In a study by Seifi et al. (2004), it was concluded that a diet
high in specific cations, resulting in blood pH becoming more
alkaline, could induce a reduced efficiency of PTH receptors in
cows thus resulting in a reduced ability to respond to a Ca
challenge, such as initiation of lactation. However, there was
no effect of treatment on serum concentration of PTH and
concentrations of PTH varied greatly. Urine pH was not
affected by treatment pre-partum, early lactation or late
lactation, but urine pH was significantly lower in week 2
compared with 6 and 12 after calving.