Progesterone, oestradiol-17  and LH during the oestrous cycle of muskoxen (Ovibos moschatus)

Abstract

Summary. Progesterone, oestradiol-17\g=b\ and LH were measured in plasma from 6 non-pregnant, captive, female muskoxen during the 1984 and 1985

Estrous synchronization and the male effect in captive muskoxen

“…As in the previous study, physical contact appears necessary to elicit a response (Rowell et al 2003). The interval between mating (ovulation) and measurable P 4 in maternal circulation averaged 3.4 d (BRED group, this study), similar to a 4-5 d interval in a previous study of the muskox estrous cycle (Rowell and Flood 1988). The 7.2-d interval between CIDR removal and apparent CL function (elevated P 4 ) in this study is comparable with an 8.5-d interval between bull introduction and apparent CL function in untreated muskoxen exposed to a bull.…”

“…Nonetheless, the modified CIDR produced high P 4 levels (mean ± SD) of 4.9 ± 2.39 ng mL -1 for the BRED group and 4.8 ± 1.79 ng mL -1 for the CTL group (Fig.1). This is approximately twice mean luteal concentrations of 2.07 ng mL -1 (CTL this study; subsequent cycle) and 2.69 ng mL -1 (range 1.4-5.3 ng mL -1 ) from previous work (Rowell and Flood 1988).…”

“…This is considerably lower than the 54% incidence of short estrous cycles previously reported in muskoxen not pre-treated with progestins (Rowell et al 2003). Short estrous cycles are a normal occurrence in muskoxen at the transition to the breeding season (Rowell and Flood 1988), similar to sheep (Legan et al 1985). The fact that exposure to P 4 at concentrations greater than normal luteal levels prevented short estrous cycles supports the assumption that, in muskoxen as in sheep, transient P 4 serves to coordinate follicular development and pituitary feedback mechanisms for the initiation of full-length estrous cycles (Legan et al 1985).…”

Relationship between Conception Date and Latitude in Muskoxen

“…Second, all values (» = 260) that lay more than 20 days after the first calving in the main group at each location were excluded in order to avoid animals that had not conceived at the first mating. Twenty days is the length of the oestrous cycle in muskoxen (Rowell & Flood, 1988). The total number of records was 657 and 392 of these were included in the final analysis.…”

“…In larger species with long reproductive cycles such as red deer (Fletcher, 1974), deer of the genus Odocoileus (Bronson, 1985;Lee, 1970) and North American wild sheep (Bunnell, 1982; Thompson et al, 1982) (Teal, 1959) and this was born out by more recent studies (Rowell & Flood, 1988). Because, superficially, advancing reproduction when spring is delayed would seem to be countetintuitive, a more detailed survey of available data was conducted.…”