, LH Secretion, Melatonin and Thyroxine in Merino and Corriedale Rams in a Subtropical Climate
Säsongsmässig variation i levande vikt, testikelstorlek, testosteron, LH, melatonin och tyroxin hos Merino och Corriedalebaggar under subtropiska förhållanden
Acta Veterinaria Scandinavica volume 39, pages 35–47 (1998)
Abstract
In the present investigation we studied the seasonal changes in live weight and testes and pituitary activity in Merino and Corriedale rams in a subtropical climate. Testes activity was measured as scrotal circumference (SC), plasma concentration of testosterone (T) and release of testosterone after exogenous GnRH injection. LH pulsatility and pituitary LH responsiveness to exogenous GnRH was measured as an index of pituitary activity. In addition, we wanted to characterize the seasonal pattern of thyroxine (T4) secretion and the 24 h secretory pattern of melatonin (M) at the winter and summer solstices in the 2 breeds. Nine Corriedale and 7 Merino adult (4-6 years) rams were kept on native pasture and managed in one group. Twice a month live weight (LW) and scrotal circumference (SC) were measured. To monitor plasma concentration of testosterone (T), and thyroxine (T4), 5 animals of each breed were bled every month except during autumn (March-May), when blood samples were collected with 15 day intervals and in spring (October) with 10 day intervals. To monitor pulsatile LH secretion, 3 rams of each breed were bled at 15 min intervals for 6 h at the winter and summer solstices and spring and autumn equinoxes. Pituitary LH and testicular testosterone response to GnRH injection was performed bimonthly from 2 animals of each breed. No effect of breed was found on any of the variables investigated. An interaction between breed and sampling date was found in LW (p<0.001) and total T response after GnRH challenge (pO.001). Sampling date had a significant effect (p<0.001) on all the variables studied. In both breeds SC decreased during autumn and increased during spring with minimum T concentrations in late autumn and maximum in mid-summer/early autumn. The lowest (p<0.05) number of LH pulses were observed in winter (June) and the highest (p<0.05) in early autumn (March). The highest LH and testosterone response to GnRH challenge was observed in autumn (April) (p<0.05) in both breeds. Baseline concentrations of M were similar in both breeds at the winter and summer solstices and high concentrations were observed during the dark period on both occasions. In both breeds thyroxine was high at the end of winter/spring (February-April) and low from the end of summer to mid-autumn (August-November). The results show that Corriedale and Merino rams under subtropical conditions have annual reproductive cycles. There was an association (p<0.001) between changes in LW and SC in the 2 breeds and this relationship was stronger in Merino rams (R2 = 0.68) than in Corriedale (R2 = 0.33) which indicates that nutritional factors may have more influence on the reproductive cycle of Merino than Corriedale rams.
Sammanfattning
En undersökning genomfördes för att studera de säsongmässiga förändringarna i levande vikt och endokrin aktivitet i testiklar och hypofys hos Merino-(n = 7) och Corriedale- (n = 9) baggar under subtropiska förhållanden. Som ett mått på testikelaktiviteten studerades testikelomfång, plasma koncentrationen av testosteron och testosteronutsöndring efter injektion av GnRH. LH pulsatilitet och plasmakoncentration av LH efter injektion av GnRH användes som ett mått på hypofysaktiviteten. Dessutom mättes de säsongsmässiga förändringarna i tyroxin och dygnsförändringarna i plasmakoncentrationen av melatonin vid vinter- och sommarsolstånden. Den statistiska analysen visade inga rasskillnader mellan Merino och Corriedale vad avser de parametrar som studerades. Det fanns en interaktion mellan ras och provtagningstidpunkt i levande vikt (p<0.001) och testosteronsekretion efter GnRH injektion. Hos båda raserna minskade testikelomfånget under hösten och Ökade under våren (p<0.05). De lägsta testosteronnivåerna uppmättes under sen höst och de högsta under sommar/tidig höst (p<0.05). LH pusatiliteten var lägst under vintern och högst under tidig höst (p<0.05). Testosteron och LH sekretionen efter GnRH injektion var högst under hösten hos båda raserna (p<0.05). De högsta koncentrationerna av melatonin registrerades under den mörka delen av dygnet hos både Merino och Corriedale både vid vinteroch sommarsolståndet. Tyroxin var högst hos båda raserna vid slutet av vintern/början av våren och lågt under resten av året. Resultaten visat att såväl Merino- som Corriedalebaggar har en säsongsmässig fortplantningscykel under subtropiska förhållanden. Det fanns ett starkare samband mellan förändringarna i levande vikt och testikelomfang (p<0.001) hos Merino (R2 = 0.68) än hos Corriedale (R2 = 0.33), vilket kan tyda på att nutritionella faktorer kan ha ett större inflytande på fortplantningscykeln hos Merino än Corriedale.
References
Arendt J, Symons AM, English J, Poulton L, Tobler I: How does melatonin control seasonal reproductive cycles? Reprod. Nutr. Develop. 1988, 28 (2B), 387–397.
Bietti A, Pedrana G, Gastel MT, Morana JA, Castril-lejo A, Piaggio J, Forsberg M, Rodriguez-Martinez H: La suplementaciĂłn nutricional evita la caida invernal en la reproducciĂłn estacionai dei carnero Corriedale uruguayo? (Nutritional supplement can avoid the winter decreasing of the seasonal reproduction in Uruguyan Corriedale rams?) 2do Simp. Intern. Reprod. Anim., 31 de octubre - 2 de noviembre, Carlos Paz, CĂłrdoba, Argentina. 1996, p. 247.
Castrillejo A, Morana JA, Bietti A, Gastel T, Molina JR, Forsberg M, Rodriguez-Martinez H: Onset of spermatogenesis in Corriedale ram lambs under extensive rearing conditions in Uruguay. Acta vet. scand. 1995, 36, 161–173.
Chandrasekhar MJ, D'Occhio MJ, Setchell BP: Reproductive hormone secretion and spermatogenic function in thyroidectomized rams receiving graded doses of exogenous thyroxine. J. Endocr. 1986, 111, 245–253.
D'Occhio MJ, Brooks DE: Seasonal changes in plasma testosterone concentration and mating activity in Border Leicester, Poll Dorset, Romney and Suffolk rams. Aust. J. Exp. Agric. Anim. Husb. 1983,23, 248–253.
Forsberg M, Tagle R, Madej A, Molina JR, Carlsson M-A: Radioimmunoassay of bovine, ovine and porcine luteinizing hormone with a monoclonal antibody and a human tracer. Acta vet. scand. 1993, 34, 225–262.
Gastel T, Bielli A, PĂ©rez R, Lopez A, Castrillejo A, Tagle R, Franco J, Laborde D, Forsberg M, Rodrigues-MartĂnez H: Seasonal variations in testicular morphology in Uruguyan Corriedale rams. Anim. Reprod. Sci. 1995, 40, 59–75.
Gibbons A, Vinent JG, Willems P, González R: Variación estacionai de la actividad reproductiva del carnero Merino Australiano en la Patogonia. (Seasonal changes in reproductive activity of Australian Merino in Patagonia). Rev. Arg. Prod. Anim. 1991,11, 449–455.
Glover TD, D 'Occhio MJ, Millar RP: Male life cycle and seasonality. In: Lamming G.E. (Editor), “Marshall's Physiology of Reproduction”, Vol. II: Reproduction in the male. 4th Ed., Churchill-Livingstone, London, 1990 pp. 213–378.
Hötzel MJ, Martin GB, Walkden-Brown SW, Fisher JS: Nutritional effects on testicular growth and LH and FSH secretion in Suffolk and Merino rams during the breeding and the non-breeding seasons. Twentysixth Annual Conference of The Australian Society for Reproductive Biology Inc. September 26-28, Brisbane, Australia 1994.
Islam ABMM, Land RB: Seasonal variation in testis diameter and sperm output of rams of breeds of different prolificacy. Anim. Prod. 1977, 25, 311–317.
Lincoln G A: Changes in pituitary responsiveness to luteinizing hormone releasing in rams exposed to artificial photoperiods. J. of Endocrinology 1977, 73, 519–527.
Lincoln GA, Lincoln CE, McNeilly AS: Seasonal cycles in the blood plasma concentration of FSH, inhibin and testosterone size in rams of wild, feral and domesticated breeds of sheep. J. Reprod. Fert. 1990, 88, 623–633.
Lincoln GA, Short RV: Seasonal breeding: Nature's contraceptive. Recent. Prog. Horm. Res. 1980, 36, 1–52.
Martin GB, Ford JR, Purvis IW: Environmental and genetic factors affecting reproductive activity in the Merino ram. In: Reproductive Physiology of Merino Sheep-Concepts and Consequences. School of Agriculture (Animal Science). The University of Western Australia, Perth. 1990.
Martin GB, Sutherland SRD, Lindsay DR: Effects of nutritional supplements on testicular size and the secretion of LH and testosterone in Merino and Booroola rams. Anim. Reprod. Sci., 1987, 12, 267–281.
Martin GB, Tjondronegoro DW, Blackberry MA: Effects of nutrition on testicular size and the concentrations of gonadotrophins, testosterone and inhibin in plasma of mature sheep. J. Reprod. Fert. 1994a, 101, 121–128.
Martin GB, Walkden-Brown SW, Boukhliq R, Tjondronegoro S, Miller DW, Fisher JS, Hötzel MJ, Restall BJ, Adams NR: Non-photoperiodic inputs into seasonal breeding in male ruminants. In Perspective in Comparative Endocrinology, National Research Council of Canada, Ottawa, 1994b, pp. 574–585.
Masters G, Fels HE: Seasonal changes in the testicular size og grazing rams. Anim. Prod, in Aust. 1984,75,444–447.
Mickelsen WD, Paisley LG, Dahmen JJ: The effects of season on the scrotal circumference and sperm motility and morphology in rams. Theriogenol-ogy, 1981,16, 45–51.
Parkinson TJ, Douthwaite JA, Follet BK: Responses of prepubertal and mature rams to thyroidectomy. J. Reprod. Fert. 1995,104, 51–56.
Parkinson TJ, Follet BK: Effect of thyroidectomy upon seasonality in rams. J. Reprod. Fert. 1994, 101, 51–58.
Parkinson TJ, Follet BK: Thyriodectomy abolishes seasonal testicular cycles in Soay rams. Proc. R. Soc. Lond. B. Biol. Sci. 1995, Jan 23,259 (1354), 1–6.
Pelletier J, Almeida G: Short light cycles induce persistent reproductive activity in Ile-de-France rams. J. Reprod. Fert. Suppl. 1987, 34, 215–226.
Pelletier D, Gamier DH, de Riviers MM, Terqui M, Ortavant R: Seasonal variation in LH and testosterone release in rams of two breeds. J. Reprod. Fert. 1982, 64, 341–436.
Pérez Clariget R, López A, Castrillejo A, Bielli A, Laborde D, Gastel T, Tagle R, Queirolo D, Franco J, Forsberg M, Rodriguez-Martinez H: Reproductive seasonality of Corriedale rams under extensive rearing conditions. Acta vet. scand. 1997,38, 109–117
Pérez Clariget R, López A, Castrillejo A, Forsberg M: Effect of season and feeding level on live weight, testes size and testosterone concentration in Uruguyan Corriedale rams. Proc. 13th International Congress on Animal Reproduction, June 30-July 4, Sydney, Australia. 1996, P1–6.
Poulton AL, Robinson TJ: The response of rams and ewes of three breeds to artifical photoperiod. J. Reprod. Fert. 1987, 79, 609–626.
Ritar AJ, Adams NR, Sanders MR: Effect of lupin feeding on LH, testosterone and testes. In: Reproduction in Sheep. D.R. Lindsay and D.T. Pearce (eds.), Cambridge University Press. 1984, pp. 76–78.
Rodriguez A: Crecimiento estacionai de la en ovinos Merino e Ideal en pastoreo (Wool seasonal growth in Merino and Polwarth sheep under forage conditions). Prod. Ovina, SUL, Paysandú, Uruguay. 1989, 1, 45–50.
Sanford LM, Palmer WM, Howland BE: Influence of sexual activity on serum levels of LH and testosterone in the ram. Canadian J. Anim. Sci. 1974, 54, 579–585.
Xu ZZ, McDonald MF, McCutcheon SN, Blair HT: Seasonal variation in testis size, gonadotrophin secretion and pituitary responsiveness to GnRH in rams of two breeds differing in time of onset the breeding season. Anim. Reprod. Sci. 1991, 26, 281–292.
Zarco, L, Stabenfeldt GH, Kindahl H, Quirke JF, Granström E: Persistence of luteal activity in the non-pregnant ewe. Anim. Reprod. Sci. 1984, 7, 1-3, 245–267.
Acknowledgments
The authors wish to thank Ing. Agr Andrés Ganzábal, Ana Nicola, Carolina Chiesa, Dr. Alvaro López, Dr. Elize Van Lier and Dr. Mariel Regueiro for technical assistance during the experimental work, Mari-Anne Carlsson and Karin Burvall for the laboratory assistance and Ing. Juan Burgueño for his excellent help with the statistical analyses. We also thank Dr. Steven Walkden-Brown for scientific support. Financial support was recieved from the International Foundation for Science (IFS) (Grant B/1917-1). Dr. Raquel Pérez Clariget is holder of a scholarship from CONIC YT of the Uruguayan Government which supports her studies in Sweden.
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Pérez, R., Forsberg, M. & Rodriguez-Martinez, H. Seasonal Variation in Live Weight, Testes Size, Testosterone, LH Secretion, Melatonin and Thyroxine in Merino and Corriedale Rams in a Subtropical Climate. Acta Vet Scand 39, 35–47 (1998). https://doi.org/10.1186/BF03547805
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DOI: https://doi.org/10.1186/BF03547805