Factors influencing gestational length in mares: A review

This article reviews the main factors involved in gestational length (GL) in broodmares. Three main groups of factors were considered: environmental, fetal and maternal factor. The main environmental factors were the mating period within the breeding season, climate, year of breeding, photoperiod, and treatment with artificial light. Within the fetal factors, genetic and breed, sex and type of pregnancy were cited. The most important maternal factors were age, breed, number of births, and nutritional state.