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