There was a discussion in a Facebook group about breeding a Shetland mare to a bigger stallion. Some had the opinion of it not being a problem but I argued against it, mostly because I have many times heard from experienced breeders and vets that Shetlands would have problems in foalings due to the fact that they are so small – and also because of the fact that we lost our first ever homebred foal with the dam when the foal was too big to be born, I could never ever take unnecessary risk for the foal of being bigger than normal by choosing a too big stallion for my mares. As well as I don’t anyway see the point in doing Shetland mixes with Welsh, Russ ponies, not to talk about bigger breeds.
In 1930s there was a study done with Shetlands and Shires, Shetland mares was covered with Shire stallions and vice versa. Also for comparision purebred Shetland-Shetland and Shire-Shire foals was studied. Shetland mares were three times covered with Shire stallion and they all foaled, though two foals had died as the bags had not broken. As in those days it was probably common, the foalings where not watched over, and so we don’t actually know why the bags where not broken. It could be that the foals in fact had died due a prolonged labour, or the bags just where too tought for the foal to break.
Anyway, these foalings where interpreted as successful in the study and therefore in the discussion used as arguement to show it is fine to cover and Shetland mare with a bigger stallion and that the mare fixes the size of the foal and it has nothing to do with the size of the stallion.
In fact the 1930s minimal research shows us that it is not that simple. The Shire mares covered with Shetland stallions, gave in fact smaller foals than when covered with Shire stallions – that tells us that, of course, also the sire’s genetics plays a part in the size of the foals as Shetland stallion’s foals did not reach the size of those purebred Shires. So genetics from both dam and sire will affect the foal’s size but how come Shetland mares still managed to have foals from Shires succesfully?
Of course the physics of the Shetland mare is of it’s own ”measurements”, so it will naturally prohibit the growth of the foal. In the Shire mares on the other hand, the Shetland stallion foals had the possibility to grow to ”full potential”, presumably for example due Shire sized placentas – they so to say, get a better start in life to grow inside a bigger mare. Still they did not reach the size of purebred Shires either – as the sires genetics affect the size of the foal and holds the growth back. So of course the Shetland mare has its limitations as she only have Shetland size womb and placenta and naturally the foal is then adapted better to its mother. It still does not mean that the sire would have nothing to say in the size of the foal as the genetics comes from both parents.
The importance of the gestation time could be nowadays researched with embryo transfer from purebred Shetlands to Shire and see if the foal is bigger in birth than if carried by a Shetland, if it is, the bigger mare then definitely would be proven to give a better start to the foal and then presumably, a small mare holds it back naturally. However, I would never ever recommend breeding a Shetland mare to other than suitable sized Shetland stallions. The reason is simple, IF help is needed, you are in bigger trouble, why take the risk? Argument below:
I started to question myself the saying that Shetlands would have more problems in foaling than horses, so I made a short survey in SurveyMonkey. This survey was only made for purebred Shetland pony foalings. For comparision it would be important to make a survey of Shetland mixes too, maybe I do it someday.
I shared the link to the survey on my Facebook page, webpage and Instagram and in a few Shetland Pony related groups on Facebook. The survey is still open and can be answered here. I keep it open until 1000 foalings is reached. Anyone can answer the survey, and there is no difference made if the answerer had one or 40 foalings, as they all contriubute to the entirety.
By this date 42 breeders have participated with totally 673 foalings, 3 % of gestation ended in abortition (which I think is a very low number). 79% of the foalings were managed without any help (compared to 87,3% in a study made with horses, linked in the end of the text). 10% of foalings needed some assistance and 5 % needed a lot of assistance of the owner or vet.
In 5 % of the foalings the breeder thought the foal had been too big or the mare too small for the foaling, in these foalings 44% of foals where lost. In 16% of tight foalings the mare died and in 22% of the cases both died. So if the foal is tight in labour, in 82% of the cases either mare, foal or both are lost (just saying, you don’t want the foal to grow too big…).
Also other problems can occure in a foaling, in 63% of these other cases of foaling problems (wrong position etc), either the foal, mare or both where lost. So a tight foaling is a bigger risk of loosing a pony than other problems in foaling.
Totally in 6,3% of foalings just the foal was lost, in 1,5% just the mare was lost and in 1,8% of foalings both were lost. Totally it tells us that 9-10% of Shetland foalings end up in a dead pony. This seems to me as a very high number as for example in the study linked in the end of the text, of 1047 births in horses, 29 foals died of different problems in foaling – that is just 2,8% of them all compared to 6,3% in Shetlands.
In most studies done of horses foalings, the result is that around 10% of foalings have some level of problems from severe to easily fixed ones (this is the number I remember was told in my exam studies also almost 20 years ago and a quick look in new studies just confirms this) – however not all of course end up in death of the mare or foal, that was just the number of possible problems! So compared to other studies of horse foalings it seems that there is maybe more Shetlands lost in foaling than in other breeds, though the % of problems themselves in foalings are not significantly higher. So in a way, what I was warned for might be true, they might not have more problems than other breeds, but when they do, it is a more serious situation than with horses. This is quite logical because it just is so much harder to help a small pony with a small pelvis and much less room where to act if help is needed, compared to a horse – if you have done both, you know what I mean…
I also asked if the breeders thought Shetlands have more problems than other breeds. Many thought they have not, however many also pointed out that standard sized ponies births are easy but minis seem to have more problems, so the smaller, maybe the more problems? I also asked what the breeders thought was a good difference in height of the stallion compared to the mare, 18 breeders thought 5 cm is enough, 16 thought 10 cm and only one though any pony sized sire is fine. Three thought any stallion of any size is fine. Many pointed out that it is not the height of the stallion but the conformation that should suit the mare, not too wide and robust stallion to a small mare. Also it was said more problems accure if the ponies are too fat. Both these things pointed out I totally agree with.
16 breeders had bred for 1-5 years, 18 had bred 5-10 years and 16 for over 10 years. Breeders came from UK, Sweden, Finland, Denmark and Austrailia. Some had left some questions unanswered and some answers where not logical but I did my best to pick correct answers which could be considered as reliable.
THANK YOU SO MUCH ALL WHO PARTICIPATED!
As a summary and personal opinion, I would say:
- Stay to Shetlands when breeding with Shetland mares
- Keep the stallion in suitable size
- Learn everything about foaling
- Keep watch so that you can help the mare if needed
- Have an experienced breeder’s and vet’s phone numbers near you
- And remember, even if Shetlands are capable of many things, including sometimes giving normally birth to foals from bigger stallions (and sometimes not, the horror stories are not so fun to brag about online I imagine…) – it doesn’t mean they have to.
Studies of foalings:
Parturition, dystocia and foal survival: A retrospective study of 1047 births, 2012, P.M. McCue, R.A. Ferris (study with Thoroughbred and Quarter horses)
Shetlands and Shires study from 1930s
And many more found with Google Scholar