Submitted to: Proceedings of Iowa Egg Symposium
Publication Type: Proceedings
Publication Acceptance Date: December 15, 2000
Publication Date: February 5, 2001
Citation: Holt, P.S. 2001. Effects of molting on salmonella enteritidis in laying hens. Proceedings of Iowa Egg Symposium. Interpretive Summary: Induced molting is a very important economic tool used by the layer industry. Our earlier experimental work showed that Salmonella serotype Enteritidis (SE) infections were worse in hens molted through feed withdrawal but not as bad when hens were molted other ways. Because of some of this work, some regulatory agencies and animal welfare groups have viewed molting through feed withdrawal as a food safety issue. However, this is not entirely proper since an overwhelming proportion of the studies that these conclusions were based came from experimental work. It is extremely important that similar molting studies be conducted on hens in real-life commercial settings to see how closely the molting effects compare between experimental and commercial hens.
Technical Abstract: Induced molting is used by the layer industry to get a second egg lay from aging flocks. Molting is an important economic tool for the layer industry, used on approximately 70% of the laying flocks in the U.S. (approximately 144 million hens annually). There are several methods to induce molt but feed removal until the hens drop a certain body weight is preferred. Previous experimental studies showed that molting depressed immunity in the birds and decreased the CD4+ T cells, the helper T cell subset. In other experiments, molting was shown to increase the severity of Salmonella enteritidis (SE) infections, the susceptibility to SE challenge, and the horizontal transmission of SE to previously uninfected hens. Few field studies have been conducted on molting but of those that have been done, the percentage of eggs contaminated with SE increased the first 5 weeks post molt. Molting has come under scrutiny from both federal lagencies and animal welfare groups as a possible food safety issue, primarily because of the previous experimental studies. Because information from experimental work cannot realistically mirror what occurs in a commercial setting, more studies under commercial settings need to be performed. This will allow industry, federal agencies, and the consuming public to make reasonable decisions about the impact of molting on the relative safety of the table egg for the consumer.