Eggshell Quality in Broilers

Dr. Andrew Olkowski of the University of Saskatchewan’s Department of
Animal and Poultry Science, didn’t know what to expect when he
undertook a study of eggshell quality and its relationship to embryo,
chick and broiler health.

Dr. Andrew Olkowski of the University of Saskatchewan’s Department of Animal and Poultry Science, didn’t know what to expect when he undertook a study of eggshell quality and its relationship to embryo, chick and broiler health.

But he didn’t expect to run into – figuratively speaking – an iceberg, he said during a presentation at the Poultry Industry Council Poultry Innovations Conference in Niagara Falls in November.

What he saw was clear – eggshell quality can indicate, but may or may not determine, the health of the embryo and the future health of the chick and chicken. That is the 10 per cent they saw.

The remaining 90 per cent is vaguely visible through the waves of data. To clarify the situation, the researchers conducted a second study to see if the underwater glimpse they got the first time around was an illusion or a new, disturbing reality.

The second study took unhatched eggs from 25 broiler-breeder farms and found much higher than expected numbers of “monstrosities,” and other significant troubles.

What he found was that eggshell quality is an indicator, or, related to a host of health issues.

These range from monstrosities, an increased percentage of unhatched eggs, more exploding eggs, more infected embryos, higher mortality and more condemnations.

10,000 eggs
In the first study, the shell quality of 10,000 eggs was evaluated based on an examination of the eggshell matrix using light. The eggs were classified as those with a normal eggshell and those with poor shell quality.

The eggs were set in marked trays for incubation in a low-risk (normal egg shell) group or a high-risk (abnormal egg shell) group.

After hatch the chicks were evaluated according to normal quality control standards. Unhatched eggs from both groups were transferred to the lab for further examination.

The chicks were then raised as commercial broilers in separate high- and low-risk groups.

Of the eggs set, more than two-thirds were in the low-risk group and just under one-third in the high-risk group.
The high-risk group had more exploded eggs, more unhatched eggs and produced a lower percentage of quality chicks.
In the unhatched eggs embryo pathology revealed significantly more infections in the high-risk group (12.1 per cent) compared with the low-risk group (4.1 per cent). The high-risk group also had more monsters (7.37 per cent) compared with the low-risk group (6.69 per cent).

The practical implications of the study are that chicks hatched from eggs with inferior shells are at a higher risk (1.6 fold) of mortality from all causes. The major cause of mortality was heart failure and the incidence of heart failure was higher (1.8 fold) in chicks from eggs with low-quality shells.

Poor eggshell quality was also associated with an increased rate of condemnations due to cellulitis (2.1 fold) and cyanosis (1.8 fold).

The study also found that eggs with poor shell quality were three times more likely than normal eggs to be infected and the susceptibility to infection is likely related to an increased rate of health conditions associated with bacterial infections such as pericarditis, peritonitis, necrotic enteritis and cellulitis.

The study provided evidence of a possible link between the health and physiological status of the parent flock and risk factors that may predispose broilers to health problems commonly seen in commercial operations.

“Over and above the health-related outcomes identified in this study was a high percentage of embryos with anatomical anomalies and monstrosities,” he said.

Monsters
Discovering greater than expected numbers  of monsters in the first study led to a second study of unhatched eggs from 25 commercial broiler-breeder flocks.

Researchers found anatomical abnormalities in 10 to 30 per cent of the examined fertile eggs, he said.

“Many embryos showed multiple monstrosities with various forms of beak, eye, trunk, leg and head anomalies.”

Two types of deformities stood out – a range of intestinal deformities and a spinal cord anomaly called spina bifida. This study resulted in the first detailed description of spina bifida in broilers.

In humans, spina bifida has been linked to exposure to chlorination byproducts in drinking water, electromagnetic fields, hazardous waste sites and pesticides.

Other deformities found in the study, such as eye defects, have been associated with nutritional factors and recent research has also identified low maternal intakes of iron, magnesium and niacin as risk factors associated with spina bifida.

The practical findings of the second study are that compared with historical data, the “rate of embryo deformities in contemporary broiler strains has increased several fold” and the “high incidence of anomalies and appearance of new forms are indicative of deteriorating genetic health of modern broiler strains.”

The study also noted that many well-developed and otherwise apparently normal embryos did not hatch because their beaks were underdeveloped or developed abnormally.

The studies point to the need for further research to look at the causes of the anomalies. “The causes of the anatomical anomalies observed in the present study are most likely milti-factoral, including factors relevant to nutrition, environment, toxic agents and genetics. Selection for rapid growth traits may be associated with higher genetic predisposition and susceptibility to nutritional and environmental factors,” he said.

Exposure to common pollutants such as PCBs, dioxins, heavy metals, hydrocarbons and others are also risk factors.
While the study began by looking at eggshell quality and health issues the outcome was “broader than expected” and future research will have to go further.

“Physical properties of the eggshell may not be the primary cause, rather the development of poor quality shell [may] reflect the problem with the metabolic/health status of the breeder hen. In the analysis of problems in the developing embryo, and the risk of disease in the offspring, we have to focus on the metabolic/health status of the breeder hen.”
“This is just the tip of the iceberg,” he said.

Table 1:  Comparison between losses associated with mortality
and condemnations between broilers hatched from low risk (normal shell)
group and high risk (poor shell) group.