Kolb (1984) summarized various types of stress conditions that apparently increase vitamin C requirements for optimal health and performance:
- Inadequate nutrition of the dam or inadequate colostrum intake;
- Enteric or respiratory disease exposure;
- Castration, vaccination, tail-docking, etc.;
- Weaning, transition from individual to group housing;
- Transport stress;
- Sudden changes and extremes of weather conditions.
Under these conditions, supplementation with 1 to 2 g of vitamin C per day has been beneficial. Lower levels would be typical of whole milk (e.g., 100 mg per calf per day). Colostrum contains several times the level of vitamin C found in whole milk, and therefore adequate colostrum intake is critical to provide short-term stores of vitamin C for the neonate.
Vitamin C is the least stable of all vitamins and is particularly susceptible to destruction by oxidation, which is accelerated by heat and light. Choline chloride is especially destructive of vitamin C. Gadient (1986) reported that vitamin C is almost completely destroyed in a vitamin premix with choline, with an average monthly loss of 40.0%. Some of the discrepancies in experimental results with calves fed vitamin C may be explained by loss of vitamin C activity due to its low stability.
When providing supplemental ascorbic acid, it is advisable to use a stabilized form. In feed-storage experiments, coated ascorbic acid was four times more stable than crystalline vitamin C (Kolb, 1984). Adams (1978) reported that coated (ethylcellulose) ascorbic acid showed a higher retention after processing than the crystalline form, 84% versus 48%, respectively. Although retention of vitamin C activity in feed containing the ethylcellulose-coated product was low, it was 19% to 32% greater than the crystalline form. The ascorbyl-2-polyphosphate form of vitamin C was developed for aquaculture applications and is significantly more stable than ethylcellulose-coated vitamin C.