Estrous characteristics and reproductive outcomes of Holstein heifers treated with 2 prostaglandin formulations and detected in estrus by an automated estrous detection or mounting device

摘要

Dinoprost tromethamine (DIN), a molecule similarto endogenous PGF_(2α), has a half-life of approximately9 min. Cloprostenol sodium (CLO), a synthetic analogof PGF_(2α), has a half-life of approximately 3 h. We hypothesizedthat treatment of Holstein heifers with CLOwould improve estrous detection rate, estrous characteristics,service rate, and overall reproductive performancecompared with DIN. Currently in the UnitedStates, heifers are largely inseminated based on signsof estrus, which is detected visually or with the aid ofmounting detection devices (MD). Automated estrousdetection devices (AED) are becoming more accessibleto producers, but it is not clear whether they presentadvantages in the reproductive management of heifers.Therefore, we hypothesized that the use of an AEDwould improve service and pregnancy rates comparedwith detection of estrus with the aid of a MD. Holsteinheifers (n = 1,019) were enrolled in the experiment at10 to 11 mo of age, when they were fitted with a HeatimeHR LD System (SCR Ltd., Netanya, Israel). At 12mo of age, we paired heifers according to estrous cyclephase and randomly assigned them to treatments in a2 × 2 design: PGF_(2α) formulation (CLO vs. DIN) andestrous detection treatment (AED vs. MD). Heifers inthe AED treatment were detected in estrus only by theHeatime HR LD System, whereas heifers in the MDtreatment were detected in estrus only by the KamarHeatmount Detector (Kamar Products Inc., Zionsville,IN). Treatments with the same PGF_(2α) formulationswere repeated 14 d after the first treatment if heifershad not been detected in estrus. A sub-group of heifershad blood sampled on the day of PGF_(2α) treatment andwithin 24 h of onset of estrus to determine progesteroneand estradiol concentrations. Treatment with CLOreduced the progesterone concentration within 24 h ofonset of estrus compared with DIN (0.04 ± 0.01 vs.0.11 ± 0.01 ng/mL). Among heifers in mid diestrus onthe day of PGF_(2α) treatment, CLO reduced the intervalto estrus compared with DIN (72.0 ± 2.2 vs. 82.4 ± 2.4h). Prostaglandin F_(2α) formulation and estrous detectiontreatment did not affect pregnancy to the first service.The interval between the first and second servicestended to be reduced for the AED treatment comparedwith the MD treatment (24.4 ± 0.5 vs. 25.7 ± 0.6d). Prostaglandin F_(2α) formulation and estrous detectiontreatment did not affect the hazard of pregnancy.Although CLO treatment may shorten the interval toestrus in heifers at mid diestrus compared with DIN,PGF_(2α) formulation did not affect reproductive performance.In the current experiment, no advantages inreproductive performance were observed when estrousdetection was based on an AED compared with a MD.