International experience has been that cervical insemination of sheep withfrozen-thawed semen usually yields unacceptably low pregnancy rates (10to 30%). An exceptional case has been Norway where non-return rates inon-farm usage are around 60%. The objective of the work described in thisreport was to develop an AI procedure for Irish conditions, based initiallyon Norwegian protocols, using semen from individual rams. Such aprocedure would greatly facilitate and enhance genetic improvementprogrammes for sheep.The work undertaken had two separate aspects:-(i) studies on semen, including processing and freezing methods,laboratory evaluation of semen quality post thawing and therelationship of in vitro evaluation to fertilisation rate in vivo(ii) studies on pregnancy rate following AI in relation to issues such asram breed effects, effects of synchronisation, operator differences andthe role of ewe breed inducing the timing of ovulation and variousphysical and physiological assessments of the cervix at AI.The main results in relation to semen studies were that, while a range ofdifferential staining procedures could be used to objectively evaluate semenwith respect to proportion of live speramatozoa and the integrity of spermcells after thawing, these results were not useful as indicators of fertilisationcapacity in vivo. The in vitro fertilisation (IVF) of sheep oocytes recoveredfrom abattoir material gave promising results as a method for evaluating thefertilisation capacity of frozen-thawed semen. The technique requiresfurther validation.
AGRIP End of Project Reports
Teagasc End-of-Project Reports