EGG SHELL DISORDER: THEIR CAUSES AND CONTROL

EGG SHELL DISORDER, India is 3^rd largest producer of eggs in the world. It is considered as one of the most nutritious and economical animal food proteins available in country. Broken and poor egg shell qualities are responsible for major economic loss to the poultry farmer.

There are many factors which affecting the meat and egg quality. Some of these can directly affect the egg production, especially the eggshell.  Altered shell structures are an indication of the infectious or non infectious disease and also help to determine causes that affecting a poultry farms. EGG SHELL DISORDER

EGG DEVELOPMENT PROCESS

Egg development is the 20 to 25hrs long process take place inside the reproductive organ of laying birds. Birds have only one functional ovary the left one. When young pullet reaches the 20weak of age then yolk is released from the ovary and received by infundibulum, it remains here for 15min. Then moves down into the magnum where inner and outer shell membrane are added along with water and minerals salts. After spending 3hrs in this process it moves down to isthmus, where albumen is added around the yolk. This process takes about an hour. Next the partly formed egg moves into the uterus, or shell gland, where it receive shell layer. After 21hrs later egg passes through the vagina and lay outside takes only one minute.

SOME COMMON TYPE OF EGG SHELL DISORDER

• Misshaped egg shell- These eggs are too small or large or differ from normal shapes.

Causes: Immature shell gland, Stress, Overcrowding, Avian Influenza, Newcastle disease, infectious bronchitis, Egg Drop Syndrome 76.

• Soft shell egg- Laid with an incomplete shell, only a thin layer of calcium is deposited on the shell membrane.

Causes: Excessive phosphorus consumption, heat stress, bird age (older hen), saline water supply, mycotoxins.

• Shell less egg- Laid without a shell layer, these eggs are protected only by the shell membrane.

Causes: Immature shell gland, Avian Influenza, Newcastle Disease, infectious bronchitis, Egg Drop Syndrome 76, Inadequate nutrition, Calcium, increased phosphorus, manganese, or vitamin D3.

• Dispigmented egg –The degree of brown color in the egg shell is determined by the quality of deposited pigment in the cuticle.

Causes: Infectious bronchitis, Bird age (older hen), High stress in the flock, Egg Drop Syndrome 76, Use of chemotherapeutic agents (i.e. sulfonamides and nicarbazin).

• Flat /slab sided egg- eggs are flattened at the side because 2^nd egg entered inside uterus whereas 1^st one is still not laid.

Causes- infectious bronchitis, Stress, frights and disturbances, Overcrowding in coop/run, Sudden increase in daily light hours.

• Wrinkled eggshell- Eggs with thinly creased and wrinkled surfaces.

Causes: Stress, Infectious bronchitis, Defective shell gland, Overcrowding.

• Corrugated egg– Corrugated appearance of shell. This is a product of double ovulation, and the shell formation is disturbed.

Causes-Extra large egg size, Newcastle disease, Infectious Bronchitis, excessive use of antibiotics, copper deficiency in the hen’s diet, Excess calcium, a defective shell gland.

• Calcium deposit- An extra layer of calcium can be seen all over the egg or on just one end.

Causes: Defective shell gland, Disturbances during calcification, Excess calcium in the diet.

• Blood on egg shell- Usually from pullets in early lay, eggs are contaminated by smears of blood from a prolapsed cloaca, vent pecking, or cannibalism.

Causes: Overweight pullets, Pullets coming into lay, sudden increases in day length, Poor hygiene, Cage trays, Belt pick-up system.

• White banded egg- If two eggs come into contact with each other in the shell gland pouch, normal calcification is interrupted. The first egg retained in the pouch will have an extra layer of calcium seen as the white band marking.

Causes: Stress, Changes in lighting.

• Cracked shell egg- This problem includes hair line cracks, star cracks, or large cracks that result in a hole in the shell.

Causes: Heat stress, Saline water, Bird age (older hen), inadequate nutrition, Calcium and vitamin D3, mycotoxins.

• Broken and mended- The egg shell got cracked during the calcification process and mended just before being laid.

Causes- Stress, frights or disturbance during the calcification process.

FACTORS THAT AFFECTING THE EGG SHELL QUALITY

• Bird Age –Egg shell strength/thickness decreases as hens get older. Because Egg size increases with increasing hen age at the same time as shell weight stays the same.

• Young age- At early age of birds, eggs can be fragile because the eggshell mineralization process is not yet fully efficient.

• Nutritional deficiency- Deficiency ofcalcium, vitamin D, insufficient water supply, increase level of phosphorus in feed also causes the defect in egg shell.

• Disease condition – Various kind of disease like Infectious Bronchitis, Egg Drop Syndrome, Avian Influenza, Mycoplasma gallisepticum etc disease compromises the health of the bird may result in defective eggs with drop in production.

• Heat Stress –High temperature and hot water can reduce the feed intake of birds and limits the availability of blood calcium for egg shell formation. Along with long light exposure in winter may reduce the egg shell quality.

• General Stress –high population density and rough handling of birds increases the stress level as a result white- banded egg shell, slab- sided egg, misshapen eggs etc incidence occurs.

CONTROLING MEASURE TO PREVENT EGG SHELL DISORDER –

• Feed suppliments-adequate supply of minerals and vitamins improve eggshell quality in layers.  Vitamin D is necessary for calcium metabolism, Vitamin C help to relive stress condition. Minerals like calcium, phosphorus prevent the demineralization of bone of birds; sodium bicarbonate supplementation during heat stress may improve egg shell quality.

• Water supply- water should not be “softened” or treated with lime, resins, salts, or chelating agents before supply to birds.  Provision of cool drinking water during summer seasoncan alleviates the effects of heat stress.

• Vaccination programme – regularly immunization programs are important to prevent the impact of infectious diseases that affect poultry houses.

• Biosecurity- Good biosecurity practices are an important factor to minimize the incidence of disease outbreaks in poultry farms.

• Good management- Management plays an important role in the prevention of egg shell quality. Avoid overcrowding, handle with care can reduce the stress or heat stress of birds.

CONCLUSION-

          As seen above many factors can affect egg shell quality and egg internal quality. An awareness of factors allows an egg producer to monitor eggs and optimize egg quality. Good management and best practice with respect to bird husbandry like feeding, careful egg collection, handling and processing all contribute to the quality of the final product.

Preety Singh¹ and Somesh Kumar Joshi²

¹Assistant Professor, College of Vety Sci. & A.H., Bilaspur, DSVCKV Durg (C.G.) (drpreety22singh@gmail.com)

²Veterinary Assistant Surgeon, Livestock Development Department, DDVS Balod, (C.G.)