9) heat detection, natural service and artificial insemination

Babcock Institute for InternationalDairy Research and DevelopmentUniversity of Wisconsin-MadisonDairyEssentials9) HEAT DETECTION, NATURAL SERVICE ANDARTIFICIAL INSEMINATIONMichel A. WattiauxBabcock InstituteINTRODUCTIONEfficiency of reproduction is one of themost critical aspects of a profitable herd.Economic losses resulting from delayedreproduction have multiple facets:• The lifetime milk production of thecows is reduced because peak milkproduction does not occur as oftenand the dry periods are extended;• The number of calves born per yeardecreases, giving fewer opportunitiesto cull cows with low milkproduction, and slowing the possiblegain in the genetic value of a herd;• The direct costs for treatment ofreproductive disorders, breeding andveterinary fees are increased.HEAT DETECTIONIn order to maximize productive life, acow must be bred within 80 to 90 daysafter calving. This will enable her toproduce a new calf every 12.5 to 12.8months. Longer calving intervals havedetrimental effects on lifetime milkproduction.Whether a producer uses artificialinsemination or natural service, heatdetection is a critical component of goodreproductive management on the farm.In either case, recording of cows in heatand dates of services is necessary topredict future heat or calving dates and tomanage the cows accordingly.What is heat?Heat is a period of acceptance for mating(sexual receptivity) that normally occursin non-pregnant, pubescent heifers andnon-pregnant cows. This period ofreceptivity may last from six to 30 hoursand occurs every 21 days on the average.However, the interval between two heatsmay vary normally from 18 to 24 days.Signs of heatDetection of heat calls for acuteobservation. Most cows have a pattern ofbehavior that changes gradually from thebeginning to the end of a heat. The bestindicator that a cow is in heat is when shestands and allows herself to be mountedby herdmates or a bull (Figure 1). A seriesof signs that may help to identify cowsthat need to be observed closely aresummarized in Table 1.Figure 1: A cow is in heat when shestands immobile when mounted byanother cow or bull. A cow that mountsanother cow may or may not be in heat.240 Agriculture Hall, 1450 Linden Dr., Madison, WI 53706 USA, phone: 608-265-4169, babcock@calshp.cals.wisc.edu 33

Dairy Essentials: Reproduction and Genetic SelectionTable 1: Signs of estrus in dairy cowsSTANDING HEAT• Stands immobile when mounted.• Displays signs associated with earlyand late heat.EARLY AND LATE HEAT• Bellows like a bull.• Displays general signs of nervousness.• Rushes forward as if attacking; headto-headposition with another cow isfrequently seen.• Butts or pushes against the sides ofother cows.• Sniffs the vulva or urine of otheranimals; this is sometimes followedby inversion of the nostrils.• Cows circle each other, the one inheat attempting to rest her chin onthe back of the other; this may or maynot lead to mounting activity.• Pink and swollen vulva and clearmucous discharge are visible.INCIDENTAL SIGNS 1• Depressed appetite and milk yield.• Dirty animal (manure on flanks).• Tailhead has roughened appearancewith possible hair loss.1Non-specific signs whose occurrence depends on aparticular situation.Daily patterns in signs of heatThe onset of heat activity follows adistinct pattern, with most activityoccurring in the late evening, through thenight, and in the early hours of themorning. Research shows that more than70% of mounting activity takes placebetween 7:00 at night and 7:00 in themorning (Figure 2). In order to detectmore than 90% of the heats in a herd,cows should be observed carefully in theearly hours of the morning, the late hoursof the evening, and at four- to five-hourintervals during the day.Other factors influencing theexpression of heatExpression and detection of heat may bemore or less easy depending on a numberof factors. For example, the type ofhousing (stanchion barn, free stall,pasture, walking path along a fence, etc.)provides various degrees of ease for thecow to express signs of heat and for theproducers to detect cows in heat. In largerherds, more than one cow may come inheat at the same time. When this occurs,the chance of detecting cows in heatincreases dramatically because mountingactivities also increase considerably. Forexample, two cows in heat at the sametime (sexually active group) cause atripling of mounting activity. In contrast,factors such as high temperature andhumidity, wind, rain, snow, confinedspace, and conditions that may causeslipping, falling or hoof pain tend toinhibit the expression of heat.Percentage of total mounting activities2015105NightNight0 2:00 6:00 10:00 14:00 18:00 22:000:00 4:00 8:00 12:00 16:00 20:00 24:00Hours of the dayFigure 2: Most often, cows express signsof heat during the night.Absence of heatHeat may not be detected in cows for thefollowing reasons:• The cow is pregnant;• The cow has calved and the heatcycle has not yet resumed (silentheat);34 The Babcock Institute

9 - Heat, Service and Insemination• The cow is anestrus because of poornutrition, severe infection of thereproductive tract, or othercomplications after calving;• The cow has cystic ovarian disease;• The producer fails to detect a cowthat actually came in heat.ARTIFICIAL INSEMINATIONArtificial insemination is a technique bywhich semen is introduced artificiallyinto the body of the uterus at the time ofheat in an attempt to cause pregnancy.The major advantages of artificialinsemination may be summarized asfollows:• It provides the opportunity to choosesires that are proven to transmitdesirable traits to the nextgeneration;• It eliminates the cost and danger ofmaintaining a bull on the farm;• It minimizes the risk of spreadingsexually transmitted diseases andgenetic defects (e.g., mule foot);• It has cumulative beneficial effectsover the years.Use of artificial insemination makes itnecessary to develop a system to identifycows and record dates of heats andinseminations. Accurate recording isnecessary to develop good reproductivemanagement on the farm and it providesthe data for breeding associations to keepaccurate herd books.NATURAL SERVICEThe use of bulls for natural serviceremains widespread even in areas whereartificial insemination has proven to bevery effective. Many farmers believe thatpregnancy rates are higher when a bull isused than when artificial insemination isused. However, when heat detection isaccurate and the insemination is properlyperformed, artificial insemination andnatural service give similar breedingsuccess.Continued use of natural service mayseem to be a paradox considering thegenetic advantages of artificialinsemination. However, there are threesituations when the use of natural servicemay be indicated:• When personnel are unwilling orinadequately trained to perform thetasks associated with heat detectionand the technique of artificialinsemination, leading to extremelypoor pregnancy rates;• When long term genetic gain is ofminor importance;• When local conditions do notprovide the infrastructure necessaryfor successful artificial insemination(access to semen, liquid nitrogenstorage tanks, telephones, etc.).Farmers with bulls on the farm shouldnever forget that bulls have caused manyfatal accidents. They represent a realdanger (especially when believed to besafe) and must be handled firmly (with nosigns of fear) and with extreme caution.In addition, bulls may spread sexuallytransmitted diseases (vibriosis andtrichomoniasis). Infected cows maybecome infertile for up to four months;or, if they conceive, early embryonic death(a form of abortion) may occur.TIMING OF SERVICE ORINSEMINATIONArtificial insemination or naturalservice lead to a pregnancy only if thespermatozoa are "at the right place at theright time." The egg is released from theovary about 10 to 14 hours after the end ofheat and can only survive unfertilized forsix to 12 hours. In contrast, thespermatozoa may live up to 24 hours inthe reproductive tract of a cow. Acommon recommendation for the besttiming of artificial insemination is the"morning-evening" rule: cows observedUniversity of Wisconsin-Madison 35

Dairy Essentials: Reproduction and Genetic SelectionWhen to Service a Cow in HeatComing into heat8 hours (0-24 h)Standing heat16 hours (3-30 h)Going off heat8 hours (2-24 h)0 6 12 18 24 HoursArtificial Insemination:Too Early Good Best GoodToo LateTooNatural Service:Early Best Too LateFigure 3: Timing of insemination or natural service for cows in heatin heat in the morning are inseminatedthe same evening, and cows ob-served inheat in the afternoon are inseminated thenext morning.In the case of natural service, the cowand the bull may be allowed to matestarting a few hours after the cow acceptsmounting until the cow refuses to bemounted (Figure 3).CAUSES OF LOWCONCEPTION RATESMore than 90% of the cows in a herdshould require fewer than three servicesto conceive. Possible causes of lowconception rates (less than 50%) may fallinto different categories:1) Problems related to heat detection:• Not servicing a cow that is in heat;• Servicing a cow that is not in heat;• Improper timing of service;• Misidentification of cows leading toerrors in records;2) Problems related to natural serviceor artificial insemination:• A bull with a low fertility;• Improper insemination techniques;3) Cow factors:• Infection of the reproductive tract;• Hormonal disorders;• Obstructed oviducts;• Anatomical defects;• Early embryonic death (cow becomespregnant, but the pregnancy is notmaintained);4) Problems related to nutrition (seeDairy Essentials: “Reproduction andNutrition”).36 The Babcock Institute