Ovarian follicular response to oestrous synchronisation and induction of ovulation in Norwegian Red cattle

Abstract

Background: Oestrous synchronisation of cattle has been widely applied to accomplish simultaneous ovulation in animals and facilitate timed artificial insemination. The main aim of this study was to investigate the ovarian follicular growth and ovulatory response to oestrus and ovulation synchronisation in Norwegian Red heifers and cows. Oestrous cycles in 34 heifers and 10 cows from 4 herds were synchronised with two PGF 2α analogue treatments 11 days apart, followed by GnRH analogue treatment for induction of ovulation. Thereafter, the ovaries were examined by ultrasonography at 3 h intervals until ovulation. Results: The luteolytic effect of the PGF 2α analogue was verified in 9 of 10 cows by progesterone contents in milk. Maximum physical activity of the cows occurred on average 69 h after PGF 2α analogue treatment. An ovulatory response was recorded in 95.5% (42/44) of the animals. A significant difference in follicle size at ovulation was found between 2 of the herds. Animals with medium sized and large follicles and heifers aged > 16 months ovulated earlier than other animals. Conclusions: The applied sequence of treatments in the study was shown to be effective in synchronizing and inducing ovulation within a relatively narrow time interval in the Norwegian Red heifers and cows, consistent with findings in other cattle breeds.

Fertility of Holstein cows and heifers submitted to timed artificial insemination and receiving one or two doses (12 h apart) of semen

“…One limitation of the standard Ovsynch program is that synchronized animals ovulate between 24 and 32 h after the second application of GnRH (Pursley et al, 1995). Likewise, other reports indicate late ovulation (30 to 40 h) after the final GnRH application (Berg et al, 2020;Cartmill et al, 2001). Thus, a proportion of cows have delayed ovulation after inducing it.…”

Cervical mucus changes can predict ovulation time in Mithun

“…Determination of ovulation time and growth of corpus luteum: Ovaries were examined every 3 rd hour by realtime transrectal ultrasound from mid-estrus (determined by arborization pattern) thereafter until ovulation as previously described by (Berg et al 2020). The ovulation time, relative to cervical mucus, was recorded as midpoint between when the ultrasound detected the dominant follicle disappearing and its earlier detection with an intact follicle 3 h prior, i.e.…”

Ovarian follicular dynamics, hormonal profiles and ovulation time in Mithun cows (Bos frontalis)

“…Ovaries were examined every 3 h from mid-oestrus (determined by arborization pattern) until ovulation as previously described (Berg et al, 2020). The time of ovulation after the end of oestrus was considered to be the midpoint between the detected disappearance of the DF and previously detected intact follicle, that is ultrasonographic determination of ovulation time minus 1.5 h.…”