Time of Ovulation Relative to Mounting Activity in Dairy Cattle

• Published in: Journal of dairy science Vol. 79; no. 9; pp. 1555 - 1561
• Main Authors: Walker, W.L., Nebel, R.L., McGilliard, M.L.
• Format: Journal Article
• Language: English
• Published: Savoy, IL Elsevier Inc 01.09.1996; Am Dairy Sci Assoc; American Dairy Science Association
• Subjects: Animal productions; Animals; artificial insemination; Biological and medical sciences; Cattle - physiology; CHOIX DE LA DATE; CICLO ESTRAL; COMPORTAMIENTO SEXUAL; COMPORTEMENT SEXUEL; Corpus Luteum - drug effects; Corpus Luteum - physiology; CYCLE OESTRAL; Dinoprost - pharmacology; DURACION; DUREE; ELECCION DE LA EPOCA; estrous behavior; Estrus - drug effects; Estrus - physiology; Estrus Detection; Female; Fundamental and applied biological sciences. Psychology; INSEMINACION ARTIFICIAL; INSEMINATION ARTIFICIELLE; Lactation; Ovary - diagnostic imaging; OVULACION; OVULATION; Progesterone - blood; RACE (ANIMAL); radiotelemetry; RAZAS (ANIMALES); Sexual Behavior, Animal - physiology; SINCRONIZACION DEL CELO; SYNCHRONISATION DE L'OESTRUS; TELEMETRIA; TELEMETRIE; TEMPERATURA AMBIENTAL; TEMPERATURE AMBIANTE; Terrestrial animal productions; Time Factors; Ultrasonography; VACAS LECHERAS; VACHE LAITIERE; Vertebrates; radiotelemetry; CL; artificial insemination; estrous behavior; STP; ovulation; HW; Farming animal; Estrus; Dairy cattle; Ox; Cow; Synchronization; Ovulation; Vertebrata; Mammalia; Investigation method; Artificial insemination; Artiodactyla; Ungulata
• ISSN: 0022-0302; 1525-3198
• DOI: 10.3168/jds.S0022-0302(96)76517-7

Time of ovulation was determined for Holstein cows (n = 51) for estruses occurring spontaneously (n = 33) or those induced by PGF2α (n = 86). Ultrasound examination of ovaries was conducted 42 to 49 d postpartum, followed by administration of 25mg of PGF2α if a corpus luteum was observed. In the absence of a corpus luteum, ovaries were reexamined weekly, and PGF2α was administered upon observation of the presence of a corpus luteum. Onset of estrus was determined by HeatWatch®, an electronic pressure-sensing system that recorded each mount associated with estrus. To determine ovulation in relation to first detected mount, ultrasound examinations were conducted at 12, 20, and 24h after the initial mount and then every 2h until 40h. Cows were assigned randomly to receive one of two treatments: 1) the cow received 25mg of PGF2α 8 to 13 d later or 2) the cow was allowed to cycle spontaneously and then was switched to alternate treatment at a third cycle. The mean estrus period, determined from mounting activity recorded by Heatwatch®, consisted of 10.1 mounts over 9.5h (6.0 mounts were ≥2s) for a total 24.1s of mounting activity. Estrus characteristics were extremely variable and were not different for estruses induced by PGF2α or for those occurring spontaneously. Mean ovulation time relative to first mount was 27.6±5.4h and was not different between spontaneous and induced estruses. Knowing the time of ovulation in reference to the first mount of estrus and being able to identify the first mount consistently and accurately with the HeatWatch® system allows for accurate timing of AI.