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dc.contributor.authorGrove, Mary Bethen_US

Estrus detection programs practiced on most U.S. dairy farms are not intense enough to provide the information needed to accurately time insemination, thus preventing AI from obtaining its full conception rate potential. Herds (n = 17) participated in a trial designed to evaluate percent pregnant relative to various characteristics of estrus. Herds utilized HeatWatch® electronic estrus detection system to detect and record mounting activity for cows in estrus. Inseminations were performed daily during a three hour interval for all cows identified in estrus the previous 24 h. Model characterizing percent pregnant for cows (services = 2661) included effects of interval from first mount to AI (P < 0.01), mounts per estrus (P < 0.01), DIM at insemination (P < 0.01), herd (P <0.05), and season of AI (P < 0.05). As mounts per estrus and days in milk increased, percent diagnosed pregnant increased. Interval affected probability of pregnancy with highest odds ratios for percent pregnant occurring >4 to 16 h following onset of estrus. Model for heifers (n = 306) included linear effects of interval (P < 0.01), season (P < 0.05), and herd (P < 0.01). In dairy heifers, as interval from first mount to AI increased, percent pregnant decreased. Timing of insemination in dairy cows can now be performed relative to first mount of estrus, with highest probability of pregnancy occurring between >4 to 16 h after onset. If onset of estrus is not known, insemination should be performed at the next most convenient time within 3 h.

dc.publisherVirginia Techen_US
dc.subjectestrus detectionen_US
dc.subjectartificial inseminationen_US
dc.subject.lccLD5655.V855 1996.G768en_US
dc.titleOptimal time of insemination in dairy cattle identified in estrus by HeatWatchen_US
dc.contributor.departmentDairy Scienceen_US
dc.description.degreeMaster of Scienceen_US of Scienceen_US Polytechnic Institute and State Universityen_US Scienceen_US
dc.contributor.committeechairNebel, Raymond L.en_US
dc.contributor.committeememberPearson, Ronald E.en_US
dc.contributor.committeememberBailey, Thomas L.en_US
dc.contributor.committeememberVinson, William E.en_US

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