Abstract
Simple SummaryIn ovine species, transcervical artificial insemination is not easy to apply, due to the tortuous lumen of the cervix that does not allow the passage of routinely used catheters. Moreover, the quality of frozen–thawed semen in small ruminants is poor and these factors negatively affect the wide spreading of superior genotypes. The aim of this study was therefore to preliminarily test three newly designed insemination catheters, with bent tips of different lengths, in terms of reproductive performances in pluriparous ewes inseminated with frozen–thawed semen. Afterwards, the outcomes of insemination with the best performing catheter were compared to those obtained in ewes previously submitted to surgical incision of cervical folds, a technique that allows transcervical intrauterine deposition of semen. The results obtained indicated that a catheter with a bent tip of 5.0 mm allowed deep and fast intrauterine insemination, leading to pregnancy rates similar to those obtained following surgical incision of the folds. Further tests on the efficiency of the catheter are needed in field conditions and on a larger number of animals to assess the feasibility of the method in wide commercial insemination campaigns.In ovine species, transcervical artificial insemination (TCAI) is limited by the poor quality of frozen–thawed semen and by the convoluted cervical lumen hampering the passage of inseminating devices. The aim of the study was to test the efficiency of three newly designed catheters with bent tips of 3.5 mm, 5.0 mm or 8.0 mm in terms of reproductive performances (experiment 1) and to compare the results of TCAI with the best performing catheter of experiment 1 to those obtained in ewes submitted to surgical incision of cervical folds (SICF) prior to insemination (experiment 2). The following parameters were assessed: time to pass the cervix; depth of cervical penetration; site of deposition of semen; pregnancy (PR); and lambing rates (LR). The results of experiment 1 indicated that the 5.0 mm tip catheter resulted in deeper and faster TCAI and higher PR and LR compared to 3.5 mm and 8.0 mm tip catheters (p < 0.05). In experiment 2, TCAI with the 5.0 mm catheter did not differ from TCAI after SICF in terms of depth of semen deposition, time to pass the cervix, PR and LR (p < 0.05). In conclusion, the use of a catheter that allowed transcervical uterine deposition of semen without excessive manipulation led to satisfactory pregnancy rates.
Highlights
The ovine cervix is characterized by a very narrow and misaligned lumen delimited by funnel-shaped folds that protrude caudally and are often in an eccentric position [1,2]
The results of experiment 1 indicated that the 5.0 mm tip catheter resulted in deeper and faster transcervical artificial insemination (TCAI) and higher PR and lambing rates (LR) compared to 3.5 mm and 8.0 mm tip catheters (p < 0.05)
The problems related to the cervical barrier and the poor fertilizing ability of frozen–thawed semen in ovine artificial insemination have so far been overcome by laparoscopic AI (LAI)
Summary
The ovine cervix is characterized by a very narrow and misaligned lumen delimited by funnel-shaped folds that protrude caudally and are often in an eccentric position [1,2]. The site of deposition of frozen–thawed sperm deep in the cervix (beyond the 3rd–4th fold) leads to consistently higher fertility rates compared to deposition at 1 cm depth in the lumen [3] These observations are supported by the poor pregnancy rates obtained when frozen–thawed semen is deposited in the external os of the cervix, ranging from less than 5% [4,5] to 36% [6]. The problems related to the cervical barrier and the poor fertilizing ability of frozen–thawed semen in ovine artificial insemination have so far been overcome by laparoscopic AI (LAI). This technique has been widely used in recent decades since it allows direct uterine deposition of frozen–thawed semen via laparoscopy. It needs trained veterinarians, anesthesia and expensive equipment to be performed and it should be considered as provisional until an efficient TCAI technique is developed (as reviewed by [10])
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