EQUUS CONSULTANTS

Do older horses need more vitamin E?

Q:As I was reading “A Greater Good” (Case Report, EQUUS 480) concerning the effects of vitamin E deficiency in youngsters, I noted that I’d seen similar signs, namely a lack of coordination, in my 32-year-old gelding. It made me wonder if anyone has done any research on seniors who are no longer able to graze pasture due to a lack of teeth.

My Arabian gelding had 24-7 access to pasture for his entire life, but by the time he reached the age of 30, he had no molars. I now feed a “complete” senior feed along with soaked timothy hay pellets. I checked the nutrition information on the senior feed, and the vitamin E content was listed as 170 IU/lb.

As horses live longer, I wonder if seniors (as well as others who may be dentally deficient for whatever reason) receiving a “complete” feed might benefit from additional vitamin E supplementation. Claire Gilmore Nacogdoches, Texas

A:First, let me congratulate you for keeping your horse healthy for so long. If your aging horse is showing signs of incoordination, my first recommendation would be to have him thoroughly examined by a veterinarian to rule out other potential causes. But, certainly, a vitamin E deficiency is something to consider for any horse who does not get any of his nutrition from green pasture.

Vitamin E is an essential nutrient that is abundant in many types of forage and pasture grasses, especially orchard grass, alfalfa, fescue and timothy. How-

ever, the vitamin E content decreases as the plant ages and degrades quickly with processing (such as heat or grinding) as well as when grasses are cut and dried into hays. Thus any horse who for whatever reason receives the bulk of his nutrition from hay or other processed forages may benefit from a vitamin E supplement.

The NRC ( Nutrient Requirements of Horses, 2007) recommends 1 IU per day vitamin E for every kg of body weight for the adult horse at maintenance. This increases to 2 IU per kg of body weight for horses in heavy work and for lactating mares. Therefore, an average 1,000-pound horse needs a minimum of 500 IU of vitamin E per day, ranging up to 1,000 IU for those with higher needs. So assuming you are feeding at least 20 pounds of feed (for a 1,000-pound horse at 2 percent of body weight), and half of that is the senior diet, your horse is consuming 1,700 IU per day of Vitamin E just from the senior feed alone.

Still, it might be a good idea to check your horse’s vitamin E levels, which your veterinarian can do with a blood test. “Vitamin E” is a collective term for a group of eight compounds called tocopherols and tocotrienols. While a blood concentration of

-tocopherol less than 1.5 ug/mL is considered deficient, this does not always result in clinical signs.

However, low levels of vitamin E can be associated with decreased immune function. Examples of other problems linked with vitamin E deficiency are white muscle disease (WMD), equine degenerative myeloencephalopathy (EDM) and equine motor neuron disease (EMND). As you know from reading the article you cited in your letter, EDM and WMD are more predominant in young, growing horses who also have a genetic predisposition.

EMND, however, can occur in adult horses. This disease results from damage to the neurons that control type I muscle fibers. Typically, horses with a vitamin E deficiency show clinical signs of EMND---including weakness, trembling and muscle atrophy---after about 18 months. It has been recommended that even healthy horses without access to green forage be supplemented with at least 1 IU per kg of body weight of additional vitamin E (500 IU per day extra) to prevent EMND. For horses affected by EMND, the recommendation is to supplement with a total of 5,000 to 7,000 IU -tocopherol per day.

Vitamin E can be supplemented to horses in either a natural or synthetic form. The two types have different absorption rates; you can find out which you’re dealing with by reading the labels. Synthetic vitamin E supplements are typically a mixture of all the iso-

A vitamin E deficiency is something to consider for any horse who does not get any of his nutrition from green pasture.

mers of tocopherol, an all-rac- -tocopherol mixture or dl- - tocopherol. You will usually see synthetic supplements identified on the label as -tocopherol acetate. The acetate requires a two-step conversion to become bioavailable to the horse: removal of acetate from the molecule and a micellization process that converts -tocopherol to a watersoluble form.

Conversely, natural vitamin E supplements are made from only one isomer (usually d- - tocopherol or RRR

-tocopherol) and in theory they are

quicker and easier to absorb. Some supplement manufacturers take it a step further and produce micellized products, which are water-soluble. These natural forms have been found to be 1.5 to 2 times more available than the synthetic versions depending on the duration of the supplementation and the physiological status of the horses used in the research. Studies have shown that in horses undergoing exercise or with a deficiency, the method of supplementation with the highest absorption would be a micellized form of -tocopherol.

In conclusion, it would definitely not hurt to supplement your older horse with vitamin E. It is an especially good idea to supplement any horse without access to fresh green forage. In this case, a vitamin E supplement to meet the NRC requirement of 1 IU per kg of body weight per day or 2 IU if in heavy exercise or lactating would suffice. However, more may be necessary in horses who are predisposed to experiencing some muscle soreness or who have muscle conditions that warrant supplementation. Carey A. Williams, PhD Rutgers, the State University

of New Jersey New Brunswick, New Jersey