7 KISSPEPTIN SLOWLY ADMINISTERED DURING PROESTRUS IMPROVES FOLLICLE GROWTH AND OVULATION IN ANESTROUS COWS

Abstract

This study evaluated whether kisspeptin (Kp) administered slowly from the moment of prostaglandin F_2α (PGF) treatment for fixed-time AI protocol of anestrous cows provides suitable dominant follicle (DF) growth similarly to eCG. Postpartum, anestrous, primiparous Nelore cows (n = 50; <8-mm follicles with no corpus luteum) and lean (body condition score 2.7 ± 0.1; 0–5 score scale) were enrolled. On Day 0, females received an intravaginal device with 1.0 g of progesterone (Sincrogest®, Ourofino, Brazil) and 2 mg of oestradiol benzoate IM (Sincrodiol®, Ourofino, Brazil). On Day 8, the device was removed, and cows were administered 500 μg of sodic cloprostenol IM (Sincrocio®, Ourofino, Brazil) and 1 mg of oestradiol cypionate IM (E.C.P.®, Zoetis, Brazil). Females were blocked by dominant follicle diameter and allotted in following groups: (1) control (CTRL), 1.5 mL of saline IM; (2) eCG, 300 IU IM of eCG (Novormon®, Intervet, Brazil); and (3) Kp SC with an osmotic minipump (9.65 μg kg^–1 of Kp diluted in saline) over 48 h. Dominant follicle growth and ovulation evaluation were performed by ultrasound at 0, 24, 48, 60, 72, 84, and 96 h after PGF treatment. Dominant follicle growth rate was calculated by difference on DF from 0 to 48 h. Ovulation dispersion was analysed by proc GLIMMIX of SAS (SAS Institute Inc., Cary, NC, USA). Follicle variables, ovulation rate, and interval from PGF to ovulation were analysed by orthogonal contrast. Differences were considered when P < 0.05, and tendencies were considered when P < 0.1. There were no difference between CTRL and growth promoters (eCG and Kp) or between growth promoters on DF diameter at 0 h, larger follicle registered from 0 h to ovulation, ovulatory DF diameter, ovulation rate, and interval between PGF treatment and ovulation (Table 1). Dominant follicle diameter at 48 h was larger for growth promoters than for CTRL. Treatment with Kp proved as efficient as eCG in the DF growth rate, with tendency (P = 0.1) to be greater than CTRL. Data from our laboratory (Sales et al. 2011 Anim. Rep. Sci. 124, 12–18.) with same model and animal profile (n = 150 per group) presented positive effect of eCG treatment for growth and size of DF. Cows treated with Kp ovulated in only 3 specific times (60, 72, and 84 h), unlike eCG (48, 60, 72, and 84 h) and CTRL (24, 48, 60, 72, 84, and 96 h; P > 0.05). Also, it is noted that Kp treatment dose and releasing does not cause negative effect on follicle growth and ovulation (down-regulation on LH releasing) or alteration on interval of PGF treatment to ovulation. Thus, synchronized anestrous cows treated with Kp delivered slowly during proestrus have similar results to eCG on follicle growth and ovulation.

Table 1.  Ovarian variables of anestrous Nelore cows treated with saline, eCG (300 IU), or kisspeptin (Kp; 9.65 μg kg^–1). Data were analysed by orthogonal contrast, where C1 = growth promoter (eCG and Kp) v. control; C2 = eCG v. Kp