29 March 2002

Simple method of sheep AI proves successful in trial

By Jessica Buss

INSEMINATING ewes using a technique which trained flockmasters can perform has proved just as successful as cervical insemination in a Norwegian trial.

Vaginal insemination is simple enough for each producer to inseminate his own ewes because only an insemination pipette is required, reports the research group headed by Heiko Paulenz. In the Vet Record, he says the cervical method is expensive because it requires specialist equipment and training.

But there is a demand for AI because it allows co-operative breeding schemes to use the same rams on different farms, now regulations restrict ram movement between farms, he says.

In the trial, 1300 Norwegian crossbred ewes on 52 farms were inseminated with liquid semen, by the producers, following training in both insemination techniques. Semen was produced by nine rams at an AI station, where it was diluted and cooled before being distributed to farms, all within four hours travelling time, for use on the same day as collection.

Ewes were inseminated to natural oestrus 12-24 hours after identification, with most farms using teaser rams to aid heat detection.

Non-return rates 25 days after insemination were the same for both methods at about 56%, when straws contained 75m sperm. However, when 150m sperm were included in each straw, results were improved by 7%, so using a higher dose of semen improved the success, says Dr Paulenz.

"But there were differences between the non-return rates of ewes inseminated from different rams. And there was a wide range in the fertility results achieved by individual producers." Three producers achieved non-return rates above 80% and one was below 30%. &#42

A simple method of sheep AI has proved as successful as the cervical technique (pictured), a Norwegian trial reports.

Cervical Vaginal

75m sperm 56% 57%

150m sperm 64% 63%