title: Timing of ovulation in relation to onset of estrus and LH peak in yak (Poephagus grunniens L.).
abstract: The objective of the study was to determine the timing of ovulation in relation to onset of estrus and the preovulatory LH peak in yaks. For this purpose, a sensitive LH enzymeimmunoassay previously established in buffaloes was successfully validated for measuring the hormone in yak plasma. Plasma LH and progesterone were estimated from blood samples collected from eight non-lactating cycling yaks at 2 h intervals after estrus onset until 6 h after ovulation (ovulation was confirmed by palpation of ovaries per rectum). The mean+/-S.E.M. preovulatory plasma LH peak was 10.11+/-0.35 ng/ml with the values ranging from 8.75 to 11.51 ng/ml in individual yaks. The mean+/-S.E.M. duration of the LH surge was 7.25+/-0.55 h with a range of 6-10 h. Onset of LH surge (mean+/-S.E.M.) occurred 3.0+/-0.65 h after the onset of estrus. Mean plasma progesterone stayed low (<0.25 ng/ml) during the entire duration of sampling. Ovulation occurred 30.5+/-0.82 h (range, 28-34 h) after the onset of estrus and 20.25+/-1.03 h after the end of LH surge. The occurrence of the LH peaks within a narrow time frame of 4-8h post estrus onset in yaks could have contributed to the animals ovulating within a narrow time interval.
authors.affiliation: National Research Center on Yak, Dirang, Arunachal Pradesh 790101, India.
authors.forename: M
authors.initials: M
authors.lastname: Sarkar
authors.forename: B S
authors.initials: BS
authors.lastname: Prakash
mesh_terms: D000818:Animals; D002417:Cattle; D004971:Estrus / Q000502:physiology*; D005260:Female; D007124:Immunoenzyme Techniques; D007986:Luteinizing Hormone / Q000097:blood* / Q000502:physiology*; D010060:Ovulation / Q000502:physiology*; D011374:Progesterone / Q000097:blood; D015203:Reproducibility of Results; D013997:Time Factors
chemical_list: D011374:Progesterone; D007986:Luteinizing Hormone