What’s the most humane way to raise a chicken? Watch and listen
Philip A. Stayer, DVM
Sanderson Farms, Inc.
The very foundation of any animal agricultural endeavor is proper care of the animals that provide products for human use. Various terms have been used throughout the years such as “animal husbandry,” “caretaking” and, more recently, “animal welfare” and “animal well-being.”
Since commercial poultry production is one of the largest segments of US animal agriculture, animal welfare has made its way to the forefront of our industry. All integrated poultry operations have written guidelines for animal welfare; most use the National Chicken Council’s Animal Welfare Guidelines and Audit Checklist.
At Sanderson Farms, animal welfare guidelines were incorporated into our growing programs and contracts long before animal welfare became a media buzz phrase. Sometimes, however, our customers who buy poultry products mandate growing conditions that aren’t common to US production systems. They’re aiming for an improved environment for flocks and, although they are well-intentioned, the end result isn’t always best for birds.
US versus European lighting
One example was a request to mirror European light-intensity requirements. In Europe, producers are required by law to keep lights above 0.3 footcandle for the duration of broiler growout. In the US, however, commercial producers have found “bar-like” light intensities below 0.1 footcandle improve performance parameters.
To respond to requests about European lighting standards, Sanderson Farms production staff and veterinarians, with the assistance of university researchers, put lighting schedules to the ultimate test: They raised birds with both types of lighting and compared the results. They considered not only the usual production parameters, they evaluated the impact of each lighting system on non-production-oriented animal welfare measures such as gait scoring and corticosterone levels.
For the uninitiated, a description of non-production parameter welfare measures may be of help.
“Gait scoring” is simply observing animals ambulate in their normal environment. In 2008, A. Bruce Webster, PhD, of the University of Georgia and others gained support for a simplified method of analysis called the “US Gait Scoring System,” which superseded more complex scoring systems. A score of “0” is balanced mobility — even if ungainly — for over 5 feet. A score of “2” denotes birds that cannot move 5 feet even with enticement. A middle score of “1” is reserved for individuals that can move 5 feet with a limp or decidedly awkward gait.
Like golf, a lower score is better, but also as with golf, not all swings are the same. Commercial broiler strains with better muscle accretion walk differently than commercial layers bred to lay lots of eggs: think lineman versus wide receiver in football.
Perhaps the most objective non-production measure of stress is the body’s corticosterone response. Commonly called the “flight or fight” hormone, corticosterone is the hormone secreted when an animal recognizes a threat to its well-being that must be rectified quickly. This steroid response focuses body resources on short-term survival versus long-term balance.
Corticosterone circulates through the blood stream so blood samples are needed for analyses. Of course, obtaining blood from an animal is a stressful event, so technicians must obtain adequate blood samples within 30 seconds of capture to prevent inducing an additional corticosterone release that will corrupt the results. This timed event is like calf roping, requiring a team of technicians: two to capture, bleed and cool blood and a third to call “calf rope” or “over time.”
Back to the Sanderson lighting study: Gait scoring indicated that birds raised in the US commercial lighting program scored better than those raised with the European program. In all replicates of the study, over 97% of birds tested in the US lighting program scored “0,” compared to less than 95.5% of birds in the European program. The US program won.
Corticosterone responses in all birds tested with either of the two lighting programs were below reported “stressed” levels. That being said, birds raised with the US lighting program had numerically lower corticosterone levels compared to birds in the European program. The birds’ own hormonal levels indicated the US program was probably less stressful than the higher intensity European program.
Production parameters are arguably the most sensitive indicator of well-being as all birds in a flock rather than a smaller sub-sample make up the average. If a flock is doing well on the whole, then livability, growth rate and feed conversion will be superior to another flock that’s not doing as well. Combining these production numbers into one figure creates a standard cost for the flock.
In the light trial, livability was over 97% for both light treatments, bodyweights were slightly higher (average 0.1 lb) for the European system and feed conversions improved (average 0.02) in the US system. The standard cost for all farms tested was consistently improved for the US system by 0.00192 $/lb, on average.
Production numbers reinforced results with non-production parameters: The US lighting program won again, and the customers who had asked for European lighting programs withdrew their request.
Natural versus artificial light
In another trial conducted at Sanderson Farms’ contract grower facilities, researchers from Mississippi State tested the notion that natural daylight was better for commercial chickens than controlled, artificial light.
At the time, old-style light translucent curtain-sided chicken houses were still in production and newer, solid-sided houses with very little natural light were starting to replace the older style. Light measured 13 footcandles in the curtain-sided houses and less than 0.1 footcandles in those that were artificially lit.
Two primary behavioral measures were taken to determine well-being. The first was simply watching chickens after personnel entered the house.
While watching the chickens, it was clear to all observers that broilers moved freely to feed and water in either lighting system, but their response to people and each other was vastly different. In brighter houses, chickens stayed at least 5 feet away from people entering their space, while in the dimmer light, they remained at observers’ feet. In addition, immature roosters in bright light faced off and sparred, but in newer houses, they didn’t demonstrate any aggressive behavior.
The second behavioral measure evaluated was “tonic immobility,” which could also be called “scared stiff.” The higher the baseline stress level, the more reluctant the bird is to upright itself after being placed on its back in a cradle. Birds more comfortable with their environment will upright themselves more often and quicker than birds that are scared stiff.
For this study, a custom-made cardboard cradle was used with a cardboard visual screen to block the sight of flock mates. Broilers strolling near the researchers were caught and calmed prior to laying them on their backs in the cradle.
Two technicians with stopwatches captured the time it took birds to upright themselves out of the cradle and the number of times they attempted to upright themselves. Broilers raised in modern housing with controlled light had lower tonic immobility scores than those raised in the older, curtain-sided houses.
Hence the title of this article about watching and listening to chickens. The studies presented here demonstrate that US commercial poultry production practices continue to evolve for the betterment of chickens, and chickens apparently appreciate technology that enhances their lives. If we take time to observe them, they will tell us what they prefer.
Posted on August 20, 2016