Abstract
Vitamin D deficiency affects canines and humans alike. Athletes are a particularly high-risk group. Further research regarding optimal intake and supplementation is needed to establish the parameters of vitamin D status in both humans and canines and to create a physiologically-relevant definition for vitamin D sufficiency. The objectives of this study were to (1) compare 25-OHD (25-hydroxy vitamin D) levels in sled dogs before and after receiving a diet supplemented with wild Alaskan salmon and (2) correlate biomarkers associated with vitamin D metabolism to 25-OHD levels in sled dogs. Plasma samples from 14 working sled dogs between 10 months and 7 years of age were collected before and after a 4-week supplementation with ≈0.45 kg of salmon/day. Samples were analyzed using enzyme-linked immunosorbent assays (ELISA) for parathyroid hormone and vitamin D binding protein (DBP); 25-OHD levels were measured via radioimmunoassay. 25-OHD and DBP in sled dogs significantly increased after a 4-week supplementation with salmon (P=0.0011 and 0.0367, respectively). Additional variations in 25-OHD were observed when separated by sex (P=0.0404) and age (P<0.0001). 57% of the dogs were deficient prior to the salmon supplementation and 14% at the completion of the study. Wild Alaskan salmon is one of the few food sources that provide appreciable amounts of vitamin D. A 4-week salmon supplementation in sled dogs was sufficient to improve 25-OHD concentrations in most sled dogs in this study. Confounding factors such as age and sex affect circulating 25-OHD levels.