The aim of the study was an attempt to define how the results of the first year of reproductive results of chinchillas testify about the reproductive effectiveness of the breeding stock. The observations were made on a chinchilla reproduction farm in Stara Miłosna. The research material consisted of 58 females, from which 311 litters were obtained. The analysis was based on number of kids from the litters during first 3 years of females' career. The research conducted revealed, that the first year of the reproductive usage of chinchillas female cannot serve as reliable basis for the evaluation of their reproductive effectiveness. The highest reproductive results were recorded in the second reproductive season. Some significant differences were recorded as far as the average amount of the young born and young reared through the nursing period between 1. and 2. year, and also between 2. and 3. year of reproductive usage of females.

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