title: Oestrous behaviour and timing of ovulation in relation to onset of oestrus and LH peak in Mithun (Bos frontalis) cows.
abstract: The objectives of the study were to evaluate the oestrus behaviour and to determine the timing of ovulation in relation to onset of oestrus and the pre-ovulatory LH surge in mithun (Bos frontalis). For this purpose, the blood samples collected at 15-min intervals for 9 h period following onset of oestrus and thereafter, at an interval of 2 h till 4 h post-ovulation for three consecutive cycles from 12 mithun cows were assayed for plasma LH and progesterone. Ovulation was confirmed by palpation of ovaries per rectum at hourly intervals. Various signs of behavioural oestrus were also recorded. The common signs of oestrus and their frequency of occurrence in mithuns were following and mounting by male mithuns (100%), standing to be mounted (100%), frequent urination (62.33%), raising of tail (65.23%), swelling of vulva (54.26%) and congestion of vulvar mucous membrane (69.87%). The pre-ovulatory LH surges consisted of several pulses (2.92 +/- 0.26 pulses/animal; range, 1-4). The mean (+/-SEM) peak level of LH for individual mithun varied from 6.99 +/- 0.44 to 12.69 +/- 2.10 ng/ml and the mean pooled LH peak concentration was 9.10 +/- 0.60 ng/ml. The highest peak (highest amplitude of LH during LH surge) was 10.83 +/- 0.76 ng/ml (range, 8.07-16.49 ng/ml). The duration of LH surge was 6.98 +/- 0.22 h (6-8 h). Onset of LH surge was at 1.23 +/- 0.17 h post-oestrus onset (range, 0.25-2.25 h). Mean plasma progesterone stayed low (<0.24 ng/ml) during the entire duration of sampling. Ovulation occurred at 26.92 +/- 0.31 (range, 26-29 h) after the onset of oestrus and 18.63 +/- 0.35 h (range, 17-20.75 h) after the end of LH surge. The occurrence of the highest LH peaks within a narrow time frame of 2- to 5-h post-oestrus onset in mithuns could have contributed to the animals ovulating within a narrow time interval. These results are very promising from a practical standpoint of potential success when AI program in this species is implemented in a big way. Furthermore, the results of the occurrence of LH pulses during pre-ovulatory LH surges, which are required for ovulation in this species of animals, is unique and species specific.
authors.affiliation: Animal Endocrinology Laboratory, National Research Centre on Mithun (ICAR), Jharnapani, Medziphema, Nagaland, India. mohan_mondal@rediffmail.com
authors.forename: M
authors.initials: M
authors.lastname: Mondal
authors.forename: C
authors.initials: C
authors.lastname: Rajkhowa
authors.forename: B S
authors.initials: BS
authors.lastname: Prakash
mesh_terms: D000818:Animals; D002417:Cattle / Q000097:blood / Q000502:physiology*; D004971:Estrus / Q000502:physiology*; D005260:Female; D007986:Luteinizing Hormone / Q000097:blood*; D010060:Ovulation / Q000502:physiology*; D011374:Progesterone / Q000097:blood; D012726:Sexual Behavior, Animal / Q000502:physiology; D013045:Species Specificity; D013997:Time Factors
chemical_list: D011374:Progesterone; D007986:Luteinizing Hormone