RED DEER, Alta. (Staff) – While artificial insemination is a common practice among beef and dairy cattle, the same can’t be said for sheep.
Artificial insemination is more common in the United Kingdom where about 37,000 ewes were impregnated this way in the last year. It’s not as common in Canada although considerable work is done in Quebec where last year about 6,500 ewes were inseminated, researchers told the recent Alberta Sheep Symposium.
The major obstacle is the sheep herself because a ewe’s reproductive tract presents unique problems, said Marg Zillig of the Nova Scotia Agricultural College in Truro, N.S.
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Difficult insertion
A ewe has a tight cervix with four to six irregular rings resembling funnels, with the small ends pointing to the rear. Bypassing these rings with an inseminating rod is difficult, said Zillig.
Although sheep present a challenge, researchers continue to look for artificial insemination methods that can be done easily on farm. Nova Scotia’s most recent on-farm tests where they entered the cervix were variable.
“Results were not as good as we had hoped,” said Zillig.
Conception rates ranged from 17 to 41 percent on five farms. Success was affected by the age of the ewes, the skill of the technician, method of insemination, source of the semen and the environment on the farm.
Among the various methods of artificially inseminating a ewe, the most reliable is the laparoscopic technique developed by Australian researchers.
Under sedation, semen is injected directly into the uterine horns. Because this is minor surgery a vet usually performs the procedure, said Harvey Cole of Olds College.
The technique has been around since 1901 but has only recently become common in the human medicine and veterinary fields.
To start, the animal is sedated and a small puncture wound is made in the abdomen. The puncture causes almost no bleeding, tissue damage nor do adhesions develop later.
Carbon dioxide is then pumped into the area where the surgery will be done. This creates an air space between the end of the scope and the area to be manipulated.
Internal organs seen
A long rod is inserted into the body through the puncture and, by watching a television screen through fibre optics in the scope, the vets can see the internal organs and perform whatever work is necessary.
There is a reduced risk of contamination and antibiotics are rarely needed. Surgery time is shorter, recovery is quicker and there is less trauma compared to traditional surgery of the past.
Conception rates from laparoscopy can be as high as 90 percent but the average seems to be 55 percent, said Cole.
“With good management 75 percent is realistic.”
