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

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