The Reproductive Characteristics of the Mare in Subtropical Taiwan

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1 9 The Reprodutive Chrteristis of the Mre in Subtropil Tiwn Jh-Cherng Ju, Huo-Cheng Peh, Jenn-Chung Hsu, Sn-Po Cheng, Shw-Ching Chiu nd Yng-Kwng Fn* Deprtment of Animl Siene, Ntionl Chung-Hsing Universit, Tihung, Tiwn, ROC ABSTRACT : The objetives of this stud were to doument the reprodutive trits of mres s influened b the month of the er in Tiwn. Reprodutive reords, lttion trits, fol birth weight (FBW) nd fol height (FBH) were olleted from Holi Equine Sttion of Tiwn. The effets of month on these prmeters were nlzed. The length of estrus (LE) ws shortest in Deember eh er. The inresing trend ws reorded from Jnur to September with signifintl (p<.5) longer period of.±. ds in September thn in Jnur nd Februr. A grdul shortening in LE ws observed from September to Deember (.±. ds, p<.5), when the shortest period of the er ws observed. Mres showed signs of estrus throughout the er, but more thn 8% were found in estrus during Mrh through Otober. The FBW ws signifintl (p<.5) ffeted b the breeding month of the er. The lowest fol weights were reorded in both September (3.7±.7 kg) nd Deember (3.8±.9 kg), whih were lso signifintl lower thn those in other months exept in Mrh, August, nd November. A trend of lower FBH from September to Deember ( m) thn those from Jnur to August ws observed. The gretest FBH ws in June (9. m). Breeding months nd onset of estrus of the mres exerted signifint effet on the inidene of glti during the lttion period. These nlses provide fundmentl informtion on dptive proesses in respet to reprodutive hrteristis of mres, whih indited n extent of limtion b these nimls in subtropil Tiwn. (Asin-Aust. J. Anim. Si.. Vol 5, No. : 9-99) Ke Words : Estrus, Gesttion Period, Birth Weight, Birth Height, Aglti, Mre INTRODUCTION Horses re sesonl breeders with extensive sexul tivit in spring, summer, nd utumn. The reprodutive le of the mre is subjeted to the gretest vriilit mong the domesti nimls. Therefore, mres n be roughl lssified into three tpes bsed on their breeding seson. The re () the defined sesonl breeders (tpe ): the estrous le of most wild breeds oinides with the longest ds of the er nd foling during restrited seson; () trnsitor sesonl breeders (tpe ): some breeds mnifest estrous les throughout the er, but ovultion onl ours during the breeding seson; (3) erround breeders (tpe 3): some domesti mres show estrous le ompnied b ovultions throughout the er (Hfez, 993). Nevertheless, most mres re sesonll polestrous nd mn of them show behviorl estrus in Februr, Mrh, nd April without ompning ovultion (Hfez, 993). Low pregnn rtes our in these months in ontrst to the better oneption rtes in M, Jul, nd August. It hs been reported tht 75-8% of mres showed sesonl or winter nestrus in utumn nd winter (Osborne, 9; Ginther, 97; Hughes et l., 975). On the ontrr, out 9% of mres show regulr estrous le nd ovulte during the long dlength period. However, the durtion of the breeding seson hs inresed * Address reprint request to Yng-Kwng Fn. Present Address: Deprtment of Animl Siene, Ntionl Chung-Hsing Universit, 5 Kuo-Kung Rd., Tihung, Tiwn, ROC. Tel: , Fx: , Emil: kfn@ drgon.nhu.edu.tw Counil of Agriulture, Exeutive Yun, ROC. Reeived M 3, ; Aepted Deember, due to domestition of this speies nd some mres even show sexul tivit throughout the er in ontrst to some wild nd semi-wild breeds, whih hve more restrited breeding seson (Gordon, 983). The niml m hve limted to lol environments to ertin degree. However, to our knowledge, no relile informtion is ville onerning the reprodutive prmeters of the mre fter limtion. We hve initited doumenting mjor bkground informtion for future development of the horse industr in Tiwn (Fn et l., 99; Ju et l., 993). In the present stud, we investigted the reprodutive performne of rossbred mres throughout the er. This informtion would be of vlue for horse owners or frm prtitioners in Tiwn nd other subtropil ountries. MATERIALS AND METHODS Dt olletion In this stud, extensive nlses of 83 reords from 39 mixed breed mres inluding Anglo-Arins, Mongolins, Thoroughbred, Qurter horses nd their hbrids, were olleted from 953 to 989 from the Holi Stud Sttion, Tiwn. Reprodutive reords inluding length or durtion of estrus (LE), gesttion period (GP), prturition nd lttion onditions, nd birth weight (FBW, kg) nd birth height (FBH, m) of fols, were olleted. Sire effets on those reprodutive trits were lso nlzed. The LE ws onsidered to be from the first d of onset estrus until the dispperne of the behviorl or phsiologil signs of het (Bk et l, 97; Squires, 993). In ddition to umultion of wter muus in the vgin

2 REPRODUCTIVE CHARACTERISTICS OF THE MARE IN TAIWAN 95 nd swelling of the vulv, the mres on het lso show some mjor behviorl signs suh s urinting, squtting, nd eversion of vulvr li or winking vulv (figure ). The GP is the period between the first d of mting nd delivering oung fol to term. Norml lttion is without n pthologil or phsiologil problems of the mre. Aglti (AGA) is the ondition lking milk seretion of the mre during the nursing period. The FBH of the fol ws the vertil mesurement from the wither to the ground nd the FBW ws mesured using n niml sle. The intensit of the estrus (INE) of the mres ws rbitrril lssified into four levels,,, nd 3, bsed on subjetive observtions on the intensit of the observle sexul tivities nd the degree of swelling nd/or the olor hnges of the mre s externl genitli. Sttistil nlsis All the dt were lulted, trnsformed, nd nlzed under the effet of the month of the er using the Generl Liner Model (GLM) in the Sttistil Anlsis Sstem softwre (SAS, 989). RESULTS The LE nd GP of the mres s well s the FBW nd FBH of the fol were nlzed from 39 nimls. Some of these reprodution-relted hrteristis re shown in tle. Averge LE, GP, FBW nd FBH of the fols were.±3.5 ds, 37±3 ds, 38.7±5.3 kg, nd 9.7±5. m, respetivel, regrdless of the month of the er (tle ). LE (figure ) inresed from Jnur to August with signifintl (p<.5) longer durtion in September (. ds) when ompred to those in Deember, Jnur nd Figure. Mre showing stne of urintion (squtting) nd swelling nd winking of the vulvr lips (rrow), prolonged rhthmi exposure of litoris, onsidered to be tpil signs of estrus. Tle. Averge reprodutive prmeters of mres in subtropil Tiwn Prmeters N Men±SEM Length of estrus (LE), ds 83.±3.5 Gesttion period (GP), ds 8 37±3 Bod mesurements of fols Birth weight (FBW), kg ±5.3 Birth height (FBH), m ±5. Sex rtios (M/F) 77.9 N: The number of totl reords ville. No signifint differene ws deteted in the sex rtio of the fols. Februr (.-. ds, p<.5). LE grdull shortened from Otober to Deember, when the shortest LE of the er ws observed (figure ). Signs of behviorl estrus were similr throughout the er. More thn 8% of these nimls were in estrus during Mrh through Otober. Effets of breeding month (BM) nd prturition month (PM) of the mres on FBW nd FBH of the fols t birth were nlzed nd re presented in figures 3 nd. The FBW rnged from 3.7 to. kg, nd ws signifintl ffeted b both the BM nd PM of the mres. The lowest FBW reorded in September nd Deember (3.7 nd 3.8 kg), were signifintl (p<.5) lower thn the FBW reorded in other months of the er exept in Mrh, August, Otober nd November. A trend of lower FBH ws lso observed during the period from September to Deember ( m) thn from Jnur to August, with the gretest men in June (9. m, figure 3). This showed tht the influenes of PM of mres on the bod mesurements of their fols were not s obvious s tht of BM. The months lso hve ffeted the perentges of nimls showing estrus, pregnn nd prturition. A lose similrit in the pttern of mres during estrus, pregnn nd prturition ws observed (figure 5). The effets of BM, PM, nd month of estrus (EM) of mres on GP re shown in figure. Comprisons mong eh month within eh vrile were mde, b whih similr profile in eh riterion ws observed. It ppered tht the length of gesttion period lso vried in different sesons. Generll, longer GP ws observed in erl spring (Jnur) to the beginning of summer (June) s shown in figure. During the nursing period, most mres showed norml lttion. However, the inidene of mres exhibiting AGA in eh month differed signifintl under the influenes of EM, BM nd PM of the mres (figure 7). The effets of EM nd BM on the inidene of AGA shred similr osilltion pttern, whih ourred with the higher months in Jnur, April, Jul to August, Otober or November. Likewise, under the influene of PM, the inidenes of

3 9 JU ET AL. LE Signs of estrus Length of estrus, ds 8 b Mres on het b b 8 % Mres on het Jn Feb Mr Apr M Jun Jul Aug Sep Ot Nov De Figure. The effet of month on the length of estrous le, signs of estrus nd perentges of mres on het in Tiwn. The observle signs of estrus were defined s,,, 3 levels of intensit (totl reords of mres N=83). Common letters (, b, ) on top of the hrt represent no signifint differenes in length of estrus (LE) (p<.5). Fol height, m Fol Ht 97 Fol Wt x 9 95 x 39 x x x x 38 9 b Jn Feb Mr Apr M Jun Jul Aug Sep Ot Nov De Months of breeding Fol weight, kg Figure 3. Effets of breeding month of the mre on the birth weight nd height of the fol. Common letters on top of the hrt represent no signifint differenes in birth weight (, b, ) nd height (x,, z) of the fol (p>.5). AGA osillted with similr pttern s tht in the other two vriles, but the pek of AGA ws shifted one month to the left of the X-xis s tht in figure 5. Sire effet on gesttion nd fol mesurements The effets of sires on pregnn onditions, gesttion periods, prturition sttus, nd bod mesurements of the fol were lso nlzed using the Generl Liner Model in SAS. No effet of stllions ws found on GP nd prturition sttus (p>.5). On the ontrr, highl signifint influenes of stllions were observed on pregnn sttus (P<.8) s well s the birth weight (p<.) nd height (p<.) of the fol (tle ). Tle. Anlsis of vrine of the stllion effet on the reprodutive trits of mres nd bod mesurements of the fols in Tiwn Independent Degrees of Men vrile freedom squre F vlue P level Pregnn sttus Gesttion period, ds Prturition sttus Fol weight (FBW), kg Fol height (FBH), m Pregnn sttus: : norml; : norml. Prturition sttus: : norml; : norml; -: ortion. DISCUSSION The estrus le of the mre Multiple ftors inluding photoperiod, temperture nd vililit of food, ffet the reprodutive le of horses. Of these, photoperiod m be one of the most importnt ftors (Burkhrdt, 97; Nishikw, 959), b whih n endogenous irnnul rhthm is snhronized with sesonl limti nd dietr hnges (Bronson nd Heidemn, 99). Durtion or length of estrus (LE) of mres m vr mong individuls nd lso mong the estrous le of the sme mre. As onsequene, the LE is influened b the ge of mres, nutritionl or feeding onditions during the erl stge of the breeding seson,

4 REPRODUCTIVE CHARACTERISTICS OF THE MARE IN TAIWAN 97 Fol Ht Fol height, m z x z x z b z Fol Wt b z Fol weight, kg Jn Feb Mr Apr M Jun Jul Aug Sep Ot Nov De Month of prturition 3 Figure. The effet of month of prturition of the mre on the birth weight nd height of the fol in subtropil Tiwn. Common letters on top of the hrt represent no signifint differenes in birth weight (, b, ) nd height (x,, z) of the fol (p>.5). Perentges, % 8 Jn Feb Mr Apr M Jun Jul Aug Sep Ot Nov De Month of the Yer % Estrus % Pregnn % Prturition Figure 5. The effet of month on perentges of estrus, pregnn nd prturition of mres in subtropil Tiwn nd phsiologi sttus suh s twin ovultions (Hfez, 993). In this investigtion, LE of the mres ws.±3.5 ds (tle ), whih is muh longer thn tht of other speies (f. - ds in pigs, -3 ds in ows). The length of estrus le in most domesti speies, suh s sows, ows, nd mres is round ds. Long durtion of the estrus in the mre m be due to the following ftors: () Folliles hve to migrte to the ovultion foss prior to rupture; () The ovries re less sensitive to exogenous FSH thn in other speies; (3) Low level of LH m del ovultion (Hfez nd Hfez, ). Observtions reorded during the present investigtion revel tht the LE of mres in Tiwn is shorter during Deember nd April nd grdull inreses fterwrds with the longest durtion in September (figure ). In other res, lthough durtion of estrus tpill dereses s the seson progresses, the shortest durtion of is estrus observed in summer (Ginther et l., 97; Hughes et l., 97; Hughes et l., 98). Shortening of the estrus most likel represents n elertion of folliulogenesis prior to ovultion with inresingl fvorle photoperiod. Furthermore, verge LE of the mres in Tiwn (. ds) is different from the LE in other res (-8 ds), whih m be ffeted b the mbient temperture s well s the dlength of the breeding seson, whih in turn lengthened the durtion of estrus leding to longer LE of the mre in Tiwn (Hughes et l., 97; Stenfeldt et l., 97). The min prt of the breeding seson ours during April through June or M through Jul in the northern hemisphere (Andrews nd MKenzie, 9; Hutton nd Mehm, 98; Hfez, 993), wheres in the southern hemisphere, it is from November to Jnur (Osborne, 9). In Tiwn, s presented in figure, lthough not neessril oneived during ll estrous periods, mres exhibited n estrus le ll the er round (polestrous) with more thn 8% of mres in het during Mrh through Otober. Environmentl temperture seems to be ke vrile tht influenes the estrous le in mres. Elevted mbient temperture ompnied with high humidit hs been problem for reprodutive performne in domesti speies in Tiwn nd other wrm res (Ron et l., 98; Mont nd Rowsk, 987; Putne et l., 988). Therefore, the onset of estrus m be mbiguous in the hot seson, whih ours round June till the end of August in this islnd. Interestingl, the distribution of the niml showing estrus over the er is bimodl (figure ), whih m be one of the unique reprodutive phenomen for mres in Tiwn. Other

5 98 JU ET AL. Gesttion periods, ds b b b b b b b b Jn Feb Mr Apr M Jun Jul Aug Sep Ot Nov De 35 Estrus Breeding Prturition Figure. The effet of month of het, breeding, nd prturition on the gesttion period of the mre in subtropil Tiwn. Common letters (, b, ) on top of the hrt represent no signifint differenes for eh riterion. Frequen of glti Estrus 7 Breeding Prturition 5 3 Jn Feb Mr Apr M Jun Jul Aug Sep Ot Nov De Months of the Yer Figure 7. Effets of estrus, breeding nd prturition month of the er on the frequen of glti of nursing mres in subtropil Tiwn ftors suh s speies will ertinl influene the reprodutive le of the mre. For instne, hlf of the Welsh nd Shetlnd ponies were found to breed throughout the er, while the others refused to breed from Otober to Mrh in the UK (Gordon, 983). Unfortuntel, detiled reords of the breed were not ville in this investigtion, whih m onfound with the effet of other ftors suh s dlight nd temperture. Gesttion period of the mre Gesttion period (GP) in the mre rnges from 35 to 3 ds nd is influened b mternl size, fetl genotpe, nd the stge of the breeding seson when oneption ours (Hfez, 993). The verge gesttion period of the mres presented in this stud is 37±3 ds (tle ), whih fll within the rnge of GP reported in equines (Jinudeen nd Hfez, 993). Interestingl, when the effet of behviorl estrus, breeding, or prturition under the influene of month were nlzed, length of GP in reltion to those vriles differed between months of the er with similr trend (figure ). Generll, longer GP ws found during Jnur through M nd shorter ones during June through Deember. A signifintl shorter GP ws found in September thn in Februr or Mrh in ll riteri exmined (figure ). Similr results were lso found b Howell nd Rollins (95) nd Hodge et l. (98), in whih mres bred erl in the spring ppered to undergo longer gesttions thn those bred lter in the er. However, exposure of bred mres to rtifiill lengthened dlight during the ltter third of gesttion resulted in shorter gesttionl period thn observed in mres exposed to nturl dlight. Although the mehnisms re not et ler, the photi signls might hve indiretl influened the hormonl profile of the mre (Shrp et l., 993). Whether photoperiodi informtion is somehow onveed diretl to the fetus to lter the timing of prturition initition or to lter the ourse of growth nd development requires further stud. Although the frequen of mres in estrus ws not ffeted b the month, other reprodutive trits suh s prturition, lttion or AGA m hve been gretl ffeted. ACKNOWLEDGEMENTS The uthors wish to thnk Holi Stud Sttion nd Diretor Lee, I-J, who provided vlule informtion for this nlsis. Dr. Chi-Fong Chen nd Mr. Jen-Sin Lee, who helped in photogrphing the mre, re lso gretl ppreited. This stud ws supported b grnts from Counil of Agriulture, Exeutive Yun, ROC. REFERENCES Andrews, F. N. nd F. F. MKenzie. 9. Estrus, ovultion nd

6 REPRODUCTIVE CHARACTERISTICS OF THE MARE IN TAIWAN 99 relted phenomen in the mre. Univ. Mo. Agri. Exp. St. Res. Bull. 39:-7. Bk, D. G., B. W. Pikett, J. L. Voss nd G. E. Seidel. 97. Observtions on the sexul behvior of nonltting mres. J. Am. Vet. Med. Asso. 5:77-7. Bronson, F. H. nd P. D. Heidemn. 99. Sesonl regultion of reprodution in mmmls. In: The Phsiolog of Reprodution (Ed. E. Knobil nd J. D. Neill). Rven Press New York. Vol., Chpter, pp Burkhrdt, J. 97. Anoestrus in the mre nd its tretment with estrogen. Vet. Re. 59:3-3. Fn, Y. K., J. C. Ju, S. P. Cheng, J. C. Hsu nd S. C. Chiou. 99. A surve of the bod onformtion of horses in entrl Tiwn. J. Chin. So. Anim. Si. : Ginther, O. J., H. L. Whitmore nd E. L. Squires. 97. Chrteristis of estrus, diestrus, nd ovultion in mres nd effets of seson nd nursing. Am. J. Vet. Res. 33: Ginther, O. J. 97. Ourrene of nestrus, estrus, diestrus nd ovultion over -month period in mres. Am. J. Vet. Res. 35: Gordon, I Introdution to ontrolled breeding in horses. In: Controlled Breeding in Frm Animls, Pergmon Press, New York. pp Hfez, E. S. E. nd B. Hfez.. Horses. In: Reprodution in Frm Animls (Ed. E. S. E. Hfez, B. Hfez, Lippinott Willims nd Wilkins). 7 th ed. Phildelphi. pp Jinudeen, M. R. nd E. S. E. Hfez Gesttion, prentl phsiolog, nd prturition. In: Reprodution in Frm Animls (Ed. E. S. E. Hfez. Le nd Febiger). th ed. Phildelphi. pp Hodge, S. L., J. L. Kreider, G. D. Potter, P. G. Hrms nd J. L. Fleeger. 98. Influene of photoperiod on the pregnnt nd postprtum mre. Am. J. Vet. Res. 3: Howell, C. nd W. Rollins. 95. Environmentl soures of gesttion length of the horse. J. Anim. Si. : Hughes, J. P., G. H. Stenfeldt nd J. W. Evns. 97. Clinil nd endorine spets of the estrous le of the mre. Pro. Am. Asso. Equine Prt Hughes, J. P., G. H. Stenfeldt nd J. W. Evns The estrous le of the mre. J. Reprod. Fertil. 3(suppl.):. Hughes, J. P., G. H. Stenfeldt nd P. C. Kenned. 98. The estrous le nd seleted funtionl nd pthologi ovrin normlities in the mre. Vet. Clin. North Am. :5-39. Hutton, C. A. nd T. M. Mehm. 98. Reprodutive effiien of fourteen horse frms. J. Anim. Si. 7:3-38. Ju, J. C., S. P. Cheng, Y. K. Fn, J. C. Hsu, S. K. Ching, E. V. Chen, S. H. Chng nd S. C. Chiou Investigtion of equine hemtologil onstituents in entrl Tiwn. I. Distribution of the blood ell prmeters nd the biohemil ompositions of serum. Asin-Aust. J. Anim. Si. :7-53. Mont, D. E. nd C. Rowsk In vitro evlution of erl embro viilit nd development in summer het-stressed, superovulted dir ows. Theriogenolog 8:5-5. Nishikw, Y Studies on reprodution in horses. In: Singulrit nd Artifiil Orgn Control in Reprodutive Phenomen. Jpn Ring Assoition, Toko. Osborne, V. E. 9. An nlsis of the pttern of ovultion s it ours in the nnul reprodutive le of the mre in Austrli. Aust. Vet. J. :9-5. Putne, D. J., J. R. Mler, T. S. Gross, W. W. Thther, P. J. Hnsen nd M. Drost Het stress-indued ltertions in the snthesis nd seretion of proteins nd prostglndins b ultured bovine oneptuses nd uterine endometrium. J. Reprod. Biol. 39: Ron, M., R. Br-Ann nd G. R. Wiggns. 98. Ftors ffeting oneption rte of Isreli Holstein ttle. J. Dir Si. 7:85-8. SAS Institute SAS User s Guide:Sttistis. Version.3. SAS Institute In., Cr, NC, USA. Shrp, D. C., B. D. Clever nd S. D. Dvis Photoperiod. In: Equine Reprodution (Ed. A. O. MKinnon nd J. L. Voss). Le nd Febiger, Phildelphi. pp Squires, E. L Estrous detetion. In: Equine Reprodution (Ed. A. O. Mkinnon nd J. L. Voss, Le nd Febiger). Phildelphi. pp Stenfeldt, G. H., J. P. Hughes nd J. W. Evns. 97. Ovrin tivit during the estrous le of the mre. Endorinolog 9: