Research Paper Abstract: Ascorbic acid status in pony mares and young pony foals
D. Marlin1and W.R. Allen2
1David Marlin Consulting, Cambridge, UK dm@davidmarlin.co.uk
2 The Paul Mellon Laboratory of Equine Reproduction,
“Brunswick”, 18 Woodditton Road, Newmarket, Suffolk CB8 9BJ
Introduction:
Like most animals, the horse is able to make ascorbic acid (AA; Vitamin C). However, it is not clear whether young foals have the capacity to produce adequate ascorbic acid from birth or whether this is initially dependent on supply in the mare’s milk. Ascorbic acid plays important roles, including immunity and in the formation of connective tissues, including cartilage, tendon and ligament. Low ascorbic acid status in young foals could therefore be deleterious to early development. The aim of this study was to determine the ascorbic acid concentration in the plasma of mares and young foals and in the mare’s milk.
Materials and methods:
A 10ml sample of colostrum and the 2nd milk produced at foaling was collected from 6 pony mares that foaled between April and June. At 7 days of age a 10ml jugular venous blood sample was collected from both the mares and foals into EDTA and immediately centrifuged at 400g for 10 min at °4C. EDTA plasma or milk (0.5ml) was added to 0.5 ml of 10% metaphosphoric acid containing 1 mM Na2EDTA to deproteinise the plasma. The sample was vortexed and snap frozen in liquid nitrogen and stored at –80°C. In order to reduce the oxidised form of ascorbic acid (dehydroascorbate, DHA) to measure the total concentration of ascorbic acid (tAA = AA + DHA), 0.3 ml EDTA plasma/milk was added
to 0.2 ml 10mM dithiothreitol, vortexed and left to stand at room temperature for 10 minutes.
Five hundred ul of 10% metaphosphoric acid/1mM Na2EDTA was added, the sample vortexed, snap frozen and stored at -80°C. Plasma ascorbic acid was analysed by HPLC with UV detection as described previously1. Data were not normally distributed so are presented as median and (25th-75th) percentiles. Differences between groups were
compared with a Mann-Whitney U test.
Results:
Foals had significantly higher plasma AA (p=<0.01) and tAA (P<0.01) and lower redox ratio (P<0.05) compared with mares (Table 1). There was no difference in plasma DHA (P>0.05). AA and tAA concentrations in colostrum and 2nd milk were not different and were around 10 times higher than those in the foals plasma. There was a strong positive correlation between mare plasma AA and mare’s milk AA (r2=0.89; P<0.01) and between mare plasma AA and foal plasma AA (r2=0.75; P<0.01).
Table 1. Reduced (AA), oxidised (DHA) and total (tAA) ascorbic acid and ascorbic acid redox ratio (%) in plasma and milk from 6 pony mares and their foals at 7 days of age.
Discussion and conclusion:
In 7-day-old pony foals, plasma AA was higher than in the foals mare. The mare’s AA status appears to have a large influence on the foals AA status at 7 days of life. Given the importance of Vitamin C in immune function and in growth and development, testing the AA status of mares prior to foaling and or appropriate supplementation of mares with Vitamin C may be beneficial. References: 1Marlin et al. (2002): J. Nutr. 132, 1622S-1627S.
