Enhancing Early Egg Size and Maintaining Shell Quality in Layers

 
 
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 Achieving the proper pullet body weight is the first step in maintaining good early egg size
Underweight pullets are one of the most common causes for small early eggs. It is known that underweight pullets produce more small eggs early in the production cycle.

18 week body weight
Egg weight (grams)
19 - 25 weeks
1100 g.
46.6
1200 g.
48.4
1280 g.
48.8
1380 g.
49.7
Summers and Leeson Poultry Science 62: 1155-1159, 1983.

For every additional 45 grams in body weight at 18 weeks of age, the egg size increases 0.5 grams. In addition, underweight pullets usually do not have the skeletal frame necessary to maintain good egg shell quality after 40 weeks of age. Underweight pullets tend to be underweight as layers. The pullet body weight is affected by nutrition, disease, lighting, space allotment and beak trimming.

It is important to weigh pullets regularly to monitor their growth. A good weight monitoring program begins at four weeks and every two weeks thereafter, 100 pullets are weighed. Cages should be selected representing different locations within the pullet house. All birds in the cage should be weighed. Weighing the same cages increases the accuracy of the information. The weights of birds on the return side of the feeder line should be compared with the supply side to ensure that pullets are being fed frequently enough. By weighing every two weeks it is easier to identify the factors responsible for slowed growth. Weighing should coincide with changes in feed. If flocks are not at the target body weight for their age, the feed change should be delayed to give the underweight birds a chance to catch up. The variability of the body weights is as important as the average body weight. The goal for uniformity is that 90% of the birds should be within 10% of the average body weight.

A pullet will grow at its maximum rate between 9 and 14 weeks of age. This is the time at which the skeletal structure of the bird reaches its adult size and the oviduct matures and prepares for the onset of egg production. Stressful events during this time can have profound effects on body weight gain. If possible, stressful management practices such as moving or handling birds for vaccinations or beak trimming should be avoided during this period. Beak trimming is best completed prior to six weeks of age. The most appropriate time for the first beak trimming is seven to ten days of age, with the second beak trimming, if necessary, done at six weeks. Birds will recover more quickly and suffer less growth suppression from an early beak trimming.

Move pullets to the lay house early to avoid overcrowding pullets
Moving pullets into the laying unit late (18 or 19 weeks of age) can be harmful because pullets may become overcrowded for the final two weeks prior to moving. This can result in restricted feed and water consumption for some birds. Late overcrowding of pullets can be avoided by moving at 15 to 17 weeks of age.

Lighting programs to achieve good early egg size
One way to improve pullet body weights at the onset of egg production is to delay sexual maturity. Genetic selection has been advancing the rate of sexual maturity by about one day per year. Early maturity can be a valuable trait, provided the necessary body weight has been attained. However, if at least the standard body weight is not present at 18 weeks, the light stimulation of the flock should be delayed until the standard body weight is attained. Larger early egg weight is often the result of birds being heavier at sexual maturity. Encouraging more feed consumption early in the laying period will also promote larger early egg size. Management practices such as increasing the frequency of feeding or lowering house temperature can increase feed consumption. Sexual maturity can be delayed by using a lighting program that "steps down" the amount of light given to the pullet flock during the growing period after nine weeks. An example of a step down lighting program designed to delay sexual maturity is shown below:

Step Down Program #1

Age
Hours of Light
Age
Hours of Light
1-2 days
24
15 weeks
12.5
2 days - 7 days
18
16 weeks
12
2 weeks
17
17 weeks
12
3 to 10 weeks
15
18 weeks
12
11 weeks
14.5
19 weeks
13
12 weeks
14
20 weeks
13.5
13 weeks
13.5
21 weeks to 30 weeks
15 minutes per week up to 17 hours
14 weeks
13

Step down lighting Program #2 is an alternative approach. In this program, the hours of light decrease gradually during the first ten weeks of age and are then held constant until 18 weeks. This program will have no effect on sexual maturity, because the step down in the amount of light is stopped by ten weeks, which is the time when pullets become sensitive to light. This program promotes better growth in pullets by allowing more feed consumption because of the additional hours of light provided to the young pullets.

Step Down Program #2

Age
Hours of Light
Age
Hours of Light
1-2 days
24
8 weeks
13
2 days - 7 days
18
9 weeks
12.5
2 weeks
17
10 to 17 weeks
12
3 weeks
16
18 weeks
12
4 weeks
15
19 weeks
13
5 weeks
14.5
20 weeks
13.5
6 weeks
14
21 weeks to 30 weeks
15 minutes per week up to 17 hours
7 weeks
13.5
.
Energy intake and egg size
It is generally assumed that the feed intake of laying hens will vary with the energy content of the feed. In other words, higher energy rations result in lower feed intake. While this usually does occur, the expected decline in feed intake is seldom fully achieved. The result is a net increase in energy intake for the hen. Feeds formulated with low energy ingredients such as wheat and barley often result in insufficient energy intake for hens to maintain good production (<2800 Kcal/kg). It may not be physically possible for these hens to consume enough feed to meet their energy needs, especially during the time of peak production. In such situations, egg size will be the first production trait to suffer. The decrease in egg size is a result of dietary and body proteins having to be utilized for energy, precluding their use for egg mass formation.

Phase feeding helps maintain egg shell quality throughout the laying period
Nutritional requirements change for a laying hen as it proceeds through the production cycle. The requirements of a hen during peak egg production differ greatly from her requirements later in the production cycle. The feed intake also increases between 18 and 35 weeks of age, affecting the nutrient density needed in the feed to satisfy requirements. Phase feeding is the best method of meeting these changing nutrient requirements. Phase feeding prevents overfeeding of nutrients, which unnecessarily increases feed costs. The production cycle is generally divided into pre-lay, pre-peak, peaking and post peaking phases. In order to maintain the eggshell quality in older hens, the amount of dietary calcium must be increased at each phase. An increase in dietary calcium is needed because the older hen is less efficient at absorbing calcium from the diet. To facilitate better calcium absorption, hens over 40 weeks of age should be fed a calcium source of a large particle size.

Phase feeding can prevent older hens from developing an excessively large egg size by not allowing hens to over consume sulfur-containing amino acids (methionine and cystine) and phosphorus. Keeping the egg size below 63 grams is critical to maintain good eggshell quality in white egg varieties. Chickens usually deposit the same amount of shell on eggs regardless of their size, therefore, larger eggs are prone to having thinner shells and will be more likely to crack. The egg size can be maintained through phase adjustments in the feed formulation. Reductions in the amount of dietary protein, available phosphorus and methionine help maintain egg size at a point at which good shell thickness can be sustained.

Required nutrient intake per bird per day
Peaking

(50% production to 32 weeks)

32-44 Weeks
44-58 Weeks
+58

Weeks

Protein (g)
16.25
15.75-16.25
15.25-15.75
14.75-15.25
Methionine (mg)
360
360
350
340
Methionine+cystine (mg)
670
660
620
580
Calcium (g)
3.65
3.80
3.90
3.90
Phosphorus available (g)
0.47
0.45
0.40
0.30
Phosphorus total (g)
0.67
0.65
0.55
0.45
Hy-Line 1996-97 W-77 Management Guide

Vaccination programs to enhance internal and external egg quality
It has been well documented that some infectious diseases can have an adverse effect on egg quantity and quality. Any infectious process eliciting an inflammatory response could affect egg production through an effect on feed and water intake. In addition, there is a repartitioning of amino acids and proteins away from productive activities, such as egg production, towards the more immediate need for antibody production and other components of the immune response. Newcastle disease and infectious bronchitis are known to cause drops in egg production and the formation of weak and defective eggshells because of direct damage to the oviduct. There are many successful approaches towards Newcastle and bronchitis vaccination. The strains of vaccine used and the routes of administration depend on the degree of risk for these diseases in an area. A typical program for pullets is:

Age of Pullet
Route of Administration
Strain
2 weeksDrinking waterMild strains B1B1 (Newcastle), Mass, Conn, H120 (bronchitis)
4-6 weeksDrinking water or coarse spray >80 micronsB1B1 or LaSota (Newcastle) Mass, Conn, H120 (bronchitis) or other strains prevalent in the area
12-14 weeksDrinking water or medium spray <50 micronsB1B1 or LaSota (Newcastle) Mass, Conn, H120 (bronchitis) or other strains prevalent in the area

It is important to establish good flock immunity during the growing period when the oviduct is developing and to develop a strong immunity prior to the stress of egg production. Typically the greatest challenge for bronchitis occurs after the birds are housed on the laying farm. In some situations, the pullet vaccinations are sufficient and there is no need for further vaccinations. On layer farms where a higher risk to Newcastle and bronchitis exists, there are two options for further vaccinations. One is to inject an inactivated Newcastle/bronchitis vaccine at the point of egg production (generally 14 to 16 weeks). The second option is to continue vaccinating with live vaccines through the egg production period. The interval for these live vaccinations are typically every six to ten weeks. There are advantages and disadvantages to either approach.

Live vaccinations through the egg production period
AdvantagesDisadvantages
    • stimulates good local immunity
    • potential for post-vaccination reaction
    • mass application of the vaccine
    • potential for reversion to virulence of the vaccine virus

Inactivated vaccination at the point of egg production
AdvantagesDisadvantages
    • inactivated vaccines do not spread
    • requires bird handling
    • polyvalent inactivated vaccines deliver many antigens in a single vaccination
    • accidental human injection
    • duration of immunity might not be sufficient for protection late in egg production cycle

Mycoplasma monitoring
Mycoplasma gallisepticum (MG) and Mycoplasma synoviae (MS) could play a role in problems of poor egg size and quality through the interaction with Newcastle, bronchitis and other respiratory pathogens. It has been clearly shown that the infection of the trachea with MG or MS can affect the severity of disease caused by other respiratory pathogens. MG and occasionally MS can directly effect egg production by ovarian infection. It is important to monitor for these pathogens. Breeding companies go to great lengths to ensure freedom of their stock from infection with MG and MS. It is common that commercial pullets are grown free of MG or MS and become infected after placement on infected multiple aged layer farms.

Monitoring for mycoplasma is done by submitting 25 samples per flock monthly for testing with the plate agglutination antigens.

The options for infected flocks are either vaccination or medication. Both can be beneficial in reducing the effects of infection and minimizing production losses but will not eradicate it from the flock. Both inactivated and live vaccines for MG are available. The newer live MG vaccines, 6/85 (Intervet) and TS-11 (Select), are effective and do not spread from bird to bird.

Conclusion
There are many management approaches available to a producer to increase early egg size and maintain good egg shell quality throughout the laying cycle.

Douglas Grieve, DVM, MS
Hy-Line International
Box 310, Dallas Centre
Iowa, USA

 
 
 
 
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This information published to the web on October 28, 1996.
Last Reviewed/Revised on February 26, 2010.