USING CIDRS IN SHEEP
It’s no surprise for anyone who has been following my Youtube channel, that I try to breed my sheep different times of the year. January, April, July and October.
This is to keep lambing groups somewhat uniform in size, and for even cash flow throughout the year.
However…
Sheep are a bit tricky when it comes to a breeding schedule.
They are seasonal in nature, which means they legit are NOT in the mood when our days get longer.
In Canada, for me, the trickier months to convince a ewe to get her ‘sexy back’ is April and July.
Thankfully, there’s “an app for that”.
I rely on a program that involves CIDRs (Controlled Internal Drug Release) an intravaginal progesterone insert used in the beef cattle, dairy cattle, goat and sheep industries.
In non-scientific terms, how I describe a CIDR, is basically like an IUD for sheep. Meaning, it will stop the ewe’s estrus cycle and when left in for 12-14 days, it will synchronize a group of ewes to come into heat about 24 hours after you pull them (restarts the cycle, and they will all be on that same cycle… in theory.)
NOW… before I get to the nuts (no pun intended) and bolts of this program, there are a few details in the fine print you should know before you visit this site again and tell me it didn’t work.
A CIDR WILL NOT MAKE YOUR SHEEP AUTOMATICALLY BREED, AND IT WILL NOT FIX POOR MANAGEMENT.
Sorry. That was in my yelling font. But hear me out…
Because, I learned all this the hard way.
- Get a vet you can work closely with, establish a vet/client relationship and let them be a part of your team… Trust me on this one. You need them more than you think. Many issues we have with sheep can be predicted and prevented.
- Get a good feed company that takes you seriously as a sheep farmer. Shop around. A relationship with a good feed supplier and nutritionist is gold. Don’t settle for the least cost feed if you get no additional customer service.
- Consider the breed of your sheep. Some ewes are genetically better for breeding out of season than others.
- Your sheep need to be in good health for a successful breeding season. Not too thin, and not too fat. (I’ve had both.)
- I do a couple evaluations on my ewes before I even CONSIDER keeping them for my next breeding group. I check for lumpy udders, hard teat canals, any health issues visible to my eye, any poor lambing observation notes I had made on the ewe, and poor weaning results on their prior lambs.
- Then, about 2 weeks before I breed the ewes (so around the day I insert CIDRs when I use them), I increase the plain of nutrition so the ewe feels a bit of a boost in both energy and protein. Now… in saying this, if a ewe is too skinny, you can start this earlier… if a ewe is too over-conditioned, you can wait… in fact, it may not have much effect at all on the bigger ewes. (My nutritionist makes this ration)
OK, OK GET TO THE POINT.
I was going to type out my protocol, but I found a real good one off a vet website… and they are way smarter than me. So here is where I copy and paste.
Out-of-Season Breeding
Breed and selection ~ There is a large variation between breeds in the length of breeding season. The season for each breed tends to vary around the shortest day (Dec. 21). Breeds with longer breeding seasons will be more likely to breed out of season. If the season for a breed is about 100 days long the season will tend to start 50 days before the shortest day and end 50 days after the shortest day. If the season is 70 days long, it will tend to start 35 days before the shortest day and end 35 days after the shortest day. Southdown, Cheviot and Border Leicester. Hampshire and Suffolk have the shortest season while Dorset, Rambouillet, Merino and Finnsheep have a longer season. Year round breeders are Katahdin, Barbados Blackbelly and St. Croix sheep.
Hormone Control with CIDRs
Insert progesterone impregnated CIDRs for 12-14 days. Upon removal, treat the ewes/nannies with: Folligon, Pregnant Mare Serum Gonadotrophin (PMSG).
Introduce the ram/buck to the females 24 hours after CIDR removal.
Observe all in heat after 48 hours.
The fallout rate of the CIDR varies between farms and seasons. And can be minimized with proper placement.
There is a risk of vaginal infection or injury if the operator is not gentle and with poor sanitation of equipment.
CIDRs are not recommended for first time breeders, due to the risk of injury.
Using CIDRs is the best method of synchronization because the time of ovulation can be more accurately predicted. These products must be obtained from your veterinarian along with the proper protocols including dosage. Typical pregnancy rate results are 50 per cent to 60 per cent of the ewes treated having lambs out of season. CIDRs are an effective aid in synchronizing ewes to breed out-of-season or to tighten lambing seasons.
Cautions. Do not use an insert more than once. To prevent the potential transmission of venereal and blood borne diseases, the CIDR 330 intravaginal insert should be disposed of after a single use.
If loss rates are high, re-evaluate insertion technique.
Contact a veterinarian if abnormal bloody discharge is observed during treatment.
Care must be taken when using the CIDR 330 applicator so as not to damage the vagina. Animals in poor condition resulting from illness or nutritional stress may not respond to this drug. Our staff can assist with CIDR applications, your breeding program, or train you or your staff to properly use CIDR’s.
Taken from ~ http://www.linwoodvet.ca/uploads/7H4TUtli/fallwinter_2013_small_ruminant_newsletter.pdf

Apparently, I’ve done a few things they suggest not to do.. BUT…
I’ve developed my program with my vet, and we are on the same page.
- I do use CIDRs on my first time ewes with actually really good results. But be very gentle and use lots of lube.
- I do not use CIDRs more than once, however, many producers do. They clean them, and put in a paper bag and store somewhere dry. But, I am in no way suggesting to do this. Just gossipping.
- Typically, if my ewes are in decent shape, the weather cooperates, and I don't screw up my management, my CIDR group does quite well in conception rates.
- I aim for 5 ewes for every 1 ram, but I’ve used closer to 3:1 in my July breed with good results.
WHY DO I EVEN BOTHER…
Ok, so why do I use CIDRs when so many sheep farmers don’t. I guess the short answer is that they’ve worked well in my program.
BUT... It doesn’t mean this is your only option for synchronizing sheep.
Farmers all across Canada use different management strategies that work for them. In Quebec, a popular system is a lighting strategy. I won’t go into detail, as I’m less than qualified to discuss, but I know for some, it works really well!
Others use a ‘teaser ram’ which is a vasectomized ram that can be put with a group of ewes before the actual breeding season. Again, google this as I don’t want to describe wrong.
Some use a feed additive called MGA which works very much like a CIDR program with a lot less handling of sheep. But you need a vet for a script if you are going down this road…
At the end of the day, I use this CIDR program to keep my breeding groups somewhat uniform throughout the year. I like lambing in as tight a timeframe as possible as I’m often busy in the fields half of the year and let’s face it, after 21 days of lambing, you just get tired.
AND...
My sheep just need a little ‘Barry White’ convincing a few times a year.

DISCLAIMER…
Mark told me to add this part.
So here we go… I AM NOT A VET. This is a program I have developed with mine and is custom made for MY sheep.
I encourage you (again) to establish a relationship with your own vet and develop a system that will work with you as a farm manager, and your life.
It took me some long, stubborn days to come to this realization myself and haven’t regretted a day since.