Body phosphorus mobilization and deposition during lactation in dairy cows

Abstract

Dairy cow bone phosphorus (P) mobilization and deposition and their influence on P requirements were studied over the lactation cycle. Thirty Holsteins received a common diet during the dry period and one of the following three dietary treatments that varied in P percentage during the subsequent lactation (44 weeks): (i) 0.36 throughout (constant P, 0.36-0.36-0.36), (ii) 0.36 for 30 weeks then 0.29 for 14 weeks (P changed once, 0.36-0.36-0.29), and (iii) 0.43 for 10 weeks, 0.36 for 20 weeks, and 0.29 for 14 weeks (P changed twice, 0.43-0.36-0.29). Six P balance studies were conducted during the experiment, including one during the dry period and five along lactation, based on P intake, faecal P, urinary P and milk P, when appropriate. Blood samples were taken during balance to analyse bone formation (osteocalcin) and resorption (pyridinoline) marker concentrations and rib biopsies performed to determine bone P content. Phosphorus balance was negative during weeks -4 to -1 relative to lactation for all groups and remained negative for cows fed 0.36% P during weeks 1-5, but showed a positive value for cows that received 0.43% P. The balance was close to zero for all groups at weeks 19-23 and showed a clear retention during weeks 38-42; by the end of lactation, cows re-stored most of the P mobilized earlier. The pattern in P balance was consistent with changes in blood bone metabolism marker concentrations, rib bone P content, and faecal and urinary P concentrations over the experiment, indicating that cows, irrespective of the dietary P treatments received, mobilized P from bone during the late dry period when fed a low-Ca diet and early lactation, and re-stored P in late lactation. This dynamic of P metabolism can have important implications for dietary P requirements and ration formulations.

Meta-analysis of factors that affect the utilization efficiency of phosphorus in lactating dairy cows

“…With the release of Ca from bone, P is also mobilized (NRC, 2001), which may have implications for the P requirements of early lactation dairy cows. Elizondo Salazar et al (2012) estimated that a 600-kg dairy cow may be able to mobilize up to 1,000 g of P from body reserves during the early lactation period. However, this is based on a suggestion about the possible extent of P mobilization in early lactation beef cattle (Ternouth, 1990).…”

Compensatory and catch-up growth in cattle

“…The increased demand of minerals can lead to a metabolic disorder (i.e. periparturient paresis commonly known as milk fever), which is more commonly encountered in highly productive dairy cows (Yarrington et al, 1976). Elizondo Salazar et al (2013 showed that osteocalcin concentration in dairy cows reduced after parturition and consistently increased from day 10 to 20 and reduced again from day 28 to 42.…”

“…The concentration of PYD increased and peaked soon after calving in the serum (Elizondo Salazar et al (2013) and urine (Liesegang et al (1998) of Holstein cows, decreasing again as lactation progressed. The concentration of PYD was higher in the serum of Holstein cows fed a low Ca diet (4.6 g Ca/kg DM) compared with those fed a high Ca diet (6.4 g Ca/kg DM) during early lactation (Moreira et al, 2009).…”

“…In Holstein cows OCN concentration in the plasma decreased during the first 5 weeks (4 ng/mL) of lactation and gradually increased as lactation progressed to peak (16 ng/mL) at 30 weeks in milk (Elizondo Salazar et al, 2013). The decrease in OCN during early lactation is likely to be reflect bone remodelling that is likely to occur in response to the rapid mobilisation of minerals from that skeleton at this time.…”

“…This is an important tool that provides a non-invasive method to assess bone-remodelling activity. Some earlier publications have reported the use of bone markers in bovines but all of these focused on dairy cattle (Liesegang et al, 1998;Kim et al, 2010;Elizondo Salazar et al, 2013). Dairy and beef cattle have had different genetic selection processes and this may be related to the capacity of bone formation and resorption.…”