Technical aspects of 90-day feeding
studies with rodents
Grain production
23 October 2019
• Suitability of how grain
used for feeding studies is
currently produced
• Can grain for feeding
studies be produced
utilizing field trials for
comparative assessment?
29/10/2019 6:01 PM Grain production for 90-day studies 2
Outline
• The same principle is applied to material production for
feeding and comparative assessment studies: GM and
conventional counterpart materials are produced
under similar environmental conditions
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Suitability current production
• Feeding study entries are grown in isolation:
• Ensuring material integrity and identity
• Following requirements of regulatory authorities
(e.g., USDA, CFIA)
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Suitability current production
• GM and conventional counterpart materials are grown:• In regions where the crop is typically grown
• Mimicking how farmers grow crops following accepted
commercial production practices
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Suitability current production
• As a large quantity of high quality grain is required,
this is not an ad hoc, but a carefully planned and executed
production with the goal to use harvested grain for all
feeding study needs (e.g., 90-day rat, broiler)
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Not an ad hoc production
• Grain production for feeding studies:
• Is not disturbed by data collection (which is done in
comparative assessment trials throughout the season)
• Is common production methodology
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Suitability current production
Steinberg et al. 2019
• Suitability of how grain
used for feeding studies is
currently produced
• Can grain for feeding
studies be produced
utilizing field trials for
comparative assessment?
29/10/2019 6:01 PM Grain production for 90-day studies 8
Outline
• The grain for feeding studies cannot be generated in
sufficient quantity from comparative assessment trials
designed to evaluate agronomic, phenotypic and
compositional performance
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Suitability of in-trial production
• Field trials for comparative assessment are randomized and arranged such that each entry is surrounded by plots with plants of different genetics
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Suitability of in-trial production
• Grain collected from the
middle of the plot would
have reduced potential for
cross-pollination
• Depending of the crop, this
amounts to about 0.5 to 1 kg
of grain
-T (GM test)-C (control)-R1, R2, R3(references)
C
C
R3
CT
T
T
T
R1
R2
R1
R1
R1
R2R2
R2
R3
R3
R3C
• Harvesting about 1 kg of maize grain from the middle
of the plot is not sufficient for feeding studies even if
grain is bulked across locations (32 kg)
• For 90-day feeding study, up to 372 kg of maize grain
needs to be produced per entry
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Grain quantity
Larger plots would results in:
• Substantial increase in size of the trial
• Increased spatial variation
• Adverse impact on quality of
comparative assessment data• Uneven plot size
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Size of plots
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Size of plots
• Same plot size across
entries would result in
even more substantial
increase of the trial size
• Larger plot size (even or uneven) is not a realistic option
as it will result in:
• Substantial increase in size associated with
comparative assessment trials
• Can confound the material effect with
environmental (spatial) variation in the field,
adversely influencing the quality of agronomic
and phenotypic data collected
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Size of plots
• If the plot size is kept unchanged, then the number of
replications needs to be increased from 32 to 372 to fulfil this requirement.
• Technical challenge:• Tremendous increase in number of locations (from
8 to 93 sites) or • Tremendous increase in number of replications
per location (from 4 to 47 per site)
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Replication number
Bulking of grain across replications and locations
• Is associated with unnecessary complexities
• Logistical (e.g., chain of custody)
• Technical (e.g., different locations have different
harvest times, grain amounts, moisture content or seed
size due to various production conditions)
• Would make materials used for feeding studies highly
heterogeneous
• In case that trials are conducted in more than one year
or that GM entry is tested in more than one genetic
background, bulking across locations would result in
even higher level of heterogeneity and complexity
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Bulking of grain
• Due to a large quantity required, the grain needed for feeding studies cannot be generated using comparative assessment trials even if grain is bulked across locations
• Furthermore, even if sufficient grain quantity could be produced from these trials:
• Highly heterogeneous grain could adversely impact quality of grain used in feeding studies
• Increased size of the trial could adversely impact the data collected for comparative assessment
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In summary
• Current production of grain for feeding studies is
appropriate considering the study objectives in terms of
needed grain quantity and quality
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In summary