‘GIRLS POWER’
Broodmares revenge
DOTT.SSA EMANUELA VALLE
DIP. SCIENZE VETERINARIE – UNIVERSITÀ DI TORINO
EBVS® European Specialist in Veterinary
and Comparative Nutrition
Choosing the best-bred stallion to breed a quality foal might seem like the most obvious choice, but horse breeding is a complex task that requires patience and expertise and simple solutions do not exist when dealing with horses. In reality, the quality of the foal does not only depend on the stallion, but also on other factors such as environment, training and, last but not least, the broodmare.
The maternal environment
The maternal environment is essential for the growth of the foal from the moment of fertilization of the embryo. By maternal environment we mean the environment where the foetus develops and therefore the mother’s organism. It responds to environmental and nutritional stimulation that act on the maternal metabolism. This means that the foal is metabolically programmed according to a science called ‘nutrigenomics’. In practice, the genetic expression is influenced by the environment to which the mother is exposed, and, in this context, nutrition plays a crucial role. Even if a horse has a promising genetic predisposition to become a future champion, his success depends greatly on the management of the mare, even before the embryo has been fertilized. As the foal develops during the eleven months of pregnancy the expression of all his genetic potential undergoes a delicate and complex process, characterized by dynamic interactions between the surrounding environment and the broodmare.
The maternal exclusive
Mitochondrial DNA is a maternal exclusive because, although ‘smaller’ in terms of number of genes compared to nuclear DNA, it plays a role of primary importance in the energetic metabolism. This is associated with energy consumption, performance and endurance. Its peculiarity in genetic terms is that it is inherited only from the mare, and not 50:50 as happens with nuclear DNA. Therefore, it goes without saying that there will always be a genetic component strictly and uniquely linked to the mare, which will be passed on from generation to generation in both sexes. This highlights the fact that female genetic lines also play a fundamental role in sports performance. Particularly a strong female contribution in resistance and exercise capacity has been proven. Furthermore, some recent studies indicate that mitochondrial DNA contributes to performance differences between maternal lines, such as identifying specific talents for show jumping and dressage. In the last decade, scientific progress has also made it possible to discover how much the maternal line (and therefore the mitochondrial DNA) is able to influence the duration of pregnancy and the sex of the offspring, or whether there will be a greater probability of having a colt or filly. The duration of gestation usually varies between 335 and 345 days, the mare has between 13-18% responsibility for this variation, unlike the stallion which only affects 2-3%.
Embriotransfer: a crucial choice
As well as the role that mitochondrial DNA plays, we cannot underestimate the maternal effect, by both the transmitted genetic component and the uterine environment in which the foal develops. An interesting study from a few years ago, demonstrated how much the body size of the mare influences that of the future foal. Through artificial insemination two significantly different breeds such as Shetland ponies and Shires were mixed. The result obtained was that the foals born from Shetland mares were the typical size of this breed at birth, while those born from Shires mares were noticeably much bigger, although not as big as the pure-bred foals. The difference in size of all these foals was maintained over time even after three years. Once again this means that it is not just a matter of genetics: never underestimate the maternal environment. Therefore, it is not enough to have an excellent quality donor from a genetic point of view, but the recipient does a lot! The latter can influence (even negatively) the foal at birth and in the following months/years with regards to the correct functioning of the cardiovascular system as well as energetic metabolism, ossification and therefore the risk of injuries as well as temperament.
The passport
When evaluating a horse’s genetic pedigree, reference is often made to both the stallion (Sire) and the mother’s father (Dam’s sire). However, much attention must be paid to the mare because she will contribute significantly to genetics. A quality mare can positively influence the foal in terms of health, conformation and temperament.
Effects of embryo transfer
The surrogate mother shouldn’t be picked solely on her reproductive capacity and cost. The transplant of embryos into mares that are unsuitable in terms of genetics and morphological structure imposes size limits. We must also remember that the nutritional status of the embryo donor and recipient can also influence the postnatal health of the foal.
Did you know that…
The mother effect is very noticeable in embryo transfers. The choice and nutrition of the surrogate mother partly determine the adult size and health of the foal but also his temperament and attitude to work.
