Abstract
A breeding herd of Mugalzhar horses belonging to the Suzak population, comprising 312 animals, including 196 mares, was established. A replacement young stock herd born in 2022 was formed, consisting of 48 animals, including 33 fillies and 15 colts. It was established that foals are characterized by intensive growth and development during the first six months of life. The live weight gain of colts amounted to 132.7 kg, corresponding to 1,990.5 kg of milk consumed for their growth. The increase in live weight of fillies from three days to six months of age amounted to 119.4 kg, corresponding to a mare milk yield of 1,791 kg. The study found that more than half of the mares, 55.0%, were culled after the first four lactations, mainly due to low milk productivity and reproductive disorders. After the first lactation, 17% of the mares were culled; after the second, 15%; after the third, 13%; and after the fourth, 10%. The results obtained indicate the need to improve breeding selection practices, taking into account the milk productivity and reproductive traits of mares.