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Tracking chick locomotion: determining cage size.

Approximately 98 percent of the commercial egg production in the United States today comes from caged layers. Despite the large percentage of caged layers, there is an on going tug-of-war between poultry producers and public opinion on the welfare of laying hens, specifically as it relates to determining proper cage size. Little scientific data exists to help the industry determine proper cage size requirements.

Producers find that high density cage layer systems are more profitable because housing, labor, and equipment costs are reduced and less likely to be problematic for producers. Although high density systems are cost effective, public opinion on the treatment of animals is of a greater influence today than in the past.

For example, consumers place more value and possibly have more satisfaction purchasing food products (i.e. eggs) that are procured from "happy" animals--animals that are in good health and for which the public trusts the welfare of the animals is being upheld to their highest expectations.

Currently, the minimum cage stocking density for adult layers required by the United Egg Producers is 342 square centimeters (53 square inches) and will be increased to 432 square centimeters (67 square inches) by the year 2012. However, many companies, including one of the nation's largest fast food chains--McDonald's USA--have a future goal to only purchase eggs from producers that support their corporate animal welfare guide lines. McDonald's will specify 465 square centimeters (72 square inches) per bird.

Thus, the question arises, "How do we determine the cage size actually needed by a bird?" A related fundamental question is "How much locomotion does a chicken perform given unlimited floor space?"

A channel approach

To initiate an effort toward addressing such questions, graduate students in the Department of Agricultural and Biosystems Engineering at Iowa State University, developed a special testing channel as a part of their engineering instrumentation and controls course. The channel measured 8 centimeters wide x 2.5 centimeters deep by 91 centimeters in length (3 inches wide x 1 inch deep x 36 inches in length) with a floor area of 696 square centimeters (108 square inches), shown on the previous page. The channel is equipped with 16 pairs of infrared sensors laid out in a grid approximately 4.6 centimeters (1.8 inches) apart. Time series recordings of the sensor output indicate the location of the chick in 1-second intervals as the chick moves up and down the channel at free will as shown at right.

By using a program written in Visual Basic within Excel, the total distance that a chick traveled during an allocated period of time and the speed for which it traveled from one sensor to another can be determined. The channel is also covered by 2.5 centimeters (I inch) wire mesh with dimensions of 8 centimeters wide x 20 centimeters high x 91 centimeters long (3 inches wide x 8 inches high x 36 inches long). Food and water can be consumed by the chick through a window at the end of the channel as to not disturb the sensors.

What's next?

This inexpensive prototype, which uses short range sensors successfully, monitors chick locomotion for short trials. However, it would be beneficial to modify the channel to be used for larger birds which would require long range sensors.

Chicken facilities also hold multiple birds per cage. Therefore, additional testing and enhanced technical equipment would be required to enable the identification, monitoring, and recording of individual bird movement within an allotted period of time, say 24 or 48 hours. To date, the system has not undergone a long-term, comprehensive test. However, this is a first step toward a complex but important and timely issue. The study is not designed to solve the entire problem, but results found using a scientifically based method are certainly worth following up.

Getting it right

Currently Iowa is ranked first in the nation for egg production. All producers are spending time and money to implement new cage designs or modify existing cages to meet current size requirements. With the proposed cage-size mandates and little scientific data, this may or may not be the last time producers will have to increase the cage size in their facilities.

Increasing cage size requirements have depended on the method for which the space needed for poultry is determined by: 1) cage design and feeder space, 2) maximizing egg productivity, and 3) level of fearfulness experienced by, and mortality rates of, caged poultry. While these methods may provide a good estimate, this prototype could be helpful in promoting more scientifically based methods and data for determining cage size and thus, bird welfare standards for the industry.

ASAE member Kelly E. Persyn, 515-294-5749, fax 515-294-4250,, and Hong Li, 515-294-4250, fax 515-294-5749,, are graduate students in the Department of Agricultural and Biosystems Engineering at Iowa State University, 100 Davidson Hall, Ames, IA 50011-3080, USA. Cary J. Lane, 515-294 1423, fax 515-294-3261,, is an undergraduate student in the Department of Mechanical Engineering at Iowa State University, 2025 H. M. Black Engineering Building, Iowa State University Ames, IA 50011-2161, USA.
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Author:Persyn, Kelly; Li, Hong; Lane, Cary J.
Publication:Resource: Engineering & Technology for a Sustainable World
Geographic Code:1U4IA
Date:Aug 1, 2003
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