Response of saliva Na/K ratio to changing Na supply of lactating cows under tropical conditions

Wandee Thiangtum*, Thomas J. Schonewille, Martin W.A. Verstegen, Supot Arsawakulsudhi, Theera Rukkwamsuk, Wouter H. Hendriks

*Corresponding author for this work

Research output: Contribution to journalArticleAcademicpeer-review

Abstract

BACKGROUND: Factorial determination of the sodium (Na) requirement of heat-stressed lactating cows is hindered by accurate estimates of the Na losses through sweat. Direct studies, therefore, may be needed requiring information on the time course of healthy animals to become Na depleted and the subsequent rate of repletion. The rate of Na depletion and subsequent rate of Na repletion with two levels of dietary Na to lactating dairy cows housed under tropical conditions were investigated using the salivary Na/K. RESULTS: The 12 lactating cows (salivary Na/K ratio 14.6) rapidly developed clinical signs of Na deficiency, including pica, polyuria and polydipsia, reduced body weight and reduced milk yield when fed a low-Na ration (0.33gkg-1 dry matter (DM)) for 3 weeks. Deficiency symptoms were associated with a rapid decrease in salivary Na/K ratio to -1 DM for 5 weeks did not restore salivary Na/K ratio to values of >6. CONCLUSION: A daily Na intake of heat-stressed lactating cows to a ration intake of 1.6g Na kg-1 DM was insufficient to restore Na deficiency. One week was sufficient to deplete heat-stressed lactating cows of Na, allowing for rapid dose-response studies utilizing the salivary Na/K ratio as a parameter for Na status of cows under tropical conditions.
Original languageEnglish
Pages (from-to)2480-2486
JournalJournal of the Science of Food and Agriculture
Volume97
Issue number8
DOIs
Publication statusPublished - 2017

Keywords

  • Lactating cows
  • Saliva Na/K
  • Sodium
  • Tropical conditions

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