Circulating concentrations of vitamins C, D and E vary with age but not with pneumonia status in foals during the first 5 months of life

Adequate vitamin availability is vital for cellular and immune function and for normal growth. Available data on age-related changes in serum concentrations of vitamins in foals are limited. In addition, associations between circulating vitamin concentrations and the development of bronchopneumonia in foals are not described. (1) To quantify circulating concentrations of vitamins C, D and E from birth to weaning in foals; (2) to determine associations between vitamin concentrations and the development of bronchopneumonia during this period. Prospective cohort study. Blood samples were serially collected from 100 initially healthy Warmblood foals from birth to 5 months of age. Health status was evaluated weekly, and the development of subclinical and clinical bronchopneumonia was recorded. After weaning, foals were allocated to healthy, subclinical and clinical pneumonia groups, and samples from 15 foals/group were randomly selected for vitamin C, D and E quantification via ELISA and HPLC. Data were analysed with linear mixed models (p < 0.05). Circulating concentrations of vitamins C, D and E did not differ between healthy foals and foals with subclinical or clinical pneumonia. Foal age significantly impacted vitamin concentrations (p < 0.001) in a vitamin-specific manner. Vitamins C and E concentrations increased during the first week of life and then decreased until weaning. Vitamin C concentrations were higher at pneumonia diagnosis in foals with pneumonia diagnosed at or before 8 weeks of age than in healthy foals. Vitamin D concentrations were lowest on Day 7 and then increased steadily until weaning. A small number of foals was included, and results may be specific to this study population due to environmental and farm management factors. Circulating concentrations of vitamins C, D and E vary with age in foals, but do not appear to be related to the development of bronchopneumonia.