title: Circadian rhythm of calciotropic hormones, serum calcium, phosphorus and magnesium during the shortest and longest days of the year in horses in New Zealand.
abstract: A study was conducted to determine the circadian rhythms and trends of vitamin D metabolites including 25-hydroxyvitamin D3, 25-hydroxyvitamin D2, 1,25-dihydroxyvitamin D and parathyroid hormone, in addition to serum calcium, phosphorus and magnesium concentrations in horses over 48 h on the shortest and longest days of the year in 2013. Five healthy adult horses (Equus caballus) were on a constant pasture feeding regimen, and blood samples were collected from each horse every 3 h over a 48-h period, starting at 07:00 PM on day one and finishing at 07:00 PM on day three, for the measurement of calciotropic hormones and electrolytes. There was a significant difference between the serum concentration of calciotropic hormones, iCa, tCa, P and tMg between the shortest (winter) and longest (summer) days of the year in horses. Serum concentration of 25OHD3was very low and mostly undetectable. Serum iCa, 1,25(OH)2D and PTH concentrations clearly showed a circadian rhythm on the longest days of the year and serum tCa, P and tMg concentrations showed a diurnal pattern on the longest days (summer) of the year. None of the analytes showed any circadian rhythm on the shortest days (winter) of the year. The result of this study could have significant relevance to equine athletes travelling to international equestrian competitions and facing a huge time and seasonal differences that might affect their ability to adjust their circadian rhythms to new time zones.
authors: Institute of Veterinary, Animal and Biomedical Science (IVABS), Massey University, Palmerston North, New Zealand.
authors: S
authors: S
authors: Azarpeykan
authors: Institute of Veterinary, Animal and Biomedical Science (IVABS), Massey University, Palmerston North, New Zealand.
authors: K E
authors: KE
authors: Dittmer
authors: Institute of Veterinary, Animal and Biomedical Science (IVABS), Massey University, Palmerston North, New Zealand.
authors: E K
authors: EK
authors: Gee
authors: Institute of Fundamental Sciences (IFS), Massey University, Palmerston North, New Zealand.
authors: J C
authors: JC
authors: Marshall
authors: Canterbury Health Laboratories, Christchurch, New Zealand.
authors: P
authors: P
authors: Elder
authors: Institute of Veterinary, Animal and Biomedical Science (IVABS), Massey University, Palmerston North, New Zealand.
authors: E
authors: E
authors: Acke
authors: Institute of Veterinary, Animal and Biomedical Science (IVABS), Massey University, Palmerston North, New Zealand.
authors: K G
authors: KG
authors: Thompson
mesh_terms: D000818:Animals; D002118:Calcium / Q000378:metabolism*; D002940:Circadian Rhythm / Q000502:physiology*; D006736:Horses / Q000097:blood / Q000502:physiology*; D008274:Magnesium / Q000378:metabolism*; D009520:New Zealand; D010281:Parathyroid Hormone / Q000097:blood; D010758:Phosphorus / Q000378:metabolism*; D017440:Photoperiod; D014807:Vitamin D / Q000378:metabolism
chemical_list: D010281:Parathyroid Hormone; D014807:Vitamin D; D010758:Phosphorus; D008274:Magnesium; D002118:Calcium
keywords: calcium; circadian rhythm; horse; magnesium; phosphorus; vitamin D