BREEDING
Shedding new light on breeding and broodmare management When trying to identify the next great racehorse, horse buyers have a wide array of factors to consider – pedigree, conformation, wind, radiographs, race performance of close relatives, and date of birth. The objective of selecting for animals with optimal skeletal and muscular development is a driving force in many branches of the equine industry. WORDS: BARBARA MURPHY PHOTOS: SHUTTERSTOCK, BARBARA MURPHY
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EARLINGS at annual sales are often evaluated by their size and degree of development. When purchasing weanlings as future racing prospects the task becomes even more complex, as the buyer must speculate about the shape, size, and performance capacity of the mature animal following multiple future stages of growth and development. However, what buyers and bloodstock agents need to become more aware of is that the fastest rate of maturation during a horse’s life and the majority of a foal’s skeletal development occurs during the final three months of pregnancy. This in utero maturation of the foal is under the control of the environmental signals perceived by the mare. The most important of these is the duration of daylight. By understanding how light perceived by the late term pregnant mare influences the physiology of the resulting offspring, breeders have a new opportunity to influence the health and strength of their annual foal crop. Knowledge of the lighting regime under which a mare was maintained during her final trimester will provide subsequent buyers of her offspring with important additional information to help in their quest to identify the next American Pharoah. However, this must be prefaced by highlighting that early foals, born outside their natural season when day length is shorter, are very rarely at a disadvantage thanks to the development of cutting edge 18
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veterinary treatment, therapeutic farriery, and excellent science-based nutrition plans. Thoroughbred broodmares receive the best of everything and evidence of this can be seen by the success of early born foals on the track. As we operate in a game of inches, new knowledge of the importance of light and of how our bloodstock can gain an additional edge is always welcome. To understand the importance of light for our horses we need to go back to the very beginning. Further back even than the 60 million years it has taken the horse’s doglike earliest ancestor, Eohippus, to become the elite athlete we know today and represented by the many breeds of Equus caballus. When life first emerged on our planet there was a lot of chaos and confusion. Biological processes in the first single-celled organisms happened at random throughout the day, night, and season with little, if any, spatial organization. However, as the millennia passed, an interesting phenomenon unfolded
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One of the most important biological timing phenomena of animals is the annual rhythm of reproduction for seasonal breeding mammals
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– organisms that were more in tune with the changing cycles of light and dark of their environment were more likely to survive and reproduce. This natural selection of the fittest is a result of the continuously changing photoperiod created by the rotation of our planet around its own axis and, in turn, our planet’s rotation around the sun. The gradually changing day lengths associated with the waxing and waning of the annual seasons gave rise to predictable changes in food availability, climatic conditions, and predation pressures. Thus, as animals evolved, so too did an internal timing system that provides organization to biological phenomena. One of the most important biological timing phenomena of animals is the annual rhythm of reproduction for seasonal breeding mammals. Everyone naturally associates the springtime with frolicking lambs, nesting birds, and the appearance of foals in the fields. Throughout evolution, the young of prey animals, such as sheep and horses, had a better start in life and a greater likelihood of surviving to adulthood if born during the late spring and early summer. Why is this? Well, let’s consider the needs of a new mother caring for her young in a feral environment. The lengthening and increasingly warm days of spring provide new grass growth, increased plant photosynthesis, and therefore greater nutrition for the high-energy demands of a lactating herbivore. What’s more, the longer hours of daylight provide added protection by increasing the visibility of predators and