Executive Summary
“A Comparison of Egg Solids in Selected Strains of Layer Hens: Examining the Impact of Hen Age, Egg Age, Storage Conditions and Forced Molt”
Kenneth E. Anderson
Professor/Extension Specialist
North Carolina State Univ.
Department of Poultry Science
Box 7608
Raleigh, NC 27695-7608
Patricia A. Curtis
Director and Professor
Poultry Products Quality and Safety Program
Poultry Science Department
202A Poultry Science Bldg.
260 Lem Morrison Drive
Auburn University, AL 36849
Executive Summary
Feed consumption and feed conversion for white egg layers were not significantly affected by strain. The eggs per hen housed were influenced by the strain with a difference of 18.6 eggs from the highest producing stock to the lowest. This was not reflected in the percent hen day production between the strains, and therefore may in some cases be a result in the differences in mortality between the strains. All strains reach 50% production by 138 D of age, but the variation between the strains was as high as 8 days. Egg weight and subsequent egg size distribution was influence by the strain. There were no differences in the percent of large egg produced. The differences were related to a shift, predominantly related to small and medium sizes and the extra large percentages. Those strains with the heaviest eggs had the greatest percentage of extra large eggs. The percentage of Grade A eggs was not influence by strain. The percent of Grade B and loss eggs was different between strains. The egg income and feed expenses are significantly different between strains. The combination of high egg income and low feed costs resulted in as much as $1.08/hen difference. Each of the solids measurements were significantly impacted by strain of the hen, however, the changes in solids were not consistent between the different solid measurements. The interaction of strain and hen age on the percent of albumen solids shows that the strains’ albumen secretion is different as the hens’ age. Not all strains had continually decreasing albumen solids. The percent off albumen, yolk and whole eggs solids significantly changes as the hen ages. Albumen solids generally decreased as the hen aged. Yolk generally increased over the production cycle, however, there were a few period where yolk solids decreased. Whole egg solids increased though day 266 then plateaued at approximately 24.9%. The 21 day storage period resulted in a significant shift in the percent albumen and yolk solids. The albumen solids increased and the yolk solids decreased. Surprisingly, storage did not impact the whole egg solids. There was a significant interaction between hen age and storage temperature after 21 days of storage for yolk and whole egg solids, but not for albumen.
Even though the strain body weights were different after the random allocation to the molt treatments the average hen weights and weight losses for treatments were not different. The strain of hen did not impact the feed consumption during the 2nd cycle. The HH eggs were significantly increased in the molted hens over the non-molted hens. There was also a 8.3% reduction in mortality in the NF an FR molted hens. During the 2nd cycle, the strain had the greatest influence on egg weight. The strain of the hen did influence the albumen, yolk and whole egg solids during the 2nd cycle as is did in the 1st cycle. In general, the values were lower for the 2nd cycle than for the first. The yolk solids did not necessarily increase or decrease in response to corresponding changes in albumen solids. As with the 1st cycle, the age of the hen significantly influenced the percentage of albumen and yolk solids. Whole egg solids were stable throughout the 2nd cycle. Albumen solids were 0.5% higher in eggs from molted birds. Yolk and whole egg solids were not impacted by molting. The duration of the storage had a significant impact on all solids measurements. Albumen solids decreased throughout the 2nd cycle with stored eggs having highest solids. Yolk solids decreased during storage. However, as the hen aged the differences between the fresh and store yolk solids diminished. Whole egg solids were not affected by a 4°C storage for 21 days, but did increase when storage temperature was increased to 20°C.
All production characteristics were significantly different between the brown egg layer strains except for mortality and age at 50% production. None of the egg quality characteristics were influenced by the strain of the hens. The brown whole egg solids were significantly impacted by the strain of the hen. Albumen and yolk solids were not different between the strains. However when broken down by age, strain did impact yolk solids. When all strains were group together, the age of laying hens does impact the percent albumen, yolk and whole egg solids. The 21 day storage period resulted in a significant shift in the percent albumen and yolk solids. Regardless of the temperature, storage resulted in increases in albumen and whole egg solids and decreases in yolk solids. The 20°C storage temperature for 21 days resulted in more pronounced shift in the percent solids for the albumen and yolk, but not in the whole egg solids. Hen age had a significant impact on albumen, yolk and whole egg solids when stored (both storage temperatures combined). There was no impact on albumen or whole egg solids by hen age when separating the two storage temperatures.
During the molt cycle, all the brown egg strains responded in a similar manner. However during the 2nd cycle the brown egg strains responded differently from one another. Mortality was not affected by strain. The molt program had no impact on the egg size distribution. Overall the molt program resulted in an improvement in egg quality. In the 2nd cycle the strain of hen significantly impacted egg solids however as the hen aged albumen, yolk and whole eggs solids decreased. During the middle of the 2nd cycle the percent of yolk solids fluctuated in eggs which had not been stored while the yolk solids of stored eggs remained relatively constant. Whole egg solids in the fresh eggs decreased throughout the 2nd production cycle while the whole egg solids in the stored eggs remained relatively constant. The albumen, yolk and whole egg solids responded differently as the hen age and storage temperature increased.