My mom has mentioned that the last two dozen eggs I've given her have runny whites, and I realized that most of the eggs in those dozen were from my pullets. She complained of this two years ago, with different birds, and I investigated then, but didn't find anything conclusive. I've seen answers (guesses?) ranging from nutritional issue to parasite issue. A new search found this pdf from poultrycouncil.org http://www.poultryindustrycouncil.ca/factsheets/fs_100.pdf
EGG WHITE DEFECTS IN SOME FRESHLY LAID EGGS
(Prepared by Dr. Peter Hunton, Ontario Egg Producers)
Excessive thin albumen
The white (albumen) of freshly laid normal eggs consists of three layers (see figure below.)
Careful examination of many lots of eggs reveals a few with excessive outer thin albumen. These eggs are particularly noticeable by users when they are being fried on a griddle, and the whites spread and cook before
the rest of the egg is even warm. The original observations were made by such users, who then complained to the supplier.
Dr. Steve Leeson, Dr. Jim Squires and Dr. Yoshi Mine at the University of Guelph have studied this problem with the aid of PIC research grants.
Defining the problem
A report by Leeson and Caston (Poultry Science, vol.76 pp1332-1336) described a method of measuring the area covered by the egg when broken onto a flat surface. Surface area was measured for a small sample of (10) eggs of each class and the normal eggs covered 69.3 cm2, while the spreading eggs covered 111.8 cm2.
What is the extent of the problem?
Leeson and Caston, while studying the effects of nutritional variations on the phenomenon, stated that there was considerable bird-to-bird variation, but about 5% consistently produced spreading whites.
Effects of nutrition
Experiments using crude protein levels ranging from 14% to 20% failed to demonstrate any effects on the incidence of spreading whites. Similarly, varying the dietary acid:base balance failed to produce differences.
It is clear that the incidence of runny whites is not caused by any obvious nutritional factor, at least not one of those so far studied.
Incidence in commercial practice seems to be independent of feed source.
Figure 1.
Genetic implications
It was noted in the nutritional research of Leeson and Caston that individual birds tended to produce the runny eggs. Following the completion of the feeding study, ten birds with the best eggs, and ten producing eggs with the greatest surface area (the runniest) were mated to the same unrelated male, and chicks hatched from the resultant fertile eggs. When these pullets matured, their eggs were examined for albumen (and other) characteristics, and it was noted that the progeny of the two groups of parents also showed differences in the extent of spread of their albumen. Progeny of the "runny" parents consistently laid eggs with runnier whites. While some of the other traits measured also differed at times, the area of the thin albumen was the only one which was consistently affected by selection of the female parents.
Biochemical analysis of egg albumen
In their recent report to the PIC, Squires, Leeson and Mine reported on further analyses of the egg whites of normal and runny eggs. They found no significant differences in egg weight, thick albumen weight, protein
content, albumen height or Haugh Units between the two groups of eggs. Although Haugh Unit and albumen height values were slightly lower in the eggs with spreading whites, this was not statistically significant. The
problem is therefore not the albumen height or Haugh Unit of the eggs.
It is the spreading of the thin white, and not the height or quantity of thick albumen, which distinguishes runny eggs from normal ones. However, there was more thin albumen in the runny eggs. The thin albumen also contained less total disulfide groups, which are important in crosslinking proteins together. More of the disulfide groups in the runny eggs
were also present as oxidized sulfhydryl residues rather than disulfide bonds. This suggests that the hens that produce runny eggs may have reduced levels of the enzymes needed to form the disulfide bonds during
biosynthesis of egg albumen. These differences in the formation of adequate disulfide bonds in thin albumen may be the basis for the genetic inheritance of the runny egg trait.
Conclusions
1. Occasional eggs with spreading (runny) whites are observed originating from apparently normal flocks.
2. The runny eggs tend to be laid by the same hens.
3. The existence of runny eggs has nothing to do with freshness; it can be observed in newly laid eggs.
4. The albumen height and Haugh Unit rating is not different between runny and normal eggs.
5. There are differences in biochemical composition between normal and runny eggs.
6. There appears to be a genetic effect on the incidence of runny eggs, suggesting that selection might
reduce the incidence.
EGG WHITE DEFECTS IN SOME FRESHLY LAID EGGS
(Prepared by Dr. Peter Hunton, Ontario Egg Producers)
Excessive thin albumen
The white (albumen) of freshly laid normal eggs consists of three layers (see figure below.)
Careful examination of many lots of eggs reveals a few with excessive outer thin albumen. These eggs are particularly noticeable by users when they are being fried on a griddle, and the whites spread and cook before
the rest of the egg is even warm. The original observations were made by such users, who then complained to the supplier.
Dr. Steve Leeson, Dr. Jim Squires and Dr. Yoshi Mine at the University of Guelph have studied this problem with the aid of PIC research grants.
Defining the problem
A report by Leeson and Caston (Poultry Science, vol.76 pp1332-1336) described a method of measuring the area covered by the egg when broken onto a flat surface. Surface area was measured for a small sample of (10) eggs of each class and the normal eggs covered 69.3 cm2, while the spreading eggs covered 111.8 cm2.
What is the extent of the problem?
Leeson and Caston, while studying the effects of nutritional variations on the phenomenon, stated that there was considerable bird-to-bird variation, but about 5% consistently produced spreading whites.
Effects of nutrition
Experiments using crude protein levels ranging from 14% to 20% failed to demonstrate any effects on the incidence of spreading whites. Similarly, varying the dietary acid:base balance failed to produce differences.
It is clear that the incidence of runny whites is not caused by any obvious nutritional factor, at least not one of those so far studied.
Incidence in commercial practice seems to be independent of feed source.
Figure 1.
Genetic implications
It was noted in the nutritional research of Leeson and Caston that individual birds tended to produce the runny eggs. Following the completion of the feeding study, ten birds with the best eggs, and ten producing eggs with the greatest surface area (the runniest) were mated to the same unrelated male, and chicks hatched from the resultant fertile eggs. When these pullets matured, their eggs were examined for albumen (and other) characteristics, and it was noted that the progeny of the two groups of parents also showed differences in the extent of spread of their albumen. Progeny of the "runny" parents consistently laid eggs with runnier whites. While some of the other traits measured also differed at times, the area of the thin albumen was the only one which was consistently affected by selection of the female parents.
Biochemical analysis of egg albumen
In their recent report to the PIC, Squires, Leeson and Mine reported on further analyses of the egg whites of normal and runny eggs. They found no significant differences in egg weight, thick albumen weight, protein
content, albumen height or Haugh Units between the two groups of eggs. Although Haugh Unit and albumen height values were slightly lower in the eggs with spreading whites, this was not statistically significant. The
problem is therefore not the albumen height or Haugh Unit of the eggs.
It is the spreading of the thin white, and not the height or quantity of thick albumen, which distinguishes runny eggs from normal ones. However, there was more thin albumen in the runny eggs. The thin albumen also contained less total disulfide groups, which are important in crosslinking proteins together. More of the disulfide groups in the runny eggs
were also present as oxidized sulfhydryl residues rather than disulfide bonds. This suggests that the hens that produce runny eggs may have reduced levels of the enzymes needed to form the disulfide bonds during
biosynthesis of egg albumen. These differences in the formation of adequate disulfide bonds in thin albumen may be the basis for the genetic inheritance of the runny egg trait.
Conclusions
1. Occasional eggs with spreading (runny) whites are observed originating from apparently normal flocks.
2. The runny eggs tend to be laid by the same hens.
3. The existence of runny eggs has nothing to do with freshness; it can be observed in newly laid eggs.
4. The albumen height and Haugh Unit rating is not different between runny and normal eggs.
5. There are differences in biochemical composition between normal and runny eggs.
6. There appears to be a genetic effect on the incidence of runny eggs, suggesting that selection might
reduce the incidence.
