Complex sentence: A few kennels breeding their ancestors, the St. John's water dog, were in England; at the same time a combination of sheep protection policy (Newfoundland) and rabies quarantine (England) led to their gradual demise in Canada.
Split into simpler sentences: A few kennels breeding their ancestors, the St. John's water dog, were in England. At the same time, a combination of the sheep protection policy in Newfoundland and rabies quarantine in the United Kingdom, led to their gradual demise in Canada.