Time of Ovulation Relative to Mounting Activity in Dairy Cattle

Abstract

Time of ovulation was determined for Holstein cows (n = 51) for estruses occurring spontaneously (n = 33) or those induced by PGF2 alpha (n = 86). Ultrasound examination of ovaries was conducted 42 to 49 d postpartum, followed by administration of 25 mg of PGF2 alpha if a corpus luteum was observed. In the absence of a corpus luteum, ovaries were reexamined weekly, and PGF2 alpha 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 24 h after the initial mount and then every 2 h until 40 h. Cows were assigned randomly to receive one of two treatments: 1) the cow received 25 mg of PGF2 alpha 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 9.5 h (6.0 mounts were > or = 2 s) for a total 24.1 s of mounting activity. Estrus characteristics were extremely variable and were not different for estruses induced by PGF2 alpha or for those occurring spontaneously. Mean ovulation time relative to first mount was 27.6 +/- 5.4 h 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.

Expression and detection of oestrus in cattle

“…Periodically during the day the farmer checks the computer for a listing of cows in heat. The limited data available suggests that HeatWatch operates with both an efficiency and accuracy of almost 100% in detecting cows in heat [14,22,27,29]. The limited data from this laboratory suggests that HeatWatch is an extremely powerful research tool, operates well under both indoor and pasture conditions.…”

Expression and detection of estrus in dairy cows: the role of new technologies

“…These technologies include rump-mounted devices and androgenized females (Gwazdauskas et al, 1990), pedometry (Peralta et al, 2005;Roelofs et al, 2005) and radiotelemetric devices that monitor mounting activity (Walker et al, 1996;Dransfield et al, 1998;Xu et al, 1998). Increased physical activity is a secondary sign of estrus in cattle, and pedometry systems that detect changes in the number of steps per unit time have been available for many years with some adoption by the dairy industry in the United States.…”

Preovulatory follicle diameter, growth rate and time of ovulation during induced oestrus using a CIDR® in trypanotolerant female Bos taurus N’Dama cattle

“…To optimise the results of fertilisation and to improve gestation rates among N'Dama cattle, it is important to consider identifying the best time for systematic insemination in relation to ovulation. Ovulation takes place 26.7±5.4 h after the start of heat in dairy breeds (Walker et al 1996). The interval between stopping progesterone-based treatment and ovulation varies between 69.6±2.4 h to 73.1±1 h in the Zebu Nelore (Sà Filho et al 2010a) and from 65.4±2.2 to 66.0±3.3 h in other dairy breeds (Uslenghi et al 2014).…”