Additionally , breeders were until recently unable to control their ewe 's estrus cycles .
Unlike cattle or goats , which have straight cervices that can be vaginally inseminated , ewes have a curved cervix which is more difficult to access .
Breeders were until recently unable to control their ewe 's estrus cycles .
Unlike cattle or goats , which have straight cervices that can be vaginally inseminated , ewes have a curved cervix which is more difficult to access .