Dietary cation-anion difference in rations for pregnant dried off cows

On a farm with 230 Friesian cows, winter and summer nutrition of highly pregnant dry cows was studied. Dietary cation-anion difference in the rations (DCAD) was calculated to estimate its possible connection with the incidence of milk fever and hypocalcaemia in cows. In winter season daily ration was composed of 3 kg of hay, 10-13 kg of grass silage and 10-13 kg of maize silage, with 1 kg of concentrate and 50 g of min.-vit. mixture. During summer season cows grazed and were additionally fed 3 kg of hay and 8 kg of maize silage till mid June, then until the end of season the maize silage was replaced by 10 of grass silage. A week before expected date of calving, cows were fed an additional 2 kg of concentrate. Throughout the dry period the cows were also fed 100 g of min.-vit. mixture. Dietary cation-anion difference was estimated as milliequivalent (meq) per kg of DM [(K++Na+) – (Cl-+S--)] (Oetzel, 1993). In winter months (November-February) dietary cation-anion difference ranged from 365 to 373 meq kg-1 DM. In studied months of winter season 83 cows calved, 9 of which were treated for milk fever and 5 for hypocalcaemia. In summer season (May-September) dietary cation-anion difference ranged from 27 to 238 meq -1kg DM. In studied months of summer season 73 cows calved, 6 of which were treated for milk fever and 3 for hypocalcaemia.