Influence of blanketing and season on vitamin D and parathyroid hormone, calcium, phosphorus, and magnesium concentrations in horses in New Zealand.

This research studied the impact of seasons and horse-blanketing practices on vitamin D production and other minerals involved in calcium homeostasis. The researchers discovered a clear seasonal pattern, with higher concentrations of vitamin D in spring and summer, perhaps linked to the enhanced exposure to sunlight during these periods. However, whether horse-blankets and Vitamin D3 synthesis from skin contribute significantly to a horse’s vitamin D levels requires further study.

Objective of the Study

• The study aimed to explore the influence of blanketing (covering the horse with blankets) and seasonal changes on vitamin D synthesis in horses. Moreover, it sought to investigate the interaction between vitamin D and other substances that play key roles in calcium homeostasis (i.e., the process of maintaining stable levels of calcium in the bloodstream).

Methodology

• 21 healthy horses, 5 of which were covered with standard horse blankets, participated in the study, which lasted for 13 months.
• The researchers collected blood samples to measure the concentrations of different forms of vitamin D (25-hydroxyvitamin D2 and D3, and 1,25-dihydroxyvitamin D), ionized calcium, total calcium, phosphorus, total magnesium, and parathyroid hormone.
• The study also examined grass and hay samples, analysing them for their contents of vitamin D, calcium, phosphorus, and magnesium. In addition, climate data were collected.

Findings

• The researchers found that 25-hydroxyvitamin D3 in horse serum was either undetectable or below the detection limit of the assay. The main form of vitamin D detected was 25-hydroxyvitamin D2.
• There were no noticeable differences in the rates of 25OHD2, 1,25(OH)2D, ionized and total calcium, phosphorus, total magnesium, and parathyroid hormone concentrations between the blanketed and non-blanketed horses.
• Statistically significant correlations were observed between ionized calcium and parathyroid hormone, ionized calcium and total magnesium, and dietary vitamin D and 25OHD2.
• The team found a significant seasonal trend in 25OHD2 levels—these were higher in spring and summer when the amount of sunshine and UV radiation was higher. In contrast, parathyroid hormone was higher in winter, while 1,25(OH)2D was higher in summer.

Conclusion of the Study

• The study suggests that horses may need to consume vitamin D in their diets to fulfill their requirements, but more research is needed to definitively determine the contribution of vitamin D3 synthesis in the skin to the horse’s vitamin D status.