Variations in Dietary Nutrients and Blood Metabolites in Dairy Cows During the Peri-Parturient Period in Sub-Tropical Australia

Twenty-three commercial dairies were surveyed to investigate the variation in urine pH and body condition scores prepartum as well as post-partum plasma metabolites in dairy cows grazing in sub-tropical Australia. The electrolyte content and calculated Dietary Cation Anion Difference (DCAD) were determined on a range of feeds fed to dry cows during the prepartum period. The electrolyte content of the main forages was extremely variable across farms in both potassium (1.19 to 4.53% K) and DCAD (-24 to +502 meq/kg DM). The average chloride content was surprisingly high (1.48%), and possibly contributed to the low DCAD content. Supplementary hay and corn silage were lower in both K% and DCAD with farms averaging 1.18% and +37 meq/kg DM respectively. Urine pH varied between farms (5.73 to 8.43), and 83.6% of individual cows had alkaline urine (pH>7.0). There was substantial variation between farms in plasma ionised calcium, total calcium, phosphorus, beta-hydroxybutyrate and body condition score in the periparturient cow. High incidences of sub-clinical hypocalcaemia (28.4% within 24 hours post-partum) suggest that the diet DCAD in the prepartum diet needs to be lowered.