epidemiology of pregnancy losses and practical strategies...

Epidemiology of Pregnancy Losses and Practical Strategies for Prevention Klibs N. Galvão and José Eduardo P. Santos

University of Florida [email protected]

AbstractPregnancy losses from fertilization to termareextensiveinlactatingdairycattle.Inmanycases,theyareunderestimatedbecauseoftheinability to determine conception early afterinsemination.Formostproducers,pregnancylossesareonlyquantifiedafter the initialdi‐agnosis is performedat approximately30 to45dofgestation.Recentstudiesthatprovid‐ed reliable assessments of fertilization haveled to the conclusion thatmore than60%ofallpregnanciesarelostbeforeterminlactat‐ingdairycows.Thecriticalperiodisfromfer‐tilization until the end of the differentiationphase (embryonic period) inwhich approxi‐mately85%ofthose lossesoccur.Therefore,strategiestopreventembryoniclossesshouldresult in thegreatest improvement in repro‐ductive performance. Nevertheless, althoughfetal losses are minor (approximately 15%)compared with embryonic losses, those aremorecostlythanembryoniclosses;thereforethey cannot be overlooked. Known risk fac‐torsforpregnancylossincludeprolongedpe‐riods of follicular dominance, lowprogester‐one concentration during ovulatory follicledevelopment,heatstress,postpartumdiseas‐es and disorders such as dystocia, metritis,endometritis, mastitis, fever, ketosis, lame‐ness,anddigestiveproblems,negativeenergybalance, excessive body weight loss, toxinsfound in feedstuffs such as gossypol, myco‐toxins, and ergot alkaloids, and infectiousagents suchasNeosporacaninum,Leptospiraspp., Campilobacter spp., BVD virus, and IBRvirusamongothers.Strategiesthatpreventorcontrol known risk factors should help de‐creasepregnancylossandimprovereproduc‐tiveperformance.

IntroductionPregnancy losses exert a major detrimentalimpact on the reproductive efficiency and

profitabilityofdairyherds.Averagecostofapregnancy loss was estimated at $555 butvarieddependingondays inmilk at concep‐tionandstageofgestationwhenthepregnan‐cyislost(DeVries,2006;Table1).TheCom‐mitteeonBovineReproductiveNomenclature(1972)establishedthattheembryonicperiodof gestation extends from conception to theend of the differentiation stage, at approxi‐mately42daysofgestation,andthatthefetalperiod extends from gestation day 42 to thedelivery of the calf. Losses of pregnancy be‐fore day 24 indicate early embryonic losses(usually associated with failure of maternalrecognitionofpregnancy),andthosebetweendays24and42days,indicatelateembryoniclosses.Pregnancylossesdetectedbetween42and 260 days of gestation characterize fetallossesorabortion,whereasacalfthatisborndead between 260 days and full term (ap‐proximately 280 days) is defined as a still‐birth(Peter,2000;Santosetal.,2004a).Two sources of pregnancy failure exist afterbreeding, fertilization failure and pregnancyloss.Indairycattle,fertilizationratesaresim‐ilarbetween lactatingandnonlactating cowsandtheyaveraged76.2%(rangingfrom55.3to 87.8%) and 78.1% (ranging from 58.0 to98.0%), respectively (Santos et al., 2004a).Fertilization rate was recorded at 100% inheifers (Sartori et al., 2002). Nonetheless, inlactating cows, more than 60% of the ferti‐lized oocytes are lost until term (Figure 1).The critical period is from fertilization untilthe end of the differentiation phase (embry‐onic period) in which approximately 85%(54%/63%)of those lossesoccur.Therefore,strategiestopreventembryoniclossesshouldresult in thegreatest improvement in repro‐ductive performance. Nevertheless, althoughfetal losses are minor (approximately 15%)compared with embryonic losses, those are

43

The Dairy Cattle Reproduction Council does not support one product over another and any mention herein is meant as an example, not an endorsement

2014 Dairy Cattle Reproduction Conference Salt Lake City, UT

morecostlythanembryoniclosses(DeVries,2006; Table 1); therefore they cannot beoverlooked. In this review we will focus ontheknownriskfactorsforpregnancylossandstrategiestoreducethem.

RiskFactorsforPregnancyLossProlongedPeriodsofFollicularDominanceandOocyteQualityOocytequalityiscriticalforthecontroloffer‐tilizationandsubsequentdevelopmentofthenewly formed zygote. One major factor de‐terminingoocytecompetence is thedurationof follicular dominance. Cumulus‐oophoruscomplexesrecoveredfrompersistentfollicles(13daysafterovulation)presenteddegener‐ativecharacteristicsthatwereabsentincom‐plexes recovered from follicles during thegrowingphase(7daysafterovulation;RevahandButler,1996). Ithasbeensuggestedthatsuch morphological changes are linked withlong‐term exposure to slightly elevated LHpulse frequency, advancing oocyte matura‐tion, germinal vesicle breakdown, and de‐creased oocyte quality (Mihm et al., 1999).Negative effects of prolonged follicle domi‐nanceonfertilityofdairycowshavebeenas‐sociated with impaired embryo quality de‐tectedasearlyas6daysafterAI,andnotwithfertilizationfailure(Ahmadetal.,1995;Cerrietal.,2009b).Abnormalpersistencyofovari‐anfollicles isnotrequiredtoreducefertility,because embryo quality was diminished fol‐lowing a 2‐day extension of follicle domi‐nance (Cerri et al., 2009b). This is an im‐portant observation because dominant folli‐cles from lactating dairy cows must growlarger in order to induce estrus comparedwithdairyheifersbecauseof the increase insteroidclearanceintheliverinlactatingcows(Sangsritavong et al., 2002; Wiltbank et al.,2006). Such reduction in embryo qualitycaused by prolonged follicle dominance hasbeen implicated with embryonic mortalityand reduced pregnancy per AI (P/AI) be‐tweendays30and34afterAI (Austinet al.,1999). An approach that has been shown toimprove conception rates in lactating dairycows is to reduce the interval between thefirstGnRH injectionof theOvsynchprogram

and the PGF2α injection from 7 to 5 days toreducetheperiodoffollicledominance(San‐tos et al., 2010). This approach increasedpregnancyperAI (P/AI) from30.9 to37.9%whenallcowswereevaluatedandfrom33.9to39.3%whenonlycowsthatovulatedwereevaluated (Santos et al., 2010). The increasein P/AI probably resulted from increasedembryonic survival because fertilization ratewasnotfoundtobeaffectedinpersistentfol‐licles(Ahmadetal.,1995;Cerrietal.,2009b).The only downside of this program is theneed for a second PGF2α 24 hours after thefirstonetoensureluteolysisoccurs.Cycling Status and Progesterone Concen‐trationduringFollicleGrowthOneinevery4U.S.high‐producingdairycowsfails to resume ovulation by the end of thevoluntarywaitingperiod,whichhasbeenas‐sociated with reduced fertility to the firstpostpartum AI (Santos et al., 2009). A de‐crease in P/AI for anovular cows comparedwith their cyclic herd mates is very con‐sistent,andP/AIinanovularcowsisapprox‐imately 40% lower than cyclic cows (Santoset al., 2009; Galvão et al., 2010; Bisinotto etal.,2010).InthestudybySantosetal.(2009)P/AI was 24.5 and 35.8% for anovular andcycliccowsat58daysafterAI.ReducedP/AIisprobablyaconsequenceofearlyembryoniclossbecausemostanovularcowsovulatesyn‐chronouslybut are foundopenatpregnancydiagnosis between 30 and 40 days after AI(Gümen et al., 2003). Increased risk of lateembryonic death and fetal loss in previousdefined anovular cows, however, has beendescribed in some but not all studies (Table2). Failure to detect a significant increase inpregnancy loss for anovular cows could beexplained by the lack of power of individualstudies, because the risk is consistentlygreater among anovular cows. In fact, whenthe results from 7 studies were combined,anovular cows were 2 times more likely tolosetheirpregnancies thancycliccows(San‐tosetal.,2004a).Reduced or basal concentrations of proges‐teroneduringgrowthofthepreovulatoryfol‐

44



licle have been found to affect uterine endo‐metrialmorphology(Shaham‐Albalancyetal.,1997),whichisthoughttoaffectendometrialsecretoryfunctionduringearlygestationandalso to increase the synthesisofPGF2α in re‐sponse to oxytocin (Shaham‐Albalancy et al.,2001),whichmayaffectembryodevelopmentandleadtoprematureluteolysis(Garvericketal., 1992; Cerri et al., 2011a), respectively.Furthermore, reducedconcentrationsofpro‐gesteroneduringgrowthof thepreovulatoryfolliclehavebeenassociatedwithgreaterLHconcentrations (increased LH pulse frequen‐cy), faster growth of the ovulatory follicle,reduced intra‐follicular IGF‐1concentrations,andcompromisedembryoquality(Cerrietal.,2011a,Cerrietal.,2011b;Riveraetal.,2011).Recently, itwasobserved thatovulationof afolliclefromthefirstwaveoftheestrouscyclethatdevelopsundersublutealconcentrationsof progesterone is associated with a reduc‐tion in fertility similar to anovular cows (Bi‐sinotto et al., 2010; Denicol et al., 2012). IntheU.S.,aprogesteroneinsertcontaining1.38g of progesterone (Eazi‐Breed CIDR CattleInsert, Pfizer Animal Health, Madison, NJ) isapproved for resynchronization of return toestrus (Chenault et al., 2003). Use of 1 CIDRinsert to supplementprogesterone inanovu‐lar cows has produced inconsistent results(Stevenson et al., 2006; Chebel et al., 2010)probably because progesterone concentra‐tionsareonlyincreasedbyapproximately0.7to 0.8 ng/mL (Cerri et al., 2009c). Recentstudieshavebeenabletoreestablishproges‐teronetoconcentrationsconsistentwiththatofmiddiestruscowsbyusing2CIDRinserts,andhavebeenabletorestoreembryoquality(Rivera et 2011) and P/AI (Denicol et al.,2012; Bisinotto et al., 2013). In thework byBisinotto et al. (2013), P/AI at 62days afterAIwas 28.6, 43.7, and47.3% for cowswith‐outaCLat initiationofOvsynch.Cowswith‐outaCLatinitiationofOvsynchthatreceived2 CIDRs and cows with a CL at initiation ofOvsynch,respectively.Therefore,givena25%prevalenceofanovu‐lationandthelargeimpactonearlyembryon‐

ic loss and also on late embryonic and fetalloss,managementpractices that improve cy‐clicity are expected to decrease pregnancylosses.Recently,weobservedthatcyclicityby21 days in milk was negatively associatedwithparity (less in first‐lactationcows),me‐tritis,metabolicordigestiveproblems,lossof>28kgofbodyweightandadryperiod>76days (Vercouteren et al., 2014). Therefore,strategies that prevent extended dry periodduration and loss of body weight, togetherwith reductions in the incidence of metritis,metabolic problems, and digestive problemsshould improvepostpartumcyclicityandde‐creasepregnancylosses.HeatStressHigh‐producing dairy cows are particularlysensitive to heat stress because of increasedfeed intake and metabolic rate, which chal‐lenge thermoregulation (Wolfenson, 2000).Atairtemperaturesapproaching27ºC(80°F)in humid climates, the body temperature oflactatingcowsrisesabovenormothermicval‐ues,andseverehyperthermiadevelopsasairtemperaturesrisesabove30ºC(86°F)(Wolf‐enson et al., 2000). Air temperatures above30ºC(86°F)areseeninmoststatesintheU.S.during summer, and as temperatures mayrisebecauseofglobalwarming,heatstressisexpected tobecomeabiggerproblem.Nega‐tive effects of heat stress on fertility havebeen recorded since the 1970’s (Gwazdaus‐kasetal.,1973;1975).Badingaetal. (1985)reportedthatP/AIinlactatingdairycowsde‐creasedfromapproximately48%inFebruaryandMarchtoapproximately20%in JulyAu‐gustandSeptemberasmaximumairtemper‐ature increased from approximately 21 to32°C.Heatstressaffectsfertilizationandparticular‐ly early embryo development. Sartori et al.(2002) observed reduced fertilization andfewergrade1to3embryosrecoveredonday6ofgestationwhenlactatingdairycowswereinseminated during summer compared withAI performed during winter. Similar resultswere observed by Vieira et al. (2014). Theembryo at the very early stages of its devel‐

45



opment, during days 1 to 3 of pregnancy, ishighly susceptible to hyperthermia. Laterduringdays5to8ofpregnancy,embryosbe‐come more resistant to high temperaturesbecauseoftheirincreasedproductionofheat‐shock proteins, particularly heat‐shock pro‐tein 70 after day2 of pregnancy (Ealy et al.,1993; Edwards and Hansen, 1997; Hansenand Aréchiga, 1999). Exposure to high envi‐ronmental temperatures resulted in de‐creased number of small follicles per ovary,alteredfattyacidcompositionofphospholip‐ids from follicular fluid, granulosa cells andoocytes,decreasedembryocleavage, andde‐creased development to the blastocyst stage(Zeronetal.,2001).Suchfindingswerelinkedto changes in oocytemorphology and in thefattyacidprofileoftheoocytemembrane.Asaconsequenceofpooroocytequality,invitrodevelopmental competence of embryos gen‐erated from oocytes obtained from heat‐stressed cows was largely reduced. Similarresponses were observed following in vivoproduction of embryos. Therefore, most ofthenegativeeffectsofheatstresson fertilityaffectprocessesinvolvedwithoocytematura‐tion, fertilization, andearlyembryodevelop‐ment to the blastocyst stage (Wolfenson,2000).The best strategy to minimize the negativeeffects of heat stress is to provide adequatecooling (Collier et al., 2006). Collier et al.(2006) states that successful cooling strate‐gies for lactating dairy cows are based onmaximizingavailableroutesofheatexchange,convection,conduction,radiation,andevapo‐ration, and lists the following strategies forheatabatement:airmovement(fans),wetting(soaking) the cow’s body surface, high pres‐suremist(evaporation) tocool theair inthecow’senvironment,andfacilitiesdesignedtominimize the transfer of solar radiation. AstudyinIsrael(FlamenbaumandEzra,2003)compared farms that employed intensivecooling(cowscooledinboththeholdingandfeedingareasforatotalof10coolingperiodsand7.5cumulativehoursperday),moderatecooling(cowscooledintheholdingareaonlyforatotalof6coolingperiodsand4.5cumu‐

lativehoursperday),and farmsthatprovid‐ednocoolinginsummer(JulytoSeptember).They observed that P/AI for multiparouscowswere46.6,45.8,and43.5%duringwin‐ter (December to February) and 33.8%,34.5% and 16.7% during summer for farmsusing intensive,moderate,ornocoolingreg‐imens, respectively. In primiparous cows,P/AIwere55.8,53.5,and53.9%duringwin‐ter,and40.4,34.0and14.6%duringsummerfor farms using intensive, moderate, and nocoolingregimens,respectively.Thisandotherstudies with similar findings were summa‐rized by Flamenbaum and Galon (2010).Theseresultsshowthatalthoughthenegativeeffects of heat stress cannot be eliminated,they can be largely alleviated with effectivecoolingmethods.Another strategy that has been suggested,and is being implemented in some herds isthetransferofembryoscollectedduringwin‐ter or the transfer of in vitro‐produced em‐bryos.Drost et al. (1999) demonstrated thatthe transfer of in vivo‐produced embryosfrom cows exposed to thermo‐neutral tem‐peratures increasedpregnancyrates inheat‐stressed cows compared with pregnancyratesof cowsafterAI. Similarly, transferringfresh embryos produced in vitro resulted ingreaterP/AIthanAIduringsummer(Blocketal.,2010).Conversely,Demetrioetal. (2007)showed that the probability of pregnancy at28days of gestationwas similar betweenAIand ET (fresh in vivo‐produced embryos)when cows were under heat stress (bodytemperature>40oC),whereastheprobabilitywas greater for ET when body temperaturewas < 39.5oC. Furthermore, pregnancy lossbetween 28 and 42 days of gestation wasgreater for ET compared with AI (21.5 vs10.8%; P = 0.06), and the differences weregreater when cows were under heat stress,whichwouldmakeETinthesummerlessap‐pealing(Demetrioetal.,2007).DiseasesoftheReproductiveTractFertilityisstronglyassociatedwiththehealthstatus of the cow, especially regarding calv‐ing‐relateddisordersanddiseasesthataffect

46



thereproductivetract.Thestageofgestationat which such disorders affect embryonicsurvival, however, ismostly unknown.Dairycows that presented dystocia, metritis, orclinical endometritis were 50 to 63% lesslikely to resumeovarian cyclicityby the endofthevoluntarywaitingperiod(Santosetal.,2011),whichasmentionedbeforehasmajorimplications for embryodevelopment. In ad‐dition, cows that presented at least 1 of thepreviouslyciteddisorderswas25to38%lesslikely tobecomepregnant following the firstpostpartum AI compared with healthy cows(Table3),andwere55to67%morelikelytolose theirpregnancyduringthe first60daysofgestation(Table4).Theexceptionwasthelackof effectofmetritis, althoughanegativeeffectonpregnancylosshasbeenobservedinotherstudies(Ribeiroetal.,2013;Bittaretal.,2014). Although dystocia,metritis, and clini‐calendometritisarelessprevalentingrazing‐basedcows,theirimpactinreproductiveper‐formance is similar to that observed in con‐fined cows (Ribeiro et al., 2013). Those thatpresentedatleast1ofthepreviousdisorderswaslesslikelytobecyclicby49daysinmilk,less likely to become pregnant to the firstpostpartum AI, and more likely to lose thepregnancyduring30to65daysofgestation.It has been suggested that such reduction infertility is related toboth fertilization failureandembryonicmortality.Itisclearthatbothclinical (McDougallet al.,2007;Galvãoetal.,2009) and subclinical (Gilbert et al., 2005;Galvão et al., 2010; Vieira‐Neto et al., 2014)endometritisreduceP/AIincattleandthisislikely the result of reduced fertilization andembryonic survival (Limaetal.,2013).Cowswith subclinical endometritis, diagnosed byincreased neutrophil influx into the uterus,had reduced proportion of fertilized struc‐tures (Cerri et al., 2009c). Using an in‐vitromodel toelucidate theeffectsof intrauterineinflammationonembryonicsurvival,HillandGilbert (2008) cultured bovine embryos inmediaconditionedbyeitherinflamedornon‐inflamed endometrium. Embryos cultured inthe presence of the inflamed‐conditionedmedia had fewer total and trophectoderm

cells, although no major morphologicalchanges were described. Peripartum disor‐dersofthereproductivetracthavelong‐termcarry over effects on fetal viability. High‐producing dairy cows that experienced dys‐tocia and those diagnosed with clinical en‐dometritis were 67 and 55%more likely tolose their pregnancies between the first andsecond month of gestation compared withhealthy cows, respectively (Santos et al.,2011;Table4).Similarly,grazingdairycowspresenting dystocia, metritis, or clinical en‐dometritiswere2to4foldmorelikelytolosetheirpregnanciesduring30to60daysofges‐tation(Ribeiroetal.,2013).Limaetal.(2013)observedthatthegreatesteffectonpregnan‐cy losswaswhencowshadbothclinicalandsubclinical endometritis; those cows had 3.3timestheriskof losingtheirpregnancycom‐pared with healthy cows. The inflammatoryprocess associated with uterine diseasesleads toocclusionof the endometrial glands,dilationof underlying glandswithdeposit ofconnectivetissueandformationofscartissuein the uterus (McEntee, 1990), which mayaffectplacentationandmaintenanceofpreg‐nancy.Furthermore,activationof the inflam‐matory cascade stimulates the release ofPGF2αfromtheendometriumandlutealcells,hence inducing luteolysis (Skarzynski et al.,2005).Cowswithuterinediseaseshavebeen foundtohavedecreaseddrymatterintakepre‐andpostpartum(Hammonetal.,2006;Huzzeyetal., 2007) and decreased immune functionpostpartum. Therefore, strategies that max‐imizedrymatterintakepre‐andpostpartumare expected to have a positive impact onimmune function, decrease the postpartumincidence of uterine diseases, and decreasepregnancylosses.Another very important factor affecting theincidence of uterine disease is hypocalcemia(Martinezetal.,2012;Martinezet al.,2014).In a recent study at University of Florida, itwas observed that inducing subclinical hy‐pocalcemia compromised leukocyte function(Martinezetal.,2014),andspontaneoussub‐

47



clinicalhypocalcemiaresultedinanincreasedincidence ofmetritis (Martinez et al., 2012).In fact, the probability of metritis markedlyincreased as serum calcium concentrationsdecreasedduringthefirst3dayspostpartum(Figure 2;Martinez et al., 2012). A 1mg/dLdeclineinserumcalciumbetweencalvingandthelowestvalueduringthefirst3dayspost‐partumincreasedtheriskofmetritisby28%(adjusted risk ratio=1.28;95%CI=1.10 to1.49).Therefore,strategiestopreventclinicalandsubclinicalhypocalcemiasuchastheuseofacidogenicprepartumdietsareexpectedtohave a positive impact on immune function,decrease incidence of uterine diseases post‐partum,anddecreasepregnancylosses.FeverandMastitisOther diseases not directly associated withthe reproductive tract also have been impli‐cated with impaired embryo survival. Cowswith fevers (> 39.5oC) during the first 2weeks postpartum were 40% less likely toconceive following the first postpartum AIand twice as likely to lose their pregnanciesbetweenthefirstandsecondmonthsofgesta‐tion(Santosetal.,2011;Tables3and4).Bac‐terialmastitiscanbecausedbyeithergram‐negative or gram‐positive organisms. Theformerreleasesendotoxinsfromitslipopoly‐saccharide‐containing cell wall that can in‐duceendogenousreleaseofPGF2α.Similar togram‐negative, gram‐positive bacteria cancause inflammatory responses, pyrexia, andseptic shock. Several studies have demon‐strated the negative effects of mastitis onmaintenance of gestation. Both clinical andsubclinical mastitis are associated with re‐duced conception in dairy cattle (Schrick etal.,2001).Furthermore,cowsthatdevelopedclinical mastitis during the first 45 days ofgestationwere2.7timesmorelikely(95%CI=1.3to5.6)toabortduringthenext90daysofgestationthanhealthyherdmates(Riscoetal.,1999).TheseresultswerelaterconfirmedbySantosetal. (2011;Table4).Santosetal.(2004b) demonstrated that cows developingmastitis before AI, from AI to pregnancy di‐agnosis, and after first pregnancy diagnosishad greater incidence of pregnancy losses

than cows that did not develop mastitisthroughout theentire lactation.Finally, clini‐calmastitiswasalsoassociatedwithreducedP/AI and greater risk for pregnancy loss inpasture‐based systems (McDougall et al.,2005; Ribeiro et al., unpublished results).Furthermore,Hernandezetal.(2011)report‐ed recently that occurrence of mastitis in‐creased the risk of pregnancy loss in cowswith reduced body condition score (BCS ≤2.75)at theendof thevoluntarywaitingpe‐riod, but not in those with a BCS ≥ 3.00.Therefore, additive effects of diseases andpoorbodyfatreservesmightexacerbatetheirimpactson fertilityofdairycowsby increas‐inglossesofpregnancy.Mastitis is a complicatedand costlyproblemfor thedairy farmer.Nosimplesolutionsareavailable for its prevention. Mastitis controlprograms involve: (1)maintainingclean freestalls and bedding; (2) using propermilkingprocedures;(3)regularmaintenanceofmilk‐ing equipment; (4) dipping teats before andaftermilking;(5)treatingcowsatdry‐off;(6)early identification and adequate treatmentofclinicalcases;and(7)cullingfromtheherdchronic,non‐responsivecows,andthosewithcontagiouspathogenssuchasStaphylococcusaureusandMycoplasmaspp.ChangesinBodyConditionScoreMetabolic status of the periparturient high‐producingdairycowiscloselyrelatedtofer‐tility. Cows should be managed to minimizethe negative nutrient balance observed dur‐ing late gestation and early lactation. López‐Gatius et al. (2002) indicated that a 1‐unitdropinBCSfromcalvingto30dayspostpar‐tum increased risk forpregnancy lossby2.4times. Similarly, Silke et al. (2002) observedthatcowsthatlost1unitinBCSfromdays28to 56 of gestation had a 3.2‐fold increase inriskof pregnancy lossduring the sameperi‐od. In U.S. dairy herds, cows with reducedBCSeitheratcalvingoratthetimeofthefirstpostpartumAI are at a greater riskof losingtheirpregnanciesfromday30to58ofgesta‐tion(Santosetal.,2009).Thedetrimentalef‐fectofnegativenutrientbalanceonembryon‐

48



ic or fetalmortality canbedepicted throughchangesinBCSfromcalvingtothetimeofAI.Cows that maintained their body conditionduringthefirst70dayspostpartumandthosethat lost lessthan1unitofBCSwere62and48%less likelyto losetheirpregnanciesbe‐tween the first and second month of gesta‐tion.ThenegativeeffectofBCSlossisproba‐bly at least in part related to its associationwithanovulation.Cowsthatlose>1BCSdur‐ing the first 60 days in milk (Santos et al.,2004a)orlose>28kginthefirst14daysinmilk(Vercouterenetal.,2014)arelesslikelyto be cyclic. Strategies that improve earlypostpartum dry matter intake should helpprevent excessive BCS or body weight lossandtheirnegativeeffectonfertility.ToxinsFoundinFeedstuffsCottonseedisextensivelyusedindietsoflac‐tating dairy cows as a source of protein, fat,and fiber. Cottonseed contains gossypol, apolyphenolic compound produced by thepigmentglandsofthecottonplantthatcanbetoxictomammaliancell.Severalstudieshavedemonstrated that both in vivo and in vitrogossypol influences embryo quality and de‐velopment(HernándezCerónetal.,2005;Vil‐laseñor et al., 2008). When lactating dairycowswerefeddietsdifferinginfreegossypolcontent, thosereceiving thegreatergossypoldiethadreducedP/AIandgreaterfetallosses(Santosetal.,2003).Transferofembryosintolactatingdairycowsfromgossypol‐feddonorheifersreducedP/AIcomparedwithembryosfrom heifers not fed gossypol (Galvão et al.,2006). Diets that increase plasma gossypolposearisktoestablishmentandmaintenanceofpregnancyindairycattle;therefore,shouldbeavoided.Some experimental studies have shown thatmycotoxinssuchaszearalenone inveryhighconcentrations can cause abortions in cattle,although these concentrations are not nor‐mally found in "naturally contaminated"feedstuffs.Likewise,theonlyreportsofabor‐tionsassociatedwithaflatoxinseemtobesit‐uations in which the health of the cow alsowasseverelycompromisedbythetoxin.

Ergot alkaloids are toxins produced by theClavicepsfungus,whichgrowsintheseedsofvariousgrassesandsmallgrainssuchas fes‐cue,bromegrass,wheat,oats,andrye.Thesetoxinshavebeenassociatedwithabortionsindairy cattle as well as causing other healthproblems.InfectiousAgentsAsmentionedpreviously, abortions (lossbe‐tween 42 and 260 days of gestation) repre‐sent only 15% of all pregnancy losses, buttheyarethemostcostly.Inaddition,thesearethelossesthatareeasiertopreventortostopin the case of an outbreak (abortion storm);therefore,theycanbethemostrewardingtoresolve. Most (55 to 77%) of the abortioncases submitted todiagnostic laboratories inthe U.S. go undiagnosed (Anderson, 2007).The best laboratories such as the CaliforniaAnimal Health and Food Safety LaboratorySystem(UniversityofCalifornia‐Davis),diag‐noseapproximately45%oftheabortioncas‐essubmitted.Ofthosewithadiagnosis,infec‐tious agents are the most important causes(Table5).The causative agentwith the larg‐estprevalence(Neosporosis),isalsothemostdifficult to control because no commercialvaccine is available in theU.S. and the para‐site (Neospora caninum) can be verticallytransmitted very effectively (95% efficacy)fromdamto fetus(Dubeyetal.,2007).Sero‐prevalence in the U.S. ranges from 10.3% inTexas to 60.6% in one study in California(Dubeyetal.,2007).Becauseavaccineisnotavailable and vertical transmission is veryefficient, prevention strategies should focuson identifying and segregating or culling se‐ropositiveanimalsandpreventinghorizontaltransmission by avoiding contamination offeed and water with feces from definitivehosts (dog and coyote). The second mostcommonly diagnosed cause of abortion issporadicbacteria.Adiversegroupofbacterialspeciesisassociatedwithopportunisticinfec‐tions of the placenta and fetus resulting inabortion. These bacteria are not contagiouspathogens but are commonly found in theenvironment or on mucosal surfaces. A ma‐

49



ternalbacteremia is thepresumedmeansbywhich they reach the graviduterus and sub‐sequentlyinfecttheplacenta.Bacteremiaisacommon occurrence in cows with metritis,mastitis, and ruminal acidosis,butotherdis‐eases such as pneumonia also may lead tobacteremia. Common bacteria in this groupinclude Trueperella (Arcanobacterium) py‐ogenes, Bacillus spp., Escherichia coli, Hae‐mophilussomnus,Pasteurellaspp.,Pseudomo‐nas spp., Serratiamarcescens, Staphylococcusspp.,andStreptococcusspp.(Anderson,2007).Becausethisgroupofbacteriacausesporadicabortions,goodherdhealthpracticeanddis‐ease prevention should decrease its impactonpregnancy loss.Epizooticbovineabortionis mainly found in cattle grazing foothillrangelandsinCalifornia,Nevada,andOregon.The infection is transmitted to susceptiblepregnantcattlebyanargasidtick(Ornithodo‐rus coriaceus), that feeds on deer and cattle.Following an abortion affected cattle are re‐sistant to repeat abortion (Anderson, 2007).Becausenovaccineforepizooticbovineabor‐tionisavailable,preventingexposureofnaïvecattle to the argasid tick is so far the beststrategytopreventabortions.Leptospirosisisaveryimportantcauseofpregnancylossbe‐cause it cannot only cause abortion but alsoembryonic loss. For years, themajor bovinepathogenic leptospirawaspresumedtobeL.interrogans serovarhardjo.This serovarwasconsidered the most important of the anti‐gens in the pentavalent vaccines that alsocontained serovars pomona, canicola, ictero‐hemorrhagiae,andgrippotyphosa.Incontrast,recent research using genetic sequencingfound thatL. interrogans serovarhardjowasonlyfoundintheU.K.andthemainLeptospi‐ra species found in the U.S. is Leptospiraborgpetersenii,serovarhardjo,typehardjobo‐vis. Serovar hardjo is host adapted to cattleand can establish lifelong infections in theirkidneys and reproductive tracts. Convincingdata have shown that L. hardjobovis is re‐sponsible for not only abortions of estab‐lishedpregnancies,butalsoforreducedP/AI(increased embryonic loss) associated withcarrier cows and bulls (Bondurant, 2007).Currently, vaccines exist that contain L.

hardjobovisseparatelyorincombinationwithother important Leptospira serovars men‐tionedpreviouslyandwiththemainrespira‐tory viruses (BVD, IBR, BRSV, and PI3). Pre‐vention strategies should include: (1) vac‐cinationwith a 5‐way bacterin that includesL.hardjobovisevery6months;and(2)elimi‐nation of infection in carrier animals by ad‐ministrationofantibioticsbefore firstbreed‐ingorduringthedryperiod.Thevaccinepre‐ventsinfection,butdoesnotcureexistingin‐fections.The followingtreatmentshavebeenfound to eliminate the renal carrier state: asingle injectionofoxytetracycline (20mg/kgi.m.); a single injection of tilmicosin (10mg/kgs.c.);ceftiofur(5mg/kgi.m.oncedailyfor 5 days or 20mg/kg i.m. oncedaily for 3days); or amoxicillin (15mg/kg i.m.,2 injec‐tions 48 hours apart); (3) elimination ofsources of infection such as feed or watercontaminatedbydogs, rats,orwildlife (Bon‐durant, 2007). Bovine viral diarrhea virus(BVD) remains an important cause of abor‐tion and its main means of prevention is toeliminate persistently infected animals fromthe herd combined with vaccination againstBVDevery6months.TheBVDvirusisimmu‐nosuppressive and is found in many fetusesinfected by other agents. Outbreaks of abor‐tions by organisms that normally cause spo‐radic abortion should raise suspicionofpos‐sible concurrentBVDvirus infection (Ander‐son,2007).Asmentionedbefore,currentvac‐cinesavailable in themarketaremultivalent(BVD,IBR,BRSV,andPI3);therefore,vaccina‐tionalsoshouldprotectagainst IBR,anotherimportant cause of abortion and early em‐bryonic loss in cattle (Anderson, 2007). My‐coticabortionismainlycausedbyAspergillusfumigatus,andisprobablyaresultoffeedingmoldyfeed.InfectionwithListeriamonocyto‐genes also has been associated with feedingspoiled silage, so rigorous control of qualityof feed being fed to cows should preventthese types of abortions. Campylobacteriosisis a venereal disease causedmainly byCam‐pylobacter fetus subspecies venerealis, alt‐houghC.fetusserovarsfetus,andC.jejunialsohavebeen involved.UseofAI or vaccination(cows and bulls) should prevent abortions

50



(Bondurant, 2007). Salmonella species causesporadic abortions. Most bovine abortionsare associated with Salmonella dublin, butother serotypes can be involved (Anderson,2007). Clinical salmonellosis and abortionsareobservedmostlywhenotherstressorsarepresent;therefore,goodherdhealthpracticesshouldpreventabortions.

ConclusionsRecent studies that provided reliable assess‐ments of fertilizationhave led to the conclu‐sion that more than 60% of all pregnanciesare lost before term in lactating dairy cows.The critical period is from fertilization untilthe end of the differentiation phase (embry‐onic period) inwhich approximately 85%ofthose losses occur. Therefore, strategies topreventembryoniclossesshouldresultinthegreatest improvement in reproductive per‐formance. Nonetheless, although fetal lossesare minor (approximately 15%) comparedwithembryoniclosses,thosearemorecostlythanembryoniclosses;thereforetheycannotbe overlooked. Known risk factors for preg‐nancy loss include prolonged periods of fol‐licular dominance, reduced or basal proges‐teroneconcentrationduringovulatoryfollicledevelopment,heatstress,postpartumdiseas‐es and disorders such as dystocia, metritis,endometritis, mastitis, fever, ketosis, lame‐ness,anddigestiveproblems,negativeenergybalance and excessive bodyweight loss, tox‐insfoundinfeedstuffsuchasgossypol,myco‐toxins, and ergot alkaloids, and infectiousagents suchasNeosporacaninum,Leptospiraspp., Campilobacter spp., BVD virus, and IBRvirusamongothers.Strategiesthatpreventorcontrol the known risk factors should helpdecreasepregnancy loss and improve repro‐ductiveperformance.

ReferencesAhmad,N.,F.N.Schrick,R.L.Butcher,andE.

K.Inskeep.1995.Effectofpersistentfolli‐cles on early embryonic losses in beefcows.Biol.Reprod.52:1129‐1135.

AndersonM.L.2007.Infectiouscausesofbo‐vine abortion during mid‐ to late‐gestation.Theriogenology68:474‐486.

Austin, E. J.,M.Mihm,M. P. Ryan, D. H.Wil‐liams,and J.F.Roche.1999.Effectofdu‐rationofdominanceoftheovulatoryfolli‐cleononsetofestrusandfertilityinheif‐ers.J.Anim.Sci.77:2219‐2226.

Badinga, L.,R. J. Collier,W.W.Thatcher, andC. J.Wilcox. 1985. Effects of climatic andmanagementfactorsonconceptionrateofdairycattleinsubtropicalenvironment.J.DairySci.68:78‐85.

Bittar,J.H.,P.J.Pinedo,C.A.Risco,J.E.Santos,W.W.Thatcher,K. E.Hencken, S. Croyle,M.Gobikrushanth,C.C.Barbosa,A.Vieira‐Neto,andK.N.Galvão.2014.Inducingov‐ulationearlypostpartuminfluencesuter‐ine health and fertility in dairy cows. J.DairySci.97:3558‐3569.

Bisinotto,R. S., R. C. Chebel, and J. E. Santos.2010.Follicularwaveoftheovulatoryfol‐licleandnotcyclicstatusinfluencesfertil‐ity of dairy cows. J. Dairy Sci. 93:3578‐3587.

Bisinotto,R.S.,E.S.Ribeiro,F.S.Lima,N.Mar‐tinez,L.F.Greco,L.F.Barbosa,P.P.Bue‐no,L.F.Scagion,W.W.Thatcher,andJ.E.Santos. 2013. Targeted progesteronesupplementationimprovesfertilityinlac‐tating dairy cowswithout a corpus lute‐umatthe initiationof thetimedartificialinsemination protocol. J. Dairy Sci.96:2214‐2225.

Bertolini,M.,S.W.Beam,H.Shim,L.R.Berto‐lini, A. L. Moyer, T. R. Famula, and G. B.Anderson. 2002. Growth, development,and gene expression by in vivo‐ and invitro‐produced day 7 and 16 bovine em‐bryos.Mol.Rep.Dev.63:318‐328.

Block,J.,L.Bonilla,andP.J.Hansen.2010.Ef‐ficacy of in vitro embryo transfer in lac‐tating dairy cows using fresh or vitrifiedembryosproducedinanovelembryocul‐turemedium.J.DairySci.93:5234‐5242.

Cartmill,J.A.,S.Z.El‐Zarkouny,B.A.Hensley,T.G.Rozell,J.F.Smith,andJ.S.Stevenson.2001.AnalternativeAIbreedingprotocolfordairycowsexposedtoelevatedambi‐ent temperatures before or after calvingorboth.J.DairySci.84:799‐806.

Cerri, R. L., R. C. Chebel, F. Rivera, C. D.Narciso,R.A.Oliveira,M.Amstalden,G.M.

51



Baez‐Sandoval, L. J. Oliveira, W. W.Thatcher,andJ.E.Santos.2011a.Concen‐trationofprogesteroneduring thedevel‐opmentoftheovulatoryfollicle:II.Ovari‐an and uterine responses. J. Dairy Sci.94:3352‐3365.

Cerri,R. L., R. C. Chebel, F.Rivera, C.D.Nar‐ciso,R.A.Oliveira,W.W.Thatcher,andJ.E. Santos. 2011b. Concentration of pro‐gesteroneduring thedevelopmentof theovulatory follicle: I. Ovarian and embry‐onic responses. J. Dairy Sci. 94:3342‐3351.

Cerri, R. L., S. O. Juchem, R. C. Chebel, H. M.Rutigliano,R.G.Bruno,K.N.Galvão,W.W.Thatcher,andJ.E.Santos.2009b.Effectoffatsourcedifferinginfattyacidprofileonmetabolic parameters, fertilization, andembryo quality in high‐producing dairycows.J.DairySci.92:1520‐1531.

Cerri,R.L.,H.M.Rutigliano,R.G.Bruno,andJ.E.Santos.2009a.Progesteroneconcentra‐tion,folliculardevelopmentandinductionof cyclicity in dairy cows receiving in‐travaginal progesterone inserts. Anim.Reprod.Sci.110:56‐70.

Cerri,R.L.,H.M.Rutigliano,R.C.Chebel,andJ.E.P.Santos.2009c.Periodofdominanceoftheovulatoryfollicleinfluencesembryoqualityinlactatingdairycows.Reproduc‐tion137:813‐823.

Cerri,R. L.,H.M.Rutigliano, F. S. Lima,D.B.Araújo, and J. E. Santos. 2009c. Effect ofsourceofsupplementalseleniumonuter‐ine health and embryo quality in high‐producing dairy cows. Theriogenology71:1127‐1137.

Chebel, R. C., M. J. Al‐Hassan, P. M. Fricke,J.E.P. Santos, J. R. Lima, C. A.Martel, J. S.Stevenson, R. Garcia, and R. L. Ax. 2010.Supplementationofprogesteroneviacon‐trolled internal drug release inserts dur‐ing ovulation synchronization protocolsin lactating dairy cows. J. Dairy Sci.93:922‐931.

Chebel,R.C.,J.E.P.Santos,J.P.Reynolds,R.L.A.Cerri,S.O.Juchem,andM.Overton.2004.Factorsaffectingconceptionrateafterar‐tificialinseminationandpregnancylossin

lactating dairy cows. Anim. Reprod. Sci.84:239‐255.

Chenault, J. R., J. F. Boucher, K. J. Dame, J. A.Meyer, and S. L. Wood‐Follis. 2003. In‐travaginal progesterone insert to syn‐chronizereturntoestrusofpreviouslyin‐seminated dairy cows. J. Dairy Sci.86:2039‐2049.

Collier, R. J., G. E. Dahl, and M .J. VanBaale.2006.Majoradvancesassociatedwithen‐vironmental effects on dairy cattle. J.DairySci.89:1244‐1253.

Demetrio,D.G.,R.M. Santos, C.G.Demetrio,andJ.L.Vasconcelos.2007.Factorsaffect‐ing conception rates following artificialinseminationorembryotransferinlactat‐ing Holstein cows. J Dairy Sci. 90:5073‐5082.

Denicol,A.C.,L.G.D.Mendonça,G.LopesJr.,F.A.Rivera,F.Guagnini,J.R.Lima,J.E.P.San‐tos, R.G.S. Bruno, R. V. Perez, and R. C.Chebel. 2012. Low progesterone concen‐tration during the development of thefirst follicular wave reduces pregnancyper insemination of lactating dairy cows.J.DairySci.95:1794‐806.

De Vries, A. 2006. Economic value of preg‐nancyindairycattle.J.DairySci.89:3876‐3885.

Drost, M., J. D. Ambrose,M‐J. Thatcher, C. K.Cantrell,K.E.Wolfsdorf,J.F.Hansen,andW. W. Thatcher. 1999. Conception ratesafter artificial insemination or embryotransfer in lactating dairy cows duringsummer in Florida. Theriogenology52:1161‐1167.

Dubey,J.P.,G.Schares,andL.M.Ortega‐Mora.2007. Epidemiology and control of ne‐osporosis and Neospora caninum. Clin.Microbiol.Rev.20:323‐367.

Ealy, A. D.,M. Drost, and P. J. Hansen. 1993.Developmental changes in embryonic re‐sistance to adverse effects of maternalheatstressincows.J.DairySci.76:2899–905.

Edwards, J.L., andP. J.Hansen.1997.Differ‐ential responses of bovine oocytes andpreimplantation embryos to heat shock.Mol.Reprod.Dev.46:138‐145.

52



Flamenbaum, I., and E. Ezra. 2003. A large‐scalesurveyevaluatingtheeffectofcool‐ing Holstein cows on productive and re‐productive performances under sub‐tropicalconditions.J.DairySci.86(Suppl1):19(Abstr).

Flamenbaum,I.,andN.Galon.2010.Manage‐mentofheatstresstoimprovefertilityindairy cows in Israel. J. Reprod Dev.56:S36‐S41.

Galvão, K. N., M. Frajblat, W. R. Butler, S. B.Brittin,C.L.Guard,andR.O.Gilbert.2010.Effect of early postpartum ovulation onfertility in dairy cows. Reprod. Dom.Anim.45:207‐211.

Galvão,K.N.,L.F.Greco, J.M.Vilela,M.F.SáFilho,andJ.E.P.Santos.2009.Effectofin‐trauterineinfusionofceftiofuronuterinehealthandfertility indairycows. J.DairySci.92:1532‐1542.

Galvão,K.N., J.E.Santos,A.C.Coscioni,S.O.Juchem,R.C.Chebel,W.M.Sischo,andM.Villasenõr. 2006. Embryo survival fromgossypol‐fedheifers after transfer to lac‐tatingcowstreatedwithhumanchorionicgonadotropin.J.DairySci.89:2056‐2064.

Gifford,C.A.,K.Racicot,D.S.Clark,K. J.Aus‐tin, T. R.Hansen,M. C. Lucy, C. J. Davies,andT.L.Ott.2007.Regulationofinterfer‐on‐stimulated genes in peripheral bloodleukocytes in pregnant and bred, non‐pregnantdairycows.J.DairySci.90:274‐280.

Gilbert,R.O.,S.T.Shin,C.L.Guard,H.N.Erb,and M. Frajblat. 2005. Prevalence of en‐dometritisanditseffectsonreproductiveperformance of dairy cows. Theriogenol‐ogy.64:1879‐1888.

Gümen,A.,J.N.Guenther,andM.C.Wiltbank.2003. Follicular size and response toOvsynch versus detection of estrus inanovularandovularlactatingdairycows.J.DairySci.86:3184‐3194.

Gwazdauskas,F.C.,W.W.Thatcher, andC. J.Wilcox. 1973. Physiological, environmen‐tal,andhormonalfactorsatinseminationwhichmayaffect conception. J.DairySci.56:873‐877.

Gwazdauskas, F. C., C. J. Wilcox, and W. W.Thatcher.1975.Environmentalandman‐

agemental factors affecting conceptionrate in a subtropical climate. J. Dairy Sci.58:88‐92.

Hammon,D.S., I.M.Evjen,T.R.Dhiman, J.P.Goff and J. L. Walters. 2006. Neutrophilfunction and energy status in Holsteincows with uterine health disorders. Vet.Immunol.Immunopathol.113:21‐29.

Hansen,P.J.,andC.F.Aréchiga.1999.Strate‐gies for managing reproduction in theheat‐stressed dairy cow. J. Anim. Sci.77:36–50.

Hernandez, J.A.,C.A.Risco,F.S.Lima,and J.E. Santos. 2011. Observed and expectedcombined effects of clinical mastitis andlowbody condition onpregnancy loss indairycows.Theriogenology[E‐pubaheadofprint].

Hernández‐Cerón, J.F.D. Jousan,P.Soto,andP. J. Hansen. 2005. Timing of inhibitoryactions of gossypol on cultured bovineembryos.J.DairySci.88:922‐928.

Hill, J., andR. Gilbert. 2008. Reduced qualityofbovineembryosculturedinmediacon‐ditioned by exposure to an inflamed en‐dometrium.Aust.Vet.J.86:312‐316.

Humblot, P. 2001. Use of pregnancy specificproteinsandprogesteroneassaystomon‐itorpregnancyanddeterminethetiming,frequencies and sources of embryonicmortality in ruminants. Theriogenology56:1417‐1433.

Huzzey,J.M.,D.M.Veira,D.M.Weary,andM.A. von Keyserlingk. 2007. Prepartum be‐havior and dry matter intake identifydairycowsatriskformetritis.J.DairySci.90:3220‐3233.

Lima, F. S., R. S. Bisinotto, E. S. Ribeiro, L. F.Greco,H.Ayres,M.G.Favoreto,M.R.Car‐valho,K.N.Galvão,andJ.E.Santos.2013.Effects of 1 or 2 treatmentswith prosta‐glandin F₂α on subclinical endometritisandfertilityinlactatingdairycowsinsem‐inated by timed artificial insemination. J.DairySci.96:6480‐6488.

López‐Gatius, F., P. Santolaria, J. Yániz, J.Rutllant, and M. López‐Béjar. 2002. Fac‐tors affectingpregnancy loss from gesta‐tionday38 to90 in lactatingdairy cows

53



from a single herd. Anim. Reprod. Sci.57:1251‐1261.

Lucy, M. C. 2001. Reproductive loss in high‐producingdairycattle:wherewillitend?J.DairySci.84:1277‐1293.

McEntee,K.1990.Reproductivepathologyofdomestic animals. Academic Press, Inc.SanDiego,CA.

Mann,G.E.,andG.E.Lamming.2000.Theroleof sub‐optimalpreovulatoryestradiol se‐cretion in theetiologyofpremature lute‐olysisduringtheshortestruscycleinthecow.Anim.Reprod.Fertil.64:171‐180.

Mann,G.E.,G.E.Lamming,R.S.Robinson,andD. C.Wathes. 1999. The regulation of in‐terferon‐tau production and uterine hor‐monereceptorsduringearlypregnancy.J.Reprod.Fertil.Suppl.54:317‐328.

Martinez, N., C. A. Risco, F. S. Lima, R. S.Bisinotto, L. F. Greco, E. S. Ribeiro, F.Maunsell,K.Galvão,andJ.E.Santos.2012.Evaluation of peripartal calcium status,energeticprofile,andneutrophil functionindairycowsatloworhighriskofdevel‐oping uterine disease. J. Dairy Sci.95:7158‐7172.

Martinez,N.,L.D.Sinedino,R.S.Bisinotto,E.S. Ribeiro, G. C. Gomes, F. S. Lima, L. F.Greco,C.A.Risco,K.N.Galvão,D.Taylor‐Rodriguez, J. P. Driver, W. W. Thatcher,and J. E. Santos. 2014. Effect of inducedsubclinicalhypocalcemiaonphysiologicalresponses and neutrophil function indairycows.J.DairySci.97:874‐887.

McDougall, S., R. Macaulay, and C. Compton.2007. Association between endometritisdiagnosis using a novel intravaginal de‐vice and reproductive performance indairycattle.Anim.Reprod.Sci.99:9‐23.

McDougall,S.,F.M.Rhodes,andG.A.Verkerk.2005.PregnancylossindairycattleintheWaikatoregionofNewZealand.NZVet.J.53:279‐287.

Mihm,M.,N.Curran,P.Hyttel,P.G.Knight,M.P.Boland,and J.F.Roche.1999.Effectofdominantfolliclepersistenceonfollicularfluid estradiol and inhibinandonoocytematuration in heifers. J. Reprod. Fertil.116:293‐304.

Peter A. T. 2000. Abortions in dairy cows:new insights and economic impact. Ad‐vancesinDairyTechnology.12:233‐244.

Revah, I., andW. R. Butler. 1996. Prolongeddominanceoffolliclesandreducedviabil‐ity of bovine oocytes. J. Reprod. Fertil.106:39‐47.

Ribeiro, E. S., F. S. Lima, L. F. Greco, R. S.Bisinotto, A. P.Monteiro,M. Favoreto, H.Ayres, R. S. Marsola, N. Martinez, W. W.Thatcher, and J. E. Santos. 2013. Preva‐lence of periparturient diseases and ef‐fects on fertility of seasonally calvinggrazing dairy cows supplemented withconcentrates.J.DairySci.96:5682‐5697.

Risco,C.A.,G.A.Donovan,and J.Hernandez.1999. Clinical mastitis associated withabortion in dairy cows. J. Dairy Sci.82:1684‐1689.

Rivera,F.A.,L.G.Mendonça,G.LopesJr.,J.E.Santos,R.V.Perez,M.Amstalden,A.Cor‐rea‐Calderón, andR.C.Chebel. 2011.Re‐ducedprogesteroneconcentrationduringgrowthof the first follicularwaveaffectsembryo quality but has no effect on em‐bryo survival post transfer in lactatingdairycows.Reproduction141:333‐342.

Sangsritavong,S.,D.K.Combs,R.Sartori,L.E.Armentano, and M. C. Wiltbank. 2002.High feed intake increases liver bloodflowandmetabolismofprogesteroneandestradiol‐17β in dairy cattle. J. Dairy Sci.85:2831‐2842.

Santos,J.E.P.,R.S.Bisinotto,E.S.Ribeiro,F.S.Lima,L.F.Greco,C.R.Staples,andW.W.Thatcher. 2011. Applying nutrition andphysiology to improve reproduction indairycattle.In:ReproductioninDomesticRuminantsVII, Eds.M.C. Lucy, J. L. Pate,M.F.Smith,andT.E.Spencer.NottinghamUniversity Press, Nottingham, UK, pp.387‐404.

Santos, J.E.P., R.L.A. Cerri, M. A. Ballou, G. E.Higginbotham, and J. H. Kirk. 2004b. Ef‐fect of timing of first clinicalmastitis oc‐currence on lactational and reproductiveperformance of Holstein dairy cows.Anim.Reprod.Sci.80:31‐45.

Santos, J. E., C. D. Narciso, F. Rivera, W. W.Thatcher,andR.C.Chebel.2010.Effectof

54



reducingtheperiodof follicledominanceinatimedartificialinseminationprotocolon reproduction of dairy cows. J. DairySci.93:2976‐2988.

Santos, J.E.P., H. M. Rutigliano, and M. F. SáFilho.2009.Riskfactorsforresumptionofpostpartumestrouscyclesandembryonicsurvival in lactating dairy cows. Anim.Reprod.Sci.110:207‐221.

Santos, J.E.P., W. W. Thatcher, R. C. Chebel,R.L.A.Cerri,andK.N.Galvão.2004a.Theeffect of embryonic death rates in cattleontheefficacyofestroussynchronizationprograms. Anim. Reprod. Sci. 82‐83:513‐535.

Santos, J.E.P.,M. Villaseňor, E. J. DePeters, P.H. Robinson, and C. H. Holmberg. 2003.Type of cottonseed and level of gossypolin diets of lactating dairy cows: plasmagossypol, health, and reproductive per‐formance.J.DairySci.86:892‐905.

Sartori,R.,R.Sartor‐Bergfelt,S.A.Mertens, J.N. Guenther, J. J. Parrish, andM. C.Wilt‐bank. 2002. Fertilization and early em‐bryonic development in heifers and lac‐tating cows in summerand lactating anddrycows inwinter. J.DairySci.85:2803‐2812.

Schrick,F.N.,M.E.Hockett,A.M.Saxton,M.J.Lewis, H. H. Dowlen, and S. P. Oliver.2001. Influence of subclinical mastitisduringearlylactationonreproductivepa‐rameters.J.DairySci.84:1407‐1412.

Shaham‐Albalancy,A.,Y.Folman,M.Kaim,M.Rosenberg, and D. Wolfenson. 2001. De‐layed effect of low progesterone concen‐trations on bovine uterine PGF2α secre‐tioninthesubsequentoestrouscycle.Re‐production122:643‐648.

Shaham‐Albalancy, A., A. Nyska, M. Kaim, M.Rosenberg, Y. Folman, andD.Wolfenson.1997. Delayed effect of progesterone onendometrial morphology in dairy cows.Anim.Reprod.Sci.48:159‐174.

Silke, V.,M. G. Diskin, D. A. Kenny,M. P. Bo‐land,P.Dillon,J.F.Mee,andJ.M.Sreenan.2002. Extent, pattern and factors associ‐ated with late embryonic losses in dairycows.Anim.Reprod.Sci.71:1‐12.

Silvestre, F.T.,T. S. Carvalho,N. Francisco, J.E. Santos, C.R. Staples,T. C. Jenkins, andW.W.Thatcher.2011.Effectsofdifferen‐tialsupplementationoffattyacidsduringthe peripartum and breeding periods ofHolstein cows: I. Uterine and metabolicresponses, reproduction, and lactation. J.DairySci.94:189‐204.

Skarzynski,D.J.,J.J.Jaroszewski,andK.Oku‐da. 2005. Role of tumor necrosis factor‐alphaandnitricoxideinluteolysisincat‐tle. Domest. Anim. Endocrinol. 29:340‐346.

Snijders,S.E.,P.Dillon,D.O’Callaghan,andM.P. Boland. 2000. Effect of genetic merit,milk yield, body condition and lactationnumberoninvitrooocytedevelopmentindairycows.Theriogenology53:981‐989.

Stevenson, J. L., J. C. Dalton, T. L. Ott, K. E.Racicot, and R. C. Chebel. 2007. Correla‐tion between reproductive status andsteady‐state messenger ribonucleic acidlevels of the Myxovirus resistance gene,MX2, in peripheral blood leukocytes ofdairyheifers.J.Anim.Sci.85:2163‐2172.

Stevenson, J.S.,D.E.Tenhouse,R.L.Krisher,G.C.Lamb, J.E.Larson,C .R.Dahlen, J.R.Pursley, N. M. Bello, P. M. Fricke, M. C.Wiltbank,D.J.Brusveen,M.Burkhart,R.S.Youngquist,andH.A.Garverick.2008.De‐tection of anovulation by heatmount de‐tectors and transrectal ultra‐sonographybefore treatment with progesterone in atimed insemination protocol. J. Dairy Sci.91:2901‐2915.

Stevenson,J.S.,J.R.Pursley,H.A.Garverick,P.M.Fricke,D.J.Kesler,J.S.Ottobre,andM.C. Wiltbank. 2006. Treatment of cyclingandnoncycling lactatingdairy cowswithprogesteroneduringOvsynch.J.DairySci.89:2567–2578.

Vasconcelos,J.L.M.,R.W.Silcox,J.A.Lacerda,J. R. Pursley, and M. C. Wiltbank. 1997.Pregnancy rate, pregnancy loss, and re‐sponse toheat stressafterAI at2differ‐ent times from ovulation in dairy cows.Biol.Reprod.56(Suppl.1):140(Abstr.).

Vercouteren, M.M.A.A., J.H.J. Bittar, P. J.Pinedo,C.A.Risco, J.E.Santos,A.Vieira‐Neto, andK.N. Galvão. 2014. Factors as‐

55



sociated with early cyclicity in postpar‐tumdairycows.J.DairySci.(Accepted).

Vieira,L.M.,C.A.Rodrigues,M.F.Mendanha,M.F.SáFilho,J.N.Sales,A.H.Souza,J.E.Santos, and P. S. Baruselli. 2014. Donorcategory and seasonal climate associatedwith embryo production and survival inmultiple ovulation and embryo transferprograms inHolsteincattle.Theriogenol‐ogy.82:204‐212.

Vieira‐Neto,A.,R.O.Gilbert,W.R.Butler,J.E.Santos,E.S.Ribeiro,M.M.Vercouteren,R.G. Bruno, J. H. Bittar, and K. N. Galvão.2014. Individual and combined effects ofanovulation and cytological endometritisonthereproductiveperformanceofdairycows.J.DairySci.97:5415‐5425.

Villaseñor,M.,A.C.Coscioni,K.N.Galvão,R.C.Chebel, and J. E. Santos. 2008. Gossypol

disrupts embryo development in heifers.J.DairySci.91:3015‐3024.

Wiltbank, M., H. Lopez, R. Sartori, S.Sangsritavong, and A. Gümen. 2006.Changes in reproductive physiology oflactatingdairycowsduetoelevatedster‐oid metabolism. Theriogenology. 65:17‐29.

Wolfenson, D., Z. Roth, andR.Meidan. 2000.Impaired reproduction in heat‐stressedcattle: basic and applied aspects. Anim.Reprod.Sci.60‐61:535‐547.

Zeron,Y.,A.Ocheretny,O.Kedar,A.Borochov,D. Sklan, and A. Arav. 2001. Seasonalchangesinbovinefertility:relationtode‐velopmental competence of oocytes,membranepropertiesandfattyacidcom‐position of follicles. Reproduction121:447‐454.

Table1.Costofpregnancylossafter1,4,or7months ofgestationbylactationnumberanddaysinmilkatconception1 61daysinmilkatconception 243days inmilkatconception Monthofgestation MonthofgestationLactation 1 4 7 1 4 71 110 279 578 489 739 9622 285 525 756 310 517 9333 336 562 726 121 298 7111AdaptedfromDeVries,2006.

Table2.Riskforpregnancylossbetweenthefirstandsecondmonthsofgestationindairycowsaccordingtocyclicstatus

Pregnancyloss,%(no./no.)Reference Cyclic Anovular PvalueSantosetal.,2004 15.7(195/1,245) 26.3(56/213) <0.001Bisinottoetal.,2010 13.2(235/1,780) 15.0(56/374) 0.17Chebeletal.,2010 8.7(18/207) 13.3(8/60) 0.30Stevensonetal.,2006 16.0(33/208) 31.0(25/81) <0.05McDougalletal.,2005 5(73/1,470) 9(48/534) 0.007Overall 11.2(550/4,910) 15.4(85/552) 0.004Riskratio ‐ 1.4(1.1– 1.7)

56



Table3. Impact of healthproblemsduring the first 60days postpartumonpregnancy at firstpostpartumAIofdairycows1

Healthstatus Pregnant,% AdjustedOR(95%CI)2 PvalueHealthproblem 51.4 1.0

Healthy 43.3 0.8(0.7– 0.9) 0.0011caseofdisease 34.7 0.6(0.5– 0.7) <0.001>1caseofdisease

Typeofhealthproblem3Calvingproblem 40.3 0.8(0.6– 0.9) <0.001Metritis 37.8 0.7(0.6– 0.8) <0.001Clinicalendometritis 38.7 0.6(0.5– 0.7) <0.001Feverpostpartum 39.8 0.6(0.5– 0.7) <0.001Mastitis 39.4 0.8(0.6– 1.1) 0.20Lameness 33.3 0.6(0.4– 0.8) <0.001Pneumonia 32.4 0.6(0.3– 1.3) 0.20Digestiveproblems 36.7 0.8(0.46– 1.3) 0.38

15,719postpartumdairycowsevaluateddailyforhealthdisorderson7 dairyfarmsintheU.S.AdaptedfromSantosetal.(2011).2OR=oddsratio;CI=confidenceinterval.3 Calving problem = includes dystocia, twin birth, stillbirth, and retained placenta, whichwascharacterized by presence of fetal membranes 24 hours after calving; Metritis = watery fetiduterine discharge during the first 14 days postpartum; Clinical endometritis = vaginal mucusscore>2(>10%pusinthemucus);Fever=rectaltemperature>39.5Cduringthefirst14dayspostpartum;Mastitis=presenceofabnormalmilkinatleast1mammarygland;Clinicalketosis=lackofappetiteandpresenceofketonuriausingteststrips;Pneumonia=increasedlungsoundsandrespiratoryfrequencyconcurrentwithfever;Digestiveproblem=indigestioncausedbydis‐placementofabomasum,bloatordiarrhea.

57



Table4.Impactofhealthproblemsduring thefirst60days postpartumonriskofpregnancylossduringthefirst60daysofgestationindairycows1

Healthstatus Pregnancyloss,% AdjustedOR(95%CI)2 PvalueHealthproblem 8.9 1.0

Healthy 13.9 1.7 (1.3 – 2.4) <0.0011caseofdisease 15.8 2.1 (1.4 – 3.2) <0.001>1caseofdisease

Typeofhealthproblem3Calvingproblem 15.9 1.7 (1.2 – 2.4) <0.01Metritis 11.3 1.0 (0.7 – 1.6) 0.76Clinicalendometritis 15.1 1.6 (1.0 – 2.3) 0.03Feverpostpartum 18.0 2.0 (1.2 – 3.1) <0.01Mastitis 19.8 2.6 (1.5 – 4.6) <0.001Clinicalketosis 14.6 1.6(0.8– 3.6) 0.22Lameness 26.4 2.7 (1.4 – 5.1) <0.01Pneumonia 16.7 1.9 (0.4 – 8.7) 0.42Digestiveproblems 15.8 1.8 (0.5 – 6.3) 0.35

15,719postpartumdairycowsevaluateddailyforhealthdisorderson7 dairyfarmsintheU.S.AdaptedfromSantosetal.(2011).2OR=oddsratio;CI=confidenceinterval.3 Calving problem = includes dystocia, twin birth, stillbirth, and retained placenta, whichwascharacterized by presence of fetal membranes 24 hours after calving; Metritis = watery fetiduterine discharge during the first 14 days postpartum; Clinical endometritis = vaginal mucusscore>2(>10%pusinthemucus);Fever=rectaltemperature>39.5Cduringthefirst14dayspostpartum;Mastitis=presenceofabnormalmilkinatleast1mammarygland;Clinicalketosis=lackofappetiteandpresenceofketonuriausingteststrips;Pneumonia=increasedlungsoundsandrespiratoryfrequencyconcurrentwithfever;Digestiveproblem=indigestioncausedbydis‐placementofabomasum,bloatordiarrhea.

Table5.Diagnosisofbovineabortionfrom2,296casespresentedtotheCaliforniaAnimalHealthandFoodSafetyLaboratorySystem,UniversityofCalifornia‐Davis,Davis,CA)1998‐2003)1Totaletiologicdiagnosis 44.4%(1,019/2,296)Categoriesofetiologicdiagnoseswithpercentageofdiagnosedabortions

Sporadicbacteria 24.7%Brucellosis 0.0Listeriosis <1%Salmonelosis 1.6%Leptospirosis 5.9%Capilobacteriosis 3.7%Epizooticbovineabortion 6.5%Mycotic 3.0%Infectiousbovinerhinotracheitisvirus 3.0%Bovineviraldiarrheavirus 4.0%Neosporosis 50.9%

1AdaptedfromAndersonetal.(2007).

58



Figure1.Timingandextentofpregnancylossesinthehigh‐producinglactatingdairycow.Day=dayafterbreeding;CR=conceptionrate.AdaptedfromSantosetal.(2004a).

Figure2. Probabilityofmetritis relative to the change in serumcalcium (Ca) concentrationsbe‐tween the day of calving and the lowest serum Ca concentration during the first 3 days inmilk(DIM).AdaptedfromMartinezetal.(2012).

Fertilization ~ 76%

Viable embryos ~50%

CR ~30%

1 d34%; 7%/d

CR ~40%

CR ~35%

CR ~32%

CR ~28%

6 d

28 d

90 d

42 d

180 d

Term

Day

0 d Oocytes 100%

20%; 0.9%/d

13%; 0.9%/d

9%; 0.2%/d

6%; 0.07%/d

7%; 0.07%/d 63%

61%

58%

54%

47%

34%

Per Period Cumulative

Pregnancy Loss

59



epidemiology of pregnancy losses and practical strategies...

Documents