Dairy Cow Blood Phosphorus and Bone Turnover

Blood samples were taken from each cow from the coccygeal vein on day 4 of the collection period at approximately 1200 h. This time of day was selected as being between the timepoints of provision of fresh forage and of concentrate, therefore cows would have been consuming both components during the hours preceding sampling. Samples were analyzed for total (free) P, without a destruction step, according to method ISO 6491 (ISO, 1998 ). The serum cross-linked C-telopeptide of type I collagen (CTX), a marker for bone turnover, was analyzed according to a CTX-I ELISA method (IDS Plc., Tyne & Wear, UK).