Because of a perfect storm of vitamin production problems, supplemental vitamins A and E are becoming scarce and prices are skyrocketing. Supplies probably will remain very tight well into summer of 2018. In this time of high vitamin prices and limited supply, vitamin supplementation strategies should be evaluated. The most recent dairy NRC (2001) has a vitamin A requirement of 50 IU of supplemental vitamin A/lb of body weight. For an average Jersey and Holstein cow, that translates to about 50,000 and 70,000 IU/day, respectively. That requirement is also for dry cows and growing heifers. For supplemental vitamin E, NRC recommendations are 0.35 IU/lb of body weight for lactating cows and 0.7 IU/lb of body weight for dry cows. This is approximately equal to 500 and 1000 IU/day of supplemental vitamin for lactating and dry Holstein cows and 350 and 700 IU/day for lactating and dry Jersey cows, respectively. Surveys have indicated that supplementation rates are commonly at least twice NRC recommendations.
Several controlled studies have shown that feeding vitamins A and E at NRC recommendations reduce mastitis, abortions, retained placenta, and metritis compared to feeding diets with no supplemental vitamin A or E. However, essentially no data are available showing that feeding more vitamins A and E than recommended has any additional positive effects. An exception is prefresh cows because for vitamins A and E, parturition is a critical time. Substantial amounts of those vitamins are put into colostrum and substantial amounts of those vitamins are metabolized during the process of parturition. Several studies have shown that increased supplementation of vitamin E during the last two or three weeks prepartum reduces mastitis. Supplementation rates ranged from 2000 to 4000 IU/day during the prefresh period. Similar data for vitamin A are not available.
Recommended vitamin supplementation strategies:
1. Feed vitamins A and E at NRC levels. In many situations, this will reduce vitamin supplementation by about 50%.
2. If prices continue to climb and vitamins become scarce, then:
- Prefresh cows should be the highest priority and be maintained at NRC levels for vitamin A and probably 2000 IU/day for vitamin E. A prefresh period of 2 or 3 weeks is adequate with respect to these vitamin recommendations.
- If you do not have a separate prefresh group from the far-off dry cows, the next priority would be to meet NRC requirements for vitamins A and E for all dry cows.
- I would try to provide some supplemental vitamins A and E to all cows, but lactating cows would be the lowest priority. These cows consume a lot of feed and the feed is usually better quality than that fed to dry cows. Lactation diets can contain substantial basal vitamin E and B-carotene (precursor to vitamin A); therefore, they will be consuming more vitamins than dry cows. If vitamin A becomes very scarce, I think you can reduce vitamin A supplementation to about 50% of NRC for several months (all the past overfeeding of vitamin A has likely increased liver stores of retinol, which can be used to meet the vitamin A needs for an extended period of time). Likewise, vitamin E supplementation to lactating cows could probably be cut to 50% of NRC in the short term (a few months).
Vitamin E supplementation of bred heifers can likely be reduced to well below NRC until about 60 days prepartum. Also, some vitamin A supplementation should be provided to these animals (perhaps 50% of NRC).