Two recently completed research projects conducted at Purdue University uncovered some of the challenges with cage-free laying hens and the long-term financial impacts that a company may experience, according to an announcement from the U.S. Poultry & Egg Assn. (USPOULTRY) and the USPOULTRY Foundation, which funded the studies.

Dr. Darrin Karcher at Purdue University and colleagues from the U.S. National Poultry Research Center of the U.S. Department of Agriculture's Agricultural Research Service conducted the two projects to examine the role and impact of northern fowl mites on laying hens in a cage-free environment and assessed horizontal transmission of Salmonella Enteritidis and Salmonella Kentucky infection of laying hens in indoor cage-free housing.

According to Karcher, research has shown that salmonella persistence and transmission in poultry flocks can be influenced by various housing facility characteristics and flock management practices. However, he said the effect of different housing system options on food safety remains unresolved.

Further, Karcher said ectoparasites, such as northern fowl mites, have created challenges in cage-free housing systems that affect bird welfare and egg quality. The impact of northern fowl mite infestation on salmonella shed is not known, he noted.

Karcher said the objectives of these projects were: (1) to assess horizontal transmission of infection and invasion of internal organs after experimental S. Enteritidis and S. Kentucky infection of laying hens in indoor cage-free housing, and (2) to examine the role and impact of northern fowl mites on laying hen performance, welfare and egg safety in a cage-free environment.

For the first objective, Karcher said the results suggest that salmonella infection can spread rapidly and extensively among hens in cage-free indoor housing, including a high frequency of internal organ involvement for invasive serovars such as S. Enteritidis. Vaccination reduced but did not prevent either internal organ colonization or horizontal transmission of infection, Karcher reported.

He added that this finding confirms prior research that established salmonella vaccination can be a useful tool within comprehensive risk reduction programs but may not unilaterally provide complete protection against pathogen infection.

For the second objective, Karcher reported that differing results of the two experiments indicate that management decisions will have a dramatic impact on the ability of northern fowl mites to establish within a cage-free flock.

The intact beak of pullets can play a role in mitigating ectoparasites in cage-free environments yet contributes to the exacerbation of cannibalism and large amounts of feather loss, Karcher said.

The reduction in egg production and decrease in feather coverage may translate into decreased product for sale and an increase in costs as extra heat may need to be provided to account for the loss of feather cover, he noted.

Moreover, Karcher said pullets with trimmed beaks allow the northern fowl mite population to increase over the course of their production, resulting in a long-term infestation that can cause depressed egg production, influence egg quality measures and affect overall hen welfare.

Karcher concluded that these projects uncovered some of the challenges with cage-free laying hens and the long-term financial impacts a company may experience.