A standardized cage measurement system: A versatile tool for calculating usable cage space 1

2012 Poultry Science Association, Inc. A standardized cage measurement system: A versatile tool for calculating usable cage space 1 A. S. Kiess,* P. Y. Hester, 1 J. A. Mench, R. C. Newberry, and J. P. Garner # * Department of Poultry Science, Mississippi State University, Mississippi State 39762; Department of Animal Sciences, Purdue University, West Lafayette, IN 47907; Department of Animal Science and Center for Animal Welfare, University of California, Davis 95616; Center for the Study of Animal Well-Being, Washington State University, Pullman 99164; and # Department of Comparative Medicine, Stanford University, Stanford, CA 94305 Primary Audience: Egg Producers, Agricultural Engineers, Cage Manufacturers, Regulatory Bodies SUMMARY The United Egg Producers husbandry guidelines for cages recommend a minimum of 432 to 555 cm 2 (67 to 86 in. 2 ) of usable space/hen, defined as floor space that is of sufficient height for hens to stand upright. Because there is neither a quantitative value given for cage height nor an established method for calculating usable space, meeting this guideline poses challenges for producers. The objectives of this study were to design a tool that could be used to calculate usable space and evaluate the effect of cage height on that space. Based on some reported hen behavior, it has been suggested that cage height should be at least 35.6 to 40.6 cm (14 to 16 in.), the effect of these height specifications on usable space was assessed. Using cage measurements taken from 180 commercial houses, we found that usable space declined as the specification for cage height increased from 30.5 to 47.0 cm (12 to 18.5 in.), with this decline occurring more rapidly for A-frame than vertical cages. When cage height was set at 35.6 cm (14 in.), almost all houses had cages with usable space. When it was set at 40.6 cm (16 in.), 97.5% of houses with vertical cages and only 30% of houses with A-frame cages had cages with any usable space. Although additional investigation into the effects of cage height on hen productivity and welfare is required to establish a scientifically justified cage height recommendation, this tool will be useful for producers and engineers in determining usable space across a range of hen strain sizes and cage designs. Key words: cage design, cage height, usable space, laying hen, animal well-being 2012 J. Appl. Poult. Res. 21 :657 668 http://dx.doi.org/10.3382/japr.2011-00491 DESCRIPTION OF PROBLEM The configuration of primary enclosures can have major effects on poultry well-being and production. The performance, behavior, and health of caged laying hens can be affected by factors such as cage shape, depth, and height [1, 2]. Many guidelines and standards now 1 Corresponding author: phester@purdue.edu

658 JAPR: Field Report exist that specify aspects of the cage environment, not only in terms of cage design but also of management of the cage space, to ensure the well-being of hens. Two general types of standards are used: engineering (or resourcebased ) standards, which often specify numerical values for a given aspect of the husbandry system, and performance (or animal-based ) standards, which typically specify outcomes for the animal [3]. An example of an engineering standard for cage space would be requiring provision of a minimum number of square centimeters (square inches) per hen, whereas an example of a performance standard would be requiring that hens be given enough space to turn around. To comply with standards, managers must be able to measure the aspects of husbandry stipulated in the guidelines. However, this is not always straightforward. In the case of engineering standards, unless cage size components are very precisely defined, complexities of cage design can result in inconsistencies in the way that specific measurements are taken, especially when making comparisons across different styles of cages. Furthermore, performance standards may require quantifying information for which no measurement method has been established. The Commission of the European Communities (CEC) [4] and the United Egg Producers (UEP) [5] standards for laying hens kept in conventional cages can be compared as examples of the 2 types of standards (Table 1). The CEC [4] has provided engineering standards for floor space and cage height, allowing all the cage floor area to be counted toward the 550 cm 2 (85.3 in. 2 )/hen as long as a minimum height of 40 cm (15.7 in.) is provided in 65% of the cage, with no part of the cage having a height of less than 35 cm (13.8 in.). In contrast, the current UEP [5] guidelines include a performance standard for cage height, requiring that a hen be provided with at least 432 cm 2 (67 in. 2 ) of usable floor space, with usable space defined as space that is unobstructed and of sufficient height for the hens to stand comfortably. The UEP [5] guidelines thus provided Table 1. Different criteria used in 2 sets of guidelines for conventionally caged laying hens Guidelines Recommendations Calculator 1 United Egg Producers (UEP) [5] Commission of the European Communities (CEC) [4] 432 to 555 cm 2 (67 to 86 in. 2 ) of usable space/hen Sufficient height for a hen to stand comfortably upright Cage floor slope not to exceed 8 Sufficient feeder space to allow all hens to feed Set floor space allocation as recommended by UEP [5] and examine usable colony size. Examine actual floor slope. Set feeder space allocation. Examine colony size to meet feeder space. 550 cm 2 (85.3 in. 2 ) of space/hen, measured parallel to the room floor (not the recommendation, and examine allowable Set floor space allocation to CEC [4] cage floor) colony size (horizontal). 10 cm (3.9 in.) of feeder space/hen Set feeder space allocation. Examine colony size to meet feeder space. 10 cm (3.9 in.) of drinker trough space/ hen or 2 nipple or cup drinkers/cage At least 65% of the floor (or usable space) provides a cage height of 40 cm (15.7 in.) Cage height of not less than 35 cm (13.8 in.) at any point Cage floor slope not to exceed 8 (grade of 14%) 1 The calculator column indicates how to calculate the recommendation. Set feeder space allocation. Examine colony size to meet feeder space. Examine actual number of nipple or cup drinkers. Set specified height to 40 cm or 15.7 in. Examine % of floor usable. Set specified height to 35 cm or 13.8 in. Examine all area beneath ceiling usable. Examine actual floor slope.

Kiess et al.: USABLE CAGE SPACE greater flexibility by allowing for adjustment of colony size to compensate for constrained cage height, and to accommodate hen strains of different sizes, but they are less specific regarding how to determine whether hens have the required amount of floor space. No standardized method has been reported for measuring cages, which are typically not simple rectangular boxes, or for calculating the resulting allowable colony size. Consequently, the primary goal of the current study was to design such a method and provide a measuring tool applicable to multiple cage designs, which was then used to examine the effects of different cage height specifications on allowable colony sizes. MATERIALS AND METHODS Design of the Standardized Cage Measurement System 659 The variation in size and shape of existing laying hen cages was first assessed by searching industry websites for technical drawings of cage designs. From this informal survey, it was clear that an extremely flexible system was needed to calculate summary variables (for example, usable space) from a single set of measures. The solution was to view the cross-section of a cage as a deviation from a rectangle at 3 of its corners (Figure 1 and Table 2). Thus, the rectangular cross-section of the cage is described by the front height and floor depth. This rectangle Figure 1. Measurements taken from the side of a cage for the standardized cage measurement system. The cage depicted is from a row of cages in a battery system. All measurements are taken parallel or perpendicular to the lower front section of the cage (overhang base). Typically, the wire mesh of the cage will be aligned to this bottom front corner (point A in Figure 3); thus, the mesh as shown in the cage diagram can be used as a guide. The tilt angle of the cage does not affect these measures. Thus, for a tilted cage, the overhang base will not be plumb vertical, but all measures are still taken perpendicular or parallel to the overhang base. Tilt angle is measured as the deviation of the overhang base from plumb vertical.

660 JAPR: Field Report Table 2. Definitions of and instructions for obtaining measurements of cages for input into the standardized cage measurement system calculator 1 Measure 2 Definition and instructions Front height, 3 cm or in. Back height, cm or in. Floor back offset, cm or in. Floor depth, cm or in. Ceiling depth, cm or in. Width, cm or in. Ceiling overhang, cm or in. Overhang base, cm or in. Tilt angle, The vertical distance between the cage floor and the cage ceiling at the front of the cage The vertical distance between the cage floor and the cage ceiling at the back of the cage; if the ceiling slopes in the back, measurement stops at the point where the slope begins The vertical distance that the base of the floor at the back of the cage is offset from the base of the front of the cage; this is not the same as the cage tilt angle The horizontal distance between the front of the cage and the back of the cage at the base of the floor The horizontal distance between the front of the cage (excluding the ceiling overhang if present) and the back of the cage at the ceiling; if the ceiling slopes in the back, measurement stops at the point where the slope begins The distance across the front of the cage between 1 cage divider and the next The horizontal distance that the ceiling extends beyond the base of the front of the cage The vertical distance from the floor of the cage front to the point where the cage front makes an angle The angle at which the base of the front of the cage is tilted from plumb vertical, measured using an angle locator 1 See Figure 1 for cage schematic. 2 All measures are obtained either parallel to the bottom front face of the cage (vertical measurements) or parallel to the front ceiling of the cage (horizontal measurements). These 2 dimensions are always perpendicular and typically align with the wire mesh of the cage. In tilted cages, these measures will not be parallel or perpendicular to plumb vertical. 3 The calculator is designed to be independent of the measurement unit. As long as centimeters or inches are used consistently, either can be used. can then be modified to account for the floor slope, a sloping ceiling at the back, a protruding overhang at the front, and the tilting of the entire cage in the framing system. Sample of Cages The standardized cage measurement system described here was used to sample conventional Table 3. Definitions of and calculations for outcome measures derived from inputs 1 into the standardized cage measurement system calculator 2 Outcome measure Definition Calculation Maximum effective floor The total amount of floor space in the cage Floor depth (line AB) 3 width area, cm 2 or in. 2 Maximum allowable colony size, no. of hens Space at maximum allowable colony size, cm 2 or in. 2 /hen Minimum available height as stocked, cm or in. Space/hen as stocked, cm 2 or in. 2 The total number of hens allowed in a cage, taking into account the maximum effective floor area and the recommended floor space allocation The actual amount of space an individual hen is provided, taking into account the maximum effective floor area and the recommended floor space allocation The lowest height within the cage at which the stocked hens achieve the recommended floor space allocation The amount of floor space each hen is provided Maximum effective floor area floor space allocation (round down) Maximum effective floor area maximum allowable colony size Solve for allowable height at usable depth = maximum allowable colony size floor space allocation maximum effective floor area Maximum effective floor area stocked colony size 1 The user enters the inputs of cage dimensions (floor depth, width, and specified height of the cage), floor space allocation (cm 2 or in. 2 /hen), and stocked colony size, which are used to calculate outcomes. 2 These outcome measures are currently used by producers when stocking hens in cages without regard to cage height requirements. 3 See Figure 3 for defining distances.

Kiess et al.: USABLE CAGE SPACE cages in 180 commercial houses located in different regions of the United States. Cage measurements (Table 2) were taken, to the nearest 1/4 in., from every tier in the cage stack. To measure the tilt angle of the cage floor, we used an angle locator providing readings to the nearest degree [6]. The cage stacking arrangement (A-frame or vertical) was also noted because these 2 types of cages have very different designs. Each tier of the stack was measured separately because in both A-frame systems with curtain backs and vertical systems with dropping-boards, top tier cages are typically configured differently from those on the lower tiers. Standardized Cage Measurement System Calculator A calculator application was created using Microsoft Excel [7], and the validity of the calculations was verified manually and by using alternate software. To use the calculator, cage measurements are taken parallel and perpendicular to the front face of the cage (which usually corresponds to the front edge of the wire mesh when viewing the cage from the side); the angle to which the whole cage is tilted from vertical is 661 then measured (Figure 1). These cage measurements are entered into the calculator, and the calculator displays a diagram of the cage (Figure 2), with outcome measures (Tables 3 to 6). Some outcome measures take into account the cage floor slope (effective measures), whereas others do not (horizontal measures). Some outcome measures depend solely on the dimensions of the cage. These include maximum effective floor area (Table 3), mean height, and actual floor slope (Table 6). The remaining outcome measures generated by the calculator are affected by 1 or more of the parameters set by the user, including 1) floor space allocation (cm 2 or in. 2 /hen); 2) feeder space allocation (cm or in./hen); 3) stocked colony size (number of hens); and 4) the height specification (cm or in.) to be used for calculating usable floor space, defined in this paper as the amount of available cage floor space that has at least the specified cage height. Calculations The procedures for calculating usable floor space and usable depth (i.e., how much of the cage depth can be used to meet the floor space Figure 2. The Standardized Cage Measurement System Calculator in Microsoft Excel [7]. Cage measurements (cm or in., or degrees for tilt angle) are entered in the top left-hand box, and the cage is drawn to the right. Measures are calculated on the right using inputs entered in the boxes on the left. Color version available in the online PDF.

662 JAPR: Field Report Table 4. Definitions of and calculations for horizontal outcome measures derived from inputs 1 into the standardized cage measurement system calculator 2 Outcome measure Definition Calculation Usable depth, cm or in. Available height, cm or in. Horizontal usable space, cm 2 or in. 2 Horizontal usable space/ stocked hen, cm 2 or in. 2 Allowable colony size (horizontal), no. of hens All usable area beneath ceiling, cm or in. The horizontal distance from the front of the cage until the specified height is reached The height of the cage at the usable depth The area of the cage usable in the horizontal plane The area of the cage usable in the horizontal plane per hen, given the stocked colony size The number of hens that can occupy the cage, taking into account the horizontal usable space and the recommended floor space allocation In tilted cages, the cage back extends over the cage floor. This tests whether the floor, excluding the area under the cage back, is usable in its entirety. requirement, given parameters such as specified height and stocking density) can be visualized in Figure 3. The calculator program first parses the Solve for specified height The height of the cage at the usable depth, or if none of the cage is usable at the specified height, then the maximum height available Width usable depth Width usable depth stocked colony size Effective usable floor space floor space allocation (round down) Is usable depth equal to or greater than horizontal distance AC 3? 1 The user enters the inputs of cage dimensions (specified height and width of the cage), floor space allocation (cm 2 or in. 2 /hen), and stocked colony size which are used to calculate outcomes. 2 These outcome measures take into account a specified cage height requirement when measures are taken parallel to the room floor along a horizontal plane. 3 See Figure 3 for defining distances. measurements for errors or conflicting measurements, and then calculates the position of key points on the cage (labeled A to G) relative to the Table 5. Definitions of and calculations for effective outcome measures derived from inputs 1 into the standardized cage measurement system calculator 2 Outcome measure Definition Calculation Effective usable depth, cm or in. Effective usable floor space, cm 2 or in. 2 Floor usable, 4 % Allowable colony size, no. of hens Space at allowable colony size, cm 2 or in. 2 Relative colony size, 4 % The distance from the front of the cage until the specified height is reached, taking into account the effect of tilt angle on the cage The amount of space the cage provides up to the point where it reaches the specified height Effective usable floor space as a percentage of the maximum effective floor area The number of hens that can occupy the cage, taking into account the effective usable floor space and the recommended floor space allocation The actual space provided to each individual hen, taking into account the effect of specified height Allowable colony size as a percentage of the maximum allowable colony size Floor depth (line AB) 3 usable depth horizontal distance AB Effective usable depth width 100% effective usable floor space maximum effective floor area Effective usable floor space floor space allocation (round down the number of hens) Effective usable floor space allowable colony size 100% allowable colony size maximum allowable colony size 1 User enters the inputs of cage dimensions (floor depth and width of the cage) and floor space allocation (cm 2 or in. 2 /hen) which are used to calculate outcomes. 2 Effective distances are measured parallel to the cage floor. These outcome measures take into account a specified cage height requirement when measures are made relative to the tilt angle of the cage. 3 See Figure 3 for defining distances. 4 For comparisons across cages, some measures are expressed as a percentage of their equivalent measure.

Kiess et al.: USABLE CAGE SPACE 663 Figure 3. Procedures for figuring usable floor area and depth. a) The calculator first parses the measurements for errors or conflicting measurements, and then calculates the position of key points on the cage (labeled A to G), relative to the bottom of the front of the cage (which is placed at the origin of the graph). b) The cage is then rotated around point A by the appropriate tilt angle. c) The hatched areas are not usable. The usable cross-sectional area of the cage is bounded by 1) a vertical line through point A; 2) the cage floor (line AB); 3) the cage ceiling, comprising lines ED, DC, and CB as necessary; and 4) a vertical line at the back of the cage, determined by setting the usable depth or solving for a specified height. The calculator determines the usable floor area for a given usable depth (if such a solution is possible) and figures the usable floor area at a usable depth derived from the desired stocking density and colony size for the cage. In both cases, densities are figured in, or from, effective usable depth (i.e., the actual distance AB). Color version available in the online PDF. bottom front of the cage, which is placed at the origin of the graph (Figure 3a). The cage is then rotated around point A using the appropriate tilt angle (Figure 3b). The hatched areas (Figure 3c) are considered unusable. The usable cross-sectional area of the cage is bounded by 1) a vertical line through point A; 2) the cage floor (line AB); 3) the cage ceiling, comprising lines ED, DC, and CB as necessary; and 4) a vertical line at the back of the cage determined by setting the usable depth or solving for usable floor space. The outcomes for usable floor space and depth

664 JAPR: Field Report Table 6. Definitions of and calculations for outcome measures derived from inputs 1 into the standardized cage measurement system calculator 2 Outcome measure Definition Calculation Mean height, cm or in. The average height of the cage Figure entire cross-sectional area of cage to the right of point A, 3 and by usable depth Cage volume, cm 3 or in 3 /hen The cage volume available/hen Figure entire cross-sectional area of cage to the right of point A, and by width stocked colony size Actual floor slope, The angle at which the cage floor is tilted as a consequence of the floor back offset and tilt angle The linear feeder space available to each hen of a cage depend on the specifications being applied and which of the 2 measures is defined by the specifications and subsequently solved for (Tables 3 to 5). The calculator first figures the measures, ignoring specified cage height and the measures detailed in Table 3. The calculator determines the available height for a given usable depth (if such a solution is possible) by first using the specified floor space allocation and stocked colony size to figure the effective area required. The usable depth parallel to the horizontal axis of the graph is then figured from the ratio of the effective area required to the maximum effective area. The calculator then simply measures the vertical distance between line AB, and lines ED, DC, or CB, as appropriate. Conversely, to figure usable depth (and the other measures derived from usable depth), the calculator finds the greatest usable depth where the vertical distance between line AB, and line ED, DC, or CB, is equal to the specified height. From these values, the calculator figures one set of measures as horizontal measures (Table 4), and then as effective measures (Table 5). Measures expressed as percentages are identical when measured either in the horizontal plane or parallel to the cage floor and therefore are given only once (Table 5). The CEC [4] standard states that no point in the cage should have a height of less than 35 cm (13.8 in.). Strictly interpreted, this recommendation would be unworkable because, in a tilted cage, the back wall creates a small pocket of space where height approaches 0 at the back of the cage. To test a standard of this type, the calculator figures whether the specified height is met for the floor area under the cage ceiling (i.e., up to point C in Figure 3, referred to as all area beneath ceiling usable as defined in Table 4). Data Processing Arctangent (vertical distance AB 3 horizontal distance AB) Feeder space/stocked hen, Width stocked colony size cm or in. Colony size to meet feeder The maximum colony size that provides the Width feeder space allocation (round space, no. of hens desired feeder space allocation down) 1 User enters the inputs of cage dimensions (width of the cage), stocked colony size, and feeder space allocation which are used to calculate outcomes. 2 These measures are unaffected by the method of space and stocking density. 3 See Figure 3 for location of points and defining distances. To examine the effect of different specified cage heights on usable floor space and stocking density, outcome measures (Tables 3 to 6) were calculated for each tier in a house separately and averaged for each house. The percentage of houses with some usable floor space, the mean usable floor space at the different specified heights (expressed as the percentage of floor usable; Table 5), the mean allowable colony size (expressed as relative colony size for the minimum UEP [5] recommended density of 432 cm 2 or 67 in. 2 ), and the mean of the minimum cage height at the maximum colony size for each cage were calculated. For the last 3 of these summary measures, the tiers in a house were first averaged, and then the houses were averaged. This process was repeated for cage height specifications increasing in 1.3-cm (0.5-in.) increments over a height range of 30.5 to 49.3 cm (12 to 19 in.).

Kiess et al.: USABLE CAGE SPACE 665 Figure 4. The effects of different specified heights on cages measured from 180 houses. In all graphs, A-frame and vertical cages are plotted separately, because these 2 designs differ. a) The proportion of houses with any usable cages (i.e., with cages with usable space >0). In some houses, only cages in the top row are usable at certain specified heights. b) The mean usable space, at different specified heights, of all the cages in the survey. To compare across cages, usable space is expressed as a percentage of floor area for each cage. Note that because most A-frame cages are tilted, usable space will always be slightly less than maximum floor space because the back wall forms a steeply sloped ceiling. c) The mean allowable colony size in the usable space, at different height specifications, of all the cages in the survey. To compare across cages, colony size is figured for usable space for each cage and is expressed as a percentage of the colony size that would be allowed on the total floor area. In both cases, 432 cm 2 (67 in. 2 )/hen is used, and colony size is rounded down to the nearest bird. d) The distribution of minimum cage height at the maximum colony size for hens stocked at 432 cm 2 (67 in. 2 ) in A-frame and vertical cages. The largest colony that could be stocked in a cage was figured, given the total floor area and the proportion of the cage that would be needed to stock birds at 432 cm 2 (67 in. 2 )/bird. RESULTS AND DISCUSSION The CEC [4] standards for hens in conventional cages are not applicable in Europe as of 2012 because of the conversion to furnished cages. However, they are of interest in other regions of the world (including the United States), where hens are currently housed in conventional cages, because they include a specific cage height requirement as a part of the recommendations (Table 1). Therefore, the calculator was used to evaluate whether the cages in the 180 houses surveyed in this study would meet those standards. The UEP [5] standards, on the other hand, require adjusting the stocking density to compensate for the height of the cage, so the effect of varying cage height specifications on usable floor area was also assessed; A-frame and vertical cages are shown separately because of the differences in their design (Figure 4). None of the A-frame cages and only 33.9% of the vertical cages surveyed met the CEC [4] space standards. With regard to the criteria in the UEP [5] guidelines, Figure 4a shows the percentage of houses in which at least some area of the cage provided each specified height (i.e.,

666 JAPR: Field Report were usable, given a particular height specification). The percentage of A-frame-style houses with any usable cages decreased dramatically above a specified cage height of 35.6 cm (14 in.), whereas the percentage of vertical cage houses with any usable cages did not begin to decrease until a specified height of 40.6 cm (16 in.) was exceeded (Figure 4a). The total percentage of usable floor space in the 180 houses surveyed declined dramatically as the specification for height was increased from 30.5 cm (12 in.) to 47.0 cm (18.5 in.; Figure 4b). The percentage of mean usable floor space for A-frame cages declined more rapidly than that for vertical cages. At a specified stocking density of 432 cm 2 (67 in. 2 ), allowable colony size also declined dramatically as the cage height specification was increased (Figure 4c). At heights greater than 35.6 cm (14 in.), allowable colony size decreased in both A-frame and vertical cages. Vertical cages allowed for a larger colony size than A-frame cages, but allowable colony size still decreased steeply at specified heights greater than 35.6 cm (14 in.). The distribution of minimum cage heights at the maximum colony size for hens stocked at 432 cm 2 (67 in. 2 ) in the 180 houses surveyed is shown in Figure 4d. The median cage height at the maximum colony size was approximately 26.7 cm (10.5 in.) for A-frame cages and 40.6 cm (16 in.) for vertical cages [means of 25.4 cm (10 in.) and 40.6 cm (16 in.), respectively]. A difficulty in applying the UEP [5] recommendations is that they involve a judgment about how much height is required for a hen to stand comfortably upright. The limited scientific information available on the effects of cage height on hen behavior is derived mainly from studies on brown-egg-laying strains of hens. Dawkins [2] found that, when given a choice between 2 cages, single brown hens of 1 strain spent more time in cages with heights of at least 49.5 cm (19.5 in.) at the front and 40.6 cm (16 in.) at the back than in cages providing less vertical space, suggesting that they were more comfortable standing in the taller cages. In addition, 25% of all head movements occurred above 40 cm (15.7 in.) [2]. Nicol [8] observed that brown hens of the same strain, housed in pairs in experimental cages with flat floors and ceilings and provided a cage height of 55 cm (21.7 in.), performed head stretching, head scratching, and body shaking activities more frequently than did hens provided a cage height of 30 cm (11.8 in.); a cage height of 42.5 cm (16.7 in.) gave intermediate results, although skewed toward those for the greatest cage height. The higher level of performance of these comfort behaviors was considered to indicate better hen welfare in the taller cages [8]. In furnished colony cages housing hens of multiple brown hybrid strains, no differences were observed in hen behavior or distribution between connected cages providing vertical space of 44 cm (17.3 in.) at the front and 38.0 cm (15 in.) at the back as compared with 51 cm (20.1 in.) at the front and 45 cm (17.7 in.) at the back, except for greater head scratching and yawning activities in the taller cages [9]. These could again be construed as indicating increased comfort. When hens were given the choice of staying in a cage containing 10 hens or moving through a narrow gap to an adjoining empty cage (with the gap requiring some effort to pass through), more hens moved to the other cage if its minimum height was 45 cm (17.7 in.) rather than 38 cm (15 in.) [10], again suggesting a preference for taller cages. Although the above data provide some insights into cage height requirements for brown hybrid strains, they provide little insight into suitable height requirements for the White Leghorn strains typically used in the United States, which tend to have smaller body frames than brown hybrids [11]. Mench and Blatchford (J. Mench and R. A. Blatchford, Department of Animal Science and Center for Animal Welfare, University of California, Davis, unpublished data) used kinematic analysis to evaluate the 3-dimensional space of 10 Hy-Line CV-20 White Leghorns hens while performing various behaviors. They found that the height of hens when standing averaged 34.8 cm (13.7 in.), although the tallest height recorded during standing was 41.1 cm (16.2 in.). To set a scientifically based cage height standard, these data will need to be complemented with more comprehensive data on the effects of cage height on the productivity, health, and behavior of White Leghorns. However, they do provide a starting point for as-

Kiess et al.: USABLE CAGE SPACE Figure 5. Quick response code for the hen cage calculator (http://www.bitly.com/hencagecalculator). 667 sessing how cage height specifications affect usable floor area in current conventional cages. At a height of 35.6 cm (14 in.), the calculator shows that 100% of the floor space in vertical cages is usable and that 60% of the floor space in A- frame cages is usable. At a height of 40.6 cm (16 in.), however, although approximately 80% of the floor space in vertical cages is usable, less than 25% of the floor space in A-frame cages can be considered usable. On the basis of the results of the current study, the standardized cage measurement system calculator is flexible enough to figure outcomes for a variety of different standards. Out of the 180 houses evaluated in this study, 98.3% of A-frame houses would have sufficient usable space under the UEP [5] guidelines in at least some of their cages given a 35.6-cm (14-in.) height specification, whereas only a minority (30.0%) would have such space given a 40.6-cm (16-in.) height specification. No A-frame houses could meet the standards of the CEC [4]. For houses with vertical cages, 100% would have cages with usable space given a 35.6-cm (14-in.) height specification, whereas 97.5% would at a 40.6-cm (16-in.) height specification, but only 33.9% could meet CEC [4] standards. The main objective of this study was to create a tool that provides scientists, egg producers, engineers, regulatory bodies, animal care auditors, and manufacturers with accurate information on the amount of usable space provided by different cage configurations. It was also intended to help illustrate how the height of a cage influences the amount of space made available to poultry engaged in activities other than resting (lying down). This standardized cage measurement system calculator will be an important asset to those involved in making decisions concerning well-being issues and to individuals responsible for making sure requirements for cage space are met. It can be downloaded from the permanent link http://www.bitly.com/hencagecalculator. The quick response code for the link is shown in Figure 5. CONCLUSIONS AND APPLICATIONS 1. Of the houses evaluated, 67% had A- frame cages and 33% had vertical cages. 2. At a cage height specification of 40.6 cm (16 in.), A-frame cages could barely meet the recommendations set forth by the UEP [5] for usable space, and did not meet CEC [4] standards. On average, vertical cages provided more usable space than did A-frame cages. 3. The adoption of new cage systems by producers will depend not only on height and usable floor area, but also on production variables as well as the extent to which the cages can meet potential future requirements for enrichment, such as perches, nests, and foraging areas. 4. There is a need for studies that evaluate the effect of cage height on production and welfare parameters, especially for White Leghorns. REFERENCES AND NOTES 1. Adams, A. W., and J. V. Craig. 1985. Effect of crowding and cage shape on productivity and profitability of caged layers: A survey. Poult. Sci. 64:238 242. 2. Dawkins, M. S. 1985. Cage height preference and use in battery-kept hens. Vet. Rec. 116:345 347. 3. Grandin, T. 2010. Chapter 3. Implementing effective standards and scoring systems for assessing animal welfare on farms and slaughter plants. Pages 32 49 in Improving Animal Welfare: A Practical Approach. T. Grandin, ed. CABI Publishing, Wallingford, Oxfordshire, UK. 4. Commission of the European Communities (CEC). 1999. Council Directive 99/74/EC: Laying down minimum standards for the protection of laying hens. Off. J. Eur. Commun. L 203//53 (19 July). 5. United Egg Producers (UEP). 2010. United Egg Producers Animal Husbandry Guidelines for U.S. Egg Laying Flocks. United Egg Producers, Alpharetta, GA.

668 JAPR: Field Report 6. Magnetic Angle Locator, Johnson Level & Tool Mfg. Co., Inc., Mequon, WI. 7. Microsoft Corporation, Redmond, WA. 8. Nicol, C. J. 1987. Effect of cage height and area on the behavior of hens housed in battery cages. Br. Poult. Sci. 28:327 335. 9. Albentosa, M. J., J. J. Cooper, T. Luddem, S. E. Redgate, H. A. Elson, and A. W. Walker. 2007. Evaluation of the effects of cage height and stocking density on the behavior of laying hens in furnished cages. Br. Poult. Sci. 48:1 11. 10. Albentosa, M. J., and J. J. Cooper. 2005. Testing resource value in group-housed animals: An investigation of cage height preference in laying hens. Behav. Processes 70:113 121. 11. Hester, P. Y., D. A. Wilson, P. Settar, J. A. Arnago, and N. P. O Sullivan. 2011. Effect of lighting programs during the pullet phase on skeletal integrity of egg-laying strains of chickens. Poult. Sci. 90:1645 1651. Acknowledgments We thank Alexis Miller of Purdue University (West Lafayette, IN) for aiding in data collection. We also thank the producers who provided access to their facilities for this study. This study was funded by the US Poultry & Egg Association (Tucker, GA).