The effect of MgSO4 addition and the increasing doses of calcium and phosphorus during ending drying period on the occurrence of hypocalcaemia and hypophosphataemia in dairy cows

The aim of the presented study was the estimation of optimal Ca and P levels applied before calving together with anionic salt addition, as an element of hypocalcaemia and hypophosphataemia prevention. The experiment was carried out during the dry period on 48 cows with similar milk yield in the previous lactation. Cows were divided into four groups. In group I (control) the amount of minerals was in accordance to NRC standards. In experimental groups (groups II-IV), two weeks before calving, cows received 140 g/day/head of hydrated magnesium sulphate to achieve dietary cation-anion difference at the level of about 50 mEq/kg DM. In groups II and III cows received calcium carbonate (100 g/day) 10 days a.p. (antepartum) (group II), or 5 days a.p. (group III), while cows in IV group received dicalcium phosphate (100 g/day) for 5 days a.p. Application of MgSO₄ × 7H₂O significantly affected the urine pH of cows from group III and IV 4-5 d. before calving – 6.45 and 6.81, respectively. The acidification of urine was observed after calving in group IV (7.13). In cows from group II (100 CaCO₃ 10 days a.p.) urine pH decline was not found (7.97-7.75). In that group the incidences of hypophosphatemia were noted (blood serum inorganic P level 1.41-1.46 mmol/l). Addition of magnesium sulphate prevented hypocalcaemia occurrence – 4-5 d. before calving the concentration of ionized Ca in blood serum was 1.11, 1.13 and 1.16 mmol/l (respectively for group II, III and IV). Reproductive functions were significantly improved after the application of CaCO₃ and CaHPO₄ for 5 days a.p. in comparison with control and group II – progesterone concentration in the blood serum on the 45th day of lactation was 1.396 – 1.409 vs 0.799 – 0.401. The correlation between progesterone and inorganic P level in serum was almost significant. Based on the obtained results a treatment optimal in prevention of hypocalcaemia and hypophosphataemia is the application of 50 g CaCO₃ and 50 g of CaHPO₄ for the last 5 days of the dry period together with MgSO₄ × 7H₂O given for 14 days a.p.