Successful transcervical uterine flushing can be performed without or reduced dose of oestradiol benzoate in cervical relaxation protocol in Dorper ewes

Abstract

This study assessed the efficiency of cervical relaxation protocol using none, half or full dose (1.0 mg) of oestradiol benzoate in Dorper ewes subjected to non‐surgical embryo recovery (NSER). Thirty‐six pluriparous ewes received progestogen sponge (60 mg) for 9 days plus eCG administration (300 IU i.m.) 24 hr before sponge removal. Ewes were not mated and were randomly assigned to receive at 16 hr before NSER 37.5 µg d‐cloprostenol i.m. and different doses of oestradiol benzoate: 0.0 mg (0EB group; n = 12); 0.5 mg (0.5EB group; n = 12) or 1.0 mg of oestradiol (1.0EB group, n = 12). All ewes received oxytocin (50 IU) i.v. 20 min before NSER, which was performed 8 days after sponge removal. Corpora lutea were counted by transrectal ultrasonography 24 hr before NSER. After procedure, the ewes were kept in natural breeding period to check their post‐NSER fertility. NSER was performed in 91.7% (33/36) of the animals with overall fluid recovery efficiency over 97% (p > .05). The cervical transposing with Hegar dilator was longer (p < .05) in 0EB (4.2 ± 0.3 min) compared to 0.5EB (1.7 ± 0.3 min) and 1.0EB group (1.5 ± 0.3 min). The cervical transposing with mandrel/catheter was longer (p < .05) in 0EB (2.4 ± 0.5 min) than 1.0EB group (1.3 ± 0.5 min). Overall duration of uterine flushing was 25.4 min with structure recovery rate of 43.5%, with no difference among groups (p > .05). The post‐NSER fertility was higher (p < .05) in 0.0EB (90%) than 0.5EB group (36.4%). In conclusion, NSER can be successfully performed in Dorper ewes by using a cervical relaxation protocol without oestradiol benzoate.

Use of oxytocin to attain cervical dilation for transcervical embryo transfer in sheep

“…Despite the fact that we observed no difference between the treated groups, it was possible to achieve CT rates close to 85% using only oxytocin. Recently, Dias et al (2020) reported CT rates close to 100% in Dorper ewes after administration of a CDP composed of PGF2α and oxytocin (50 IU). Khalifa et al (1992), using a higher dosage (400 IU) and the same method of administration, also reported the efficiency of using only oxytocin for favourable CT outcome (83%).…”

“…This discrepancy in CT between control groups suggests that other variables such as breed, CT technique and operator experience may have an effect on CT rates in sheep. Dias et al (2020) also suggested that there may be a breed effect in response to the same CDP. Another observation is that our transposing rates improved around 20% in the treated groups; however, a considerable amount of animals could have had achieved CT without the influence of hormones.…”

“…However, such concern is not a new topic of debate; since 2006, the European Union has restricted the use of oestrogenic compounds for oestrous synchronization in cattle, and its use is also restricted in the United States (Food & Drug Administration–European Commission, 2020; Lane, Austin, & Crowe, 2008). In Dorper ewes, the reduction of oestradiol dose or its absence in protocols for transcervical uterine flushing has been reported to have no significant effect on fluid recovery or structure recovery rates (Dias et al., 2020), indicating that oestradiol can be eliminated from cervical dilation protocols (CDPs) for non‐surgical embryo recovery (NSER).…”

“…States (Food & Drug Administration-European Commission, 2020;Lane, Austin, & Crowe, 2008). In Dorper ewes, the reduction of oestradiol dose or its absence in protocols for transcervical uterine flushing has been reported to have no significant effect on fluid recovery or structure recovery rates (Dias et al, 2020), indicating that oestradiol can be eliminated from cervical dilation protocols (CDPs) for non-surgical embryo recovery (NSER).…”

Ultrasonographic cervical evaluation: A tool to select ewes for non‐surgical embryo recovery

“…During the first cervical transposing, the number and anatomical arrangement of rings (according to its ‘analog clock’ position and its distance from the central axis) were recorded in both trials for creation of a cervical map (CM; as proposed by Fonseca et al., 2019a and applied by Dias et al., 2020) in the ewes that cervix was completely transposed. The idea is to sketch a schematic sequence of ‘clocks’ (the number of clocks drawn is related to the number of cervical rings).…”