Many factors can influence egg quality and appearance. These factors will vary depending upon the housing environment, genetics, drugs, feed ingredients, or chemicals used in agriculture. As egg production methods become more varied—for example, changing from cage to free range—and as layer strains are selected for the environment and hens age, the number of defects in eggs is increasing. The emphasis on locally produced food in the “slow food movement” also has changed what the hens are exposed to and made the way they are handled increasingly variable. It is important for producers to understand what may cause certain egg defects and to provide a solution in their production system.
The following chart identifies a number of defects in eggs, their possible causes, and corrective measures you may take.
| Shell | ||
| Defect | Cause | Corrective Measure |
Abnormal shell color:
|
Nicarbazine | Do not allow in hen area or in feed. |
| Chlortetracycline (600-800 gm/ton), Aureomycin | Use dosages recommended for treatment. | |
| Exposure to gas leaks (natural gas or propane) from heaters | Maintain gas lines and equipment in proper working order; gas leaks are an explosion hazard as well. | |
| Long-term stress | Minimize hen stress in the production system. Watch out for problems with density, nutrition, environment control/temperature, noxious gases. | |
| Respiratory disease; infectious bronchitis (IBV) | Follow the recommended vaccination program during rearing; include periodic booster vaccinations. | |
| Excessive calcium in the feed (causing brown shell eggs to be off-color) | Ensure that the diet formulation contains the correct amount of calcium according to the Nutrient Requirements of Poultry, 1994, 9th edition, National Research Council. | |
| Mottling of shell (bright spots or moist appearance around pores, observed by candling) | Failure of the egg cuticle on the shell to dry quickly after laying. High humidity in the production house or cooler As a result, water is retained by protein in the spongy later of the shell. |
Lower humidity in the egg-holding cooler below 80% RH. Humidity can be difficult to lower in hen houses, but cuticle drying may be accelerated with increased ventilation. |
| Disease – infectious bursal disease (Gumburo) | Make sure that layer stock come from parent stock vaccinated against IBD (Gumburo). | |
| Crowding | Avoid overstocking. | |
| Abnormal shell colors due to egg washing: white to brown | Iron (FeSo47H2O) above 1 ppm | Have iron content checked in well water used for washing eggs; keep below 1 ppm. |
| Faded color | Low calcium or crab shell in layer diets | Raise calcium level for increased shell color and improved shell thickness. |
|
Arasan (tetramethylthiuram disulfide) | Do not feed to allow hens access to grains treated with Arasan; law requires treated seeds to be dyed. |
| Sulfanilamide (sulfa drugs) | Use according to directions or veterinary prescription. | |
| High hen house temperatures | Control the temperature. Provide cool water and air movement. | |
| Respiratory diseases: Newcastle disease, infectious bronchitis (IBV), laryngotrachetis (LT), Mycoplasma gallisepticum (MG), and egg drop syndrome | Follow the recommended vaccination program during rearing; include periodic booster vaccinations. | |
| High salt (NaCl) | Feed less salt and/or reduce other mineral salts in the diet. Changes are dependent on current levels and regional needs. | |
| Drugs used for rodent control | Keep rodenticides away from poultry. | |
| Age of hen | Eggs can be misshapen from young hens with an immature shell gland. This can occur in the older hens. Replace single-cycle flocks after 75 weeks of age. | |
| Constant flock agitation or fear response | Choose a site that is isolated to minimize disturbances. Avoid sudden noise. Minimize activities around the hens. Dim the light intensity in the house. Ensure predators do not have access to the hens, hen house, or paddock. | |
| Exposure to chemicals such as BAPN (beta-Aminopropionitrile fumarate), which causes premature passage of the egg through the oviduct | The exposure could come on multi-species farms where BAPN is used to treat older horses for muscle injuries; do not feed to hens or allow access to it. | |
| Reduced calcium intake | Provide increased calcium levels in the diet based on strain, outside temperatures, and feed intake. Supplement diets with oyster shell or crushed calcium as a free-choice option for the hens. | |
| Excessive calcium in the feed (causing sandy shell texture) | Ensure that the diet formulation contains the correct amount of calcium according to the Nutrient Requirements of Poultry, 1994, 9th Edition, National Research Council. | |
| Breed (heredity) | There are strain differences in shell quality. | |
| Porosity (heavily mottled) | Breed of hens | Select a strain bred for good shell texture. |
| Hen age | Sell hens after 12 to 14 months of lay or molt the flock to improve shell structure. | |
| High temperatures, usually associated with the season of the year | Keep the hen house cool; hold eggs in a cool place. | |
| Floating air cell (tremulous or moving air cell) | Rough handling | Handle eggs gently and orient them correctly in the carton. This is not a quality fault when assigning egg grades. |
| Tainted shells with crystalline structures (content off-flavor) | Paradichlorobenzene insect fumigant | Do not feed treated grains to birds. |
| Albumen (Egg white) | ||
| Defect | Cause | Corrective Measure |
| Pink | Cotton seed meal | Avoid using it in the laying hen diet. |
| Yellow coloring in albumen | Hepzide | Do not feed to hens in lay. |
Viscosity
|
Increased alkalinity (pH), loss of CO2 | Quickly refrigerate eggs at or below 45°F. Use an approved shell coating, such as egg oil. |
| Respiratory diseases: Newcastle disease, infectious bronchitis (IBV), laryngotracheitis (LT), and Mycoplasma gallisepticum (MG) | Prevention: Follow the recommended vaccination program during rearing; include periodic booster vaccinations. | |
| Breed (heredity) | Select strains of known albumen production quality. | |
| Arasan (tetramethylthiuram disulfide) | Do not feed or allow hens access to grains treated with Arasan; law requires treated seeds to be dyed. | |
| Vanadium | Use sources of phosphorus in feeds known to have little to no vanadium. | |
| Age of hens | Replace hens after 75 weeks of age. | |
| Ammonia | Improve ventilation; use a litter or manure amendment; remove droppings frequently. | |
| High temperatures | Collect eggs 3 to 5 times per day; hold in refrigerated temperatures (at or below 45°F). | |
| Sulfanilamide (sulfa drugs) | Use according to directions or veterinary prescription. | |
| Noncovered eggs cartons | Utilize enclosed egg cartons to slow gas exchange through pores. | |
| Partially cooked | Avoid excessive heat when washing eggs. | |
| Flecks or spots in albumen after cooking | Protein inclusions colored with pigment caused by porphyrin, which is found in brown-shelled eggs | Select a strain known for producing clear eggs. |
| Early growth of mold in shell | Be sure to collect eggs in a timely manner and refrigerate them quickly. Segregate floor eggs from regular collection. | |
| Cloudy white |
Not a defect—it is associated with very fresh eggs or eggs held in a way that minimized CO2 loss |
Eggs should be stored at or below 45°F as soon as possible after lay. |
| Green rot and other types of microbial spoilage | Bacteria, molds, and fungi from eggs that may have been laid in the litter or on the range paddock and not found on the day of lay Also found in unwashed eggs stored before processing. Poultry fecal matter and poultry house dust are excellent transfer points for bacteria |
Maintain clean nesting materials; gather eggs 3 to 5 times a day. Be sure to collect and dispose of floor eggs. Use clean water for washing eggs; maintain the egg wash water temperature at 90°F, or 20°F warmer than the warmest egg. Use recommended amounts of detergents and sanitizers; keep equipment clean. Check wash water for iron content (it should be below 2 ppm) |
| Example: Green rot (Pseudomonas fluorescens) | Detected with ultraviolet lamp candler; other types of advanced spoilage are easily detected with regular candling techniques. Egg wash water containing 2 ppm of iron or more could promote bacterial growth by deactivating natural antimicrobials in the albumen. | |
| Off-odors and off-flavors | Chemicals for treating parasites | Use chemicals recommended for the control of lice and mites. Do not use materials capable of imparting odors or flavors to eggs, such as Beta-hexachlorocyclohexane (BHC), lindane, or hexaphine. |
| Odorous flowers, fruits, or vegetables in egg storage areas | Do not store strongly scented flowers, fruits, or vegetables in the same area with eggs. Due to the natural respiration of an egg, scents and odors are easily transferred to the egg contents. | |
| Blood and meat spots | Before and during ovulation there may be hemorrhaging (capillary crossing the stigma) | Maintain a tranquil environment. Hens that are scared or stirred up prior to ovulation are more likely to produce increased blood spots. A vitamin pack with vitamins A and K may be given. Aureomycin may be given. |
| Breed (heredity) | Select strains with a low incidence of this problem. Brown egg strains have an approximately 25% greater incidence rate. | |
| Pigmented protein inclusions | Strain related; it’s more prevalent in brown egg strains. | |
| Extended periods of intermittent light | Use 16 hours of light. | |
| Protein inclusions colored with pigment caused by porphyrin, which is found in brown-shelled eggs | Select strains with low incidence of this problem. | |
| Yolk | ||
| Olive or salmon-colored | 5% or more cottonseed meal | Avoid use in laying hen diets. |
| Platinum (colorless) | Possible infection | Consult a veterinarian for an antibiotic to treat the infection. |
| Pale color | Lack of xanthophyll or use of small grains lacking pigment | Increase xanthophyll content in the diet using items such as corn, corn gluten, alfalfa leaf meal, or marigold petals. Feed recommended levels of xanthophyll-bearing materials for desired yolk color. Yellow = 13 mg of xanthophyll per pound of feed. Medium orange = 23 mg of xanthophyll per pound of feed. Orange = 34 mg of xanthophyll per pound of feed. The maximum color will occur 10 days after the hens are placed on feeds for yolk color. |
| Green | 100 to 250 mg of sodium chlorophyllin in feed | Avoid feeding to hens. |
| Seed pods of Capsella bursapastoris (Shepherd’s purse) or Thlaspi arvense (field pennycress) | Use clean grains in feeds; clean weeds from range paddocks. | |
| Greenish-brown | 5 gm or more of pimento peppers fed daily to each hen | Use smaller amounts for a desirable color in egg yolks. |
| Orange-pink | Red pepper | Avoid feeding to hens. |
| Yellow to orange | Hens eating substances such as sea weed (algae); dehydrated alfalfa meal; corn gluten meal; flower petal meal; dried chili peppers; powdered African red peppers; dried sweet potatoes; dried carrots; corn-oil products, and food-grade, fat-soluble dyes | Increase xanthophyll content in the diet using items such as corn, corn gluten, alfalfa leaf meal, or marigold petals. Feed recommended levels of xanthophyll-bearing materials for desired yolk color. Yellow = 13 mg of xanthophyll per pound of feed. Medium orange = 23 mg of xanthophyll per pound of feed. Orange = 34 mg of xanthophyll per pound of feed. The maximum color will occur 10 days after the hens are placed on feeds for yolk color. |
| Misplaced egg yolk |
If small end of the egg is up, with yolk in the large end—egg albumen is thin and/or the yolk has a high fat content |
Practice acceptable gathering, packaging, cooling, and storage of eggs, both pre- and post-processing. Place eggs small end down in the carton. |
| Blood and meat spots | Ovarian hemorrhages—this tendency may be inherited | Select strains with a low incidence of this problem. |
| Mottled or blemished yolks | Nicarbazine | Do not feed to layers. |
| Cottonseed meal | Avoid use in layer diets. | |
| Piperazine citrate | Do not use frequently or continuously. | |
| Movement of water from the albumen across the vitelline membrane into the yolk | Cool eggs quickly and keep them cool. Collect eggs 3 to 5 times per day, and collect floor eggs daily. | |
Viscosity
|
Crude cottonseed oil (malvalic acid and sterculic acid) | Avoid use in layer diets. |
| Yolks laid internally, which result in a distended abdomen and an upright posture over time | Remove these hens from the flock. | |
| Freezing of intact eggs (27°F or below) | Maintain shell egg storage at 45°F or below, but higher than the freezing point. | |
| Off-odors and off-flavors | Insecticides for external parasites Strongly scented fruits and vegetables in the storage area |
Always keep insecticides and other chemicals in a separate area safely away from food items. Do not store eggs with pungent items. |
| Chemicals or washing compounds | Follow the manufacturer’s recommendations for use. | |
| Flat | Weak vitelline membrane Older hens produce eggs with a weaker vitelline membrane |
Gather eggs 3 to 5 times per day and cool them quickly to 45°F. This slows water movement from the albumen into the yolk. |
| Stuck yolk | Newcastle disease | Vaccinate the flock properly. |
| Storage at a high temperature | Gather eggs 3 to 5 times per day and cool them quickly to 45°F. | |
| Extended storage time | Market eggs promptly and practice proper inventory rotation. | |
| Large temperature shifts | Consistently maintain the egg storage temperature at or below 45°F. Avoid large shifts in the egg temperature. | |
| Other Egg Abnormalities | ||
| Egg within an egg | Reverse peristalsis in the oviduct | Reduce hen stress, particularly sudden, acute stressors |
| Soft shell or shell-less (membrane) | Incomplete or not deposition of calcium for shell formation Low dietary calcium |
Calcium should be at or above NRC recommendations of 3.25%, but commercial strains need even higher levels. |
| Diseases such as avian influenza, respiratory infections, Newcastle disease, or egg drop syndrome | Follow the recommended vaccination program during rearing; include periodic booster vaccinations. | |
| Fear or stress can trigger early oviposition of an egg at any point in shell formation | Choose a site that is isolated to minimize disturbances. Avoid sudden noise. Minimize activities around the hens. Dim the light intensity in the house. Ensure predators do not have access to the hens, hen house, or paddock. | |
| Some hens have a genetic disposition to produce shell-less eggs | Select a strain known for good shell quality. | |
Additional Resources
Anderson, K. E. 2015. Final Report of the Thirty Ninth North Carolina Layer Performance and Management Test. Vol. 39, No.5. December.
Beyer, R. S. 2005. Factors Affecting Egg Quality. Kansas State University Agricultural Experiment Station and Cooperative Extension Service, EP-127, March.
Davis, J. J. 1921. “Scientific Note: Effect of Feeding Paradichlorobenzene-Treated Feed to Poultry.” J of Economic Entomology 14: 509.
Fitzsimmons R. C., M. Newcombe, and I. E. Moul. 1989. “The Long-Term Effects of Feeding Ground and Whole Cottonseed to Laying Hens.” Can J Anim Sci 69: 425–429.
Gerber, N. 2012. Factors Affecting Egg Quality in the Commercial Laying Hen: A Review. Egg Producers Federation of New Zealand Inc. Poultry Industry Association of New Zealand. 96 D Carlton Gore Road, Newmarket, 1023, Auckland.
King’ori, A. M. 2012. “Egg Quality Defects: Types, Causes, and Occurrence: A Review.” J Anim Prod Adv 2(8): 350–357.
Lorenz, F. W., H. J. Almquist, and G. W. Hendry, 1933. “Malvaceous Plants as a Cause of ‘Pink White’ in Stored Eggs.” Science 77: 606.
Nagalakshmi D., S. V. R. Rao, A. K. Panda, V. R. B. Sastry. 2007. “Cottonseed Meal in Poultry Diets: A Review.” J Poult Sci 44: 119–134.
National Research Council. 1994. Nutrient Requirements of Poultry: 9th Edition.
Phelps, R. A., 1966. “Cottonseed Meal for Poultry: From Research to Practical Application.” World’s Poultry Sci J 22: 86–112.
Ryu, K. N., H. K. No, and W. Prinyawiwatkul. 2011. “Internal Quality and Shelf Life of Eggs Coated With Oils from Different Sources.” J Food Sci 76 (Jun–Jul): S325–9. doi: 10.1111/j.1750-3841.2011.02177.x.
Sherwood, D. H. 1958. “Factors Affecting Egg Quality—A Review.” Poultry Science 37: 924–932.
Tarver, F. R. and T. A. Carter. 1979. Factors Affecting Shell-Egg Quality. AG-169. Raleigh, NC: The North Carolina Agricultural Extension Service. (Revised from Folder 228).
U.S. Department of Agriculture-Agricultural Marketing Service. 2000. Egg-Grading Manual. Agricultural Handbook Number 75. USDA-AMS-Poultry Programs-STOP 0259 1400 Independence Avenue, SW, Washington, DC 20250-0259.
Waldroup P. W. 1981. “Cottonseed Meal in Poultry Diets.” Feedstuffs 53: 21–24.
