EN
Successes in breeding of all animal species are mostly determined by high reproductive indices. That´s why tested were 127 purebred Arabian stallions used in Polish breeding in the years 1971-1998, siring 5 or more heads of progeny. For every stallion collected were data concerning number of mares bred, born foals, open periods, abortions, stillborn, dead or destroyed foals, as well as mares, who died being in foal to a given stallion. There was found an increase of intensivity of reproductive utilization of leading sires in the tested period, compared with earlier seasons. At the same time observed was, however, a more frequent occurrence of undesirable traits. Currently prolonged sirelines distinguished themselves with higher reproductive indices. There was observed also a higher share of stallions siring 5 or more heads of progeny per stallion and season. On the other hand, reducing representation of sirelines continued in our breeding might cause unwanted changes in the genetic pool of our broodmares´band, prevented by the Program of Purebred Arabian Horse Breeding in Poland.