August 29, 2011
No Nutritional Difference Between Free-Range And Cage-Produced Eggs
Cholesterol levels in eggs from both sources found to be lower than expected, prompting a revision in USDA guidelines
Eggs produced by free-range hens are often perceived by the public to be nutritionally superior to eggs obtained from layers kept in traditional battery cages. However, a recent scientific study has called this popular perception into question by finding essentially no differences in the nutritional quality of eggs produced by hens from both management systems, said the Poultry Science Association (PSA). The findings also showed that cholesterol levels in all eggs were lower than U.S. Department of Agriculture guidelines, prompting the USDA to review and revise downward its estimates for average cholesterol levels in eggs.
The study, “Comparison of Fatty Acid, Cholesterol, and Vitamin A and E Composition in Eggs from Hens Housed in Conventional Cage and Range Production Facilities,” appeared in the July issue of Poultry Science, a journal published by PSA. Its author, Dr. Kenneth E. Anderson, a Professor in the Department of Poultry Science at North Carolina State University, collected data for the study in 2008 and 2009. The study was conducted concurrently with the North Carolina Layer Performance and Management Test (NCLP&MT), which evaluates the major commercial layer lines used in the United States.
“The key takeaway from this research is that an egg, no matter where it´s produced, is a very nutritious product. Eggs from a range production environment did have higher levels of total fat than eggs produced by caged hens, but they did not have higher levels of cholesterol. Perhaps the most striking finding was that both cage- and range-produced eggs actually have lower cholesterol levels than previously believed, which has led the USDA to lower the cholesterol guidelines for eggs in the USDA Nutrient Database for shell eggs to 185 mg per egg, down from 213 mg,” said Dr. Anderson.
Dr. Anderson conducted his study in North Carolina using more than 400 Hy-Line Brown pullets. The pullets were raised in accordance with the laying environment (range or cage) in the 37th NCLP&MT. All of the pullets in the study were hatch mates. Identical rearing dietary programs were used for both the range and cage pullets, with the only difference being the access the latter group had to the range paddock, a common hay mixture for North Carolina comprising both warm- and cool-season forages.
Pullets designated for the range facilities were brooded on litter until 12 weeks of age and then moved to a range environment. At 17 weeks, they were then moved to one of three production range paddocks. A parallel pattern was followed for the cage hens, which were reared in a cage rearing facility, and then at 17 weeks assigned to one of three groups of laying cages. All other rearing parameters were maintained as similar as possible.
Egg samples were collected at 50, 62, and 74 weeks of age during the productive life of the flock and sent to four different laboratories commonly used for egg nutrient analysis. The results showed no influence of housing environment (range or cage) on egg levels of vitamin A or vitamin E. However, β-carotene levels were higher in the range eggs, which, according to Dr. Anderson, may have contributed to the darker colored yolks observed in these eggs during the study. The study also found no difference in cholesterol content between range- and cage-produced eggs.
Based on these results, Dr. Anderson concluded that “a significant nutritional advantage of eggs produced by chickens housed on range versus in cages could not be established.”
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