Effects of FSH and LH on ovarian and follicular blood flow, follicular growth and oocyte developmental competence in young and old mares.

Objectives of the experiment were to determine the effects of mare age and gonadotropin treatments on dominant follicle vascularity, ovarian blood flow and dominant follicle growth and to associate follicular vascularity with oocyte developmental capacity. Growing follicles >30 mm from young (4-9 years) and old (>20 years) mares were assessed for blood flow using color Doppler ultrasonography before maturation induction with recombinant equine LH (eLH) and immediately prior to oocyte collection at 20-24 h after eLH. Pulsed Doppler was used to obtain resistance indices of ovarian arteries ipsilateral to preovulatory follicles. For eFSH-treated estrous cycles, eFSH administration was started after detection of a cohort of follicles ≥20 to <25 mm and continued until a follicle >30 mm. Oocytes were harvested using transvaginal, ultrasonic-guided aspirations and cultured and injected with sperm at 40 ± 1 h after eLH. Presumptive zygotes were incubated, and rates of cleavage (≥2 cells) and blastocyst formation were obtained. Embryos were transferred nonsurgically into recipients' uteri, and pregnancy rates were assessed. Vascularity (number of color pixels per total pixels) was higher (P=0.003) in the follicles of old compared to young mares, with no significant interaction of eFSH or eLH. Effects of eFSH and time from eLH on follicle vascularity were not significant. The vascularity of follicles associated with oocytes that did compared to those that did not form blastocysts was greater (P=0.048), although follicular vascularity was less (P=0.02) for follicles associated with oocytes that did compared to those that did not develop into pregnancies. Resistance indices were not different for age, eFSH treatment, time after eLH administration and oocyte developmental potential. Growth of the dominant follicle was not associated with vascularity, although advanced age tended (P=0.09) to have a negative effect on follicle growth.

Effects of age and equine follicle-stimulating hormone (eFSH) on collection and viability of equine oocytes assessed by morphology and developmental competency after intracytoplasmic sperm injection (ICSI).

Young (4 to 9 yr) and old (>or=20 yr) mares were treated with equine follicle-stimulating hormone (eFSH), and oocytes were collected for intracytoplasmic sperm injections (ICSI). Objectives were to compare: (1) number, morphology and developmental potential of oocytes collected from young v. old mares from cycles with or without exogenous eFSH and (2) oocyte morphology parameters with developmental competence. Oocytes were collected from preovulatory follicles 20 to 24 h after administration of recombinant equine LH and imaged before ICSI for morphological measurements. After ICSI, embryo development was assessed, and late morulae or blastocysts were transferred into recipients' uteri. Cycles with eFSH treatment resulted in more follicles (1.8 v. 1.2) and more recovered oocytes (1.1 v. 0.8) than those without eFSH. Age and eFSH treatment did not effect cleavage, blastocyst and pregnancy rates. Treatment with eFSH had no effect on oocyte morphology, but age-associated changes were observed. In old mares, zona pellucidae (ZP) were thinner than in young mares, and perivitelline space and inner ZP volume (central cavity within the ZP) were larger and associated with oocytes that failed to develop. These results suggest that administration of eFSH can increase the number of oocytes collected per cycle. Oocyte morphology differed with age and was associated with developmental competence.