Top 5 health problems for egg-laying hens

Egg-laying hen health problems for U.S. flocks, both cage-free and cage-housed, are relatively under control today, according to Dr. Eric Gingerich, veterinarian, Diamond V.

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iStockphoto.com/rrodrickbeiler | Cage housing alleviates many health problems for hens, but the relative inactivity of the birds in cages contributes to calcium depletion being a more significant health problem in cages than in cage-free flocks.
iStockphoto.com/rrodrickbeiler | Cage housing alleviates many health problems for hens, but the relative inactivity of the birds in cages contributes to calcium depletion being a more significant health problem in cages than in cage-free flocks.

Egg-laying hen health problems for U.S. flocks, both cage-free and cage-housed, are relatively under control today, according to Dr. Eric Gingerich, veterinarian, Diamond V.

He told the audience at the Midwest Poultry Federation Convention’s Layer and Pullet Health Workshop that pullet health is good as well. The Association of Veterinarians in Egg Production’s health survey, conducted most recently in October 2014, provides insight into the relative importance of field health problems for layers and pullets in the U.S. (Tables 1 & 2).

Egg-laying hen health problems in cages

Colibacillosis continues as the most significant disease problem in U.S. cage-housed layer flocks (Table 2). Gingerich said these E. coli infections are mainly associated with young layer flocks when mortality rates of 0.5-4.0 percent per week starting shortly after placement in the layer house can occur. He said it is believed that this condition is most often a secondary infection after upper respiratory tract challenges from Mycoplasma gallisepticum (MG), Mycoplasma synoviae (MS), ammonia, infectious bronchitis (IB), or other such insults early in the lay cycle.

Gingerich explained that colibacillosis also may be a primary problem if water lines in the layer house are contaminated with E. coli. A post-molt colibacillosis syndrome can also be seen in some flocks due to declining immune system function, an ascending infection of the reproductive tract, upper respiratory infections, etc. The live E. coli vaccine, introduced in mid- to late 2006, has been increasingly used successfully as a preventative and as a treatment in the face of an outbreak in most areas.

Calcium depletion and focal duodenal necrosis were tied for the health problem of second-highest importance for cage-housed layer flocks last year. Gingerich said calcium depletion or “soft bones” are normally associated with low intake of calcium, phosphorus, and/or vitamin D3, particularly early in production along with low feed intakes. He predicted this condition will be an ongoing issue for layer flocks because it is exacerbated by the higher egg production rates accompanied with lower feed consumption that can be expected along with the continued improvement in management and genetics.

Focal duodenal necrosis (FDN) is believed to be caused by Clostridium colinum, and Gingerich said it is under-diagnosed in the field. He characterized this disease as being widespread and subclinical causing lesions in the duodenum, which results in loss of egg weight gain and/or egg production depending on the severity of the infection. The antibiotics chlortetracycline or bacitracin can be used to successfully treat or prevent the disease. Fermentation metabolite, probiotic, prebiotic, and botanical products are being evaluated for their usefulness in prevention of focal duodenal necrosis.

Health problems of cage-free hens

Cannibalism continues to be seen in cage-free flocks especially in high-light-intensity situations, Gingerich reported, and it was ranked by veterinarians as the most important health problem for cage-free layers. In these cases, he said that the 10-day or younger rule for beak trimming results in longer beaks than desired compared with a beak trim at four to eight weeks of age and that this may result in an increase in incidence and severity of cannibalism. Because this is a major problem for cage-free flocks that are gaining market share, he said primary breeders are placing more selection emphasis on reducing this trait. He suggested that the increasing use of large colony cages may also increase the level of cannibalism in cage-housed flocks.

Coccidiosis and colibacillosis were tied for second in level of importance as health problems for cage-free layers. Gingerich suggested that the coccidiosis problem is an indication that immunity is not being developed adequately in the pullet house.

Infectious bronchitis (IB) has a low prevalence in flocks but remains a health concern due to its importance in some cage-free layer flocks. Gingerich reported that variant strains of bronchitis virus are usually the problem. He reported that response to these problems includes incorporating all of the available vaccine strains into the pullet program, making sure the pullet live and killed vaccines are administered properly; preventing the entry of variant strains using good biosecurity, particularly when it comes to egg pickup and egg handling materials; and/or utilizing a live booster program in lay.

Pullet health problems

Coccidiosis and secondary necrotic enteritis remain as the major pullet health problems for cage-free and cage-housed flocks (Table 1). Gingerich reported that coccidiosis is an increasing problem in caged pullets and that vaccine usage as an intervention is on the rise.

Marek’s disease was rated as the second most important pullet health problem in cage-free flocks. He said this is due to early exposure to Marek’s virus-laden dust from the prior flock in the house that is not removed by the cleaning and disinfection program between flocks. He explained that the Marek’s vaccine requires five to seven days to provide full immunity.

Infectious bursal disease (IBD) was rated as the second most important health problem for cage-housed pullets. Gingerich said its subclinical form may lead to immunosuppression after the pullets' maternal antibody has subsided. He reported that the use of the recombinant HVT-vectored IBD vaccine has greatly aided farms with infectious bursal disease problems.

Post-Salmonella enteritidis bacterin-induced hepatitis syndrome was rated as the fifth most important health problem for cage-housed pullets. He said it can result in up to 7 percent mortality starting two weeks after the administration of the bacterin. The syndrome appears to have a genetic basis for susceptibility, as he reported that it has not been found yet in one strain of birds. The cause of this problem continues to be unknown at this time.

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