Eggs & Their Care
Eggs & Their Care
Extension Bulletin 382, Poultry Pointers 29 (revised), 1955
Egg quality is the combined elements of an egg which increase the market value to the producer, the keeping qualities to the distributors, and the nutritive and eye-appeal value to the consumer.
Exterior Quality: An egg is judged to have good exterior quality if the shell is sound, smooth, oval shaped, evenly colored, and clean.
Interior Egg Quality: The interior quality of an egg is estimated by candling. To have good interior quality, the yolk must be well centered and relatively non-mottled. The chalazae must be indistinct and the air cell small.
Yolk Color: Egg yolk color varies from a light cream to a deep orange, depending principally on the amount of pigment bearing feeds the hen receives. Yellow corn, alfalfa products, and fresh green feeds are the most common sources of these pigments. Top-quality eggs need to have uniform yolk color. This can be obtained by keeping the birds confined and using a feeding program that controls intake of pigmented feeds.
Albumen Color: Normally the albumen is a clear, semi-transparent mass. Some old hens will lay a milky albumen. Slightly smoky or cloudy albumens are quite common in eggs. This is normal in eggs less than one day old, in eggs with oil processed shell, in eggs in which the albumen stands up well around the yolk, and in eggs that have been held at low temperatures. So a cloudy albumen is frequently associated with freshness, high quality, and proper holding temperatures. Riboflavin may cause a greenish yellow color in albumen.
Double-yolk Eggs: Pullets starting to lay are likely to be inconsistent in releasing yolks for the first few months. Occasionally two or more yolks are released by the ovary at the same time and start down the oviduct together, producing a double-yolk egg. Few hens consistently lay double-yolk eggs.
Shell-less and Soft-shelled Eggs: A large number of shell-less and soft-shelled eggs often are produced during the first few weeks after the pullets come into production. This is because the shell-forming portion of the oviduct does not function correctly. Pullets will normally stop laying this type of egg soon after they reach full production. Such eggs are often produced by hens which have had a respiratory disease such as Newcastle disease or bronchitis.
Thin- and Rough-shelled Eggs: Shell thickness is an inherited characteristic. Rough, pebbly, chalky, or thin egg shells may be caused by an abnormal uterus. Frequently, such eggs are produced by hens coming back into production after having a respiratory disease, especially Newcastle disease and bronchitis. Thin-shelled eggs may be caused by either too little calcium or too little vitamin D in the diet. Eggs from hens which have been in heavy production for a long period usually have much thinner shells than eggs produced in the first few months of lay.
Disc- or Moon-shaped Flat Surface on Egg: An egg held in the uterus by the hen after the shell is formed causes the next egg to show a pinched-in disc-like area where it lay against the first egg as its shell was applied. These two eggs are then laid on the same day. The first-formed egg has a rough or sandy surface.
Blood Spots: The tendency for a hen to produce blood spots is inherited. A marginal deficiency of vitamin A in the diet greatly increases the incidence of blood spots in the eggs; however, an excess of vitamin A in a diet does not eliminate the problem. Blood spots range in size from pin-points to large masses of blood covering most of the yolk. A large clot may diffuse through the albumen, resulting in a bloody white. Blood spots or eggs with bloody whites are classed as inedibles, solely because of appearance.
Meat Spots: Pieces of material of unknown origin are frequently found in the albumen. Meat spots, when present, may vary in color with shell color of the egg. White eggs will usually have white meat spots and brown eggs will have brown meat spots. There is some evidence that production of meat spots is an inherited tendency.
Off-Odor and Flavor: These are discussed in the section on maintaining egg quality.
Egg Grades and Sizes
According to the laws of the state of Washington, only eggs of quality equal to Grade B or better can be sold at retail. The requirements to be met by eggs to make Grades AA, A, or B are listed in Table 1.
In addition to meeting the grade requirements listed in Table 1, any egg which has a cracked shell with the shell membranes still intact, may be sold as a cracked egg or “chex.” However, all eggs sold as “chex” also must have an interior quality of Grade B or better.
In each quality grade, six sizes of eggs may be sold. The sizes are classed as shown in Table 2.
Maintaining Egg Quality
Preventing Shrinkage: Holding eggs in a room with a high temperature and low humidity will cause shrinkage because water is evaporated from the eggs. Eggshell is porous and permits exchange of gases. The contents of thin-shelled or very porous-shelled eggs shrink more rapidly than those of thick-shelled eggs.
Checked Eggs: “Chex” (cracked eggs) are caused by careless handling, too few nests or not enough nesting material, infrequent gathering, poor containers, and thin shells. They account for a loss to the poultryman that can be largely overcome by proper management.
Odors and Flavors: Keep eggs away from any material with a strong, penetrating odor. Storage of eggs even for a few days near material with an undesirable or strong odor may cause an odor and flavor in the eggs. Onions, cabbages, apples, potatoes, garlic, gasoline, kerosene, stove oil, and any moldy, musty, or spoiled material are a few of the most common items which should not be kept near eggs.
Feed: Feed may cause dark-colored yolks and poor shells, as previously indicated. Aside from this, however, feed has little influence upon the quality of the egg. Cottonseed meal in the laying mash may cause egg yolks to become a dark olive color. Up to 5 per cent cottonseed meal has no ill effects, unless it has a high content of the chemical called gossypol.
Usually feed does not cause fish-flavored eggs. Sometimes certain hens lay eggs with a “fishy” flavor, regardless of feed. These individual hens can sometimes be identified by the odor of their breath. Large quantities of green material or silage in the ration cause egg yolks to be darker, more variable in color, and less desirable. Small amounts of green material and silage may be used without fear of coloring the yolk too much.
Keep Eggs Clean: Clean nests are the first essential in the production of clean eggs. Clean, dry litter and well-drained yards are of prime importance. Damp, dirty litter, water fountains too close to the nests or feed hoppers, dirty egg containers, and a dusty egg room all will reduce the percentage of clean eggs produced.
Eggs soiled with droppings, egg material, and straw or blood stains are classified as dirty eggs. For eggs that become soiled, the only safe method for cleaning is the use of a dry, abrasive cleaner. Such cleaning is a slow expensive process; therefore, great effort should be made to produce nest-clean eggs. Washing of eggs, even with a sanitizing detergent, is not recommended as a method of cleaning because of the much greater risk of green and black rots developing in the washed egg.
Gather Eggs Frequently: Provide at least one nest for every five hens. Keep plenty of nesting material in the nests and also keep them clean. Gather the eggs at least three times daily. This greatly aids in producing clean eggs, reducing breakage, and in maintaining egg quality.
Cool Eggs Before Casing: Warm eggs deteriorate more rapidly than do cool eggs. It has been found that eggs placed in the cases while warm require at least 12 hours to cool down to room temperature. Those held in galvanized buckets cool in three-fourths of that time (9 hours). When the eggs are gathered and held in a wire basket, less than half the time (5 hours) is required to reach the same temperature. Therefore, allow the eggs to cool in wire baskets before transferring them to pre-cooled, humid egg cases.
Temperature and Humidity: A temperature of 50° F. is entirely satisfactory for holding eggs for a short time if a humidity of 75 to 78 per cent is maintained. This humidity is present when the wet bulb reading is 47° F. and the dry bulb reading is 50° F.
Cool and Humidify Cases: It is extremely important that the carton or case, with fillers and flats, be cooled before the eggs are placed in it. Eggs left in a warm, dry carton or case lose moisture rapidly and the grade is consequently lowered. A dry case may draw as much as a pound of moisture from 30 dozen eggs in 48 hours. One means of having an adequate supply of cooled cases and/or cartons is to place the packing materials in the egg cooler the night before the day they are to be used. This gives time for the packing material to cool and to gain in humidity.
Hints on Casing Eggs: Extra large or long eggs shouldn’t be placed in the fillers. They require special handling. If there are a large number of big eggs, stagger them with slightly smaller eggs to give a safer pack. Always place eggs in the case or carton small end down. If the large end is placed down, the air cell is more likely to break away, forming a free moving air cell. This lowers the grade. To reduce evaporation and the chance of egg breakage place the lids on the cases when they are filled.
Handle Eggs Carefully: At all times, both before and after packing, eggs should be handled with care to reduce breakage or the formation of mobile air cells. Eggs with bubbly air cells are C grade.
Market Regularly: Market eggs as frequently as possible and always at least once each week. During the trip to market, protect eggs against heat and sun during the summer, and against cold during the winter. During all seasons, keep eggs dry during their trip to market.
Breeding for Desirable Eggs: Rough and thin shells, as well as other abnormal egg characteristics, are often caused by certain individual hens. The inheritance of egg weight and shell color has long been a known fact. Quality of albumen, shell strength, and the ability of the egg to withstand heat, age, and transportation can also be improved by breeding.
Selection and breeding for desirable egg characteristics is one way to improve initial quality of the egg. The tendency to lay eggs with meat or blood spots is also influenced by heredity. The commercial poultryman would do well to inquire of hatcherymen about these characteristics when making his choice of stock to purchase.
Preserving Egg Quality
There are many ways to preserve interior quality of eggs. The two following methods are very popular and are considered excellent.
Refrigeration: The cooler an egg is kept, down to 29° F, the slower the rate of breakdown of albumen and yolk quality. An egg will lose approximately as much albumen quality in five hours at 100° F. as in three weeks at 32° F. For direct (non-storage) marketing, eggs should be kept at temperatures of about 50° F. Avoid taking eggs from a cool room into a warm humid room to prevent sweating. The moisture condensation on the shell makes it difficult to handle the eggs without dirtying the shells, resulting in grade loss. Refrigeration of eggs from the nest to the consumer is one practical means of marketing quality eggs.
Oiling: Oiling is an excellent method of preserving eggs. Oiling preserves eggs just as well as water glass. It has the added advantage of allowing the eggs to be kept in cartons or cases for easy handling. For best results eggs should be oiled not later than the day after gathering. Use a light-grade mineral oil, or commercial oil prepared for this purpose. The oil should be free from odor, but does not need to be colorless. Many oil companies market an inexpensive and satisfactory oil especially designed for use in oiling eggs.
Oil eggs by dipping them in the oil, being sure to submerge the egg completely; then drain for a few minutes on a rack. Place the eggs in cartons or cases for storage. The oil does not need to be heated, but should be kept clean at all times and at a temperature higher than egg temperature.
Interior quality of eggs can be preserved either by refrigeration or oiling. There is some consumer resistance to oiled eggs based on association with use of oil on storage eggs. Very few eggs are stored at the present time due to a more uniform year-around production. Oiling used with refrigeration and rapid turn over will deliver the best quality egg commercially possible to the consumer.
Planning Your Eggroom
Your eggroom should be planned for maintenance of egg quality, convenient working, and economy of construction and operation. Because every farm is different we can only offer suggestions. Your eggroom should be planned to fit your farm.
Reduce travel distance from the laying houses to the eggroom by having your eggroom centrally located. Such a location will reduce the tendency to allow eggs to accumulate in baskets in the feedroom. To maintain quality, move the eggs directly from the nest to the egg room cooler.
To maintain egg quality use two rooms for the greatest comfort of work and economy of operation. One room is a mechanically refrigerated room held at about 50° F. and 75 to 80 per cent relative humidity. (Wet bulb about 3° F below dry bulb.)
The other room is the workroom for cleaning and packing eggs. Keep temperature in the workroom as low as possible for satisfactory working conditions, preferably below 65° F For most seasons this temperature can be maintained in an insulated room.
In warm weather it can be cooled by fans blowing in air from the north side of the building during the night. In freezing weather some auxiliary heat will be necessary. Keep the humidity in the workroom low to prevent the sweating of eggs brought from the cooler holding-room. A suggested plan for a two room egg-room is shown in Figure 1.
Exact dimensions of the egg holding-room and the workroom will depend upon flock size. Every farm is different and will need to work out its own needs and arrangements. The egg holding-room needs to be large enough to hold enough cases for one week’s production. This would mean storage space for 16 cases per 1,000 layers. The use of a slatted-rack for egg baskets allows circulation around warm eggs.
A 10’ x 12’ coldroom will handle the production of 6,000 hens with marketing of eggs once a week. If twice-a-week marketing is followed it will hold eggs from 10,000 hens.
There are numerous variations and features that can be included in eggrooms and egg handling facilities. For example, conveyors can be used to move cases from the workroom to the coolroom. Similarly, they can be used to get cases from the coolroom to the delivery truck. Some poultrymen prefer to use pallets for handling their full cases. This will depend upon the buyer and/or egg handler and his type of equipment.
It is very important to have competent refrigeration men design the refrigeration installation in order to produce the desired conditions. For example, the location of the blower to prevent an inrush of warm air is important. Working out your needs from Table 3 will assist you in discussing your needs with your refrigeration supplier.
Points to Remember for a Satisfactory Coolroom
1. Temperature – 50° F; range 5° F.
2. Humidity – 75 to 80 per cent relative. (Will need supplemental source of moisture whenever outside temperature is below 40° F, unless coolroom is allowed to go below 50° F)
3. Continuous operation of evaporator fan to maintain low velocity air movement over warm eggs and avoid warm spots.
4. Extra attention to insulation during construction will reduce operating costs. This includes walls, ceiling, and floor.
Thoroughly cool all eggs and cases prior to packing in order to save space in the holding-room. With such practice, the cases can be stacked directly in piles. Then it is only a matter of keeping them cool. In the coolroom have racks or hangers in the air stream to cool the baskets of eggs. Care, therefore, must be exercised in not piling cases directly in front of the fan on the cooling unit.
The workroom, as shown in Figure 1, must provide ample space for egg cleaning and packing. If eggs are graded into cartons, provision must be made for candling and for sizing the eggs. There should also be some space for storage of surplus empty egg cases. At least one day’s supply of cases or cartons should be kept in the egg holding-room. Rotate this supply so that eggs are packed in only cool, humid containers. A 12’ x 14’ workroom should give ample space for handling eggs from a flock of 10,000 hens if eggs are not graded and cartoned.
Selecting the Unit Cooler
Several makes of coolers on the market are well adapted for cooling eggrooms. The high humidity in the room makes it necessary to have a large cooling coil to prevent frosting. The amount of heat to be removed and construction of the coolroom will determine the size of the unit needed. Table 4 indicates the amount of heat that must be handled by the cooling unit. With this information and your eggroom size, your dealer can tell you what size you need.
It is desirable to install the units of this circulating fan so it stays on continually in the cool box. This will greatly reduce variability in temperature in different areas in the coolroom. It is desirable to arrange the room so that egg baskets with warm eggs can be placed near the unit cooler.
Some General Precautions For Your Egg Coldroom
In painting the eggroom, be sure you use non-odorous paint. It is very difficult to rid a refrigerated room of paint odor.
Be sure to get a good vapor-seal between the insulation and the outside atmosphere to prevent moisture accumulation in the insulation. Use an approved vapor barrier paper. A detailed wall cross section is shown in Figure 2.