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  Discussion on Research Summary: Very High Levels of Vitamin E Not Helpful
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Board Administrator
Username: admin

Posted on Tuesday, Apr 10, 2007 - 9:14 am:

Though many feel NRC recommendations a bit low there are some who feel horses can benefit from very high (5 to 10 times NRC) levels of vitamin E. This experiment suggests otherwise.
DrO

Equine Vet J Suppl. 2006 Aug;(36):617-21.
Oral vitamin E supplementation on oxidative stress, vitamin and antioxidant status in intensely exercised horses.

Williams CA, Carlucci SA.
Rutgers, the State University of New Jersey, Cook Campus, Department of Animal Science, 84 Lipman Drive, New Brunswick, New Jersey 08901, USA.

REASONS FOR PERFORMING STUDY: Vitamin E is the most commonly supplemented antioxidant in horses; however, previous research is not conclusive as to the recommended level for exercising horses. OBJECTIVE: To evaluate the effects of 3 levels of vitamin E supplementation on oxidative stress and vitamin/antioxidant status in intensely exercised horses to determine the optimal level of vitamin E supplementation. METHODS: Twelve unfit Standardbreds were divided into 3 groups, supplemented orally with 0 (CON), 5000 (MOD), or 10,000 (HI) iu/day of DL-alpha-tocopheryl acetate. The 3 x 3 Latin square design consisted of three 4 week supplementation periods with 4 week wash out periods between. After each period, horses underwent a treadmill interval exercise test. Blood samples were collected and heart rate (HR) measured before, during and after exercise. Data were analysed using ANOVA with repeated measures in SAS. RESULTS: The CON group had lower HR throughout the test compared to the MOD and HI groups (P<0.05). There was an increase in plasma retinol (RET), beta-carotene (BC), red blood cell total glutathione and glutathione peroxidase with exercise (P<0.05), but all groups returned to baseline after 24 h. Plasma alpha-tocopherol (TOC) increased from baseline with exercise (P<0.0001) in all groups; treatment differences were observed at 24 h (P<0.05). The HI and CON groups had lower BC compared to the MOD group (P = 0.05). CONCLUSIONS: Horses supplemented with vitamin E, at nearly 10-times the 1989 NRC recommended level, did not experience lower oxidative stress compared to control horses. Additionally, lower plasma BC levels observed in the HI group, which may indicate that vitamin E has an inhibitory effect on BC metabolism. POTENTIAL RELEVANCE: Supplementation above control levels is not more beneficial to oxidative stress and antioxidant status in intensely exercising horses; indeed, levels 10 times in excess may be detrimental to BC and should be avoided.
Member:
majoda92

Posted on Tuesday, Nov 13, 2007 - 7:18 pm:

I currently supplement several of my older horses with 5000IU of vitamin E daily. One horse was tested as being very deficient in the vitamin, and showed much improvement in his hind end strength and flexibility when supplemented. Another mare is on 10,000 IU daily after experiencing some neurological and balance issues. She is also showing improvement, so I am hestitant to reduce her intake. Of course, I don't want to overdose any of them, or waste money on needless supplementation. Should I have the horses tested to see if supplementation is necessary?
Moderator:
DrO

Posted on Wednesday, Nov 14, 2007 - 6:13 am:

Diane I have some questions. What were the horse's plasma levels prior to supplementation? Were the horses also evaluated for adequate selenium in the diet and blood levels of glutathione peroxidase? Why were such high dosages of Vitamin E chosen?
DrO
Member:
majoda92

Posted on Wednesday, Nov 14, 2007 - 11:24 am:

Thanks for getting right back to me. The vet is coming out today to recheck the mare with the neurological symptoms. I will ask her to draw blood, and also get the levels of the other horse who tested low.
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