KASTELIC, J. P.

MAPLETOFT, R. J.

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IV Congresso Internacional da Associação Brasileira de Estudos CanadensesSYNCHRONIZATION OF ESTRUS IN CATTLE (' G P PS El AINSL-r'ARATAtJ.P. Kastelíc'f and R.J. Mapletoft"lEMBRAPA, CPPSE (Pecuária Sudeste), São Carlos, SP, Brasil, 13560-9702Agriculture and Agri-Food Canada, Lethbridge Research Centre,Lethbridge, Alberta, Canada TU 4B13Departrncnt ofHerd Medicinc and Theriogenology, Western College ofVeterinary Medicinc,Univcrsity of Saskatchcwan, Saskatoon, Saskatchcwan, Canada S7N 5B4INTRODUCTIONThe purpose of this article is to briefly review synchronization of estrus in cattle, with an ernphasison recent developments. Throughout this revicw, the day of ovulation is defined as Day O (therefore, theday of cstrus is approximately Day -1).OVARIAN FUNCTIONFollicle growth occurs in waves, the simultaneous development of several follicles (Adams,1994; Kastclic, 1994). Most eows have either 2 or 3 waves during an estrous eyelc. One follicle perwave beeomes dorninant and grows for sevcral days (maximum diarnetcr, approximately 1.5 em) andsuppresscs growth of the remaining follicles in the wave (diametcr usually < 1.0 em). The first wave ofthe eycJe usually starts around Day O, grows for about 6 days, rcaches a plateau, and then begins toregress a few days after a new wave starts (Day 9 or 10). ln a three-wave cycle, the dominant folliclc ofthe second wavc also grows for a few days but ultimatcly regresses, with emergence of thc third wavcaround Day 17. Late in the eycle, thc dominant follicle (of the second or third wave) does not reach aplateau, but continues growing and ovulates. A corpus luteum (CL) forms at the site of ovulation. lnpregnant caule, the CL is maintained until just prior to parturition, but in nonpregnant cattlc, rcleasc ofprostaglandin F2a (PGF) from the uterus (approximately Day 17) causes the CL to regressoProstaglandinSynthetic PGF (and its analogues) are commonly used to synchronize estrus (Larson and Bal!,1992; Odde, 1990). Treatrnent with PGF will cause regression of a responsivc CL; responsivenessbegins as early as Day 5, incrcases to about Day 12 and then plateaus. By Day 17 the CL may beundergoing spontaneous regression induced by endogenous PGF. The viable dominant follicle prcscnt atthe time of CL regression grows and ovulates (Kastelic et aI., 1990; Kastelic and Ginther, 1991). WithPGF treatment on Day 5, the dominant follicle of Wave 1 is still growing (interval from treatment toovulation, 3 days). With treatment on Day 12, the dominant follicle of Wave 2 is carly in its growthphasc (treatment to ovulation averagcs 4.5 days). In cattle treated on Day 8, ovulation usually oceursfrom the dominant follicle of Wave 1 (4 days) but occasionally occurs from Wave 2, approximately 6days aftcr treatment. Due to this variation in interval from treatment to ovulation, fcrtility will usually behigher when cattlc are bred after dctection of cstrus cornpared to breeding at a fixed time. The stage 01'the estrous cyclc that PGF treatment is given also affccts fertility; pregnancy rates are usually higherwhen cattle are treated with PGF after mid-cycle compared to early in the cyclc (e.g., Day 14 versusDay 7).There are many trcatment regimens using PGF. Cattle that are eycling should have a responsiveCL approximately 70% of the time. Rectal palpation and treatment of cattle with an apparently responsiveCL should incrcasc the proportion that respond; however, errors in deteetion of a rcsponsivc CL andIailurc to dctcct cstrus result in about 75% of treated cattle being dctccicd in cstrus (Gaines, 1994). Withnatural scrvicc, ali femaJes can be given PGF 96 hours after the start of buli exposure; those bred priorto PGF treatrncnt will not have a responsive CL (Whittier et aI., 1991). Estrus detection and breeding for555IV Congresso Internacional da Associação Brasileira de Estudos Canadenses5 days and then giving all nonbred cattle PGF works very well, but estrus detection and breeding arespread out over about 10 days. If less than 20% of cattle are detected in estrus by the fifth day, theneither the cattle are not cycling and/or estrus detection is poor.Some recent synchronization regimens have used analogues of gonadotropin releasing hormone(GnRH), followed by PGF 6 or 7 days later. Treatment with GnRH causes the dorninant follicle toovulate (if it is in the growing or early static phase) or to undergo atresia (if it is no longer viable), withemergence of a new follicular wave within 2 or 3 days aftcr GnRH treatment (Pursley et al., 1995;Kastelic and Mapletoft, 1997). Estrus will be detected in a rninority of cattle in the interval betweenGnRH and PGF; however, 60 to 70% of the cattle will be detected in estrus within 4 days after PGFtreatment (Twagiramungu et al., 1995). The synchrony of cstrus, and in particular ovulation, can beconsiderably increased by giving a second dose of GnRH, 36 to 48 hours after PGF. Timed insernination18 to 24 hours aftcr the second dose of GnRH has resulted in acceptable fertility, especially in cows,although fertility in heifers seems to be lower. In one study (Pursley et al., 1995), PGF was given 7 daysafter GnRH and a second dose of GnRH was given 36 hours (heifers) or 48 hours (cows) after PGF. Anew follicular wavc emerged after the first GnRH treatment in 1801'24 heifers and in 20 of20 cows. Ali20 cows and 1801' 24 hcifcrs ovulated a newly forrncd dominant follicle between 24 and 32 hours aftcrthe second GnRH treatment. All 20 eows were inserninated 24 hours aftcr the second GnRH treatmentand 10 became pregnant.A common approach is two treatments with PGF 11 days apart, although fertility may be betterif this interval is increased to 14 days (Folman et al., 1990). One protocol (Ferguson and Galligan, 1993;Fuhrmann, 1993) utilizes PGF injections at 14-day intervals.The voluntary waiting period (minimuminterval from calving to first breeding) is determined and ali postpartum cattle 3 to 17 days prior to thevoluntary waiting period are injected with PGF. Fourteen days later, these cows are again treated withPGF and bred according to signs of cstrus activity. Any cattle not detected in estrus will receive PGF onthe next treatment day (14 days later) and will be bred upon signs of estrus or at 80 hours after treatmentif estrus has not been detected by that time. Pregnancy diagnosis is conducted as early as possible, preferablyat 14-day intervals, and nonpregnant cows are included in the group of cattle treated with PGF.MELENGESTROL ACETATE (MGA)Various progestins (progesterone-like compounds, including MGA) have been utilized for estroussynchronization (Larson and Ball, 1992; Odde, 1990; Patterson et al., 1989). Progestin treatment formore than 14 days will synchronize estrus, but fertility at the induced estrus will be reduced duc toimpairment of sperm transport, ovum fertilization and cleavage. These effccts are transitory, and are nolonger apparent at the next estrus.The progestin most commonly used for estrous synchronization is MGA. The advantages ofMGA include low cost (fcw cents per day), oral adrninistration (usually mixed in grain) and extrcmclylow toxicity. One regimen is to fccd 0.5 mg MGAlhead/day for 14 days, followed by treatment with PGF17 days aftcr cessation 01' MGA (Patterson et al., 1989). This regimen has been reported to give well-synchronized cstrus with good fertility, especially in beef cattle in moderate (compared to fair or poor)body condition (Yelich et al., 1995a). Furthermore, separating suckling calves from their dams for 48hours, starting 2 days after the last feeding of MGA, increased the percentage of 2- and 3-year old damsconceiving early in the breeding season (Yelich et al., 1995b). Most cattle will be in estrus a few daysafter cessation of MGA; however, they are not bred until the estrus following PGF treatment. Pregnancyrates will bc optimized by detecting estrus and breeding accordingly. Insemination at 72 hours after PGFtreatment has resulted in good fertility in some herds but not others (King et al., 1994; Larson et al.,1996). Therefore, one approach is to inserninate all cattle at 72 hours after PGF and then either detect estrusand inseminate from 72 to 120 hours or expose females to bulls starting at 96 hours (King et al., 1994).A short-term regimen is to feed MGA (0.5 mg MGNhead/day) for 7 to 9 days with PGF givenon thc last day, Howcver, caule that lack a CL (duc to ancstrus or spontaneous CL regrcssion duringMGA treatment) develop a large ovarian follicJe that elcvates serum estradiol concentrations and reduces556IV Congresso Internacional da Associação Brasileira de Estudos CanadensesREFERENCESAdams, G.P. (1994) Control of ovarian follicular wave dynarnics in cattle: Implications for synchronizationand superstimulation. Theriogenology 41: 19-24.Arruda, R.E, Madureira, E.H., Mizuta, K, Gusmões, P.P., von Zuben, c., Visintin, J.A. and Rodrigues,P.H.M. (1997) Sincronização do estro em fêmeas bovinas com o use de aceto de melengestrol (MGA)- prostaglandin F2, e CIDR-B. Revista Brasileira de Reproducão Animal 21:97-99.Bergfelt, D.R., Lightfoot, KC. and Adams, G.P. (1994) Ovarian synchronization following ultrasound-guided transvaginal follicle ablation in heifers. Theriogenology 42:895-907.Bo, G.A., Adams, G.E, Pierson, R.A. and Mapletoft, RJ. (1995) Exogenous control offollicular waveemergence in cattle. Theriogenology 43:31-40.Ferguson, J.D. and Galligan, D.T. (1993) Prostaglandin synchronization prograrns in dairy herds. Part1. The Compendium on Continuing Education for the Practicing Veterinarian 15:646-655.Folman, Y., Kaim, M. Herz, Z. and Rosenberg, M. (1990) Comparison of methods for the synchronization01' estrous cycles in dairy cows. 2. Effects of progesterone and parity on conception. JournalofDairy Science 73:2817-2825.Fuhrmann, T. (1993) Tak.ing control of reproduction in dairy herds. In: Society for Theriogenology,Proceedings for Annual Meeting. Jacksonville, Florida. pp. 97-106.Gaines, 1.0. (1994) The use of gonadotropin re1easing hormone and prostaglandin for programmedbreeding of dairy cattle. ln: Society for Theriogenology, Proceedings for Annual Meeting. KansasCity, Missouri. pp. 108-120.Kastclic, J.P. Knopf, L. and Ginther, O.J. (1990) Effect of day of prostaglandin F2a treatment on sclcctionand development of the ovulatory follicle in heifers. Animal Rcproduction Scicncc 23: 169-180.Kastelic, J .P. and Ginther, O.J. (1991) Factors affecting the origin of the ovulatory follicle in hcifers withinduccd lutcolysis. Animal Reproduction Science 26: 13-24.Kastclic, J.E (1994) Ovarian follicular dcvelopment in cattle. Vcterinary Mcdicinc 89:64-71.Kastclic, J.P., McCartney, D.H., Garcia, A., Olson, W. and Mapletoft, RJ. (1996) Estrus synchronizationin cattle using cstradiol, mclengestrol acctate and PGF. Theriogcnology 46: 1295-1304.Kastclic, J.P., Olson, W.O., Martinez, M., Maplctoft, RJ. and Machado, R. (1997) Sincronização doestro em bovinos Hercford-Angus com Crestar. Revista Brasileira de Reprodução Animal 21 :101-103.Kastc1ic, J .P. and Mapletoft, R.J. (1997) Ovarian follicular responses in dairy cattle treated with GnRHand c1oprostenol. Canadian Veterinary Journal (In press).King, M.E., Danicl, M.J., Tcague, L.D., Schutz, D.N. and Odde, K.G. (1994) Comparison of timedinscrnination with inscmination at estrus following synchronization of cstrus with a MGA-prostaglandinsystcm in bccf heifers. Theriogenology 42:79-88.Larson, L.L. and Ball, EJ.H. (1992) Regulation of estrous cycles in dairy cattle: a revicw. Theriogenology38:255-267.Larson, R.L., Corah, L.R. and Pctcrs, C.W. (1996) Synchronization of estrus in ycarling beef heiferswith the mclengestrol acetate/prostaglandin F2a system: efficiency of timed insernination 72 hoursafter prostaglandin treatment. Thcriogenology 45:851-863.Madurcira, E.H., Barbuio, J.P., Arruda, R.P., Bertan, C.M., Mizuta, K, Brazzach, M.L., Barnabc, R.C.and Rodrigues, P.H.M. (1997) Sincronização do estro em fêmeas bovinas usando acetato demclcngestrol (MGA) associado à prostaglandina F2a C ao 17B-cstradiol. Revista Brasileira deReproducão Animal 21 :94-97.Mauck, H.S., King, M.E., Holland, M.D., LeFever, D.G. and Odde, KG. (1994) Comparison of twoMGA-PGF2asystems for synchronization of estrus in beef heifers. Theriogenology 42:951-961.Oddc, K.G. (1990) A review of synchronization of estrus in postpartum cattle. Journal of AnimalScience 68:817-830.Patterson, D.J., Kiracofe, G.H., Stevenson, J.S. and Corah, L.R. (1989) Control of the bovine estrouscycle with melengestrol acetate (MGA): a review. Journal of Animal Science 67: 1895-1906.558IV Congresso Internacional da Associação Brasileira de Estudos CanadensesPursley, J.R., Mee, M.O. and Wiltbank, M.C. (1995) Synchronization of ovulation in dairy cows usingPGF2a and GnRH. Thcriogcnology 44:915-923.Tribulo, H.E., Bo, G.A., Kastelic, J.P., Pawlyshyn, V., Barth, A.D. and Mapletoft, RJ. (1995) Synchronousovulation in hcifers treatcd with E-17B and CIDR-B vaginal devices. Thcriogcnology 43:340.Twagiramungu, H., Guilbault, L.A., and Dufour, J.J. (1995) Synchronization of ovarian follicular waveswith a gonadotropin-releasing hormone agonist to increase the precision of cstrus in cattle; a review.Journal of Animal Scicncc 73:3141-315l.Whittier, J.c., Caldwcll, R.W., Anthony, R.V., Srnith, M.F. and Morrow, R.E. (1991) Effect of aprostaglandin F 2a injection 96 hours after introduction of intaet bulls on estrus and calving distributionof becf cows. Journal of Animal Scicncc 69:4670-4677.Yclich, J. v., Mauck, H.S., Holland, M.D. and Oddc, K.G. (1995a) Synchronization 01' cstrus in sucklcdpostpartum bcef cows with melengestrol acetate and PGF2a• Theriogcnology 43:389-400.Yelich, J.V., Holland, M.D., Schutz, D.N. and Oddc, K.G. (1995b) Synchronization of estrus in sucklcdpostpartum beef cows with melengestrol acetate, 48-hour calf removal and PGF 2" Thcriogcnology43:389-400.559

Synchronization of estrus in cattle.

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Synchronization of estrus in cattle.

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