Evaluating drinking water quality of Vahdat cooperative's dairy farmsý

Results of several studies indicated that more than 80 percent of the total water consumed by lactating cows was by drinking. Water quality is an important issue in the water consumption and dairy cattle performance. Due to the importance of livestock drinking water quality, water samples of 70 volunteer dairy farms were examined. Thus, two samples (in winter and summer of 2010) were collected from trough of each dairy farm. Samples sent to laboratory for determination of EC, TDS, Hardness, Total alkalinity, Fluoride, Chloride, Bicarbonate, Sulfate, Nitrate, Nitrite, Phosphor, Calcium, Magnesium, Sodium and potassium. In addition, a questionnaire for each farm as the supplementary information was collected. Then, all data were analysed by the GLM procedure of SAS software. The results were compared with standard values using one- sample T-Test. the farms based on water quality categorized by Cluster procedure of SAS. Results were reported separately for each dairy farm. Based on a questionnaire, information of dairy cows production was obtained and correlation between factors affected water quality and milk production was examined. Results showed a there is not a significant different between the two seasons in terms of chemical quality With the exception of hardness, calcium, fluoride and potassium. Calcium and hardness content of tap water in summer (42.96 % 1.54 and 213 11.36 ppm, respectively) higher than these contents (33.6% 1.6 and 180 8.9 ppm, respectively) in winter (p 0.05). Fluoride content of well water in summer was higher than (0.35 0.02 ppm vs 0.28 0.01 ppm) in winter (P 0.01) and potassium content of well water in winter was higher than (12.59 1.31 vs 9.21 0.83 ppm) in summer. TDS content and EC value of well water (3222.3 214 ppm and 4572.8 307.8 s/ cm, respectively) were higher than tap water ( 282 7.2 ppm and 403 10.3 s/ cm, respectively) (P0.05). Results indicated that chloride in more than 80 percent of well water sample and 10 percent of tanker water sample was higher than standard value. TDS, EC, Ca and K in more than 50 percent of well sources were higher than the maximum limits (p 0.05). Hardness content in 75 percent of well source and more than 20 percent of tanker source were higher than the maximum limits and K content in more than 40 percent of well source and less than 10 percent of tanker source was higher than standard limits. Based on this study, tap water source had no health problem. Results indicated that negative significant correlation was found between hardness (p0.05) and Mg content (p0.01) with milk yield (-25% and -30%, respectively). Kay word: drinking water, dairy farm, chemical quality of water, well, tap water, dairy cow. : Abstract