Rare Bloodlines Revisited 2019 - Overview

Introduction

Border Black Prince, foaled 1987, is behind many of the ponies on the rare bloodlines list. Photo courtesy Michael Goddard

I did my first identification of rare bloodlines in Fell Ponies in 2007 based on the sires and dams of the 2005 and 2006 foal crops. I have now completed a second analysis of rare bloodlines. It updates the 2007 study and then analyzes the sires and dams of the 2017 and 2018 foal crops. This article provides an overview of the research. Subsequent articles will go into more depth about the various findings.

Methodology

How does one identify a rare bloodline? One tool is the Mean Kinship analysis. Mean Kinship (MK) is a calculation that measures the relatedness of a particular pony to the rest of the ponies in a given population. I have a database of Fell Pony pedigrees and the ability to run the MK analysis on sires and dams of foals born in a particular year. This sort of MK analysis gives insight into our breeding population.

My database only includes ponies appearing in the stud books of the Fell Pony Society. In addition to UK ponies, FPS registers ponies from The Netherlands as well as from the United States, Canada, Germany, France, Poland, the Czech Republic, Sweden, and Denmark. I know there are purebred ponies being born in Australia, and I suspect there are also purebred ponies born in Germany that are not registered with FPS. Ponies from those populations are not currently in my database.

For an MK analysis, I can specify how many generations are considered in the computations. I chose to include five generations. Almost ten percent of the ponies in the 2018 sire/dam analysis did not have full five generation pedigrees. In 2006, that number was 14.5%, so with time, as would be expected with a closed stud book, pedigrees are becoming more complete. Incomplete pedigrees exist due to: 1) the inspection scheme and grading up program instituted in the 1960s, and 2) prior to the inspection scheme, some ponies were registered without complete pedigrees.

For the purposes of my current study, a rare bloodline is defined as one having low relatedness to the rest of the population. When using Mean Kinship to identify rare lines, a low mean kinship value means low relatedness to the rest of the population. There are occasions, however, when a low MK may not mean a rare bloodline. For instance, if a pedigree only goes back two or three generations, that pony may have a low MK value because it has fewer ancestors to compare with those of other ponies. But since we don’t know what other ponies might be behind the pony with the short pedigree, I’ve opted to keep ponies with low MKs and short pedigrees in my analysis.

A second case where a low MK may not be a rare bloodline is if a particular pony is itself inbred, meaning it has the same pony in its pedigree multiple times. In that case, the pony may have a low MK value, but the low MK value may at least be in part due to the fact that the pony has fewer relatives (because of replication of some ancestors) to compare to the rest of the population. Therefore, its low MK value may not accurately reflect how it should be ranked as a conservation priority.

Globetrotter Polikarpov has a low mean kinship value from being linebred on the Dene stud and having the rare Linnel Rapier behind her.

courtesy Libby Robinson

For example, Darrenvale Dior, a dam of a 2017 foal, has a low MK value but her pedigree shows repeats of the popular stallion Lunesdale Jerry four times. Yet she also has numerous rare ancestors. On the other hand, the mare Globetrotter Polikarpov who also had a foal in 2017 also has a very low MK value. This mare has numerous ponies from the Dene stud behind her, a rare line, with repeats of the stallion Linnel Rapier from another rare line. Polikarpov might therefore be considered a higher conservation priority than Dior.

After pondering the problem of low MK values by high inbreeding, I’ve come up with an analysis that will identify the rarest of the rare, taking into account replication within a pedigree. Because it will be quite time consuming, I have opted to present the current state of my research and will return to that more detailed analysis at a later time. 

For my current analysis, I took the 20 ponies with the lowest mean kinships from each of the two years under consideration, ‘06/’07 and ‘17/’18. By taking two years at a time, mares who are not bred every year are more likely to be considered in the analysis. I combined the ’06 and ’07 top 20 into a single list and the same for the ’17 and ’18 top 20. For each of those two top 40 lists, I removed ponies that were duplicated and combined full siblings into a single entry. Finally, I annotated the list with the source of rarity of each pony. Table 1 shows the ‘17/’18 list.

(c) Jenifer Morrissey, 2019

Incomplete Dutch Pedigrees Resolved

I did my first analysis of rare bloodlines in 2007 based on the sires and dams of the 2005 and 2006 foal crops. At that time, there were a number of Dutch Fell Ponies for whom I had incomplete pedigrees, meaning the analysis was not as accurate as it could be. Thanks to detailed research done for me by Joke Postma of the Westerkwartier stud in The Netherlands, all pedigrees are now complete in my database. As a result, I have an updated list of rare bloodlines from the 2005/2006 time period.

North American and Dutch Divergence?

One result of the more recent analysis that jumped out was the number of North American ponies that showed up on the list. With over a quarter of the ponies on the list being born in North America, one has to wonder if our bloodlines on this side of the pond are diverging from the worldwide population. With the growing popularity of the breed here, this is a natural progression and only becomes a concern if our ponies start diverging in type as well. As long as we maintain good type in our ponies, as our stock genetically diverges, our ponies become more valuable as outcrosses for the worldwide population. In addition to the presence of North American ponies on the rare bloodlines list, two Dutch ponies and one German pony also showed up.

The Netherlands has been importing and breeding Fell Ponies as long or longer than North America has, yet there are fewer Dutch ponies on the recent rare bloodlines list than North America. There are several possible explanations for this difference. In the US, one breeder is responsible for a significant percentage of our homebred ponies, while in the Netherlands there are many smaller breeders contributing to the homebred population. There is less concentration, then, of stallion lines in The Netherlands versus in the US. Also, Dutch breeders tend to export ponies back to the UK for breeding at a higher rate than North America does, making the Dutch and UK populations somewhat more similar in terms of bloodlines. I’ve removed the German, Dutch and North American ponies from the rare bloodlines list for this first version of Table 1. I will revisit the North American and Dutch ponies in a future article.

Mare Lines

Three of the ponies in Table 1 are stallions, so more than 80% of the rare lines listed are mares. This is not surprising, since stallions are used more often than mares so will be more often repeated in pedigrees than mares. And sometimes mares are the only living progeny of a stallion line, for instance the stallion Swineside Lad is only represented today through the progeny of Bowthorne June and Lucky Jewel.

Pony Type

I was concerned by one anecdotal finding of my research. When I reached out to fellow breeders for pictures to illustrate this article, a few of them remarked what a good pony type the pony in the photograph was. For me a Fell Pony is indeed a pony, yet to my eye we have many horsey looking purebred Fell Ponies. For pony types to be represented in the rare bloodlines list is therefore very disappointing. I understand that there may have been other reasons those ponies have been selected out of the gene pool, but I also know that proper ponies can sometimes be hard to find in our breed.

More to Come

In future stories, we’ll be looking more closely at the North American and Dutch ponies in the rare bloodlines list. The ‘06/’07 list also needs to be revisited since the Dutch pedigrees are now all complete. In addition, a few ponies show up frequently on the list and need to be identified. So, more to come!