TECHNICAL ARTICLES Broilers/Layers/Breeders

Signature Complete Laying Feed

Many factors affect egg quality. These include genetics, feed quality and environment. Sometimes poor egg quality is not caused by a single factor but a combination of factors. Good flock management can reduce or prevent a few of these problems. The most reliable factor of egg quality is age. A young pullet produces smaller eggs with stronger eggshells and albumen that stands firm. As the hen ages the shell becomes thinner and the albumen begins to weaken and run. The list below highlights the possible causes and solutions to common problems experienced with egg quality.

The shell :

01. Misshapen Eggs

These eggs have a range of distortions, including soft ends and uneven or ribbed surfaces. Thin patches or excessively chalky areas may also be seen. They are more common with older hens, but may also indicate a disease such as Infectious bronchitis or egg drop syndrome (either present or past). If the condition persists, veterinary advice should be sought. Replace hens after 12 to 14 months of lay to reduce the chances of misshapen eggs.

02. Middle-Banded Eggs

A sudden shock can cause a temporary halting within the egg-laying system. If there is an egg there at the time, it may end up with an extra band or ridge around it. There is normally nothing to worry about, provided that the flock is not subjected to regular disruptions.

03. Soft-Shelled Eggs

The first pullet egg may be soft-shelled until her system gets into its stride. If the problem persists, make sure that the birds are getting a balanced diet which will usually contain calcium and phosphorus in the right ratio (around 3.5-4% calcium to 0.3-0.5% phosphorus). Providing a little coarse limestone will ensure that any deficiency is rectified, for the birds will not take more than they require.

It is when soft-shelled eggs or misshapen ones are produced regularly that there is a need for concern. Veterinary advice should be sought. Conditions that adversely affect eggs include Newcastle disease and Infectious bronchitis, but there would be disease symptoms showing in the birds themselves if either of these was present. Egg drop syndrome (EDS) is also a viral infection that results in a reduced number of eggs, as well as an increased number of pale-shelled eggs. Birds do recover from it but egg production may not get back to its previous level and there may still be a proportion of deformed ones produced. It can be vaccinated against.

04. Dark Shells Becoming Pale

Shells that are normally dark brown may become lighter for a number of reasons, including stress, illness or lack of appropriate food. The main reason, however, is strong sunlight on the back of the hens. Ensure that the flock is shaded from direct sunlight.

05. Egg with Blood on the Shell

This is often the result of straining on the part of the hen, where large eggs are involved. It may also be the case with a pullet first coming into lay. Avoid giving pullets too much artificial light until they are well grown before the onset of lay. If the shells have small spots of blood on them, rather than streaks, then suspect the presence of red mites. Treat with an anti-mite preparation from the vet or specialist suppliers.

The Albumen:

01. Watery Albumen

This is more common in hot weather. It is also more frequent in older hens. Occasionally it can be a reaction to vaccination. In this case, a multi-vitamin supplement in the water can help. Infectious bronchitis may also be the cause in an unvaccinated flock. If the condition persists, veterinary advice should be sought.

02. Cloudy Albumen

This may be caused by rapid refrigeration of newly laid eggs at temperatures of 0 to 4 °C. Keep eggs refrigerated at approximately 7 °C.

03. Blood and Meat Spots

This is usually the result of blood, due to hemorrhaging before and during ovulation, escaping from the ovarian follicle and becoming embedded in the albumen. It can sometimes be the result of shock or stress and normally corrects itself. There is some evidence that there is a hereditary tendency for this condition, so select strains with low incidence. Continuous intermittent periods of light may also be the cause, this may be corrected by using 15-16 hours of light.

The Yolk:

01. Pale Yolks

95% or more yellow maize used in the feed will result in the natural pigmentation of egg yolks (on the Roche scale it would be 7 or an 8). As soon as a higher percentage of white maize is used in the feed, the egg yolks become paler. There is nothing wrong with this, however, customers prefer deeper yolks often having the erroneous perception that such eggs are more ‘free-range’ or ‘natural’. A deeper egg yolk may be achieved by adding artificial colourants to the feed.

02. Bright Orange Yolks

Too much yolk colour pigment in the feed, either artificial or natural. The Roche scale is the standard way of determining degrees of yellow-orange in the yolk.

03. Double-Yolk Eggs

It is caused when two yolks are released into the oviduct at the same time and are then encased by one shell. It can also be caused by a sudden shock.

Date published: 2007-08-10

Rowena Sewjee