The poultry industry is vertically integrated, which means the industry has a tremendous amount of control of their products. It is distinctly different from many other animal industries. In that egg producers own and manage nearly every aspect of their business (e.g., rearing of birds, feeding, housing, husbandry, and marketing of their product) and are capable of meticulously monitoring the entire process. Poultry producers usually do not own the primary breeding stock (i.e., the parent lines supplying their operation), these birds are purchased from primary breeders.Raising Layers (Leghorns): The purpose of this section is to provide a general overview of a typical layer cycle in terms of chick placement, vaccination schedules, lighting, heating/cooling, feeding, molting, and removal of layers. Keep in mind, there are a number of ways to rear laying hens. It would be very unlikely that any two companies rear layers exactly the same way. However, all companies use a slight variation of the typical rearing program detailed in this section. Management differences for rearing layers may be accounted for by economics (breed selected, vaccination package and decision when to molt), producer preference (breed and strain selected), and/or geography (breed selected and vaccination package).
Hatching and Placement: Egg producers purchase their layer stock (i.e., day old leghorn chick) from an egg-type hatchery. Hatcheries deliver chicks to the producer within one to two days of hatching. At arrival, chicks are either placed in typical layer pens or reared in a pullet house. At the hatchery, chicks are vaccinated according to the producer’s specifications. For details regarding a typical vaccination schedule see Table 1.
Lighting and Temperature: Lighting and temperature conditions for a typical layer production period are shown in Tables 2, and 3 respectively. For those chicks reared in layer cages, a biodegradable mat is generally placed in the pen. The mat allows chicks to better locate feed while also providing time for the chicks to slowly adjust to the wire mesh floor. Within a week, the biodegradable mat is removed or degrades into the litter pit. A single layer cage may occupy as many as fifty chicks, but as they mature, cage density is lessened. Chicks placed in pullet houses are reared on a floor covered with absorbent materials, such as pine shavings. During the first week, pullet chicks are usually beak trimmed. Pullets started on the floor remain there for approximately 10 to 15 weeks and then move to a layer facility. In either case, from chick placement through approximately 16 weeks of life, the pullets are fed according to body weight gain and/or age. The goal is to raise a strong and healthy bird that can support egg production. As noted in Table 2, daily light exposure (photoperiod) begins to increase at Week 16. This increase in light exposure triggers hens to begin laying eggs. If the laying hen has not reached proper body weight (usually 3 lbs.) by Week 18, egg production will cease very quickly, following the onset of the laying period. Hence, it is important for the young laying hen (pullet) to attain the proper body weight that will support egg production. In tandem with light manipulation, the diet is also altered in order to support egg production.
Feeding: It is assumed that layers, unlike birds raised specifically for meat, regulate their feed intake. Layers are generally reared on full feed (ad libitum). The feed is offered to birds via the chain system. The chain system transports feed into the metal feeder at precise times during the day. In general, 2 inches of feeder space is allotted per pullet and 2.5 inches or more for each adult laying hen (Animal Care Series, California Poultry Workshop, 1998). Table 4 illustrates the dietary protein and energy recommendations based on age in of typical layer. Young birds are fed a high protein diet (20 percent) during the first few weeks of life. This level continuously decreases until it reaches approximately 12 to 15 percent protein during egg production. In addition to monitoring dietary protein, producers must closely examine other ingredients. During the laying phase, lysine, methionine, calcium, and phosphorus are precisely monitored to support maximum egg production.
Egg Production: As shown in Table 2 and Table 4, producers begin to photostimulate and manipulate the diet around 18 weeks of age in order to support egg production. Minor nutrients have also been manipulated such that calcium levels in the diet are approximately five to seven times greater than phosphorus levels. When a flock (group of hens) first enters egg production, the rate of egg lay will be around 10 to 20 percent. This means that 10 to 20 percent of the hens are laying eggs at 18 to 22 weeks of age. The flock quickly reaches peak egg production (90 plus percent) around 30 to 32 weeks of age. Post-peak egg production (after 30 to 32 weeks of age) continually decreases to approximately fifty percent around 60 to 70 weeks of age. At this point an economic decision must be made by the producer; fifty percent production is near the "break-even" point for egg producers (e.g., feed cost = market price of eggs). When the flock reaches 50 percent production, producers commonly decide to molt the flock in order to achieve a higher level of egg production. As a rule of thumb, it takes approximately 10 weeks from the beginning of a molting program to be back at 50 percent production following the molt. Post-molt egg production will increase such that peak egg production reaches about 80 percent. Peak production following a molt is short-lived and the flock generally returns to 50 percent production by 100 to 110 weeks of age. Many producers (one-third to one-half) will induce a second molt, this is the same process that occurred at 60 to 70 weeks of age. The second molt is commonly dictated by the current egg prices and the availability of replacement pullets. As previously stated, once flock egg production falls below fifty percent, an economic decision is made whether to molt the birds or the hens to a spent-hen processing facility. The majority of hens are between 100 and 130 weeks of age when they reach the end of their egg production cycle. The time span between 100 and 130 weeks of age can be accounted for by management decisions. Thus hens may be molted a second time and then sent to a spent hen facility (120 to 130 weeks of age) or sent directly to a spent hen facility following the first molt (100 to 110 weeks of age). After the flock vacates the layer house, the house is stripped of all organic matter and sanitized before another flock enters the house.
Egg Collection: In layer facilities, there are two primary methods of egg collection, a) in-line facilities, and b) off-line facilities. In either case, hens lay eggs onto an angled wire floor which rolls the egg toward the front of the cage (floor angle is generally eight to ten degrees) onto a nylon belt. The belt transports eggs out of the house either to the egg processing facility or to a storage cooler. Since the processing facility and cooler remove eggs from the house, based on hourly demand, eggs may reside on the belt for as long as 12 to 14 hours, but most are collected within a few hours post-lay. The first type of layer facility is the in-line facility. In this facility, eggs move directly from the layer house to the egg processing facility. Once the eggs enter the egg processing center, within minutes to 12 to 14 hours post-lay, they are washed (detergent solution near 100o F, pH 11.0 that removes soil), visual inspected (checked for eggshell problems, cracks, and blood spots), and then graded for packaging. Following packaging, eggs are moved to a cooler room (40-45o F), where they await shipment to retail outlets. Egg producers commonly deliver eggs to retail outlets within one week of lay. The second type of layer facility is the off-line facility. This facility functions nearly identical to the in-line facility except that the eggs are transported out of the house directly to an egg cooling room. In this method, the eggs remain in the cool room for approximately two to three days, and then they are transported to an egg processing facility via a refrigerated truck. These eggs are treated identically as those from the in-line operations.
Table 1. A typical vaccination schedule for leghorns.
| Week of Vaccination | Type of Vaccination |
| Day old | Marek's |
| 15 days (1/2 dose) | Infectious Bursal |
| 20 days (1/2 dose) | Infectious Bursal |
| 25 days | Bronchitis, New Castle, Infectious Bursal (Typical Brand name Combo Vec. 30) |
| 30 days | Bronchitis, New Castle, Infectious Bursal (Typical Brand name Combo Vec. 30) |
| 49 days | Bronchitis, New Castle, Infectious Bursal (Typical Brand name Combo Vec. 30) |
| 10 Weeks | Fowl Pox and Laryngotracheitis (commonly referred to as LT) |
| 12 Week | Combo Vac 30 |
| 13 Week | Avian Encephalomyelitis (commonly referred to as AE) |
| 16 Week | New Castle |
Table 2. Lighting program for the leghorn
| Age | Amount of Light (L) and Dark (D) |
| 0 to 3 Days | 22(L):2(D) |
| 3 days to 1 Week | 20(L):4(D) |
| 1 to 2 Week | 18(L):6(D) |
| 2 to 3 Week | 16(L):8(D) |
| 3 to 8 Week | 14.5(L):9.5(D) |
| 9 Week | 14(L):10(D) |
| 10 Week | 13.75(L):10.25(D) |
| 11 Week | 13.50(L):10.50(D) |
| 12 Week | 13.25(L):10.75(D) |
| 13 Week | 13.0(L):11.0(D) |
| 14 Week | 12.75(L):11.25(D) |
| 15 - 17 Week | 12.5(L):11.50(D) |
| 18 Week | 13.50(L):10.50(D) |
| 19 Week | 14.5(L):9.5(D) |
| 20 Week | 15(L):9(D) |
| 21 Week | 15.5(L):8.5(D) |
| 22 Week | 15.75(L):8.25(D) |
| 23 Week | 16(L):8(D) |
| 24 Week | 16.25(L):7.75(D) |
| 25 Week throughout production cycle | 16.5(L):7.5(D) |
Table 3. Temperature control during a layer cycle
| Week | Temperature (F) |
| 1 | 90 |
| 2 | 85 |
| 3 | 80 |
| 4 | 75 |
| 5 | 70 |
| 6 throughout layer cycle | 70 |
Table 4. General Feeding Guidelines for Layers
| Nutrient | Starter 0-6 weeks | Grower 6-8 wk | Developer 8-15 wk | Pre-Layer 15-18 wk | Layer |
| Protein % | 20.0 | 18.0 | 16.0 | 14.5 | 15.0 |
| Met. Energy, Kcal./lb. | 1325-1375 | 1350-1400 | 1375-1425 | 1350-1400 | 1300-1450 |
Source: http://ag.ansc.purdue.edu/; California Poultry Workshop, 1998. Animal Care Series: Egg-Type Layer Flock Care Practices, Published by the University of California, Davis, 2nd Edition; and Salisbury Manual of Poultry Diseases, 7th Edition. Salsbury Laboratories. Charles City, Iowa. Photo courtesy of student.britannica.com