Tuesday, June 29, 2010
One of the most exciting things about the world we live in, is its ability to continually create new life. New life, whether plant or animal, is enthralling and exciting to most everyone. Participating with and observing the generation of new life in horses is one of the more rewarding parts of being an equine vet.
Breeding season is just about wrapped up for the year, except for a few problem breeders and some performance horses. Overall, we noticed a significant decline in the number of mares being bred this year. This is certainly an understandable, given the current economic climate, especially here in Michigan, and the challenge of marketing horses in this environment. That said, we continue to do a significant amount of breeding work.
This year we have had good success breeding mares with frozen semen. It seems the industry trend is starting to shift toward the use of frozen semen, rather than fresh cooled, though the vast majority of mares are still breed with fresh cooled semen. Breeding with frozen semen is a bit more challenging, because the sperm do not survive after thawing nearly as long as what they do with fresh cooled. Because of that, it is very important to be ‘spot on’ with the timing of breeding. We work very hard to breed these mares within 6 hours of ovulation. In our experience, mares bred with frozen semen tend to have more of a uterine inflammatory reaction than those bred with fresh cooled. Because of this, we usually lavage (rinse out) the uterus of these mares after breeding.
Most mares, however, are still bred with fresh cooled semen. With fresh cooled semen the stallion is collected and the semen is sent to us for delivery the next day. This continues to be the industry standard for breeding mares and we see very good conception rates with this method. The biggest challenge we have had this year with this seems to be the growing unreliablity of fed-ex to get the shipment here the next day. We have had a number of instances, where for whatever reason, the package has not been delivered on time. Then when the package does finally arrive the mare has already ovulated. These occasionions are extremely frustrating for both the mare owner and us. The reason for most of these delays fed-ex ascribes to 'circumstances beyond our control' (i.e. inclement weather) or mislabeled packaging from the sender.
If you have a mare in foal for next year, now is a good time to think about follow up ultrasounds to monitor fetal development, spot potential problems and determine the gender of the foal. After the initial pregnancy check, done with ultrasound between 14 and 18 days of pregnancy, we recommend a second ultrasound between 25 and 30 days of pregnancy. By this time, we are able to visually see a heartbeat in the fetus. This check is best done before day 35 of pregnancy, because if there is an abnormality with the pregnancy, it can be difficult to get mares back into heat to rebreed after day 35-40 of pregnancy.
Fetal gender determination has becoming increasingly popular over the past several years. In my hands, this has been extremely reliable. I have had the opportunity to do several hundred of these over the past several years, and to the best of my knowledge have not been off track on one. In order to have accurate results, it is critical that this ultrasound evaluation take place between 60 and 70 days of pregnancy. This check also allows us to get a good assessment of fetal development and viability, as the head, legs, heart, skeleton and several other structures are clearly distinguishable. We cannot do anything about changing the gender, but it does provide knowledge and allows the farm to plan for what is coming for next year (whether to paint the stall pink or blue).
It is also wise to reconfirm pregnancy at 90-100 days. Once mares reach this stage of pregnancy, they are generally secure. This is also the time that we start pregnant mares on their ‘pregnant mare vaccines.’
In some mares, especially those deemed high risk pregnancies, we will ultrasound them late in pregnancy to both assess fetal stress and measure placental thickness. We do not do these late term ultrasounds as a matter of routine, but in certain cases, these checks can provide invaluable information.
So for those of you expecting foals for next year, there is a quick recap of what can do and what we recommend to monitor fetal development. If you are not expecting a foal for next year, it is never too early to start planning for next year. Going through the experience of breeding and raising your own foal can be one of the most exciting aspects of having and managing horses.