Superovulatory response and oocyte recovery after ovum pick up in feed restricted heifers with two profiles of AMH
Résumé
Anti–Müllerian hormone (AMH) was found to be a reliable endocrine marker of the population of small antral gonadotropin-responsive follicles in the cow. The measurement of circulating AMH concentrations can help predicting the follicular and ovulatory responses to gonadotrophin treatment in cows (Rico et al., 2009, Rico et al., 2012). The aim of this study was to determine the superovulatory response and the number and quality of oocytes recovered by Ovum Pick Up (OPU) in feed restricted heifers (LWG: 600g/d) with two profiles of AMH. Sixteen Holstein heifers (15.8 ± 1.2 months old; LW: 370±41.2 kg) were grouped according to AMH concentrations: low (L = 1-80 pgmL-1; n=7) or high (H: >150 pgmL-1; n=9). Plasma concentrations of AMH were determined using AMH GENII ELISA kit (Beckman Coulter France, Roissy CDG, France), as described previously (Monniaux et al., 2008). OPU was performed during two periods (P1 and P2) at an interval of 6 weeks. Two OPUs were performed in each period. Before each OPU, estrous cycles were synchronized with subcutaneous 3mg Norgestomet implants (Crestar; MSD, Angers, France) inserted under the convex surface of the ear for 9 days. On the day of implant insertion, heifers received an i.m. injection of GnRH (Receptal®, Intervet, Angers, France). Two days before implant removal, 500 μg cloprostenol (Estrumate®; Schering-Plough, Levallois-Perret, France) were injected. On day 2.5 of the synchronized estrous cycle (day 0 was the day of estrus), heifers were superovulated with a total dose of 300 μg follicle-stimulating hormone (pFSH; Stimufol ; Reprobiol, Belgium) divided into 5 i.m. injections given 12 h apart, at decreasing doses. Cumulus–oocyte complexes were collected by OPU 12 h after the last FSH injection (day 5 of the cycle). Oocytes were graded for quality as, 1, 2, 3 and 4, according to Marquant-Le Guienne (1998). Before OPU all follicles (diameter 3-12 mm) were counted. The statistical analyses (Student’s T test and data correlation) were performed using GraphPadprism. There was a high correlation in both periods 1 and 2 between AMH concentrations and the number of follicles aspirated (P1: r=0.86, P<0.0001; P2: r=0.74, P<0.001), the number of oocytes collected (P1: r= 0.83, P< 0.0001; P2: r=0.81, P < 0.0001) and the number of quality 1, 2 and 3 oocytes (P1: r=0.84, P<0.0001; P2: r=0.82, P<0.0001). Animals with AMH H had significantly higher numbers of aspirated follicles, total oocytes and 1, 2 and 3 quality oocytes than AMH L animals (Table 1). The percentage of 1, 2 and 3 quality oocytes and the percentage of follicles aspirated were similar between AMH H and AMH L. There was no significantly difference between periods. The number of oocytes aspirated was not altered by multiple stimulations.