Effect of administration of the C6 Kisspeptin analogue in jennies in estrus

Abstract

Kisspeptin (KPs) are the most potent stimulating neurotransmitter of GnRH release from GnRH neurons. The administration of KP stimulates LH and/or FSH release. In small ruminants KPs analogues were able to induce an LH surge followed by ovulation in both cyclic and acyclic animals while in mares were able to lead to an increase of the LH/FSH plasma levels but not ovulation. Aim of this study was to compare the endocrinological effect, ovulatory and pregnancy rates effect of C6 KPs analogue in jennies. Ovarian activity of 9 Amiata jennies was monitored daily by transrectal ultrasound for 3 complete estrus cycles in which jennies in estrus were assigned, alternatively, to one of the 3 treatment groups: 50 nmol of the Kps analog C6 twice, 24 hours apart (C6 group); 0.4 mg buserelin acetate once (Bu group); 2 mL of saline once (CTRL group). Blood samples for [LH] were collected g-1 (-24h) g0 (h0, before treatment), h2, h4, h6, h8, h10, h24 (before second treatment with C6), h26, h28, h30, h32, h34, h48and every 24 hours until ovulation. Jennies were inseminated once at h24 with fresh extended semen of a donkey stallion. Pregnancy diagnoses were performed 14 days after ovulation. Significant higher plasma [LH] were found after induction between Bu and CTRL group at h6 and h8 (P<0.05), while tendentially higher differences were found between Bu/C6 groups and CTRL at h10. Five/9, 4/9 and 2/9 jennies of the Bu, C6 and CTRL groups, ovulated between 24 and 48 hours after induction, respectively (P>0.05). Pregnancy rates after artificial insemination were not different among groups (CTRL: 6/9, 66.7%; C6: 7/9, 77.8%; Bu: 6/9, 66.7%; P>0.05). In this study C6 showed to be able to tendentially and limited in time increase plasma [LH], compared to CTRL. Ovulation rates of C6 after induction were comparable to Bu even if not different to CTRL. Pregnancy rates were comparable to what reported in literature for donkey fresh extended semen for each group. Further studies using higher doses and/or more animals are needed.