When it comes to multipurpose vitamins, vitamin E heads the list. Research results show correcting an apparent inadequacy of this essential antioxidant nutrient with vitamin E supplementation may:
- Boost litter size by an average of one pig per litter;
- Help increase the immunocompetence of sows, particularly in protecting against the costly mastitis-metritis-agalactia (MMA), and
- Be readily transferred in the sow's milk to help head off deficiency in her piglets.
Why supplemental vitamin E improves sows' reproductive performance still isn't fully known, but it's thought that vitamin E helps stimulate the formation of prostaglandins -- naturally occurring hormone-like substances that are involved in reproduction. To supplement for that extra pig per litter, Dr. Donald Mahan, swine specialist at The Ohio State University, recommends adding levels of 40 to 60 IU per kg of diet.
In aiding the immune system, vitamin E acts as an antioxidant to help maintain the integrity of cellular membranes and prevent cellular damage throughout the sow's body. To obtain a significant immune response from vitamin E, Mahan recommends 60 IU of supplemental vitamin E per kg of diet, along with 0.3 ppm of selenium.
This vitamin E recommendation is considerably higher than the current National Research Council (NRC) recommendation of 22 IU per kg of diet for swine at mature weight, but it's consistent with concentrations used in current feeding programs. It's also supported by recent university studies, which suggest that the NRC should increase its current vitamin E recommendations for gestating and lactating sows' rations.
Michigan State University researchers, for instance, studied the immunological effects of sow rations. The four treatments were:
- 60 IU supplemental vitamin E and 0.3 ppm selenium;
- 60 IU supplemental vitamin E, no selenium;
- No supplemental vitamin E, 0.3 ppm selenium;
- No supplemental vitamin E, no selenium.
The sows' immune systems provided the greatest response when the ration contained both supplemental vitamin E and selenium. The response decreased, with variations, when either vitamin E or selenium was absent. And it was weakest when both were absent. The study also corroborated studies with rats (Bendich et al., 1986), which found that a vitamin E deficiency weakens the immune system before other signs of deficiency appear.
Naturally occuring Vitamin E can be destroyed by grinding, exposure to air, storage and contact with trace minerals.
As the Michigan State research suggests, selenium and vitamin E work hand in hand. Both are tissue antioxidants. Vitamin E works in cell membrane fractions. Selenium has its effect in the cytosol fraction. Thus, the functions are independent and additive. To get the maximum benefit from both vitamin E and selenium, they need to be fed through gestation and lactation.
Nursing pigs get a much needed boost when their dams receive supplemental vitamin E. Pigs are born with almost no vitamin E because there is very little placental transfer. Thus, the newly born pig must rely on passive immunity derived from the dam's colostrum. In addition to providing immunity, colostrum is the piglet's only source of vitamin E. The pigs' long-term survival is related directly to the amount of colostral immunoglobulin received in the hours immediately after birth.
A recent Canadian study (Nemec et al., 1994) assessed supplemental vitamin E levels for the dams, in this case gilts, and the protection afforded their pigs. The investigators divided the gilts into three groups and supplemented their rations with three levels during gestation: 22 IU per kg of vitamin E (the NRC recommendation), 44 IU per kg and 88 IU per kg. Only when gilts received four times the NRC recommendation did their pigs' blood plasma show higher levels of immunoglobulin on the day of birth, thus improving their immune status. (Giving the dam a prepartum vitamin E injection did not affect the pigs' serum immunoglobulin levels.)
During lactation, the investigators increased the gilts' vitamin E supplementation to 55 IU per kg, 110 IU per kg and 220 IU per kg. By day 14, the gilts had shown a significant, dose-dependent increase in their milk immunoglobulins.
Supplemental vitamin E, available in the sow's milk, may also help prevent fatal reactions to the iron injections routinely given to baby pigs, because iron promotes the production of the oxygen free radicals that vitamin E inactivates.
At weaning, a pig's need for vitamin E is probably even greater than at birth. Both the stresses of early weaning -- especially moving, crowding and diarrhea -- and the pig's fast growth rate call for vitamin E's antioxidant properties. The needs showed up clearly in another study: Four weeks after weaning, pigs from sows not supplemented with vitamin E had a significantly higher incidence of heart muscle degeneration, yellowing (ceroid) body fat and liver lesions than did pigs from supplemented sows. In the second parity, all of the pigs from unsupplemented sows had gut edema, whereas none of the pigs from supplemented sows did.
Although using injectable vitamin E and selenium to supplement pigs may help reduce mortality, providing additional vitamin E in both sow and postweaning pig rations may be more effective. In commercial trials, pigs needed injection of at least 40 mg of vitamin E per kg of body weight to maintain stable blood levels.
When analyzing sows' rations for naturally occurring vitamin E and the necessary supplemental level, don't overestimate the vitamin E content in the ration (Figure 1). Even if the ration's ingredients appear to provide adequate levels, remember that naturally occurring vitamin E has not been stabilized and is more prone to damage. It can be destroyed in the feed by grinding, storage, exposure to air and contact with trace minerals.
