An invisible danger lurking ins t o red corn could put the cattlefeeding on the grain at risk,university experts warn .

The danger lies in the fungalfamily A s p e rg i l l u s , s p e c i f i c a l l yA s p e rgillus flavus. While difficult todetect, the common mold grows onvarious grains, like cottonseed andpeanut, but it is mostly known for itse ffects on corn — and the harshoutcome for cattle producers feedingthe infected grain.

As John Reagor, toxicologist at theTexas Ve t e r i n a ry Medical DiagnosticLab, explains, the mold produces atoxic byproduct known as aflatoxin.Poisonous to humans, poultry andlivestock, the toxin, once ingested,has detrimental effects on pro d u c t i o nnumbers and herd health.

The Food and Dru gAdministration (FDA) has strictlyregulated the toxin in dairy cattle foryears, since aflatoxin can be passedto milk products and, there f o re, tohumans. But less stringentregulations exist for beef cattle feed,Reagor says, primarily because thetoxin isn’t typically found in themeatcase. “The main danger is thee ffects it has on the live animal andthe pro d u c e r ’s bottom line.”

While other animals like poultryand swine may be more sensitive to

aflatoxicosis than beef cattle, Reagorsays, it remains a principal concern .

“ T h e re are probably morep roblems in beef herds than peoplerecognize, simply because of what itdoes in those herds. It causesreduced perf o rmance primarily inthat it suppresses the immunesystem, making animals moresusceptible to common diseases,” hesays. “Aflatoxicosis may be anunderlying cause of disease that noone re a l i z e s . ”

G rowth of a toxi nThe widespread fungus thrives

during drought, high temperature sand high humidity and is, there f o re ,m o re prone to areas exhibiting suche n v i ronmental conditions as foundin the South, Southeast and parts ofthe Corn Belt.

Joseph Krausz, Texas A&MExtension plant pathologist, sayswhen drought stress occurs duringpollination, plants become moresusceptible to A s p e rg i l l u s s p o res.

“If the corn plant isphysiologically growing well andv i g o ro u s l y, the fungus can’t getestablished well and, there f o re, isn’table to produce the toxin,” he says.“But once the plant becomess t ressed, many of its natural defensesa re n ’t quite up to par. We see someof these pathogens, like A s p e rg i l l u sf l a v u s , attack the corn plant andbecome established. It’s just like inhumans; if we become stressed orw e ’ re not getting essential nutrients,w e ’ re more prone to illness.”

Insects also play a role in aflatoxininfestations, he notes. Insects candamage ears of corn and bre a kt h rough seed coats, making the plantm o re susceptible to the mold. Plus,insects can carry spores to silks andk e rnels. “Insect damage can definitelyi n c rease the frequency and amount ofaflatoxin problems,” Krausz says.“But the drought stress and hott e m p e r a t u res usually have to be therefor high aflatoxin levels to develop.”

University publications showt e m p e r a t u res ranging from 80º F to100º F and a relative humidity of85%, or about 18% grain moisture ,a re optimum for the mold’s gro w t hand aflatoxin production. The moldalso develops or continues to developin stored corn, depending onm o i s t u re content, temperature andcondition of grain going into storage.

“If grain moisture is allowed torise much above 13% to 14% grain

m o i s t u re in storage, then the funguscan start to develop, and we canbegin to see these hot spots within abin or silo where the aflatoxin canbuild up as the fungus gro w s , ”Krausz says.

F o rt u n a t e l y, last year’s gro w i n gseason exhibited unusually moistconditions and calm temperatures inmany parts of the nation norm a l l ya ffected. Although experts likeKrausz are n ’t expecting manyp roblems with stored grain this year,cattlemen shouldn’t disre g a rdaflatoxin just yet. It remains anelusive pro b l e m .

“ You can go many years andnever suspect a problem,” says ScottBarao, University of Mary l a n danimal scientist. “Then, we’ll have ad rought or some other stress on thec o rn crop, and you start hearingabout aflatoxin concern s . ”

1 0 7Feb r u a ry2 0 0 5

Hi d d e nDan g e r s

S t o ry & photos byC R YSTA L A L B E R S

Some st o red feed su p pl ies could ca rr y t ox i ns .

S co t t Ba ra o, Unive rsi t y o f Ma ry land anima l sci e n t ist, says he most l y s e esa f la toxi np roble m s a m o ng integ ra ted grain and livesto cko p e ra t i o ns. T h ese opera t i o ns will o fte nfeed livesto ck the by p ro d u c t s o f the grain side of the operation.

The toxi n - p ro d u ci ngA s p e rg i ll u s f l av u s g rows o nea rso f corn as a ye ll owis h -

g reen fe l t l i ke or pow d e ryg rowth, Texas A & M ’ s J os e p hK ra usz says . [ P H OTOS CO U RT ESY

O F I OWA STAT E U N I V E R S I TY E X T E N S I O N ]

( Co nt i n u ed on page 108)

Feb r u a ry2 0 0 51 0 8

happen there, too,” he says. “If afeedmill or storage facility isn’t watchingm o i s t u re content and drying the graindown well, you can have problems, butyou generally see it with guys who areh a rvesting their own feed or marketingtheir grain to others.”

An elusi ve proble mCattle feeding on aflatoxin-infected

c o rn may experience reduced feede ff i c i e n c y, reduced feed intake,re p roductive failures, incre a s e dsusceptibility to stress and disease, andlower milk production. Depending onthe level of contamination, continuedaflatoxin intake can result in anemia,rectal prolapse, liver and kidney damage,and even death. Calves and any animalsunder stress, like weaning calves or bre dheifers, are more prone to the effects ofthe toxin.

“Older animals can tolerate the toxinbetter than younger animals or thosewith a lot of stress,” Barao says. “Inlactating beef cows, it gets passed ont h rough the milk, and it can influence

Once the mold is produced, it becomesstable, making it difficult for heat, cold orlight to affect it, one University ofMissouri publication re p o rts. The moldcan withstand temperatures up to boiling,and although toxin levels in corn maydecline, traces of the toxin may be pre s e n tfor years.

Barao says he mostly sees aflatoxinp roblems among integrated grain andlivestock operations.

“A lot of times, when you have a grainand livestock operation, the livestock willbe fed byproducts from the grain side ofthe operation. Low-quality corn andb roken kernels can often be fed in thesesituations,” he says. “Guys that like to feedb y p roducts like that should be very care f u l

in a year that’s prone to aflatoxinp ro d u c t i o n . ”

P roducers who purchase grain fro mmills or large feed facilities are n ’t off thehook, either, Barao notes, although theyn o rmally have less of a chance ofp u rchasing infected corn .

“The mills usually watch it morec l o s e l y. They can’t risk an aflatoxino u t b reak, but that doesn’t mean it can’t

H i dden Dange rs ( f rom page 107)

“One of the wea k n ess es in test i ng is t ha ta f la toxin usu a ll y d o esn ’ t o ccur un i fo r ml y i ng rain,” says K ra usz, re fe r r i ng to toxi n - p ro n eh o t sp o t s l o ca ted ha p ha za rd l y t h ro u g h o u tsto red grain su ppl i es .

1 0 9Feb r u a ry2 0 0 5

baby calves, too. Calves will begin todisplay the symptoms more seriouslythan it might be affecting the cow at them o m e n t . ”

The diff i c u l t y, Reagor says, is linkingsuch common symptoms to the root ofthe pro b l e m .

“A whole gamut of things — poornutrition, parasites, etc. — could causethese symptoms and poor perf o rm a n c ein cattle. They’re such commonsymptoms to a number of diff e re n tdiseases,” he says. “That’s the numberone problem in identifying the cause asaflatoxin. Testing is the only way to doi t . ”

H o w e v e r, producers can’t justexamine a handful of kernels to detectthe mold. Krausz says it’s usuallyinvisible to the eye. “If you have a fieldbadly infected, you can peel back thehusk and sometimes see the fungus as ay e l l o w i s h - g reen, feltlike or powderyg rowth,” he says. “Once that combinegoes through, though, and it’s allh a rvested, the visual aspects just are n ’tt h e re . ”

“ I t ’s deceiving,” Barao acknowledges.“ You can find moldy kernels and have noaflatoxin, and you can find norm a l -looking kernels and have high levels ofaflatoxin. So, mold on kernels may getyou thinking about it, but testing will bere q u i red to know for sure whether youhave aflatoxin.”

Although the toxin is norm a l l yundetectable to the eye, Reagor says

p roducers feeding whole corn should bew a ry of smaller- t h a n - n o rmal kern e l s .

“If they have corn with a lot of littlebitty kernels in it, it may have gro w nunder droughty conditions,” he says. “Ift h e y ’ re half the size they should norm a l l ybe, that’s a clue to me that it should bechecked for aflatoxin.”

A lot of broken and discolored kern e l scan also indicate potential pro b l e m s ,

Krausz says, but “re a l l y, the ultimate testwill have to be using some of the methodsfor detecting the amount of aflatoxin usingsome of the serological kits that area v a i l a b l e . ”

Test i ng for toxi nsOnce a producer suspects aflatoxicosis,

Barao, Krausz and Reagor suggest he or( Co nt i n u ed on page 110)

“ Older anima ls can tole ra te the toxin bette rt han yo unger anima lsor those with a lot o fst ress,” Ba rao says .

Feb r u a ry2 0 0 51 1 0

s e rological test, have replaced past, less-reliable testing and can detect smallquantities of specific contaminants ingrain samples. “The ELISA test isrelatively quick and cheap,” he says.“ Tests can run anywhere from $15 to$30, depending on who is perf o rm i n gt h e m . ”

Such tests will determine the severityof infected feed and how it should beused next. The FDA re c o m m e n d saflatoxin levels in corn or other grainsnot exceed 100 parts per billion (ppb) ifthe feed is intended for breeding cattle,or 300 ppb if the feed is intended forfinishing cattle.

If results show high levels of thetoxin, Reagor recommends getting ridof contaminated corn altogether andreplacing it with clean, noninfectedgrain. But lower levels of aflatoxin canbe managed — with certain pre c a u t i o n s .Some producers blend aflatoxin-infectedc o rn with noninfected grain to lessenthe toxin’s effects. “If you’re blending,you want to leave plenty of room fore rro r,” he says. “You wouldn’t want totake a set amount of corn infected at 200ppb and blend it with the same amountof corn at 0 ppb aflatoxin to come upwith 100 ppb. Instead, shoot for 50 ppbto allow for any levels of aflatoxin thatw e re n ’t detected earlier. ”

she take a sample of feed for testing.H o w e v e r, taking an accurate feed sampleposes its own set of difficulties.

“One of the weaknesses in testing isthat aflatoxin usually doesn’t occuru n i f o rmly in grain,” Krausz says, re f e rr i n gto toxin-prone hot spots locatedh a p h a z a rdly throughout stored grain

supplies. “Getting a proper sample can bea real hit-and-miss. One time a probe mayhit a couple hot spots, and they may get ahigh amount of aflatoxin. If they do itagain 10 minutes later, they may find thenumber isn’t quite as high because theyd i d n ’t hit the hot spots.”

A South Dakota State Universitypublication suggests producers take 10pounds (lb.) of corn from each feed sourc e ,

consisting of several smaller subsamplestaken from diff e rent spots and mixedt o g e t h e r. Samples should be placed incloth or paper containers and submitted toa feedmill, local elevator or university labfor testing.

R e a g o r, who conducts tests at a Te x a sA&M lab and makes subsequentrecommendations to producers, saysseveral testing pro c e d u res, like the ELISA

H i dden Dange rs ( f rom page 109)

P re ve n t i ng afla toxi n - i n fe c ted co r nis d i f f i cul t to ma na ge si n ce envi ro n-m e n ta l co n d i t i o ns co n t rol t h em old ’ s g rowth. A South Dako taS ta te Unive rsi t y pu bl i cation, Af l a-t ox i ns: Haza rd s in Gra i n / Af l a t ox i co-s i s a nd Livest o ck , p rovi d es a fe wt i ps for integ ra ted grain and live-sto ck p ro d u ce rs to minimize co n-ta m i nation of corn pro d u c t s in thef i e ld and during sto ra ge .

x Re d u ce pl a n t st ress . Us ere commended pro d u c t i o np ra c t i ces to minimize pla n tst ress and ma xi m i ze yi e lds .T h ese include insect, we e dand dis ease co n t rol p ra c t i ces ,as we ll as pla n t p o pula t i o nand fe rt il i t y p ra c t i ces .I r r i gation during poll i na t i o ncan decrease pre d isp osi t i o no f the crop to afla toxin. Pla n tcorn as ea r l y as p ossi ble, andpla n t s e ve ra l d i f fe re n t hyb r i dswith diffe re n t p oll i na t i o np e r i o ds. Ca re should be ta ke nto sto re un co n ta m i na te dhyb r i dsaway f rom those tha ta re co n ta m i na te d .

x H a rvest corn ea r l y and dry i ti m m e d ia te l y. H a rvest i ng co r nwhen it is a b ove the 20%m o istu re co n te n t and dryi ng it

Aflatoxin prevention

1 1 1Feb r u a ry2 0 0 5

Barao says contaminated cornbecomes an alternative source of feedwhen blended, but “you have to bec a reful with it and strategically managethe feeding of it. The easiest place to useblended feed is in open cows, maturecows, or early- to mid-pregnancy cowsor feedlot steers that are lesssusceptible.” With time and a good feeds o u rce, the toxin will eventually flushout of animals’ systems, unless severecontamination has caused liver damage.In that case, animals may never re g a i nadequate production levels.

P re ve n t i o nTo prevent problems with

aflatoxicosis, Barao says pro d u c e r sshould monitor corn or other potentiallya ffected grain if growing conditions havebeen suitable for aflatoxin development.

“If you’re growing corn in dro u g h tconditions or you’ve bought corn thatg rew in drought conditions, you need tobe on the lookout,” he says.

For cattlemen producing their ownfeed, Krausz suggests using corn hybridswell-adapted to the environment andplanting in soil that isn’t marginal orp rone to drought stress. Also, excessiveplant populations can incre a s esusceptibility to drought, and harv e s t i n gtime plays a ro l e .

If buying corn or a commerc i a l l yp re p a red feed, Reagor says, “buy it fro ma recognized, established company that isgoing to be doing testing. If you’rebuying from a ‘mom and pop’ feed-mixing operation, ask them if they aretesting or if they’re buying corn orcottonseed meal that has been tested.The local feedmill can be selling just asgood a feed, but you need to ask if it has

been tested, especially during dro u g h ty e a r s . ”

While little can be done to contro le n v i ronmental factors causing moldg rowth, re s e a rchers and Extensionp rofessionals like Krausz will continue tomonitor aflatoxin levels and work withp roducers in recognizing a pro b l e m .

“ We’ve requested funding to continueto work on aflatoxin control and genetic

resistance to the pathogen,” he says.“ U l t i m a t e l y, I think the solution will bec o rn hybrids that are resistant to thepathogen or are in at least some way notable to produce aflatoxin. We’ll continueto work on it, and hopefully, there will be ab re a k t h rough in the not-too-distantf u t u re . ”

within 24 to 48h o u rsto a moistu reco n te n t no grea ter tha n14% grea t l y re d u ces t h ei n fection, growth and toxi np roduction by A s p e rg i ll u s.

x Avoid da maged ke r n e ls .D a ma ged ke r n e ls a re morel i ke l y to become infe c ted wi t hm olds both in the field and insto ra ge. Corn hyb r i dswith go o dh us k cove ra ge of the ear ha vebeen shown to ha ve lessi n fection and afla toxi nd e ve l o p m e n t. Adjust m e n t o fthe co m bine also can re d u cem e cha n i ca l da ma ge of t h eke r n e ls .

x S to re corn at 12% moistu reco n te n t. Ma ximum moistu reco n te n t for corn sto ra ge shouldbe 14%. Moistu re co n te n t a t o rb e l ow 12% is i d ea l for co r nsto ra ge.

x Keep sto rage and fe e d i ngfa cil i t i esclea n . Fungi ca nsu rvi ve on resi d u es le ft i nsto ra ge areas. Infection andtoxin production can re o ccur insto ra ge syste m s t ha t a re notp ro p e r l y cleaned andd isi n fe c te d .