PARATHYROID HORMONE-RELATED PROTEIN AND CALCIUM HOMEOSTASIS DURING THE PERIPARTURIENT PERIOD OF DAIRY-COWS

Abstract

Plasma and milk concentrations of parathyroid hormone-related protein (PTHrP) at various stages of pregnancy and lactation were determined in thirty-nine 3- to 16-year-old Brown Swiss and Red Holstein x Simmental dairy cows originating from 4 herds. Eighteen of the cows were separated into 2 groups: low-parity (LP, n = 8) cows if they were in their first or second pregnancy and high-parity (HP, n = 10) cows if they were in their third or greater pregnancy. Blood samples were collected from each cow on 1 occasion, 15 to 5 days before calving, and blood and milk samples were collected daily during 6 days after calving. Serum total and ionized calcium (Ca-tot and Ca2+, respectively) and milk Ca-tot concentrations were also quantified.