Using MGA to Enhance Out-of-Season
Breeding in Sheep

Out of season breeding is becoming more popular as producers move to accelerated lambing programs to try and supply product to the marketplace on a year round basis. What can controlled reproduction do? It assists in shortening the lambing period. It also allows the ewes to come into heat out of season so that they can be bred in the spring for an accelerated lambing program.

There are three out of season breeding methods. You can select breeds and genes that are more prone to longer breeding seasons. By controlling lighting you can initiate cycling. Also through the use of hormones you can bring ewes into heat out of season.

Several inquiries have been made recently about the hormonal control of out of season estrus. There are two methods available. One is the use of vaginal sponges and the other is melangesterol acetate or MGA.

Producers are using MGA across the province. This feed additive is commonly used in feedlot heifer rations. It is not licensed for use in sheep and requires a veterinary prescription for use.

The program formula involves feeding 0.125 mg of MGA twice daily for 12 - 16 days. Usually the MGA is formulated into a ewe supplement and fed at 0.25 lbs. per day per ewe. The feedings should be as close to 12 hours apart as possible. Five hours after the last feeding of MGA, 500 IU PMSG should be given.

The timing of MGA feeding and administration of PMSG must be strictly adhered to.

The ewes will come into heat 2 - 2 ½ days after the last feeding of MGA. Rams should be introduced to the ewes 48 hours after the last feeding of MGA.

Research reported by Delma Kennedy, sheep specialist with OMAF shows conception rates of between 75 to 85 % when the PMSG is administered 5 hours after last MGA feeding. This rate drops to 50 to 60 % if the drug is given at 0 hours or after 10 hours post feeding.

Please consult your veterinarian for full protocols. The one draw back of this program is you must be there to feed the ewes twice per day.

The research station at New Liskeard is currently working on a slightly different protocol for synchronizing ewes during the in-season breeding period. Based on a recommendation from Dr. Brian Buckrell of the University of Guelph they are feeding a pellet to give 0.3 mg of MGA per ewe per day, fed twice per day for 14 days. Then 8 hours after the last feeding they are injecting each ewe with 350 IU of PMSG. Their results will be known later on this winter.

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