Reproduction Abstracts

Introduction: Previous studies have proven the efficiency of GnRH for stimulating both the pulse and amplitude of LH releasing in buffaloes, but not study of kisspeptin efficiency.

Materials and methods: There were three treatments: i) kisspeptin-10 (K-10; a single i.v. of 1000 pmol/kg b.w. dosage), ii) GnRH (a single i.m. injection of 10 μg/cow dosage), and iii) distilled water (DW; a 2 ml single i.v. injection). All six animals were treated and the early luteal phase (day 10 after onset of estrus) was induced by prostaglandin F2α. Blood samples were collected every 15 min between −2 and 3 h and every 30 min after that for the next 3 h for plasma LH analysis.

Results and discussion: The frequency of the LH pulse after treatment with K-10 (mean±S.E.M.) trended greater than after GnRH and DW (2.2±0.4, 1.3±0.3, and 1.7±0.3 peak/6 h respectively). The peak of LH pulsatility occurred after GnRH injection was highest (GnRH 28.2±2.8, K-10 2.1±0.7, and DW 1.3±0.3 ng/ml) and buffalo injected with GnRH also had the the largest area under LH response curves 6 h after treatment (GnRH 2602.7±398.2, K-10 360.1±79.0, and DW 416.6±112.6 min×ng/ml) (P<0.05). In the luteal phase, GnRH treatment stimulated the ovulatory LH surge level but K-10 did not. This could indicate that the negative feedback control in the luteal phase may inhibit kisspeptin induced GnRH releasing in the hypothalamus which might not be enough to activate an LH surge.

Acknowledgements: Thailand Research Fund (Research and Researchers for Industries), Murrah Dairy Ltd Company, Veterinary Science, Chulalongkorn University Graduate Thesis Grant and The 90th Anniversary of Chulalongkorn University Fund (Ratchadaphiseksomphot Endowment Fund).