Friday, February 23, 2007

Some Basics About Twin Arabian Foals

So many searches about twin foals lead to my website every day, I thought it might be helpful to go over the basics about twinning in Arabian mares and mares in general. Statistics about the incidence of twins in horses are all over the place but the middle road seems to suggest that about 1 in 1000 pregnancies results in a mare settling twin follicles.

With today's modern medicine most of those will be detected with the use of the ultrasound and one ovum will usually be pinched off in hopes that the other will remain viable. Personally, I have never had a mare retain the second pregnancy once the other was pinched. Poling other breeders, it seems to be the usual case for them as well, suggesting the mortality for this technique is quite high. However, statistics of one study state that the success rate is 70%.

Occassionaly, the twins will be too close to pinch one off. Then the mare is monitored to see if her own body will absord one of the pregnancies. I had a mare that had the twins too close to pinch and we rechecked her at about 30 days to see if she had absorbed one. She had not, and so she was administered a drug to terminate the pregnancy. That would be the normal choice at this point. However, there is another option that is only available in some areas. There is a technique where they go in with a needle and aspirate one of the pregnancies. This treatment is relatively new and there are not statistics on it's success. I do know a breeding manager who has utilized it successfully.

Even with all of these resources, twin pregnancies in mares can slip by undetected. Statistically, they believe that of the 1 in 1000 pregnancies that results in twins in horses, somewhere between 1 in 1000 of those the mare will carry. The mortality of those pregnancies is quite high. Usually one of the twins will develop slower and be smaller. This smaller twin will eventually be crushed by the larger twin and die. It will remain in the uterus and mumify. The toxines from that will kill the larger,healthy foals and the mare will abort at about nine months.

Of those rare pregnancies that actually go close to full, or full term, statistics vary between a survival rate for one or both twins of only 8% to 14% past two weeks of age. The statistics to even reaching a full term delivery are between 1 in 200,000 to 1 in 500,000. So by the time you take all of those number into account, surviving twins are indeed very rare.

There are two reasons for the low survival rate for full term horse twins. One is many times the actual birth process is abnormal, one or both twins will be a malpresentation with all of the complications that implies.I would say it is realistic to expect if twins foals are born with no complications in their delivery they have much better odds of survival, than those with complications. The second is they are usually born with the same issues as premature or dysmature foals.
1. Low birth weight.
2. Small frame - may appear thin with poor muscle development.
3. Periarticular laxity.
4. Usually flexor laxity but occasional contracture.
5. Usually hypotonia - occasional hypertonia.
6. High compliance to chest wall - soft ribcage.
7. Low compliance to lungs - stiff lungs - respiratory distress secondary to fatigue.
8. General muscle weakness - delayed time to standing.
9. Short, silky hair coat.
10. Domed forehead.
11. Floppy ears - poor ear cartilage development.
12. Weak suckle.
13. Poor thermoregulation.
14. GI tract dysfunction.
15. Delayed maturation of renal function - low urine output.
16. Entropion with secondary corneal ulcers.
17. Poor glucose regulation.
18. Angular limb deformities

They can experience any or all of the problems of these issues and are prone to even more risk for septicemia than their premature and dysmature counterparts. Any horse twins with these problems require early detection and extensive hands on treatment.

For those fortunate equine twins that escape having any problems obvious problems at birth, there is still the possibility that they will not grow into full size horses. It is common to find twins where one or both do not continue to grow after they are yearlings. In the past, the reason for this was not known but in recent years it has been discovered that the stunted growth is directly related to crushing syndrome. It appears to be Mother Nature's way of protecting these injured horses. What this suggest would be even if twins are born and look normal and healthy, they should still have an extensive examination by an equine neo-natal specialist including a complete series of x-rays to determine the ossification of their bones. Early detection and proper intervention can help avoid many of the pitfalls facing these fragile foals including the crushing syndrome.

In summary there is rarely a good outcome when a mare has twin foals. However, sometimes it does happen. Reflections on Foaling Season 2006 is the survival story of the twin foals born on my farm. It's a detailed account of the issues and treatments involved in saving these foals. It's a long story and is being posted in segments. I hope that by telling the story in detail it might help others be better prepared to deal with twin, dysmature or premature foals and maybe to spot early when a problem is developing.

1 comment:

  1. Hi MiKael

    One of our brood mares that is in Iowa at the moment was a twin, the other one was pinched off early, we always joke that theypinched the wrong one off because she has quite a beligerant attitude LOL.

    Our B&W mare has carried twins before too but reabsorbed the pregnancy on her own, this was before she came to us.

    I am trying to remember where I saw an article recently about a woman who's mare had twins twice in a row and both sets survived. I can see the photo in my mind but can't for the life of me remember where I saw it.

    Interesting statistics. I am so glad that your two have thrived, thanks to all of your hard work.

    Hope all is well, we are bracing for an ice storm/freezing rain this evening thro to tomorrow morning.