Chicken's walk may hold clues to disease spreadChicken's walk may hold clues to disease spread
October 30, 2015
PLOTTING on a grid just how a chicken walks may one day give farmers more insight into how best to protect their flock from non-airborne pathogens.
"What this mathematical model tells you ... is how a chicken walks, meaning its pattern, how it moves around a pen," explained Dr. Arni S.R. Srinivasa Rao, a mathematical modeler in the department of biostatistics and epidemiology at the Medical College of Georgia at Georgia Regents University.
"It's a first step in learning more about how they spread infection and how best to address that," said Rao, corresponding author of a study in Mathematical Methods in the Applied Sciences.
The resulting complex series of equations Rao has developed basically shows not just the gait but also the walking patterns of chickens in a pen. Laid out on a grid, the paths chickens take, for example, from the corner of the pen to the feeder and back, look like a colorful racetrack. By plotting the patterns and multiplying them by the number of chickens in a pen, the mathematical model may help clarify how many ways and times chickens cross each other's paths -- and re-cross their own -- and the likelihood of disease spread that results from that pattern, an announcement said.
"We want to know whether we can predict the infectivity level of a particular pen from how the birds are moving," Rao said.
When chickens stray from their usual patterns, that could be an indicator of disease as well, Rao added. In fact, similar models could be developed for almost any farm animal.
Rao's next steps include taking the chicken walk model back to the pen to test whether it is an accurate predictor of at least one infection that costs poultry farmers billions of dollars annually.
Coccidiosis — caused by the Eimeria pathogen — spreads easily and rapidly among farm animals. It attacks the lining of the intestines, causing chronic diarrhea, weakness and weight loss in roughly 3% of chickens. Rao wants to help farmers know how long it takes that small amount to reach 100% of chickens in the pen in an effort to minimize loss.
While it's likely that a poultry farmer would isolate any sick chickens, in large poultry farms, that sort of individual inspection just may not be feasible, Rao said. Individual or even random testing for disease could be costly and time consuming as well. By giving farmers a mathematical heads up that a pen is at high risk, sick birds can be culled and others potentially treated.
His goal would be for farmers to take video footage -- which most already get for security surveillance -- and, possibly through animation, translate the walking patterns they see on the video into infectivity risk.
In collaboration with Drs. Fiona Tomley and Damer Blake at The Royal Veterinary College at the University of London, Rao studied chicken pens in both India and England. He noted how often the chickens eat and drink, how much time they spend moving and resting, how far they move, how often and where they defecate, as well as the paths they follow to get to the food and drink, looking for distinct patterns that increase the risk of infection.
Not surprisingly, he found plenty of opportunity for disease spread. Chickens keep walking as they defecate, so they walk right through their own and other chickens' feces. They can get feces on their beaks when they peck the ground and then spread it to the water when they take a drink.
Chickens tend to have distinct walking patterns, Rao noted. The most common patterns he witnessed were chickens moving diagonally across the pen or constantly crisscrossing, while others tend to be more sedentary, mainly roosting near food and water supplies.
A number of treatment options exist today for Eimeria, although drug resistance and cost remain a problem. Vaccines currently exist, but there can be problems with inconsistent levels of immunization in a flock as well as geographic variations in the species of Eimeria, according to a 2014 review in Veterinary Medicine: Research & Reports.
Avivagen Inc. recently announced preliminary results of a trial for its fully oxidized beta-carotene (OxC-beta) as a feed additive in broiler poultry conducted by the Institute of Agro-food Research & Technology in Catalonia, Spain.
The preliminary trial results suggest that the higher dose of oxidized beta-carotene that was tested offered a level of protection against the trial challenges. The characteristics of this broiler poultry trial, including a record heat wave during the trial, are summarized herein.
The trial was designed to test the ability of oxidized beta-carotene to maintain multiple measures of growth performance, health and food value in broilers reared under a controlled challenge with multiple stressors.
The four treatment groups were: (1) non-challenged, (2) challenged, (3) challenged plus a low-dose oxidized beta-carotene diet and (4) challenged plus a high-dose oxidized beta-carotene diet. The challenges were commonly occurring stress factors that affect production efficiency in commercial broiler facilities that could be ameliorated by the product's modes of action.
The trial ran for 35 days from late June to late July. During this time, Spain experienced a heat wave that resulted in its highest-ever recorded temperatures. The extreme heat overwhelmed the barn's cooling system, resulting in daytime inside temperatures of up to 37 degrees C, well above the optimum poultry temperature range of 26-32 degrees C. Thus, all treatment groups faced an additional and unintended heat stress.
The daily growth and final bodyweights were both affected by the experimental challenges, Avivagen said. Of the birds given oxidized beta-carotene, the results suggest that the higher dose had a protective effect: Birds receiving the high dose had final bodyweights and overall growth rates that were intermediate between the two control groups but were not statistically different from either. Specifically, birds in this group performed well enough that they were not significantly smaller than the non-challenged birds yet were not significantly larger than the challenged birds. The performance of those birds suggests that the higher dose may have limited the negative effects of the experimental challenge in this study.
The trial was certainly affected by the high barn temperatures, as the negative effect of heat stress on broiler performance is well known, the company pointed out. In the trial, all groups experienced higher-than-normal mortality, and even the non-challenged group's performance was below expectations. Avivagen believes the unintended heat stress may have reduced the effects of oxidized beta-carotene and prevented a more conclusive outcome of the trial.
Dr. James G. Nickerson, director of product validation at Avivagen, said, "We understand that production environments are characterized by complex combinations of stressors and that a single product cannot be expected to offer protection in all possible situations. The results of this study highlight the potential for OxC-beta to mitigate multiple commonly encountered stressors and provide us with important insights that will help to shape future trials aimed at bringing OxC-beta to market."
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