Some environmental effects on milk yield of holstein cows raised at Dalaman State Farm

-11- ABSTRACT Some Environmental Effects on Milk Yield of Holstein Cows Raised at Dalaman State Farm Data of 866 lactations collected from 251 cows raised between 1989 and 1996 at Dalaman State Farm in Muğla province were analyzed. Two calving seasons were determined on data set based on air temperature. These are the first calving season (November 01st - April 30th) which is within the comfort zone for cows, and the second calving season (May 1st - October 31st). In the study, 305 days milk yield, calving year, lactation number and calving season were evaluated. The effect of lactation number (p<0.01), calving year (p<0.01) and, calving season (p<0.01) on milk yield were found statistically significant for all measures by least-square variance analysis. The least-square means and standard errors of calving season in the first and the second calving periods were 7493.54±70.29 kg and 7180.63±81.08 kg, respectively. KEY WORDS : Holstein, days milk yield, calving season, calving year, lactation number.