EN
The studies were performed on 47 young mares (28 Felin, 11 Polish, 4 Biłgoraj and 4 other types of ponies) contacting with stallion-reproducers from birth or from weaning. Most mares became pregnant at less than 2 years of age, sometimes at the age of 1.5 years. The earliest age of pregnancy was 12.5 months. The season affected significantly the time of fertilization. Generally, mares became pregnant from February to June, with a peak in May. Sterile mares became pregant at the same time the following year. Fertilization of Polish and Biłgoraj ponies at the age of less than 2 years is not recommended but it is acceptable for Felin ponies. The weight and size of foals from young mares fertilized early is open to discussion. In case of ponies small foals and small adults can be desired.