Detection of calving in dairy cows
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The aim of this study was to examine the electrolyte concentrations and its changes of the precolostrum milk in order to determine the exact timing of the impending parturition. Data was collected from the precolostrum milk of 26 cows starting on day 13 before calving. Each cow was measured several times in average ±SD 6 ± 3 times. The level of Ash (%) and dry matter (%) were determined according to the relevant Hungarian standards., macro and micro elements like Ca (mg/kg), Mg (mg/kg), K (mg/kg), Na (mg/kg), Mn (mg/kg), Cu (mg/kg), Zn (mg/kg) and Fe (mg/kg) were determined by atomic absorption spectrophotometrically (UNICAM SOLAARM6, Thermo Jarrell Ash Corp, Franklin, MA, USA) while the level of phosphorus /P/ (mg/kg)/ was measured by spectrophotometrically. The results of the study showed that the measured parameters; Ash, Ca, P, Mg and Zn were increasing (P<0.020 in all cases), and that Na, Cu and Fe were decreasing (P<0.014 in all cases), while dry matter and Mn were not changing significantly (P=0.575 and P=0.461, respectively) during the last week of pregnancy. Logistic regression revealed two factors, changes of Ash (p=0.007) and K (p=0.015) associated with the beginning of calving. On the day of calving the average ± SD change of Ash and K level compared to the previous days were significantly higher (0.2 ±0.3 mg/kg and 254.1 ± 312.5 mg/kg, respectively) compared to the changes measured -7 to -1 days before calving (0.01 ± 0.18 mg/kg and 55.6 ± 173.4 mg/kg, respectively). Other methods used to detect impending parturition in cattle were also discussed.