# Presentation: 052841

## Avian Two-Generation 

**Toxicity Test**
**Detailed Review Paper**
**NACEPT**
**Endocrine Disruptor Methods Validation Subcommittee**
**August**** 2003**
**Leslie Touart**

## Detailed Review Paper:AVIAN TWO-GENERATION TOXICITY TEST

**WORK PERFORMED BY**
**	****On behalf of the United States Environmental Protection Agency**
**	****EPA CONTRACT NUMBER 68-W-01-023**

## OVERVIEW AND SCIENTIFIC BASIS OF AVIAN TWO-GENERATION TESTS

- Hormonal control of sexual differentiation in birds differs from that of mammals
- Birds lack fetoprotein
- Oviparity in birds allows retention of compounds
- Current protocols
- are not sufficiently robust to differentiate endocrine disrupting chemicals from other reproductive or developmental toxins
- are not designed to determine long-term effects of *in ovo* exposure
- Do not assess effects at the 4 critical life stages that could be sensitive to endocrine disruption

## Test Species

- Japanese Quail (*Coturnix japonica*)
- Bobwhite (*Colinus virginianus*)
- terrestrial habit
- accepted model for toxicity tests
- adaptable to laboratory conditions
- indeterminate layer
- precocial young

**Notes:**
These fish share several attributes that make them ideal test species for reproductive toxicity testing, including small size at maturity which reduces maintenance costs, and overall ease of culture.  An additional important attribute is that all three species are asynchronous spawners, meaning the ovaries contain oocytes at all stages of maturity, allowing spawning to occur repeatedly over an extended time period.  This reproductive attribute is important as it allows groups of fish to be tested for spawning success before and after chemical treatments during a relatively short time period.  It should be recognized, however, that the presence of gametes in all developmental stages may make identification of gonadal cellular targets more difficult.  

## Japanese QuailFamily Phasianidae(Pheasants/Partridges)

- Old World quail
- Rapid incubation and maturation
- Reproductively mature in 6 to 8 weeks
- Sexually dimorphic
- Can be kept in breeding condition all year (optimal 5 to 6 months)
- High rate of egg production (300 eggs per year)
- Peak production within 2-3 weeks of onset of lay
- Highly adaptable to battery cages
- Endocrine and behavioral patterns are well characterized
- Large number of cultivated strains

## Bobwhite Family Odontophoridae(New World Quails)

- Indigenous to North and South America
- Reproductively mature in 24 weeks
- sexually dimorphic
- Adapts well to laboratory
- Highly photsensitive
- females produce about 1 egg per day
- Peak egg production at 6 weeks after onset of lay
- Little deliberate selective breeding

**Notes:**
.  Spawning activity normally occurs through 14 to 15 months of age

## Advantages

- _Japanese Quail_
- Endocrine, behavior patterns known
- Small bird; occupies 230 cm2 per bird
- Reach sexual maturity by 6 weeks
- Prolific layer
- Early maturity (36 days male, 42 days female)
- Short incubation period (16-17 days)
- Males are aggressive breeders
- Males maintain high fertility (90%)
- Adapts well to breeder cages
- Produce large egg (8% of body wt)
- Naturally hardy in laboratory
- Highly photosensitive
- Dimorphism of plumage by 3 weeks
- Male cloacal gland
- History of toxicity testin
- Spermatogenesis is well characterized

- _Bobwhite _
- Less domesticated, wild type
- Small bird; occupies 400-900 cm2 per bird
- Prolific layer (somewhat less than Japanese quail)
- Males are aggressive breeders
- Males maintain high fertility (95%)
- Adapts well to laboratory
- Produces large egg (8% - 10.5% of body wt)
- Highly photosensitive
- Populations not prone to photperiodic drift
- Dimorphism of plumage color
- History of use in toxicity testing
- More yolk per egg (39.8%) by weight) compared with Japanese quail (31.9%)

## Disadvantages

- _Japanese Quail_
- Inbreeding not tolerated (impaired fertility)
- Strains differ in body weight, maturation rate, egg production, lipid deposition in body and egg
- Populations can show marked photoperiodic drift with large variability in reproductive response
- Food wastage making food consumption measurement difficult
- Most strains have colored eggshells that are difficult to candle (some white egg strains available)
- Less yolk per egg compared to bobwhite
- Little used in U.S. for toxicity tests

- _Bobwhite_
- Long incubation period (23 days)
- Long maturation period (24 months)
- Food wastage making food consumption measurement difficult
- Sex cannot be distinguished by plumage until 12 weeks of age
- Lack cloacal gland
- Spermatogenesis not characterized

## Exposure Considerations

- Exposure of parental (P1) generation
- _Pre-egg laying_
- Risk of loss of statistical power due to infertile pairs
- Effects on sexual maturation possible
- Bioaccumulation of test substance
- _post-initiation of laying_ (proven breeders)
- Statistical advantages
- removing nonproductive birds before exposure
- Use pretreatment measures as covariates
- Reduction in cost from reduced exposure period
- Rapidly of manifestation of reproductive effects observable

## Exposure Considerations (cont.)

- Exposure of offspring (F1) of parents
- No exposure (*in ovo* exposure only)
- Avoids masking of endocrine-mediated effects by high mortality of chicks from direct toxicity
- Exposure from hatch through egg-laying
- Worse case scenario
- Allows observation of effects at all life stages
- Mortality of chicks could mask endocrine-mediated effects
- F2 chicks not exposed

## Exposure Considerations (cont.)

- Combined exposure scenarios for P1 and F1
- Maximize attributes, minimize disadvantages
- Expose maximum number of reproductive processes
- Expose the maximum number of  life stages
- Increase power of test
- Not mask endocrine-related effects/not confound interpretation of results
- Worst-case environmental exposure
- Time and cost-effectiveness
- Dosing Study

## Avian Dosing Study Schematic

- P

- F1

- F2

- Egg laying begins

- P1A

- P1B

- 9 weeks

- 12 weeks

- 4 weeks

- Treatment begins

- Egg laying begins

## Routes of Administration of Chemical

**Food**
- More natural exposure, but greater than in wild
- Avoids intermittent high body loading
- Detect food avoidance/anorexia consequences
- Low labor cost for administration
- Dose estimation not precise
- Costs verifying concentration and stability high
- Effect of natural endocrine active substances in feed unknown
**Water**
- Ecologically relevant route
- Dispersion of chemical more easily achieved than in diet
- Not used for chemicals of low solubility in water
- Evaporation may concentrate chemical
- Water spillage more serious than feed spillage

**Notes:**
Water
	Besides being ecologically relevant, water is the most common laboratory route for exposing fish to EACs.  The delivery of a toxicant to water at different concentrations is well established. 

## Route of Administration (cont.)

**Bolus**
- Most accurate dose estimate
- Best for unstable or volatile chemicals
- Low analytical costs to verify dose
- Handling stress
- Greater absorption rate, saturation of hepatic enzymes
- Can result in lower tolerated test concentrations
- Intubation trauma
- Regurgitation of emetic compounds
- High labor cost of dosing

## Dosing Options

- Constant dietary concentration
- More directly comparable to environmental concentrations
- Young can receive higher doses than parents
- Constant daily dosage
- Can compare effects between life stages and species of different body size
- Both methods are highly artificial
- Determine by data needs of risk assessment process

## Statistical Approaches

- Multiple comparison methods-NOAEC
- Robust to non-normal errors
- Sensitive to loss of replicates
- Requires greater number of test animals
- NOEC/LOEC limited to concentrations on test
- Regression methods-ECx, BMD
- Less affected by loss of replicates
- Estimate a dose-response curve
- Estimation of ECx not limited to test concentraions
- Assess time-series, time lag between exposure and response

## Fitness Endpoints

- Growth Rate
- Food Consumption
- Measures of Reproductive Performance
- Fecundity
- maximum production period
- Fertilization Success
- Separation of gender-specific effects
- Fertility trials
- Gamete Viability
- Sperm motility and morphology
- Sperm mobility
- Interaction of sperm with egg perivitelline layers

## Fitness Endpoints (cont.)

- Egg quality
- Candling-distribution of background cracking
- Eggshell thickness
- Eggshell Strength
- Puncture test
- Compression test
- Eggshell matrix proteins as biomarkers
- Hatching Success
- F1 and F2 post-hatch suvivorship
- Primary, integrating production endpoint
- High CVs

## Fitness Endpoints (cont.)

- Changes in breeding behavior
- Sensitive endpoint
- Ecologically relevant
- Neurological/CNS impairment tests
- Integrated response to toxin
- Open-field tests

## Physiological Endpoints

- Organ growth and morphological changes
- Gonadosomatic index
- Organ:brain weight index(brain, thyroid, adrenal gland)
- Oocyte diameter
- Oviduct differentiation
- Developmental landmarks
- Gross landmarks
- Age at first egg
- Cloacal gland size, age at foam production
- Age of sexually dimorphic plumage development
- Age at first crowing
- Sternotracheal (syringeal) muscles
- Medualary bone
- Histopathology of juvenile and adult tissues
- Sex Ratio

## Biochemical Measures

- Biomarkers of hepatic metabolic changes
- Vitellogenin
- Alkaline-labile Phosphate Assay
- RIA, ELISA
- No universal VTG antibody available
- Quail VTG ELISA assay recently developed
- Circulating very low-density lipoprotein
- Enzymatic method in development
- Cytochrome P450 1A induction
- EROD activity
- Aromatase immunocytochemical assay

## Biochemical Measures (cont.)

- Plasma, egg and fecal/urate hormone levels
- Handling stress can alter circulating steroid levels
- Fecal/Urate sampling
- Long history of use in conservation biology (field samples) for steroid hormones
- Recent application in avian studies
- Rapid extraction methods available
- May be useful for thyroid hormones, but not tested
- RIA, ELISA assays
- Commercial kits for steroid and thyroid hormones applicable to birds

## CANDIDATE PROTOCOLS

- Short-Term Life Cycle Test (Proven Breeders):
- Proposal for a New Avian Reproduction Toxicity Test in Japanese Quail or Northern Bobwhite (OECD April 2000)
- Life Cycle Tests:
- Standard Practice for Conducting Reproductive Studies with Avian Species (ASTM E1062-86)
- OECD Test Guideline 206: Avian Reproduction Test(OECD 1993)
- EPA OPPTS 850.2300: Avian Reproductive Test (USEPA 1996); suggested adaptations for two-generation test added by EDSTAC (EPA 1998)
- Two-Generation Test:
- Proposal for a Avian Two-Generation Toxicity Test in Japanese Quail (OECD 1999)

## Recommended Protocol

- Preferred species: Japanese quail
- Exposure protocol: TBD based on Avian Dosing 				Study
- Fitness Endpoints:
- Egg production
- Fertility
- Eggshell integrity
- Embryo viability
- Hatchability
- Sex ratio
- Chick health
- Signs of toxicity

## Recommended Protocol (cont.)

- Endocrine Endpoints
- 	Gross morphology & histopathology
- Organ/gland weights/bone length(chicks)
- Organ/gland histology
- Spermatid counts & morphology
- Gross anomalies
- 	Developmental landmarks
- Feather dimorphism
- Cloacal gland size
- Sexual maturation/behavior
- 	Plasma and fecal/urate hormones
- Steroid hormones
- Thyroid hormones

## Significant Data Gaps

- Lack of clear information on source of and metabolic fate of xenobiotics *in ovo*.
- The effects of anti-estrogens in juvenile and sexually mature test species.
- The effects of anti-androgens in the developing embryo or hatchling.
- The effects of thyroid hormone agonists (or thyroid stimulation) on reproduction.
- Interactive effects of endocrine-active substances, especially natural phytosteroids in diets.

**Notes:**
There were gaps of data found during the literature review, particularly a lack of information on the reproductive endocrinology of the test species.  This paucity of information is especially true for the medaka and zebrafish.  More specific data gaps include the following:

•Male-specific effects of estrogen agonists other than VTG induction.
•The effects of anti-estrogens, especially pure or Type II anti-estrogens in sexually mature test species.					
•The effects of androgenic and anti-androgens in sexually mature test species, specifically, endpoints other than secondary sex characteristics that may be more sensitive to (anti-) androgens.
•Baseline data for thyroid hormone levels during reproduction in test species.
•The effects of thyroid hormone agonists (or thyroid stimulation) on reproduction.

## Data Gaps (cont.)

- The effects of strain differences on test outcome and interpretation: what traits are co-selected with high body weight or high fecundity; what qualities should be selected for toxicity testing in random-bred lines.
- A statistical approach for delayed effects.
- Specific information on husbandry requirements of the Japanese quail that will result in consistent results in laboratory toxicity tests.  Specifically information for dealing with fear, social stress, injurious pecking, etc.

## Implementation  Considerations and Future Research

- Pre-validation studies
- To select appropriate exposure regimen, recommend a direct performance comparison of proven-breeder and pre-breeding exposure regimens combined with nontreatment and worst-case hatch-through egg-laying F1 exposure scenarios
- Do endocrine-mediated effects occur during maturation that are overlooked when only *in ovo* exposure is considered?
- Do compounds that are directly toxic to chicks mask detection of endocrine-mediated effects?

## Implementation/Research (cont.)

- Recommend verifying the relative sensitivity of the Japanese quail and Bobwhite in a side-by-side comparison study
- Recommend determining the effects of strain selection in Japanese quail on test outcome to minimize nontreatment variability across laboratories
- If ANOVA methods are to be applied to the test, recommend investigation of statistical approach for delayed effects

## Implementation/Research (cont.)

- Recommend development of T4/T3 assays in fecal/urate samples for noninvasive monitoring of thyroid function
- Recommend PCR methods for genetic sex determination be optimized for  Japanese quail
- Recommend determining the interactive effects of phytosteroids in feed on test outcome
- Recommend evaluating/standardizing husbandry practices
- Recommend guidelines for histology preparation and examination of tissues
- Validation of the study design through interlaboratory comparisons

## Issues/Concerns

- Animal usage
- Value added of 2 gen v. 1 gen
- Japanese quail sensitivity
- Lack of avian assay in Tier 1
- Time delay in validation (& costs)
- Linkage with existing avian testing framework