Effects of controlled breeding on cervicovaginal mucus and fertility of the merino ewe

Cervicovaginal mucus (CV) from Merino ewes was more abundant, clearer and less proteinaceous during oestrus than the luteal phase. Superovulation (SOV) markedly increased mucus production and total protein concentration while Prostaglandin-F2α synchronisation (PGF2α) significantly reduced volume. Mucus pH (oestrus 6.2-6.5), biochemical profile and penetration by spermatozoa were unchanged by SOV and oestrus synchronisation with progesterone (P4) or PGF2α. Quantitative and qualitative proteomic analysis of CV mucus identified significant proteomic changes between oestrus and luteal phases. SOV and P4 altered CV mucus protein abundance at oestrus, compared to naturally cycling ewes (NAT). Variation in the percent composition of mucin, a gel forming protein, and amount of the enzyme neuraminidase (NEU1) which denatures mucin proteins, was investigated in vitro. Variable mucin and NEU1 concentrations altered the viscosity of a CV mucus simulant, the motility and viability of spermatozoa, and the mucus migrating ability of frozen-thawed spermatozoa. This thesis culminated in an investigation of oestrus synchronisation (P4 or PGF2α) on the ability of fresh, chilled and cryopreserved ram spermatozoa to traverse the cervix. PGF2α ewes had significantly lower pregnancy rates than NAT and P4 ewes (6%, 17% and 25%, respectively). Ewes inseminated with cryopreserved semen had lower pregnancy rates than those inseminated with chilled or fresh semen, though not significantly so (10%, 20% and 17%, respectively). Fertility data undoubtedly indicates that PGF2α synchronisation markedly limits the ability of ram spermatozoa of any type to traverse the cervix. This thesis confirms that exogenous hormones used for oestrus synchronisation and superovulation results in altered mucus production and characteristics, leading to a significantly altered CV environment, which may contribute to the decreased ability of spermatozoa to traverse the cervix in vivo and thus fertility in the ewe