a
s yougazeoutat yourhorse’sfield,it’sevi-
dentthatwinteris coming.theonce-green
colorof lushgrassis fadingto varyingshades
of autumnbrown.youmaybethinkingthat
thepastureis nowokforyourhorsesto graze
onfulltime—eventhoseindividualsthattend
towardobesity.Butyouwouldbewrong.
Withdecliningqualityofpasturegrassin
autumnmonths,thegrassesincreaseintheir
fructan(sugar)content,creatinga riskoflamini-
tis,a footconditionalsoreferredtoasfounder.
Let’slookatsomeofthereasonsforthisand
whatyoucandotoprotectyourhorse.WhatIs Fructan?
Plants,andinparticularcool-seasongrasses,
storetheirenergyfromphotosynthesisinthe
formofstarchandsugars,suchasfructan.
Thesesugarandstarchenergysourcesinplants
arereferredtoasnon-structuralcarbohydrates
(NSC),a termyoumayrecognizefromlabelsof
commercialhorsefeedsthatstate“lowNSC.”
Fructanconcentratesinthelowerpartofthe
plant,particularlythestems—theverytargetof
grazinghorses.Thesweeterthegrass,themore
appealingit is toa horse’stastebudsExamplesofcool-seasongrassesincludetall
fescue,perennialryegrass,Kentuckybluegrass,
orchardgrassandmeadowfescue.Fescueand
ryegrasshavethehighestfructanlevels.
Intheautumn,nightsgetcolderandplant
growthslows.Yetphotosynthesiscontinuesdur-
ingthesunnyhours,withcool-seasongrasses
continuingtoaccumulatemorefructaninthe
stems.Ambienttemperature,light,andmoisture
determinetheamountoffructanproduced.
Forexample,asphotosynthesisrampsupdur-
ingdaylighthours,sugarcontentinthegrasses
increases,sowhatmayhavestartedaslowlevels
offructaninthemorningelevatestohigher
levelsbyafternoon.(Thisis trueforalltimes
ofyear,butparticularlysoinfallmonthswhen
plantgrowthslows.)Knowingthistimeframefor
thehighestsugarcontenthelpsyoudecidewhen
is besttoturnyourhorseouttograze.
Anotherconcernis haythathasbeencutand
leftonthefieldtodrybeforebaling.Mowngrass
continuestophotosynthesizeandproduceNSCs
fora coupleofdayswhilelyinginthefieldtodry.
Hayis likelytohavelesssugarif cutatnight.
HaycanbetestedtodetermineitsNSClevels,
whichideallyshouldbelessthan 10 percent.
TestingforNSClevelsis particularlyhelpfulfor
horsesthatneedcarefulmanagementoftheir
weight,likethosethatareinsulinresistant,
cresty,andtendtobefatandaffectedbyequine
metabolicsyndrome.Talktoyourveterinarian,
a localequinenutritionist,oragricultureexten-
sionagentaboutwheretosendhaysamplesfor
analysis.WhYIs FructanBaD?
Fructanis composedofa chainofmoleculesthat
is resistanttodigestioninthesmallintestine.It
passesundigestedintothelargeintestine,where
it fermentstoproducesubstancesthatlowerthe
pHofthehindgut.
Thisacidicenvironmentresultsina die-offof
healthygutmicrobes.Oneofthesebacteriahasa
cellwallcalledendotoxin;deathofthesebacte-
riaamplifiesthepresenceofthistoxin.BYNANCYS.LOVING,DVMhay that was left out to dry for a few days
before baling will continue to build up nscs.
B BroWN/shutterstock
It might seem like the perfect time of year to be a horse,
but autumn grasses contain hidden danger.
[ october 2019 | horseillustrated.com 31 ]