Salmonella: The Chicken or the Egg

Updated: Saturday, June 01, 2019 02:59 PM

Published: Saturday, September 11, 2010 02:04 PM

Written by Margaret Gates

Are raw eggs safe to feed to your cat? You may be wondering after hearing about eggs being contaminated with salmonella. Eggs are a great food source for cats. Raw egg yolks are a good source of protein, folate, vitamin B12, omega-3 and omega-6 fatty acids. Eggs are also a good source of the antioxidant lutein. Egg whites are an excellent source of phosphorus-free protein for those cats that need a phosphorus-reduced diet. Egg whites should be served cooked, as raw egg white can interfere with biotin absorption.¹

Freshly laid eggs from a healthy chicken are remarkably free of bacteria. The shells and whites of eggs normally do an excellent job of fending off pathogens, and eggs are naturally resistant to bacteria such as salmonella.² Eggs have chemical defenses that fight bacteria. One of these is an enzyme called lysozyme. Lysozyme is also found in animals and humans in tears, saliva and nasal secretions. It has the ability to break cell walls and is effective at killing off invading germs.³ Besides lysozyme, eggs have additional enzymes and proteins that kill pathogens in other ways. But if the chickens themselves are infected with salmonella, which was the case in a recent massive egg recall, the eggs likely will be, too.⁴

The eggs you buy may have a USDA Grade A seal on the carton. Does this mean that they are safe? Actually, all the seal means is that the eggs have been graded. They are checked for size, color and cracks. The seal comes from the marketing side of the USDA, not the safety side. USDA inspectors are mandatory for meat and it is part of the meat inspector's job to look for unsanitary conditions.⁵ But the USDA views its responsibility on the egg issue differently. Its egg graders have limited responsibility for ensuring egg safety. Graders only look for unsanitary conditions in the immediate area where the grading takes place. Graders have no authority to look at laying barns.⁶ The other arm of the government's food safety effort, the FDA, has virtually no enforcement authority over egg farms and so rarely inspects them.⁷

A law regarding egg production went into effect on July 9, 2010. It gave the FDA the authority to inspect egg production facilities for the first time. Had the law been in place sooner, it could have prevented the 2010 outbreak. It mandates salmonella testing of eggs and facilities. Further, it has rules about feed and water contamination as well as the sourcing of chicks and young hens from suppliers that monitor for salmonella.⁸

How did these hens get salmonella? The contamination may have come from rodents. Rodents can carry the salmonella bacterium and deposit it in their droppings in feed troughs.⁹ Chickens end up ingesting it and passing it on to the eggs they lay. The reports for the two egg producing facilities involved in the 2010 recall are grim. Widespread rodent infestation was seen, along with huge manure buildups, wild birds in the laying houses and many other unsanitary conditions.¹⁰ Recalls such as these make people take another look at how industrial farming operations do business, and it's not a pretty sight.

Facilities where birds are caged and crowded together may affect the nutritional quality of the eggs, too. A recent study describes the degree to which the nutritional value of chicken and chicken eggs has changed since large-scale farming was introduced.¹¹ The study compared the fat and omega content of chickens from 2004 through 2008 to the content seen in chickens from the 1970s. It found that chicken today has substantially more fat than chicken from the 1970s, with fat now contributing three times as many calories as protein.¹² Chickens on large-scale farms are currently fed energy-dense foods – mainly cereals – which are available 24 hours a day. The hens get little exercise and are bred to put on weight rapidly, which means putting on fat rapidly. Lack of exercise also means a lack of fast-acting muscle fibers which are rich in omegas. The energy-dense foods are also deficient in omega fatty acids. The ratio of omega 6 to omega 3 in the bird's meat has increased to as high as 9:1, whereas 2:1 is recommended.¹³ Higher ratios are associated with the promotion of cardiovascular diseases, cancer and inflammatory and auto-immune diseases.¹⁴ In contrast, free-range birds get high levels of omegas from the foods they eat, mainly green vegetation.¹⁵ Author Michael Crawford demonstrated that the omega-3 content of chicken had dropped from 170 mg in 1970 to between 25 and 60 mg today.¹⁶

So, there are more reasons than just a smaller chance of contamination to opt for free-range chickens and their eggs; it's a healthier choice, too. Chickens that are allowed to roam and eat vegetation will be healthier and more nutritious than chickens fed an omega-deficient diet of cereals. Oh, and the birds will probably be happier, too.

Margaret Gates is the founder of the Feline Nutrition Foundation.

1. Jane Higdon, PhD, "Biotin," Micronutrient Information Center, Linus Pauling Institute, Oregon State University, August 2008.

2. John L. Ingraham, March of the Microbes: Sighting the Unseen, Belknap Press, 2010, 62-65.

3. David S. Goodsell, "Lysozyme," Protein Data Bank, Research Collaboratory for Structural Bioinformatics, September 2000.

4. "With Salmonella, It's A Chicken-Or-Egg Conundrum," Interview with microbiologist John Ingraham, NPR, "Morning Edition," August 31, 2010.

5. Alicia Mundy and Bill Tomson, "Eggs' 'Grade A' Stamp Isn't What It Seems," The Wall Street Journal, September 2, 2010.

6. Alison Young, "Food Safety Groups Slam USDA Egg Graders at Farms in Recall," USA Today, September 2, 2010.

7. Katherine Hobson, "Thursday Egg Recall Roundup: Wider Federal Investigation Underway," The Wall Street Journal, September 2, 2010.

8. Timothy W. Martin, "New Food-Safety Rules Come Amid Egg Probe," The Wall Street Journal, August 23, 2010.

9. Meerburg, G. Bastiaan, Kijlstra and Aize, "Role of Rodents in Transmission of Salmonella and Campylobacter," Journal of the Science of Food and Agriculture87,no. 15, December 2007, 2774-2781.

10. Elizabeth Weise, "FDA Reports on Rats, Manure Piles at Egg Recall Companies," USA Today, September 1, 2010.

11. Yiqun Wang, Catherine Lehane, Kebreab Ghebremeskel and Michael A Crawford, "Modern Organic and Broiler Chickens Sold for Human Consumption Provide More Energy from Fat Than Protein," Public Health Nutrition, no. 13, March 2010, 400-408.

12. Yiqun Wang and others, "Modern Organic and Broiler Chickens."

13. Yiqun Wang and others, "Modern Organic and Broiler Chickens."

14. AP Simopoulos, "The Importance of the Ratio of Omega-6/Omega-3 Essential Fatty Acids," Biomedicine & Pharmacotherapy 56, no. 8, October 2002, 365-79.

15. Yiqun Wang, Catherine Lehane, Kebreab Ghebremeskel and Michael A Crawford, "Modern Organic and Broiler Chickens Sold for Human Consumption Provide More Energy from Fat Than Protein," Public Health Nutrition, no. 13, March 2010, 400-408.

16. Michael Crawford, "Naturally Reared," Letter to the Editor in New Scientist, July 28, 2010.