Variations in Equine Spinal Columns
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I have always found the wide range of neck and back lengths in Fell Ponies baffling. A new study about other breeds helped me be less baffled!
One of the things that I’ve found baffling about Fell Ponies since I got involved with the breed is the amount of variation in the lengths of necks and backs in our ponies. I have seen necks both long like I’m accustomed to seeing on riding horses and then shorter and stronger like I’ve seen on draft horses. I have seen short backs and long underlines on some ponies and ponies called sausages by their owners because of their long barrels between front and back legs. I had thought that with a standardized breed, a closed stud book, and an emphasis on proper type in the breed description that there would be more consistency in conformation in our ponies.
You’ll understand then my interest in and then fascination with a study that came out recently involving warmbloods, Koniks, and Shetlands. The study looked at variations in spinal columns and ribs within and across breeds. I had read early in my horse-crazy days that Arabs have fewer vertebrae than other equines, but I thought that breed was an outlier. I was wrong! The study put in new context a comment I once received about a photo of one of my Fell Ponies. I was told that old timers would have said the pony had an extra rib and/or vertebra. At the time, I dismissed the comment as impossible, but now I’m understanding it with new appreciation.
The study, done in The Netherlands, looked at 30 Warmbloods, 29 Shetland ponies, and 18 Konik horses. It was done post-mortem by computed tomography without associated information about the individual equines when they were living. And because of limited access to the cadavers used in the study, the necks of the equines were not included in the study. While the study was looking at the outset at Warmbloods, the Shetland and Konik were included because they were considered more primitive breeds against which it was hoped comparisons could be made.
The abstract says, “The as-standard-described-equine-formula of 18 [thoracic], 6 [lumbar] and 5 [sacral] vertebrae was seen in 78% of Konik horses, but only in 53% Warmblood horses and 38% Shetland ponies.” (1) Here was the first ah-ha moment: the ‘as-standard’ count of vertebrae is anything but standard! There’s variation, especially in the one pony breed studied. In fact, the Shetland showed more variation in many of the measurements taken.
Then the discussion of number of ribs showed similar findings. While 90% of specimens had 18 pairs of ribs, Shetlands varied in a few specimens from 17 to 19 pair, while the other breeds didn’t have this wide range. One Shetland had different numbers one side to the other.
Like any good study, the authors came up with as many more questions as they answered. For instance, did some of the differences seen in Warmbloods result from selective breeding for back mobility? Did any of the noted differences have implications for performance?
None of the three breeds in this study are closely related to the Fell Pony, but the variations in findings certainly suggest that there would be variation in the Fell Pony spinal column as well. Given that our breed has been valued for its ability to be used in a variety of ways (ride, drive, draft, pack), it also makes sense we could have variation in the underlying anatomy. Overall, I am grateful for the revision to my understanding of the ‘as-standard’ formula for equine vertebrae. I highly recommend reading the full paper, a link to which is included in the footnote (or click here), if you are at all interested in this topic; I’ve just scratched the surface here regarding how varied equine spinal columns can be.
1) Spoormakers TJ, Veraa S, Graat EA, van Weeren PR, Brommer H. A comparative study of breed differences in the anatomical configuration of the equine vertebral column. Journal of Anatomy. 2021;239:829–838. https://doi.org/10.1111/joa.13456
© Jenifer Morrissey, 2022
