Induced Termination of Pregnancy in Domestic Farm Animals

Document Type: Review Article

Authors

Department of Veterinary Gynecology and Obstetrics, College of Veterinary and Animal Science, Rajasthan University of Veterinary and Animal Science, Bikaner Rajasthan, 334001, India

Abstract

Induced abortion may be desired during a normal or abnormal pregnancy. The methods of induced abortion differ between species mainly because of different sources for progesterone production during pregnancy between species and within a species according to different stages of gestation. In cows and buffaloes, pregnancy can be effectively terminated from 5 to 150 days by administration of luteolytic doses of prostaglandin F2 alpha (PG). From 150 days onwards and till term bovine and bubaline pregnancies can be safely terminated by administration of a combination of PG and dexamethasone. During the last month of pregnancy in these two species, pregnancy can be successfully terminated by using either a PG or dexamethasone. In goats pregnancy can be terminated during the entire gestation by administration of luteolytic doses of prostaglandins. In sheep pregnancies up to 55 days can be terminated by administration of 100 µg cloprostenol or 10-12 mg of dinoprost. From day 55 onward the termination of sheep pregnancies requires the administration of single or multiple injections of dexamethasone. Early pregnancy (day 5-34) termination in the mare can be achieved by physical methods or administration of PG. The same treatment is effective in terminating pregnancies between day 35-120 but repeated injections are required and because the endometrial cups continue to exist for a couple of days after pregnancy termination, mares do not return to estrus for prolonged periods. The termination of equine pregnancy after 4 months is difficult till term. The results of administration of PG or corticosteroids is suboptimal and manual disruption of the fetus after dilation of the cervix with PGE2 creams is more reliable method of pregnancy termination.

Keywords


AdamsW.M. and Wagner W.C. (1970). The role of corticoids in parturition. Biol. Reprod. 3,223-228.
Al-Gubory K.H., Solari A. and Mirman B. (1999). Effects of luteectomy on the maintenance of pregnancy, circulating progesterone concentrations and lambing performance in sheep. Reprod. Fertil. Dev. 11,317-322.
Alm C.C., Sulliwan J.J. and First N.L. (1974). Induction of premature parturition by parentral administration of dexamethasone in the mare. J. Am. Vet. Med. Assoc. 165,721-722.
Alm C.C., Sulliwan J.J. and First N.L. (1975). The effect of corticosteroid (dexamethasone), progesterone, estrogen and prostaglandin F2 alpha on gestation length in normal and ovariectomized mares. J. Reprod. Fertil. 23,637-640.
Amin S.O. and El-Sheikh A.S. (1973). Progesterone in placenta, uterine tissue and residual ovarian tissue of the Egyptian buffalo. Indian J. Anim. Sci. 43,457-461.
AndersonA.B.M., Flint A.P.F. and Turnbull A.C. (1975). Mechanism of action of glucocorticoids in induction of ovine parturition: effect of placental steroid metabolism. J. Endocrinol. 66,61-70.
Arora R.C. and Pandey R.S. (1982). Changes in peripheral plasma concentrations of progesterone, estradiol-17β, and luteinizing hormone during pregnancy and around parturition in the buffalo (Bubalus bubalis). Gen. Comp. Endocrinol. 48,403-410.
Audicana L. and Harvey M.J. (1993). Termination of early pregnancy in sheep with dinoprost or cloprostenol:comparison of two commercial preparations. Vet. Rec. 133,574-576.
Barth A.D. (1986). Induced abortion in cattle P 205. In: Current Therapy in Theriogenology. Morrow D.A. Ed. W.B. Saunders, Philadelphia.
Barth A.D., Adams W.M., Manns J.C. and RawlingsN.C.(1978). Induction of parturition in beef cattle using estrogens in conjunction with dexamethasone. Can.Vet. J. 19,175-180.
Barth A.D., AdamsW.M., Manns J.G., Kennedy K.D., Syndenham R.G. and Mapletoft R.J. (1981). Induction of abortion in feedlot heifers with a combination of cloprostenol and dexamethasone. Can.Vet. J.22, 62-64.
Batista M., Reyes R., Santana M., Alamo D., Vilar J., Gonzalez F., Cabrera F. and Gracia A. (2011). Induction of parturition with Aglepristone in the Majorera goat. Reprod. Dom. Anim. doi:10:1111/j.1439-0531.2011.01759.x.
Bennett D.G. (1988). Artificially controlled versus spontaneous parturition in the mare. Comp. Contin. Edu. Pract. Vet. 10, 506-516.
Binns W., James L.F., Shupe J.L., Thacker E.J. (1962). Cyclopian type malformation in lambs. Arch. Environ. Health., Chicago. 5,106.
Bosc M.J., De Louis C. and Terqui M. (1977). Control of the time of parturition in sheep and goat. P 89. Proc. Manag. Reprod. Sheep Goat Symp. Madison, WI.
Bosu W.T.K. and Mc Kinnon A.O. (1982). Induction of abortion during midgestation in mares. Can.Vet. J.23,358-360.
Bosu W.T.K., Geribary S.J.A. and Barker C.A.V. (1979). Peripheral plasma levels of progesterone in pregnant goats treated with prostaglandin F. Theriogenol. 11,131-148.
Braun W.B. (1997). Induced abortion. Pp. 576-579. In: Current Therapy in Large Animal Theriogenology. Youngquist R.S Ed. Philadelphia.
Braun W.B. (2007). Induced abortion. In: Current Therapy in Large Animal Theriogenology. Youngquist R.S. and Threlfall W.R. Eds. 2nd Ed. W.B. Saunders, Philadelphia.
Bretzlaff K.N. and Ott R.S. (1983). Doses of prostaglandin F2 alpha effective for induction of parturition in goats. Theriogenol. 19,849-853.
Brozos C., Mavrogianni V.S. and Fthenakis G.C. (2011). Treatment and control of periparturient metabolic diseases: pregnancy toxemia, hypocalcaemia, hypomagnesemia. Vet. Clin. North. Am. Food Anim. Pract. 27,105-113.
Buttle H.L. (1978). Maintenance of pregnancy in hypophysectomized goats. J. Reprod. Fertil. 52,255-260.
Camillo F., Marmorini P., Romagnoli S., Cela M., Duchamp G. and Palmer E. (2000). Clinical studies on daily low dose oxytocin in mares at term. Equine Vet. J. 32,307-310.
Carbalum T.C., Oakes G.K., Jansen C.A., Yu H.K., Buster J.E. and Nathaneilsz P.W. (1982). Induction of parturition in sheep by low dose intrafetal infusion of synthetic adrenocorticotropin at 120-130 days of gestation. Endocrinol. 110,408-415.
Card C. (2010). Induction of abortion and parturition. Pp. 15-19. in: Proc. Annu. Meet. Italian. Assoc. Equine. Vets.Carrara., Italy.
Carvalho A.F. (2007). Immunolocalization of progesterone receptors in binucleate trophoblastic cells of buffalo (Bubalus bubalis) placenta. Biotemas. 20,99-106.
ComptonC.W. and Mc Dougall S. (2010). A longitudinal study of reproductive performance and management of 82 dairy herds in the Waikato region with differing policies on the routine use of induction of parturition. New ZealandVet. J. 58,175-183.
Copeland D.D., Schultz R.H. and Kemtrup M.E. (1978). Induction of abortion in feedlot heifers with cloprostenol: A dose response study. Can.Vet. J. 19,29-32.
Currie W.B. and Thorburn G.D. (1977). Parturition in goats: studies on the interactions between the fetus, placenta, prostaglandin F and progesterone before parturition, at term or at parturition induced prematurely by corticotrophin infusion of the fetus. J. Endocrinol. 73,263-278.
Currie W.B., CoxR.I.and Thorburn G.D. (1976). Release of prostaglandin F regression of corpora lutea and induction of premature parturition in goats treated with estradiol 17β. Prostaglandins. 12,1093-1102.
Daels P.F., Mohammed H., Montavon S.M.E., Stabenfeldt G.H., Hughes J.P., Odensvik K. and Kindahl H. (1995). Endogenous prostaglandin secretion during cloprostenol-induced abortion in mares. Anim. Reprod. Sci.40,305-321.
Day A.M. (1977). Doprostenol for termination of pregnancy in cattle. B The induction of abortion. New ZealandVet. J.25,139-144.
Day A.M. and Southwell S.R.G. (1979). Termination of pregnancy in goats using cloprostenol. New ZealandVet. J.27,207-208.
Denamur R. and Martinet J. (1955). Effects del ovariectomie chez la Brebis pendant la gestation. Cr. Senac. Soc. Biol. 149,2105.
Derks J.B., Giussani D.A., Van Dam L.M., Jenkins S.L., Winter J.A., Zhao X.F., Hammond G.L. and Nathaneilsz P.W. (1996). Differential effects of betamethasone and dexamethasone fetal administration on parturition in sheep. J. Soc. Gynecol. Invest. 3, 336-341.
Dobson H. and Kamonpatana M. (1986). A review of female cattle reproduction with special reference to a comparison between buffaloes, cows and zebu. J. Reprod. Fertil. 77,1-36.
Douglas R.H., Squires E.L. and Ginther O.J. (1974). Induction of abortion in mares with prostaglandin F2 alpha. J. Anim. Sci. 39,404-407.
Drost M. (2007). Complications during gestation in the cow. Theriogenol. 68,487-491.
Duggan V.E., Holyoak G.R., Mac Allister C.G. and Confer A.W. (2007). Influence of induction of parturition on the neonatal acute phase response in foals. Theriogenol. 67,372-381.
Echternkamp S.E., Hays W.G. and Kwasnicka W.G. (1987). Synchronization of parturition in beef cattle with prostaglandin and dexamethasone. Theriogenol. 28,337-347.
Edey T.N., Alston B.T. and Taylor P. (1982). Early induction of parturition and initiation of lactation in sheep. Theriogenol. 18,255-260.
El-Belely M.S., Zaki K. and Grunert E. (1988). Plasma profiles of progesterone and total estrogens in buffaloes (Bubalus bubali-s)around parturition. J. Agric. Sci. 111,519-524.
First N.L. and Alm C.C. (1977). Dexamethasone-induced parturition in pony mares. J. Anim. Sci. 44,1072-1074.
Fylling P. (1971). Premature parturition following dexamethasone administration to pregnant ewes. Acta. Endocrin. Copenh. 66,289-295.
Fylling P., Sjaastad O.V. and Velle W. (1973).Mid term abortion induced in sheep by synthetic corticoids. J. Reprod. Fertil. 32, 305-306.
Garcia T.S., Barth A.D. and Mapletoft R.J. (1992). The effects of treatment with cloprostenol or dinoprost within one hour of induced parturition on the incidence of retained placenta in cattle. Can.Vet. J.33,175-183.
Ginther O.J. (1992). Reproductive Biology of the Mare.: Basic and Applied Aspects. 2nd Ed., Cross Plains Equiservices. P 450.
Gross T.S. and Williams W.F. (1988). In vitro steroid synthesis by the placenta of cows in late gestation and at parturition. J. Reprod. Fertil. 83,565-573.
Haluska G.J., Lowe J.E. and Currie W.B. (1987). Electromyographic properties of the myometrium correlated with the endocrinology of the prepartum and post partum periods and parturition in pony mares. J. Reprod. Fertil. Suppl. 35,553-564.
Hamon M., Clarke S.W. and Houghton El. (1991). Production of 5 alpha-dihydroprogesterone during late pregnancy in the mare. J. Reprod. Fertil. Suppl. 44,529-535.
Han X., Rossdale P.D. and Ousey J.L. (1995). Localisation of 15-hydroxy prostaglandin dehydrogenase (PGDH) and steroidogenic enzymes in the equine placenta. Equine. Vet. J. 27,334-339.
Harman E.L. and Slyter A.L. (1980). Induction of parturition in the ewe. J. Anim. Sci. 50,391-393.
HarrisonF.A. (1982). Dexamethasone induced parturition in sheep. Br. Vet. J. 138,402-408.
Henricks D.M., Rawlings N.C., Ellicott A.R., Dickey J.F. and Hill J.R. (1977). Use of prostaglandin F2 alpha to induce parturition in beef heifers. J. Anim. Sci. 44,438-441.
Hillman R.B. and Ganjam V.K. (1979). Hormonal changes in the mare and foal associated with oxytocin induction of parturition. J. Reprod. Fertil. 27,541-546.
Hillman R.D. and Lesser M.S. (1980). Induction of parturition. Vet. Clin. North. Am. Large. Anim. Pract.2,333-344.
Hilman R.B. (1975). Induction of parturition in mares. J. Reprod. Fertil. 23,641-644.
Holm L.W. (1966). The gestation period of mammals. In: Comparitive Biology of Reproduction in Mammals. Rowlands I.W. Ed. Academic Press London.
Honnas C.M. (1988). Hydroamnios causing uterine rupture in a mare. J. Am. Vet. Med. Assoc. 193,334-336.
Hunter D.L., Erb R.E., Randel R.D., Garverick H.A., Callahan C.J. and Harrington R.B. (1970). Reproductive steroids during late gestation. J. Anim. Sci. 30,47-59.
Ingoldby L. and Jackson P. (2001). Induction of parturition in she- ep. In. Practice. 23,228-231.
Irving G., Jones D.E. and Knifton A. (1972). Progesterone concentrations in the peripheral plasma of pregnant goats after ovariectomy and replacement therapy. Res. Vet. Sci. 13,301.
Jainudeen M.R. and Hafez E.S.E. (2000). Gestation, prenatal physiology and parturition. Pp. 140-155. In: Reproduction in Farm Animals. Hafez B. and Hafez E.S.E. 7th Ed. Lippincott Williams and Wilkins.
Jeffcott L.B. and Rossdalee P.D. (1977). A critical review of current methods of induction of parturition in the mare. Equine Vet. J. 9,208-215.
Jones S.L. and Fecteau G. (1995). Hydrops uteri in a caprine doe pregnant with goat-sheep hybrid fetuses. J. Am Vet. Med. Assoc.206,1920-1922.
Kask K., Konigsson K., Kindahl H. and Gustafsson H. (2001). Clinical and endocrine investigations after dexamethasone and prostaglandin induced premature parturition-A case report. Acta. Vet. Scand. 42,307-310.
Kassam A., Bon Durant R.H., Basu S., Kindahl H. and Stabenfeldt G.H. (1987). Clinical and endocrine responses to embryonic and fetal death induced by manual rupture of the amniotic vesicle during early pregnancy in cows. J. Am. Vet. Med. Assoc. 191,417-420.
Kastelic J.P., Cook R.B., Mc Mohan L.R., Mc Allister T.A., Mc Clelland L.A. and Cheng K.J. (1996). Induction of parturition in ewes with dexamethasone and cloprostenol. Can.Vet. J. 37,101-102.
Klem M.E., Kreider J.L., Harms P.G., Potter G.D., Kraemmer D.C. and Godke R.A. (1982). Induction of parturition in the mare with prostaglandin F2 alpha. Prostaglandins. 24,89-96.
Koenig M.V. and Contreras P.A. (1984). Alteraciones del metabolism energetic en ruminates y sus principales manifestaciones clinicas. Arch. Med. Vet. 16,7-13.
Kordts E. and Jochle W. (1975). Induced parturition in dairy cattle: A comparison of a corticoid (flumethasone) and a prostaglandin (PGF2α) in different age groups. Theriogenol. 3,171-178.
Kornmatitsuk B., Konigsson K., Kindahl H., Gustafsson H., Forsberg M. and Madej A. (2000). Clinical signs and hormonal changes in dairy heifers after induction of parturition with prostaglandin F2 alpha. J. Vet. Med. A. Physiol. Pathol. Clin. Med. 47,395-409.
Lange W. (1989). Use of prostaglandin analogs to induce abortion in PMSG donor mares. Monatshefte Fur Veterinarmedizin. 44,605-608.
LeVoie V.A. and Moody E.L. (1973). Estrogen pretreatment of corticoid induced parturition in cattle. J. Anim. Sci. 37,770-775.
Leadon D.P., Rossdale P.D., Jeffcott L.B. and Allen W.R. (1982). A comparison of agents for inducing parturition in mares in the previable and premature periods of gestation. J. Reprod. Fertil. Suppl. 32,597-602.
Lewing F.J., Proulx J. and Mapletoft R.J. (1985). Induction of parturition in the cow using cloprostenol and dexamethasone in combination. Can.Vet. J.26,317-322.
Ley W.B., Hoffmann J.L. and Crisman M.V. (1989). Daytime foaling management of the mare. 2: induction of parturition. Equine Vet. J. 9,95-99.
Ley W.B., Parker N.A., Bowen J.M., Di Grassie W.A. and Jack N.E. (1998). How do we induce the normal mare to foal. Proc. Annu. Conv. Am. Assoc. Equine Pract.44,194-197.
Liggins G.C. (1973). Hormonal interactions in the mechanism of parturition. Mem Soc. Endocrinol. 20,119-139.
Lofstedt R.M. (1986). Termination of unwanted pregnancy in the mare. P 715. In: Current Therapy in Theriogenology. Morrow D.A. Ed. 2nd Ed. W.B. Saunders , Philadelphia.
Macpherson M.L., Homco L., Varner D., Blanchard T., Harms P., Flanagan M. and Forrest D. (1995). Transvaginal ultrasound guided allantocentesis for pregnancy elimination in the mare. Biol. Reprod. Nono.1,215-223.
Macpherson M.L., Chaffin M.K., Carroll G.L., Jorgensen J., Arrott C., Varner D.D. and Blanchard T.L. (1997). Three methods of oxytocin-induced parturition and their effects on foals. J.Am. Vet. Med. Assoc. 210,799-803.
Macpherson M.L. (2000). Induction of parturition. In: Recent advances in equine theriogenology. Ball B.A., Ed., www.ivis.org. documentNo.A0211.0900.
Macpherson M.L. and Reimer J.M. (2000). Twin reduction in the mare: current options. Anim. Reprod. Sci. 60-61,233-244.
Macpherson M.L. (2007). Identification and management of the high risk pregnant mare. Proc. Annu. Conv. Am. Assoc. Equine. Pract. 53,293-304.
Macpherson M.L. (2010). Management of the high risk pregnant mare. Pp. 118-124 in: Proc. Annu. Meet. Italian. Assoc. Equine. Vet . Carrata.
Madej A., Kindahl H., Nydahl C., Edquist L.E. and Stewart D.R. (1987). Hormonal changes associated with induced late abortions in the mare. J. Reprod. Fertil. Suppl. 35,479-84.
Mansell P.D., Cameron A.R., Taylor D.P. and MalmoJ. (2006). Induction of parturition in dairy cattle and its effects on health and subsequent lactation and reproductive performance. Aust. Vet. J. 84,312-316.
Maule-Walker F.M. (1983). Lactation and fertility in goats after the induction of parturition with an analogue of prostaglandin F2 alpha, cloprostenol. Res. Vet. Sci.34,280-286.
Memon M.A., Lock T.F. and Nelson D.R. (1981). Induction of parturition with prostaglandin F2 alpha in cows with hydroallantois: a case report. Theriogenol. 16,681-683.
Milton A., Welker B. and Modransky P. (1989). Hydroallantois in a ewe. J. Am. Vet. Med. Assoc. 195,1385-1390.
Mobini S., Heath A.M. and Pugh D.M. (2002). Theriogenology in sheep. Pp. 129-186. In: Pugh DM Ed., Sheep and Goat Medicine. W.B.Saunders Co., Philadelphia.
Momont H. (2005). Bovine reproductive emergencies. Vet. Clin. North. Am. Food. Anim. Pract. 21,711-727.
Morin D.E., Hornbuckle T., Rowan L.L. and Whitley H.E. (1994). Hydroallantois in a caprine doe. J. Am. Vet. Med. Assoc. 204,108-111.
Morton J.M. and Butler K.L. (1995). Reductions in milk production after induced parturition in dairy cows from commercial herds in south-western Victoria. Aust. Vet. J. 72,241-245.
Nancarrow C.D., Evison B.M. and Connell P.J. (1982). Effect of embryos on luteolysis and termination of early pregnancy in s-heep with cloprostenol. Biol. Reprod. 26,2263-2269.
NasserL.F., Bo G.A., Barth A.D. and Mapletoft R.J. (1994). Induction of parturition in cattle: effect of traimcinolone pretreatment on the incidence of retained placenta. Can Vet. J. 35,491-496.
NasserL.F., Rezende L.F., Bo G.A. and Barth A. (2008). Induction of parturition in Zebu-cross recepients carrying in vitro produced Bos indicus embryos. Theriogenol. 69,116-123.
Ott R.S., Nelson D.R. and Memon M.A. (1980). Dexamethasone and prostaglandin F for induction of parturition in goats.  Vol III P 492. In: Proc. 9th Int. Cong. Anim. Reprod, Madrid Spain.
Ousey J.C., Dudan F. and Rossdale P.D. (1984). Preliminary studies of mammary secretions in the mare to assess fetal readiness for birth. Equine Vet. J. 16,259-263.
Ousey J.C., Rossdale P.D. and Cash R.S.G. (1987). Plasma concentrations of progestagens, estrone sulfate and prolactin in pregnant mares subjected to natural challenge with equid herpes virus-1. J. Reprod. Fertil. Suppl. 35,519-528.
Ousey J.C., Freestone N. and Fowler A.L. (1998). The effects of oxytocin and progesterone on myometrial contractility in vitro during equine pregnancy. Pp. 179-180 in: Proc. 7th Int. Symp. Equine Reprod.
Ousey J.C. (2006). Hormone profiles and treatments in the late pregnant mare. Vet. Clin. North. Am. Equine Pract. 22,727-747.
Owens J.L., Bindon B.M., Edey T.N. and Piper L.R. (1985). A note on the effects of dexamethasone induced parturition on ewe behavior and lamb survival in prolific Booroola Merino ewes. Anim. Prod. 41,417-420.
Paccamonti D.L. (1991). Elective termination of pregnancy in mares. J. Am. Vet. Med. Assoc. 198,683-689.
Parmigiani E., Ball L., Lefever D., Rupp G. and Seidel Jr. G. (1978). Elective termination of pregnancy in cattle by manual abortion. Theriogenol. 10,283-290.
Pashen R.L. (1980). Low doses of oxytocin can induce foaling at term. Equine. Vet. J. 12,85-87.
Pashen R.L. (1982). Oxytocin-the induction agent of choice in the mare. J. Reprod. Fertil. 32,645.
Pashen R.L. (1984). Maternal and fetal endocrinology during late pregnancy and parturition in the mare. Equine. Vet. J. 16,233 -238.
Pastor J., Loste A. and Saez T. (2001). Gestational toxemia in sheep. Pequenos Rumiantes. 2,18-24.
Peters A.R. and PooleD.A. (1992). Induction of parturition in dairy cows with dexamethasone. Vet. Rec. 131,576-578.
Phogat J.B., Bugalia N.S. and Gupta S.L. (1994). Clinical efficacy of dexamethasone in prolonged gestation and valethamate bromide in dystocia due to insufficient dilation of cervix in buffaloes (Bubalus bubalis). Indian. Vet. J. 71,1085-1087.
Prakash B.S. and Madan M.L. (1985). Induction of parturition in water buffaloes. Theriogenol. 23,325-331.
Purohit G.N. (2006). Parturition related disorders in sheep and goats. Pp. 227-231. In: National Seminar on Innovations and Recent Advances in Reproduction for Augmenting Small Ruminant Production. CSWRI, Jaipur, Rajasthan, IndiaCompendium.
Purohit G.N., Gupta A.K., Gaur M., Sharma A. and Bihani D. (2006). Periparturient disorders in goats. A retrospective analysis of 324 cases. Dairy Goat. J. 84,24-33.
Purohit G.N. (2010). Parturition in domestic animals: A review. Webmed Central REPRODUCTION. 1(10):WMC00748. Pp. 1-18. http://www.webmedcentral.com//article_view/748.
Purvis A.D. (1977). The induction of labor in mares as a routine breeding farm procedure. Pp. 145-160 in: Proc. 23rd Annu. Conv. Am. Assoc. Equine. Pract.
Pycock J. (2008). Problems in late pregnancy. Pp. 241-243. 10th International Congr World Equine. Vet. Assoc. Moscow.
Ragon A.C. (1997). Induced abortion. Pp. 177-178. In: Current Therapy in Large Animal Theriogenology. Youngquist R.S. Ed., W.B. Saunders Philadelphia.
Ragon A.C. (2007). Induced abortion. In: Current Therapy in Large Animal Theriogenology. Youngquist R.S. and Threlfall W.R. Ed., 2nd Ed. W.B. Saunders Philadelphia.
Randel R.D. and Erb R.E. (1971). Reproductive steroids in the bovine. VI Changes and interrelationships from 0 to 260 days of pregnancy. J. Anim. Sci. 33,115-123.
Rathwell A.C., Asbury A.C. and Hansen P.J. (1987). Reproductive function of mares given PGF2 daily from day 42 of pregnancy. J. Reprod. Fertil.Suppl. 35,507.
Roberts S.J. (1986). Veterinary Obstetrics and Genital Diseases. Indian edn., C.B.S. Publishers, New Delhi.
Ross J., Palmer J.E. and Wilkins P.A. (2008). Body wall tears during late pregnancy in mares. J. Am. Vet. Med. Assoc. 232,257-261.
Rossdale P.D., Pashen R.L. and Jeffcott L.B. (1979). The use of synthetic prostaglandin analogue (fluoprostenol) to induce foaling. J. Reprod. Fertil. 27,521-529.
Rubianes E., Rodas E., Benesch A., Carrau A. and Ferreira A. (1991). Lambing and placental expulsion time after dexamethasone induced parturition in Corriedale and Polwarth ewes. Theriogenol. 36,329-334.
Schuler G., Wirth C., Klisch K., Pfarrer C., Leiser R. and Hoffmann B. (1999). Immunolocalization of progesterone receptors in bovine placentomes. Biol. Reprod. 61,797-801.
Schuler G., Greven H., Kowalawski M.P., Doring B., Ozalp G.R. and Hoffmann B. (2008). Placental steroids in cattle: hormones, placental growth factors or by products of trophoblast giant cell differentiation. Exp. Clin. Endocrinol. Diabetes. 116,429-436.
Shenavai S., Hoffman B., Dilly M., Pfarrer C., Ozalp G.R., Caliskan C., Seyrek-Intas K. and Schuler G. (2010). Use of progesterone (P4) receptors antagonist aglepristone to charachterize the role of P4 withdrawal for parturition and placental release in cows. Reprod. 140,623-632.
Shevah Y. (1974). A note on the use of dexamethasone for inducement of parturition in Finn x Dorest ewes. Anim. Prod. 18,89-92.
Shukla S.P., Pandey A. and Nema S.P. (2008). Emergency induction of parturition in buffaloes. BuffaloBull. 27, 148-149.
Sioan C.A.(1977). Induced abortion in cattle. Theriogenol. 7,43-51.
Silver M. and Fowden A.L. (1991). Response of the fetal adrenal to ACTH in the foal near term. J Endocrin. 131,69.
Skinner J.D., van Bloom A., Gouws D.J. and Jochle W. (1970). The effect of shortening gestation length with flumethasone on pelt quality of Karakul lambs. Proc. South. Afr. Soc. Anim. Prod. 9,193.
Squires E. and Tarr S. (1994). Use of transvaginal ultrasound-guided puncture for elimination of equine pregnancies during days 50-65. J. Equine Vet. Sci. 14,203-206.
Squires E.L. and Bosu W.T.K. (1993). Induction of abortion during early to midgestation. P 563. In: Equine Reproduction. Mc Kinnon A.O. and Voss J.L. ed. Lea and Febriger, Philadelphia.
Squires E.L., Hillman R.B., Pickett P.W. and Nett T.M. (1980). Induction of abortion in mares with equimate: effect on secretions of progesterone, PMSG and reproductive performance. J. Anim. Sci. 50,490-495.
Stellflug J.N., Weems Y.S. and Weems C.W. (1997). Clinical reproductive physiology of ewes. Pp 594-598. In: Currebt Therapy in Large Animal Theriogenology. Youngquist R.S. ed. W.B. Saunders, Philadelphia.
Terblanche H.M. (1983). Clinical and endocrine studies during normal and induced parturition in mares. J. South. Afr. Vet. Assoc. 54,105-113.
Thorburn G.D., Nicol D.H. and Basett J.M. (1972). Parturition in the goat and sheep: changes in corticosteroids, progesterone, oestrogens and prostaglandin. J. Reprod. Fertil. Suppl. 16,61.
Tibary A., Fite C., Sghiri A. and Bakkoury M. (2006). Pregnancy complications and evaluation for fetal well being. Pp. 196-206 inProc. 9th International Congr. World. Equine. Vet. Assoc. Marrakech, Morrocco.
Thomas P.G.A. (1997). Induced Abortion. Pp. 303-306. In: Current Therapy in Large Animal Theriogenology.Youngquist RS Ed. W.B Saunders Philadelphia.
Thomas P.G.A. (2007). Induced Abortion. In: Current Therapy in Large Animal Theriogenology.Youngquist R.S. and Threlfall W.R. Ed. 2nd Ed. W.B Saunders Philadelphia.
Tontis A. and Zwahlen K. (1987). Pregnancy toxemia of small ruminants with special reference to pathomorphology. Tierarztl Prax. 15,25-29.
Tyrell R.N., Lane J.G., Nancarrow C.D. and Connell P.J. (1981). Termination of early pregnancy in ewes by use of a prostaglandin analogue and subsequent fertility. Aust. Vet. J. 57,76-78.
Ullmann M.B. and Reimers T.J. (1989). Progesterone production by binucleate trophoblastic cells of cows.J. Reprod. Fertil. Suppl. 37,173-179.
Van Leeuwen W., Noden P.A. and Dieleman S.J. (1983). Induced abortion with two prostaglandin F2 alpha analogues in mare: plasma progesterone changes. Vet. Q. 5,97-100.
Van Rensburg S.J. (1971). Reproductive physiology and endocrinology of normal and habitually aborting Angoradoes. Onderstepoort J. Vet. Res. 38,1-6.
Villani M. and Romano G. (2008). Induction of parturition with daily low dose oxytocin injections in pregnant mares at term: clinical applications and limitations. Reprod. Dom. Anim. 43,481-483.
Villaroel A. and Lane V.M. (2010). Effect of systematic parturition induction of long gestation Holsteincows on calf survival, cow health, production, and reproduction on a commercial farm. Can.J. Vet. Res. 74,136-144.
Webster G.M. and Haresign W. (1981). A note on the use of dexamethasone to induce parturition in the ewe. Anim Prod. 32,341-344.
Weems C.W., Vincent D.L. and Weems Y.S. (1992). Roles of prostaglandins (PG) F2α, E1, E2 adenosins, estradiol 17β, histone H2A, and progesterone of conceptus, uterine or ovarian origin during early and mid pregnancy in the ewe. Reprod. Fertil. Dev. 4,289-295.
Wichtel J.J., Evans L.E. and ClarkT.L. (1988). Termination of midterm pregnancy in mares using intra-allantoic dexa methasone. Theriogenol. 29,1261-1267.
Wimsatt J. and Nathaneilsz P.W. (1995). Prostaglandin H synthase activity in the sheep placenta during cortisol induced labor at 128-131 days of gestation and during spontaneous delivery at term. Prostaglandins Leukotrienes and Essential Fatty Acids. 53,53-58.
Wittek T., Friees J. and Elze K. (1998). Histology of the endometrium, clinical-chemical parameters of the uterine fluid and blood plasma concentrations of progesterone, estradiol 17β and prolactin during hydrometra in goats. Small Rumin. Res. 30,105-112.
Yotov S., Dimitrov D. and FasulkovI.(2009). Hydrometra in a sheep after oestrous synchronization and insemination in the anoestral season. Slovenian Vet. Res. 46,143-147.