Body phosphorus mobilization and deposition during lactation in dairy cows
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Date
2012Author
Elizondo Salazar, Jorge Alberto
Ferguson, James D.
Beegle, Douglas B.
Remsburg, Darren W.
Wu, Zhiguo
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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.
External link to the item
10.1111/j.1439-0396.2012.01291.xCollections
- Zootecnia [368]