Posted From: 22.214.171.124
|Posted on Monday, June 21, 2004 - 04:01 pm: ||
In many places on this board I have seen the statement " a mare will not have a foal larger than she can deliver". This is scientifically not true and many mares have died disproving it. Mares and stallions should be complimentary in almost every way, but foals are not produced with only the best qualities of each. Responsible breeders should aim, over the course of many generations, to improve on size if desired, not with a single breeding.
Posted From: 126.96.36.199
|Posted on Thursday, June 24, 2004 - 01:04 am: ||
Actually, I am afraid the above statement is incorrect with reference to the size observations, as can be proven by reference to the following scientific studies, all of which have found that the size of the foal is determined primarily by the size of the mare and not the stallion:
This latter - and most recent study - says in the summation: "Thus, the results indicate that in equids, maternal size interacts with both the maternal and fetal genotypes to control the rate and extent of fetal growth by influencing the gross area of the diffuse allantochorion, and the density, complexity and depth of the microcotyledons on its surface" - and hence does not produce a foal "too large" for the mare.
- Walton A, Hammond J. (1938) The maternal effects on growth and conformation in the shire horse-shetland pony crosses. Proc Royal Soc. B, 125, 311.
- Hammond J (1955) Progress in the Physiology of Farm Animals, Vol 2. Butterworth Scientific Publications, London, England.
- Influence of maternal size on placental, fetal and postnatal growth in the horse. I. Development in utero WR Allen, S Wilsher, C Turnbull, F Stewart, J Ousey, PD Rossdale, and AL Fowden; Reproduction (2002) 123 445-453
From the above, it can be clearly seen that for many years, it has indeed been scientifically proven that the mare size controls the foal size at delivery.
There are many causes for dystocia not related to fetal size. One area where we probably can agree is that depth of chest, and width of hips and shoulders in the foal can cause foaling problems, and in this regards, one would be well advised to review the pelvic opening diameter of the mare, and the type of build of the foal that the stallion typically throws. Again though, this is still very different from the concept that a small mare bred to a tall stallion will result in a foaling problem - which (unless there are other areas of dysparity) it will not.
Posted From: 188.8.131.52
|Posted on Thursday, June 24, 2004 - 06:37 pm: ||
Thankyou for your response Jos. This is good news for a stallion owner. I have refused mares which were too small. Everything I read suggested it was risky.