EGG SIZE AND SHELL QUALITY- AN OVERVIEWsmestudio.firstname.lastname@example.org
EGG SIZE AND SHELL QUALITY
In Nigeria, the table eggs are sold by numbers unlike the developed countries where eggs are sold by weight. So the farmer has to decide whether he wants more number of medium size eggs per bird or lesser number of large size eggs per bird on hen housed basis.
IMPORTANCE OF EGG WEIGHT
There is a strong correlation between early and late egg weights and it is the latter which needs to be controlled. The positive relationship between body weight at sexual maturity and egg size is clear, and may be beneficial for early egg size. However, it is less desirable for late egg size since this higher body weight will affect egg size throughout the whole life of the flock.
There is a close negative relationship between egg production and egg size. A drop in production leads to an increase in egg weight as the bird maintains egg mass. A flock with poorer production has a higher egg weight, particularly after peak.
FACTORS INFLUENCING THE EGG SIZE
Like all other economic traits, egg size is majorly influenced by genetics, environment and nutrition.
1. EGG WEIGHT- GENETICS:
The egg size is very much influenced by the genetics of the bird. Most of the geneticists around the world are focusing on more number of eggs (around 360) per bird in 80 weeks cycle with an average egg weight of 62-63gm. If the management is good, it is very much possible to tap the full genetic potency of the layer. Though the egg size is to a large extant genetically determined, but within this given range, we can manage to either increase or decrease the egg size to suit the particular market needs.
2. EGG WEIGHT- BODY WEIGHT AND SEXUAL MATURITY
The larger the body weight at first egg, the larger that hen’s eggs will be for her entire life. For maximum egg size do not stimulate maturity with lights, until the birds get standard body weight. The brown layer pullets start dropping eggs from 17-18th week on wards in well managed farms. One of the problems with early maturing pullets is a high percentage of small eggs. Early maturity pullets start returns early and are more profitable layers in the markets where the eggs are sold by numbers like in Nigeria. At the same time, we should make sure that the advantage of early maturity is not outweighed by too many small eggs. 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. 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, stocking density and beak trimming.
It is important to weigh pullets regularly to monitor their growth. A good weight monitoring program begins from 1st week onwards. Compare the body weights with standards. It is better to weigh the same set of the birds every time for more accuracy. It is very easy in cage system of rearing. Cages should be selected representing different locations within the pullet house. All birds in the cage should be weighed. By weighing every week it is easier to identify the factors responsible for slowed growth. 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. The most appropriate time for the first beak trimming is five to ten days of age, with the second beak trimming, if necessary, done before nine weeks. Birds will recover more quickly and suffer less growth suppression from an early beak trimming.
The most important factor affecting early egg size is body weight at housing. It is crucial. Therefore use every means possible to bring pullets into production at the recommended target body weight. This could be done by using appropriate rearing feeds and the lighting programme. Another factor is the season of maturity which has significant effect on early egg size. The flock maturing during summer months eat less, and mature under
the influence of increasing day length but at a lesser body weight. These birds lay more small eggs. Try to give higher plane of nutrition and delay the light to get better body weights at maturity. The flock maturing in rainy season eat better and achieve good body weights. These birds start late and have good early egg size. They can be stimulated with light to put them in to production in time.
The energy intake is the main factor governing the egg mass output of the laying hen and more attention should be given to the energy requirements, particularly during the period covering 2-3 weeks before onset of production and up to peak production. This is the most critical period in the hen’s life. Protein and amino acid intake particularly Methionine has been shown to influence egg size under a variety of environmental and dietary situations.
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.
AGE HOURS OF LIGHT
1-7 WEEKS 24 hours of light
8- 20 WEEKS 12 HOURS (natural day light)
21 Weeks to 30 Weeks 15 minutes per week up to 17 hours (Maximum)
3. EGG WEIGHT AND NUTRITION
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. Feeds formulated with low energy ingredients such as wheat offal and Cassava often result in insufficient energy (<2700 Kcal/kg) intake for hens to maintain good production. 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.
Watch the egg size carefully. The flock should come to normal size and there should be no small eggs after 27 weeks. If the egg size is still small (below 60gms), the following may be attempted. Increase the methionine level in feed preferably by adding synthetic methionine. Increase the level of fatty acids by giving additional fat in feed. This can be done by adding good quality fresh rice meal up to 6% in feed. Addition of vegetable oil like Soya oil up to 3% gives excellent results in improving the egg size when the feed consumption goes down in extreme hot season.
4. EGG SIZE- HEALTH STATUS OF THE BIRD
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 size and quality. Any infectious process could affect egg production through an effect on feed and water intake. In addition, there is a re-partitioning 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, infectious bronchitis and EDS 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. The Infectious bronchitis problem can be tackled by giving Ma5 strain during rearing period and an inactivated vaccine before onset of lay. It is also advisable to give Lasota vaccine every 4-6 weeks during laying cycle. Regular monitoring of titre is very important. The ND+IB+EDS( 3 in 1) oil vaccine before onset of lay will take care of these three diseases.
5. EGG SIZE- HEAT STRESS
During summer season the feed consumption goes down and there by the calcium intake of the birds, leading to reduced egg size and shell quality. Take sufficient summer precautions to avoid heat stress. Addition of 2 to 3 kg of Sodium bicarbonate in feed will help in maintaining the shell quality.
EGG SIZE AND SHELL QUALITY AT LATER HALF OF THE LAYING PERIOD.
The egg size goes up with age unless controlled. It is advisable to not to target extra large egg size. If the egg size is too large, the percentage of production may go down, which will ultimately reduce the number eggs per bird in its life span. Some farmers do not like the oversize eggs. The size of the egg can be maintained to a desired level by manipulating the protein and Methionine content of the ration.
Nutritional specification can partially control late egg size. This should, however, be balanced with the birds’ need to receive the correct nutrition if maximum egg production is to be achieved. The most important nutrients for control of egg size are linoleic acid, protein and specific amino acids. Reducing the level of one, or a combination of these nutrients, in the diet will reduce egg size. However, this reduction should not be before 40 weeks of age as this will reduce egg production.
Reducing the linoleic acid content of this diet would be beneficial, but it is worth noting that this is more difficult to achieve in maize based diets. Lower total protein in the diet may also be beneficial but a reduction in dietary protein can also reduce egg numbers as well as egg size.
The introduction of LAYER MASH -2 from approximately 45 weeks of lay may be beneficial in helping to control late egg size.The most significant amino acid affecting egg weight is methionine. Reducing the methionine content of the LAYER MASH-2 is another option for controlling late egg size. Therefore, whilst it is possible to control late egg size by manipulating nutrition, such an approach should be exercised with caution so that egg production is not adversely affected. Available phosphorous can be reduced to 0.37% and Methionine to 0.39% to control late egg size. Concentrate on feed servings at the end of the day. Never skip evening feeding. Any disturbances in feeding, may adversely affect the shell strength. The amount of the egg albumin is very important to the size of the egg. Egg albumin is almost entirely protein. Because the egg demand for protein is so great, any excess of dietary protein results in an increase in the amount of albumin. The egg size is larger even though the yolk is smaller.
The egg shells are poorer in quality at the end of the laying cycle. The reason could be that the hen is capable of generating a uniform daily quantity of eggshell material throughout the life and as eggs get progressively larger, the shell material must be spread over a larger area, and thus is thinner. Experiments have shown that the shell weight remains almost constant throughout the egg production period. Reducing egg size by reducing the protein in the ration for older hens does seem to improve shell quality. Limiting the feed quantity by high energy rations does limit the calcium intake. An increase in calcium level is essential when the feed consumption is low. This also can be achieved by top dressing the feed with coarse Oyster shell grit. The bird also regulates the intake as per the need. 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 sulphur-containing amino acids (methionine and cystine) and phosphorus. Keeping the egg size below 63 grams is critical to maintain good eggshell quality.
FEEDING COARSE-PARTICLE OYSTER SHELL OR LIMESTONE
The formation of eggshell material and its deposition usually occurs during the night hours when the hen is not eating. If the source of dietary calcium is finely ground, the calcium passes through the gizzard quickly and little is available to the bird when the egg shell is being deposited. To improve the situation, two thirds of the dietary calcium supplement should be in the form of large size, flaked oyster shell or coarse limestone. This material leaves the gizzard more slowly so a larger amount passes the intestinal wall during the dark hours when the egg shell is being formed. There is more benefit during the later part of the laying cycle. The utilization of calcium is best in oyster shell and poorest in lime stone. Phosphorus also plays a major role in shell quality. Too little total phosphorous will prevent proper shell calcification as will too much. One of the chief causes of poor eggshell quality and strength is an excess of phosphorous in the diet. Excess phosphorous binds calcium while being excreted. The rations low in total phosphorous increase bone deformities and increase the hen-house mortality. Increase the calcium levels during this period to maintain the egg shell quality. Add 1% calcium carbonate to the later half production rations. In acute cases, oral drugs like ULTRACAL-D (Calcium+vitD3) can be given to the birds to improve shell strength.
There are many management approaches available to a producer to increase early egg size and control late egg size and maintain good egg shell quality throughout the laying cycle. Controlling late egg size requires the achievement of a balance between body-weight control, egg production and egg size.
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