We have 2 mares that have been hard to get in foal. Currently both are in foal and are being given 300mg of progesterone in oil injections daily. They were both treated with the oxtocin protocal prior to breeding. Both were started on progesterone at day 5 post OV. One is currently 35 days pregnant and the other is 16 days. Both mares cervical tone is good. However uterine tone is very poor in both mares. We have 2 other mares on Progesterone as well and their tone is great. All 4 mares have a history of losing pregnacy between 20 and 120 days. We have about 50 mares on the farm and do our own repo work so I am very confident in my assesment of their tone and know what pregnant mare tone normally is. I am a concerned about the tone of these 2 older mares and wandered if Regumate would be better or is progesterone in oil equally as benefical. I only put mares on any progesterone supplementation as a last resort. I have not done the blood work to see what their level is mainly because by the cost of the blood work over 3 days I could buy enough progesterone to carry them to 100 days pregnant anyway. I do wish their was a better way to administer the progesterone in oil besides injection as most mares get needle shy very soon. My question is with cervical tone being good and uterine tone poor is it need for alarm?? Also your thoughts on my progesterone issues. Would increasing the amount of progesterone to 400 or 500mg daily help?
Injectable progesterone in oil at the 300mg/day dose has been shown to be as effective as Regumate at pregnancy maintenance in research-created pregnancy threat situations.
There is an excellent summary of the use of progestins in pregnant mares presented by Dr. Peter Daels on the IVIS website (log in may be required to view that .pdf document).
For more information about progestin supplementation - and specifically Regumate use - you can view the article on Regumate use that appears on this site (follow that link).
WRT to uterine tone in the pregnant mare - remember that it often normally decreases steadily from about 25-30 days on.
If you do wish to continue supplementation, BET Pharm have a biorelease formulation that has been shown to elevate progesterone levels for 7 days (so one injection every 7 days is all that is needed).
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