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The Green Book

Fostering Health: The Pastured Poultry Approach to Dealing with Avian Influenza

 

Published in APPPA Grit Issue 87 (May/June 2015) by Susan Beal DVM, Mike Badger, and Terrell Spencer

Pasture-based production for poultry provides several natural barriers to the transmission of diseases such as Avian Influenza. These natural barriers are not often discussed from the conventional biosecurity point-of-view, but are validated by the experience of pastured poultry producers, poultry research science, and the common-sense that is the cornerstone of any agricultural system.

A Pastured Perspective to Flock Health

A pastured poultry approach to protecting the flock from Avian Influenza starts with a production environment that promotes a healthy immune system, and in some cases, directly contrasts the conventional confinement production environments.  

Sunlight: Avian Influenza is particularly sensitive to ultra-violet radiation, and that’s what’s found in direct sunlight. A foundational principle to a pastured poultry model is the regular movement of the birds to fresh pasture; pasture that has been sterilized by the sun before and after poultry actively forage on it. Incorporating natural sunlight into the winter housing and the brooder also bring the sanitizing effects of sunlight into all phases of production and should be practiced as much as possible.  

Forage: Ideally, pastured birds obtain a diverse and complete diet by foraging on green vegetation and insects, consuming a balanced feed ration, and drinking clean, fresh water. Poultry texts prior to the 1950’s promoted the importance of green, natural feeds to the health and nutrition of the flock. As the birds were moved inside and nutritional “balance” was achieved by the addition of vitamins to the feed, the importance of forage as a natural source of vitamins and other nutrients diminished. Currently, conventional poultry management opinion actually considers access to forage as a threat to flock health, despite research suggesting otherwise. Pastured poultry producers continue to prove, through profitable flock production, that natural forages result in healthy flocks, typically with no antibiotic inputs.  

Pasture Rotation: By using planned, regular pasture rotation, the birds do not spend time on a buildup of moist litter. By removing the birds from their litter at an early age when the chicks are old enough to leave the brooder, the air quality within the flock’s living space is fresh with minimal ammonia and levels that stress poultry health.  

Less Stress: The lower stocking rates common in pastured flocks typically yield a lower stocking density. A lower density results in a less stressful environment for the pastured flock, allowing for natural flock behaviors and preventing the stress of overcrowding. Additionally, poultry do not have to undergo invasive procedures such as debeaking or dubbing, as the stimulation of the natural environment prevents poultry from attacking each other because of high stocking rates. Just as in humans, less stress promotes an immune system functioning at optimum levels.  

As we look at flock health and biosecurity from the pastured poultry perspective, we should pause long enough to ask the question, “Does confinement actually favor the rapid mutation or spread of highly pathogenic avian influenza within a flock that’s confined inside?” A confinement poultry operation houses tens of thousands of individual birds inside a climate controlled space, and a single farm may house millions of birds at any given time. This provides several favorable conditions for avian influenza to thrive. Birds are in a close proximity to one-another, and the poultry houses are proximal to each other as well, facilitating the bird-to-bird spread of the virus. The chicken barns exclude natural, sanitizing and drying environmental factors, such as sunlight and heat, both of which work to naturally destroy the virus. By excluding natural environment factors and restricting movement to the barn, the flock is continually exposed to accumulating dust, litter, and feces as the flock grows, compromising the immune system of the flock.

About Avian Influenza

Avian Influenza virus is classified as either low pathogenic (LPAI) or high pathogenic (HPAI). Migratory wildfowl are typically carriers for the LPAI strains, and this has minimal, if any, effect on the waterfowl. However, in the current United States outbreak, the USDA has observed HPAI strains in wild fowl in Washington, Oregon, Idaho, California, and Utah (as of May 1, 2015). Domestic poultry infected with LPAI may go undetected because such infections often result in no symptoms or very mild symptoms, such as a slight reduction in egg production or feed conversion in meat types.  

The H5 and H7 low pathogenic subtypes of Avian Influenza are capable of mutating into the high pathogenic forms (H5N8 and H5N2 in the current outbreak), which can quickly spread throughout a susceptible poultry flock. Depending on the species of fowl, mortality can be high. In the current outbreak, turkeys have a very high mortality, whereas laying hens seem to be showing moderate morbidity and lower mortality. After the initial cases of dead or overtly ill birds, the rest of the laying flock levels out and does not show extreme symptoms.   Due to federal response, the actual mortality in any flock that tests positive for HPAI is always 100% fatal, as all surviving birds are destroyed in an attempt to prevent the further spread of the virus. The federal depopulation strategy is one of the most frightening aspects of the virus because the loss and destruction of all poultry on a farm carries grim economic and emotional realities.  

The pastured poultry community needs to cut through the fear and understand some fundamental realities. Avian Influenza is found in virtually all wild waterfowl, and short of exterminating all wild populations, Avian Influenza is not new and will not go away anytime soon. This makes all poultry vulnerable to some risk of infection with Avian Influenza.  

Consider, however, poultry that have been infected with low pathogenic forms of H5 and H7 have been shown to develop immunity to the related subtypes of the high pathogenic forms. That means a prior infection with H7 LPAI is protective against H7 HPAI, but not against highly pathogenic H5 strains and vice versa.   Pastured poultry producers have reason to be positive and to stay the course. There is a clear disparity in the number of backyard flocks testing positive compared to the large-scale commercial flocks despite increased surveillance and awareness. In the USDA context, the backyard designation fails to distinguish the pastured poultry flocks grown for market and profit, which adds further ambiguity to the make-up of the infected backyard flocks. Also, commercial poultry operations continue to be infected at a frequent rate, despite heightened biosecurity.  

Pastured poultry producers need to stay informed about the risks associated with Avian Influenza, but realize physical biosecurity cannot provide complete protection for a flock with compromised immune systems. Producers should stand firmly behind pastured poultry production as a natural model of prevention against infection, while also focusing on common-sense biosecurity practices to lessen the farm’s exposure to all poultry diseases.

 

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