Sample Storage & Stability
Proper storage and handling of avian biological samples is critical to preserving DNA integrity and ensuring accurate test results. This document provides detailed stability data, storage guidelines for each sample type, and recommendations for holding periods before extraction or shipment to SENO.
General Principles of Sample Preservation
DNA degradation begins immediately after sample collection due to active nucleases released from damaged cells. The goal of proper storage is to slow or halt this degradation. Key factors affecting DNA stability include:
- Temperature — Lower temperatures slow enzymatic degradation
- Humidity — Moisture promotes microbial growth and nuclease activity
- Light exposure — UV light causes DNA crosslinking and fragmentation
- Time — DNA degrades progressively; earlier extraction yields better results
- pH and chemical environment — Stabilization buffers (FTA cards, swab solutions) preserve DNA chemically
Storage Conditions by Sample Type
| Sample Type | Short-Term Storage (< 2 weeks) | Long-Term Storage (> 2 weeks) | Critical Notes |
|---|
| Freshly plucked feathers | Room temp (15–25°C), dark, dry | Room temp in dark container | Avoid humidity > 60%; mold degrades DNA completely |
| Blood (EDTA tube) | 2–8°C (refrigerator) | −20°C or −80°C | Freeze within 7 days of collection for best recovery |
| Blood (FTA card, dried) | Room temp (15–25°C) | Room temp with desiccant | Stable for years when moisture is excluded |
| Blood (filter paper spot) | Room temp (15–25°C) | Room temp with desiccant | Stable for up to 6 months |
| Swab in stabilization buffer | 2–8°C (refrigerator) | −20°C | Buffer contains nuclease inhibitors |
| Tissue (post-mortem) | 2–8°C (refrigerator) | −80°C | Freeze immediately after collection; avoid freeze-thaw cycles |
| Semen | 2–8°C (short term) | −80°C | Requires specialized cryopreservation buffer |
DNA Stability Data (SENO Internal Validation)
SENO has conducted extensive internal validation studies to quantify DNA stability across sample types and storage conditions. The following data represents percentage of intact DNA relative to a freshly extracted reference sample.
| Storage Condition | Sample Type | Storage Duration | DNA Intact (%) | PCR Success Rate |
|---|
| Room temp (15–25°C) | Feather (freshly plucked) | 30 days | > 90% | > 95% |
| Room temp (15–25°C) | Feather (freshly plucked) | 90 days | > 80% | > 90% |
| Room temp (15–25°C) | Feather (freshly plucked) | 180 days | > 60% | > 75% |
| Room temp (15–25°C) | Blood (FTA card) | 30 days | > 95% | > 98% |
| Room temp (15–25°C) | Blood (FTA card) | 365 days | > 90% | > 95% |
| Room temp (15–25°C) | Blood (FTA card) | 5 years | > 80% | > 85% |
| 4°C (refrigerator) | Blood (EDTA) | 3 days | > 98% | > 99% |
| 4°C (refrigerator) | Blood (EDTA) | 7 days | > 95% | > 97% |
| 4°C (refrigerator) | Blood (EDTA) | 14 days | > 85% | > 90% |
| −20°C (freezer) | Blood (EDTA) | 6 months | > 90% | > 95% |
| −20°C (freezer) | Blood (EDTA) | 2 years | > 80% | > 90% |
| −80°C (deep freeze) | Tissue | 1 year | > 90% | > 95% |
| −80°C (deep freeze) | Tissue | 2 years | > 85% | > 92% |
| Room temp (15–25°C) | Swab (stabilized) | 14 days | > 95% | > 97% |
| Room temp (15–25°C) | Swab (stabilized) | 30 days | > 85% | > 90% |
| 4°C (refrigerator) | Swab (stabilized) | 30 days | > 95% | > 98% |
| −20°C (freezer) | Swab (stabilized) | 6 months | > 90% | > 95% |
Key Takeaways from Stability Data
- FTA cards provide the most robust long-term room-temperature preservation — DNA remains > 80% intact for at least 5 years when stored dry
- Freshly plucked feathers degrade faster than FTA blood — ship within 2–4 weeks for optimal results
- EDTA blood degrades significantly after 7 days at 4°C — freeze or extract within the first week
- Stabilized swab samples maintain excellent integrity for 14 days at room temperature, making them practical for international shipping without cold packs
Temperature and Humidity Tolerances
| Sample Type | Min Temp | Max Temp | Max Humidity | Freeze-Thaw Sensitivity |
|---|
| Feather (envelope) | 5°C | 40°C | 60% RH | Not applicable (do not freeze) |
| Blood (EDTA) | 2°C | 25°C | N/A | High — avoid repeated freeze-thaw |
| Blood (FTA card) | −20°C | 50°C | 50% RH | N/A — do not wet after drying |
| Swab (stabilized) | −20°C | 35°C | N/A | Moderate — avoid after buffer added |
| Tissue (frozen) | −80°C | −20°C | N/A | Very high — aliquot before freezing |
Signs of Sample Degradation
Inspect samples upon receipt or before shipment for the following indicators of compromised DNA quality:
| Sign | Sample Type | Indication | Recommended Action |
|---|
| Mold growth (visible spots, musty odor) | Feathers, swabs, FTA cards | DNA severely degraded | Request re-collection |
| Discoloration (dark brown or black) | Blood (EDTA) | Hemolysis; DNA may be partially degraded | Extract immediately or request re-collection |
| Desiccation (feather shaft cracked, no visible follicle) | Feathers | Follicle cells lost | Re-collect with fresh plucking |
| Buffer leakage from swab tube | Swab | Sample may have dried out | Request re-collection |
| Thawed cold pack in shipment | Blood (EDTA) | Temperature abuse | Check for hemolysis; request re-collection if present |
Storage Recommendations by Time Until Shipment
Shipment Within 48 Hours
| Sample Type | Storage | Notes |
|---|
| Feather | Room temp in paper envelope | No special requirements |
| Blood (EDTA) | 2–8°C | Do not freeze |
| Blood (FTA card) | Room temp | Ensure dry before packaging |
| Swab (stabilized) | 2–8°C | Cold pack recommended in warm weather |
Shipment Within 1–4 Weeks
| Sample Type | Storage | Notes |
|---|
| Feather | Room temp in dark, dry place | Acceptable up to 4 weeks |
| Blood (EDTA) | −20°C | Freeze after 7 days |
| Blood (FTA card) | Room temp with desiccant | Stable indefinitely |
| Swab (stabilized) | −20°C | Freeze if > 14 days |
| Tissue | −80°C | Freeze immediately |
Shipment After Extended Holding (> 4 Weeks)
| Sample Type | Storage | Notes |
|---|
| Feather | Re-collect preferred | DNA yield drops > 40% after 4 weeks |
| Blood (EDTA) | −80°C | Aliquot to avoid freeze-thaw cycles |
| Blood (FTA card) | Room temp with fresh desiccant | Replace desiccant every 6 months |
| Swab (stabilized) | −80°C | For long-term biobanking |
| Tissue | −80°C or liquid nitrogen | For indefinite preservation |
Effect of Freeze-Thaw Cycles
Repeated freeze-thaw cycles cause mechanical shearing of DNA and activation of residual nucleases. The impact varies by sample type.
| Number of Freeze-Thaw Cycles | EDTA Blood (4°C/−20°C) | Swab (−20°C) | Tissue (−80°C) |
|---|
| 1 | Minimal loss (< 5%) | Minimal loss (< 5%) | Minimal loss (< 3%) |
| 2 | Moderate loss (10–15%) | Moderate loss (10–15%) | Low loss (< 8%) |
| 3 | Significant loss (25–30%) | Significant loss (20–25%) | Moderate loss (10–15%) |
| 4+ | Severe loss (> 40%) | Severe loss (> 35%) | Significant loss (> 20%) |
Recommendation: If long-term storage or multiple analyses are anticipated, aliquot samples into single-use volumes before freezing.
Shipping Temperature Requirements
| Sample Type | Required Shipping Temperature | Shipment Method |
|---|
| Feathers | Ambient (15–25°C) | Standard padded envelope |
| Blood (FTA card) | Ambient with desiccant | Padded envelope or box |
| Blood (EDTA), < 7 days | Refrigerated (2–8°C) | Insulated box with cold pack |
| Blood (EDTA), frozen | Frozen (−20°C) | Insulated box with dry ice (UN3373) |
| Swab (stabilized), ≤ 48 h | Ambient or refrigerated | Padded envelope or box with cold pack |
| Swab (stabilized), > 48 h | Frozen (−20°C) | Insulated box with dry ice (UN3373) |
| Tissue, frozen | Frozen (−80°C) | Insulated box with dry ice (UN3373) |
Packaging Guidelines for Temperature Control
Ambient Shipment (Room Temperature)
- Suitable for: Feathers, FTA cards, filter paper spots, stabilized swabs (< 48 hours)
- Use: Paper envelopes inside a padded mailer
- Avoid: Plastic bags, heat-sealed pouches (traps condensation)
Refrigerated Shipment (2–8°C)
- Suitable for: EDTA blood (< 7 days), stabilized swabs
- Use: Insulated box with a double-walled cold pack
- Key step: Condition cold packs at 4°C (not frozen) for refrigerated, not frozen, transit
Frozen Shipment (−20°C or below)
- Suitable for: Frozen EDTA blood, frozen swabs, frozen tissue
- Use: EPS (styrofoam) insulated box with sufficient dry ice
- Key step: Use ≥ 3 kg dry ice for international shipments; declare as UN3373 (Biological Substance, Category B)
Cross-References