Manipulating The Breeding Season In Sheep Flocks

There are several options available to alter the reproductive cycle of sheep; I am going to discuss the use of vasectomised rams (teasers) and the CIDR ovis synchronisation programme.

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Teaser Rams

Using raddles, teaser rams can identify the ewes that are in heat so that they can be inseminated with high genetic merit semen.

The animals that we select to vasectomise should be animals rejected as a reproductive ram but that are in good body condition and without lameness or any problem that makes it impossible for them to mount the ewes. Following this we should be able to retain teaser rams in our flock for up to three years.

We can also use vasectomised rams with young ewes that are going to have their first heat. It’s known that first contact with a mature tup can provide undue stress for ewe lambs, resulting in poor fertility due to rejecting the ram or not having a regular cycle. Mixing teaser rams with young ewes two months before breeding season means that the ewe gets used to the ram. They also get used to being mounted, which means the fertility in your flock improves so there are more lambs born and the final income would be much bigger. In addition, leaving ewes away from the rams for at least 30 days and then mixing them with the teasers can have a small synchronisation effect in the flock but not as well as other methods like CIDR.

CIDR Ovis Synch

CIDRs are a device that use progesterone to synchronise oestrus in ewes. The benefits include a shorter lambing period, which reduces labour costs and also an advanced breeding season that provides an opportunity to utilise spring grass more efficiently for lamb production. Lambs sold in April and May generate on average a 21%greater return over those sold in the summer months.

CIDRs are very easy to put in and remove using the applicator. Like the cow CIDR, the device has a “T” shape which means that it has good retention rates. The CIDR has to be removed 12 days after insertion followed by a PMSG injection; 1–2 days after that, the ewe should be in oestrus. CIDRs have fewer problems such as vaginal discharge on removal compared to other methods like vaginal sponges.

Moreover, the system has shown to be effective for induction and synchronisation at all stages of the oestrus cycle (see graph below), which makes it very easy to set up AI protocols. This gives us the chance to improve our genetics with the possibility of using semen with high genetics.

In summary, using teaser rams can synchronise our ewes and shorten the lambing season but not as effectively as CIDRs. Using CIDRs, we can synchronise and move our lambing season to the most suitable month for your farm.

If you are interested in either of these techniques to improving the fertility efficiency of your flock, please call the practice on 01332 294929 and we will be very happy to help you.

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