摘要：The present study was designed to investigate the effects of season and lactation number on milk yields in Holstein dairy cows at Kabul Bini Hesar Dairy Farm. For this purpose, data were collected from the dairy farm herd book records during 1392-1393 (2013-2014). Considering the milk yield stages of the cows, the total milk production was highest during the spring season 18,454.95 ± 33 L followed by summer 17,060.85 ± 34.5 L while the lowest milk production obtained in winter 16,398.45 ± 31.5 L. Moreover, the average daily milk production of the cows was significantly different (p < 0.05) between the 1st, 2nd and 3rd lactations and the amounts were 12.04 ± 0.7, 13.24 ± 0.8 and 14.10 ± 0.6 L/day respectively. Milk yields of individual cows were gradually increased from 1st to 3rd lactation. The highest milk yield was recorded in 3rd lactation and the lowest was in 1st. From this study it was found that season and lactation number had a significant effect on the milk quantity.
