Daily and seasonal rhythms of serum glucose concentrations in Holstein cows

Abstract

To investigate possible daily and seasonal rhythms of serum glucose concentrations in lactating dairy cows, every three hours blood samples were taken sequentially over 27h. Twelve cows were used, six in their first lactations (Group A) and six in their third lactations (Group B), during winter, spring, summer and autumn 2002. Animals were in a commercial farm in Argentina, and were on an alfalfa-based grazing system, with two milkings per day. Blood samples were taken from the jugular vein, centrifuged, and analyzed for serum glucose concentrations with an autoanalyzer. The existence of a periodic pattern was verified with a Fourier analysis. Circadian rhythms were observed with frequency near 0.279 rad/h. The mesor and amplitude values were higher in winter. The acrophases for different seasons are similar. The highest levels of glucose were found at 4h (winter), 20h (spring), 6h (summer) and 10h (autumn). In conclusion, when animals are in natural conditions, it is possible detect daily rhythms in the serum glucose concentration.

Keywords:

• Chronophysiology
• daily rhythms
• glucose
• dairy cows

Acknowledgements

This work was carried out within project CAI + D 2002, financed by the Universidad Nacional del Litoral (Santa Fe, Argentine). The authors are grateful for gifts of reagents for chemical analysis to Wiener Lab., Rosario, Argentina.