Ecol. aspects of transgenic crops

Robert Kriegel kriegelr at
Thu Apr 20 15:38:54 EDT 2000

Chris Durden requested references for the effects of bt-corn on livestock.
The following is a recent post from the DAIRY-L discussion list containing

Bob Kriegel
lepidopterist and systems analyst


1. In 1996, we [the we is Marj Faust] conducted a trial at the Iowa State
University Dairy 
Teaching and Research Farm to characterize milk composition from
dairy cows fed detectable levels of Bt proteins from Bt corn plants in
their feed.  We studied one Event 176 Bt hybrid (KnockOut), one
Bt11 hybrid (YieldGard), and one non-bt hybrid (control hybrid) that
was a genetic counterpart to the Event 176 Bt.  Cows were fed
rations containing one of these three hybrids as whole-plant green
chop corn; the fresh green chop was the sole forage source in the
TMRs.  Previous work on the protein produced by these
transgenic hybrids indicated that the Bt proteins were degraded
rapidly in the ensiling process, and so, to maximize the exposure of
our cows to these Bt proteins, we selected to feed green plant
material (whole-plant green chop).  Between all groups, we detected
no difference in feed intake, no differences in milk production (lowest
group averaged >84 lbs. daily), no differences in milk composition
(protein, fat, lactose, other solids, total solids), and no differences in
udder health as measured by milk SCC.  Furthermore, no transgenic
proteins, transgenic DNA, or plant source DNA were detected in milk
samples collected during the feeding trial.  Details of this study can
be found in:

Faust, M., and L. Miller.  1997.  Study finds no Bt in milk.  Integrated
Crop Management.  IC-478 Fall Special Livestock Edition.  Iowa State
University Extension.  Ames.  pp 6-7.

2. Subsequent work in our ISU laboratory to study nutritional
composition identified no differences in nutritional characteristics (P
> .05) for whole-plant chopped corn material and silage (using PVC
mini silos) from Bt (MON810, YieldGard) hybrids and their respective
non-Bt genetic counterparts.  We studied a wide range of analytes
including digestibility parameters, such as IVTD, IVDMD, and Cell
Wall Digestibility.  These findings are reported in:

Faust, M. A.  1999.  Research Update on Bt Corn Silage.  Proc. 4-
State Applied Nutrition and Management Conference.  MWPS-4SD5.
 MidWest Plan Service.  Ames.  Iowa.

and an additional summary of this original article is available through:

Dairy Online Connection

3.  Findings from work completed in other laboratories agree with our
own findings, namely that performance for livestock (dairy cows, beef
steers, beef cows, etc.) fed Bt corn (silage, corn grain, grazed corn
residues) is at least as good as performance for livestock fed
conventional (non-Bt) counterparts.  References for these write-ups

Russell, J. and T. Peterson.  1999.  Bt corn and non-Bt corn crop
residues equal in grazing value.  Extension News, June 30, 1999.
Iowa State University Extension, Ames.

J. D. Folmer, G. E. Erickson, C. T. Milton, T. J. Klopfenstein.  2000.
Utilization of Bt corn residue and corn silage for growing beef steers.
J. Anim. Sci.  78(Suppl. 1):P271.

J. D. Folmer, R. J. Grant, C. T. Milton.  2000.  Effect of Bt corn silage
on short-term lactational performance and ruminal fermentation in
dairy cows.  J. Dairy Sci.  83:P272.

4.  These data and other results indicate that factors other than the
presence of the Bt gene and Bt proteins play a much larger role for
defining the nutritive value of silages.  These factors can include:
genetic background of individual hybrids; local growing conditions
including soil, insect, degree day, etc. factors; harvest
maturity/moisture; length and uniformity of chop at harvest; silage
packing; use of effective silage cover; rate of feed out; and even
mixing and feedbunk management.

5.  Lately, I'm hearing about more cases when cow genetics likely are
limiting milk production.  When milk production isn't up to snuff, we've
all become conditioned to concentrate on forage and nutritional
factors.  In fact, there are considerable differences out there in dairy
genetics, and we need to again begin considering cattle genetics on
many of our dairies as another factor that will limit milk production.

Again, my bottom line is that I have found no scientific substantiation
for your client to **avoid** planting Bt corn or other biotech crops.
Instead, I would encourage your client to:

*  select hybrids that are most appropriate for their particular needs -
i.e. **silage** hybrids best suited for their environmental and pest


*  manage, harvest and ensile/store these hybrids appropriately to
maximize feeding value.

    For those of you who are interested in this discussion and in
Biotechnology in plants and livestock, I'd like to let you know that
ADSA, ASAS, and FASS will be co-sponsoring a special
symposium entitled, "Biotechnology in the Global Marketplace," on
Monday, July 24 at the Joint ADSA/ASAS Annual Meeting in
Baltimore.  Symposium details and registration information will be
posted on the meeting web site shortly (like today or tomorrow):


    Marj Faust -

Marj. Faust, Extension Dairy Specialist
123 Kildee Hall, Iowa State University
Ames, Iowa  50011
phone: 515.294.2793     fax: 515.294.2393
e-mail  mafaust at

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