Milk fever is one of the most important metabolic disease in dairy cows .that sustain a great cost on the dairy cattle industry and has a lot of secondary complications even in treated cows .because of this, investigators struggle to find the way of prevention of milk fever. Using anionic salts in pre partum ration of dairy cows is the most customary and useful method, but the effect of these salts on metabolic parameters and other production diseases remain a matter of debate. The objective of this study was to estimate the effect of pre partum feeding anionic-supplemented ration on occurrence of milk fever and other calving related diseases, and also to determine the effect of anionic salts on blood metabolites. Sixty cows were selected and randomly divided into two groups during a 9 month period in a commercial dairy farm in suburb of Mashhad. Thirty cows were received anionic ration for 21 days to parturition and the other group (no=30) were fed usual dry period ration. Blood samples were collected from each cow three times at 21 days before parturition and on postpartum days of 3 and 21. Blood samples were taken from coccygeal vein using evacuated tube and serum was separated within 1 hour after sampling and frozen till analysis. Urine samples were taken using urine catheter twice at day 21 and 7 pre-partum to monitor optimal acidification. Calcium, inorganic phosphorus, magnesium, chloride, cholesterol, urea, creatinine, total protein, albumin, sodium, potassium, NEFA, BHB, glucose, and AST were measured in the serum using automated biochemical analyzer. Blood pH and bicarbonate were measured using blood gas analyzer within 1 hour after sampling. The animals were tracking for disease occurrence during 4 months after parturition. The results of the study showed, the probability of milk fever occurrence (odd ratio) is 5 times greater in the control group than treatment group. Also the probability of culling in control group is 2 times greater than treatment group. In this study, significant differences (P<0.05) was observed in blood calcium, albumin and AST at day 3 and phosphorus and creatinine at day 21 between treatment (received anionic salts) and control groups. There was not significant difference of BHB, NEFA and glucose between 2 groups. Significant time related changes (time of sampling) were observed on blood calcium, magnesium, sodium, chloride, cholesterol, urea, creatinine, total protein, albumin, glucose, BHB, NEFA, AST, pH. In this study, we observed the more probability of culling in cows with milk fever and the cows with the parity more than 4 (P<0.05). Also we observed that the parity more than 4 cause the increasing probability of lameness in cows (P<0.05). The results of this study showed, with using anionic salts pre-partum, calcium balance and metabolism could be improved and the probability of milk fever occurrence and culling rate were decreased. Energy metabolism was not influenced by anionic salts feeding.

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