Intracervical application of hyaluronan improves cervical relaxation in the ewe

Artificial insemination (AI) using frozen semen is a key method to enable rapid genetic improvement but its use in the sheep industry is currently limited by poor fertility. Laparoscropic AI is most effective but has not gained popularity due to cost and welfare considerations. Transcervical intrauterine AI (TCAI) may offer a practical alternative but the complex anatomy of the ovine cervix limits adequate penetration of the inseminating pipette. Hyaluronan (HA) is a glycoaminoglycan whose content in the cervix increases at oestrus and which may contribute to the degree of natural relaxation observed at this time. This study investigated the effect of intracervical application of HA on the depth of cervical penetration in sheep. Oestrus was synchronised on three occasions in 48 Welsh mountain ewes with progesterone sponges and PMSG. Each animal initially served as its own untreated control. Ewes were subsequently treated intracervically with 25 mg of: (2i) low molecular weight (MW) HA; (2ii) high MW HA or (2iii) both low and high MW HA (n = 16/group) at 52 h after sponge removal or with low MW HA at: (3i) 50 h; (3ii) 52 h or (3iii) both 50 h and 52 h. Depth of cervical penetration measured at 54 h was increased from 1.22 cm to 3.66 cm by treatment with low MW HA (P ≤ 0.001), with no differences between the number of treatments (1 or 2) or the time at which the HA was administered (50 or 52 h). High MW HA alone or together with low MW HA had no effect. In conclusion, intracervical application of low MW HA 52 h after sponge removal increases cervical penetration up to 3.4cm to allow TCAI in sheep.