Effects of Cage Versus Floor Rearing Environments and Cage Floor Mesh Size on Bone Strength, Fearfulness, and Production of Single Comb White Leghorn Hens1,2

Effects of Cage Versus Floor Rearing Environments and Cage Floor Mesh Size on Bone Strength, Fearfulness, and Production of Single Comb White Leghorn Hens12 K. E. ANDERSON3 Department of Poultry Science, North Carolina State University, Box 7608, Raleigh, North Carolina 27695-7608 A. W. ADAMS Department of Animal Sciences and Industry, Kansas State University, Manhattan, Kansas 66506

1994 Poultry Science 73:1233-1240

INTRODUCTION Received for publication January 31, 1994. Accepted for publication April 18, 1994. a The use of trade names in this publication does not imply endorsement by the North Carolina Agricultural Research Service or Kansas Agricultural Experiment Station of the products named or criticism of similar ones not mentioned. Contribution Number 94-290-J, from the Kansas Agricultural Experiment Station, Manhattan, KS 66506. 3 To whom correspondence should be addressed.

Growing replacement layer pullets in cages rather than floor environments is the current norm in the egg industry because of the reduced housing, labor, and equipment costs. However, the differences between the pullets' growth in these two environments as examined by Rowland and Harms (1970) and Deaton et al. (1985) indicated that pullet development was

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ABSTRACT Fourteen hundred pullets were reared at densities of 304 and 735 cm2 in cages and floor pens with litter, respectively. Feeder spaces of 2.7,4.0, and 5.4 cm per bird were held constant during the brooding growing period. At 18 wk of age, the birds were housed four birds per cage (348 cm2 per bird) in a force-ventilated, light-controlled house with two rows of stair-step cages. In two rows, the standard 2.5 x 5.0 cm welded wire flooring was replaced randomly with 2.5 x 2.5 cm welded wire in eight-cage sections. Egg production, egg quality, feed conversion, and mortality were measured over a 48-wk production cycle. At 68 wk of age, a sample of hens was selected and euthanatized, and the right leg was excised for further evaluation. Rearing environment, rearing feeder space, or type of layer floor mesh had no significant effects on hen-day production or feed conversion. Hens reared in cages produced heavier (P < .001) eggs with a higher percentage of Grade A eggs and had fewer body checks than floor-reared birds. Femur, tibia, and shank lengths were not affected by the rearing treatments or the type of flooring in the layer cage. Tibia breaking strength was not different for the rearing systems or hens maintained on 2.5 x 2.5 vs 2.5 x 5.0 cm welded wire mesh flooring. Hens reared in floor pens on litter displayed a higher level of fearfulness at the end of the production cycle. The reduced (P < .05) body weights associated with cage rearing and reduced feeder space did not negatively affect the production variables. Alteration of the mesh size of layer cage floor had no effect on the production levels of the hens. (Key words: layer, floor type, feeder space, bone strength, rearing environment)

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over into the laying cycle, thus creating an excessive fear response in the flock. Leg and foot problems can cause production losses in commercial egg production facilities. King (1965) showed that, as area per bird (density) decreased, production declined and mortality increased due to osteoporosis. He attributed the mortality to cage layer fatigue brought on by a decrease in bone mass caused by disuse. Singsen et al. (1969) found that nutrition and the laying environment (floor vs cage) can influence the incidence of cage layer fatigue. T a u s o n (1980), Simonsen et al. (1980), and Simpson and Nakaue (1987) determined that wire flooring can cause damage to the feet and legs of birds, thus diminishing their welfare. Tauson (1980) showed that foot health, as determined by intact matrices, was improved by reducing the slope of the floor, better galvanizing, epoxy coating, or additional wire in the floor grid for toe support. Simonsen et al. (1980) and Simpson and Nakaue (1987) found that wire flooring increased foot injuries in birds compared with floors with litter, although the differences were not significant. Simpson and Nakaue (1987) also found an increased incidence of leg deformities in birds on wire floor. These problems may have been exacerbated by the hen density and population. These studies indicate a contribution of cage flooring to the incidence of leg problems in layers. The hens stand on the 2.5 x 5.0 cm mesh wire flooring by hooking their toes over the wire with the foot pad suspended below the cage floor. This mesh size does not allow the hens to distribute their weight evenly over the entire foot, which could result in changes in the bone structure and muscle distribution in the legs. The objectives of this study were to elucidate the carry over effects of cage vs floor rearing and rearing feeder space on egg production and the fear response of the hens. The hypothesis of increased foot support in the cage floor as a means of improving bone structure was also evaluated. In addition, the effects of different mesh sizes of flooring types on leg and bone structure were evaluated.

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improved by floor rearing. They examined skeletal structure and digestive organs and found that floor-reared pullets had stronger tibias, greater percentage leg bone ash, and heavier digestive organs than cage-reared pullets. These improvements were attributed to the differences in activity levels and movement capabilities and the fact that the birds had access to the litter as a mineral and fiber source. This suggested floor rearing could be advantageous for the overall productive potential of the flock by reducing problems with cage layer fatigue. On the other hand, broilers were shown to be significantly heavier at market age when raised in cages (Reece et al, 1971; Deaton et al, 1985), and Anderson et al. (1979) found a similar response in turkeys. These researchers attributed the weight difference to the lower activity and floor area for the caged broilers and turkeys. When cages are used, growth and skeletal development of the pullets must be monitored to negate possible adverse effects of density or feeder space. Anderson and Adams (1992) showed that highdensity rearing environments for replacement layer pullets resulted in a significant reduction in BW at 18 wk of age. The weight depression was found to be related to reduced feeder space rather than increased density. Excessive weight reduction could affect subsequent production of the flock. In addition, Bell (1969) and Davami et al. (1987) reported significantly reduced BW for 18-wk pullets when feeder space was reduced. In addition to the reduced BW under high-density environments, Hansen (1976) found that hens may exhibit hysteria after being housed in laying houses. New environments or drastic changes in current ones may induce this behavior. Kujiyat and Craig (1983) found no differences between the tonic immobility (TI) response of cage- or floor-reared birds. However, those in 17-hen colony cages had significantly longer TI duration than those in 5-hen cages, which seems to indicate that TI response increased as the population size within an enclosure increased. If floor-reared pullets are more fearful because of the large population associated with floor pens, this may carry

CAGE FLOOR AND REARING ENVIRONMENT ON LEGHORN PRODUCTION

MATERIALS AND METHODS

Surplus chicks were distributed in floor and cage environments to match those of the chicks in the research trial and were maintained to be used as replacement. To maintain bird populations and densities, any deaths were noted in cages and floor pens, and dead birds then were replaced by birds from like environments. At 4-wk intervals, all birds were weighed and corresponding feed weigh-back was done beginning at 4 wk of age. When the rearing period ended at 18 wk of age, final body weight and feed consumption were determined. At 19 wk of age, the pullets were housed in double-deck stair-step cages located in a windowless, force-ventilated, laying house. Four pullets were placed in each cage (30.5 cm wide x 45.7 cm deep),

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Instron Corp., Canton, MA 02021.

which allowed 348 cm 2 per bird. Two rows of double-deck stair-step cages represented Blocks 1 and 2, which contained 12, eight-cage sets each. The layer cage flooring was changed from 2.5 x 5.0 cm to 2.5 x 2.5 cm welded wire in six sets of eight cages in each of two blocks. Four birds from each rearing environment were placed in a randomly selected cage within each of the 12 eight-cage sets. This provided 24 birds from each rearing treatment for each mesh size of layer cage floor. The two remaining cages were designated as spare cages, in which birds used as replacements were kept in like environments. The birds were fed the Kansas State University layer ration (18% CP, 2,671 kcal ME/kg, 3.2% Ca, and .81% P) throughout the laying period. Mortalities were recorded daily, and then dead birds were replaced with hens from the same rearing treatment and laying house environment to maintain constant density. Eggs were counted 3 d each week, and numbers were converted to 7-d percentages; feed was weighed back each 28-d period during the experiment to determine the feed consumption and conversion. The fearfulness levels of the hens was measured at 54 wk of age using Hansen's (1976) technique as modified by Jin and Craig (1988). At 67 wk of age, hens from each experimental unit and treatment combination were selected randomly by wing-band number and killed by cervical dislocation. Measurements were taken of the length of the femur, tibia, and shank, and the right tibia was then excised for further analysis. The tibias were handled according to the procedure outlined by Crenshaw et al. (1981). Briefly, the bones were cleaned of excess tissue, and the peak breaking force determined using an Instron Model 1122.4 The bones were supported by two fulcrum points (27 mm apart), and force was applied midshaft. Force was applied at constant rate of (300 m m / m i n ) to all bones, and the peak force automatically recorded by an electronic, 500-kg, load cell set for reading at 10% of capacity. After breaking, the bones were dried for 24 h at 100 C and extracted with dimethyl-ether for 36 h in a Soxhlet. The bones were ashed at a temperature of 600 C for 12 h,

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Fourteen hundred chicks of a commercial strain (Babcock B-300) were purchased on September 9, 1989 from a local hatchery. The chicks were wing-banded and randomly assigned to either floor pens 2.3 x 3.8 m with litter (119 chicks per pen) or double-deck brooding growing cages 76.2 x 55.9 cm (14 chicks per cage). Both rearing pens and cages were located in the same curtain-sided, naturally ventilated, brooding-rearing house. The chicks were fed the standard Kansas State University pullet rearing dietary regimen consisting of Starter: 21% CP, 2,823 kcal ME/kg, from 0 to 6 wk; Grower: 18% CP, 2,864 kcal ME/kg, 7 to 12 wk; and Developer: 16% CP, 2,950 kcal ME/kg, 13 wk to housing. The floor areas per bird (density) were 735 cm 2 per pullet in the floor pens and 304 cm 2 per pullet in cages. These densities were selected to represent recommended densities of Consortium (1988) and Anderson and Adams (1992). Feeder space was provided by tube feeders with lids for the floor pens and feed troughs for the cages. Total trough space was held at 2.7, 4.0, or 5.4 cm per bird for cages and floor pens by constructing covers for the trough and tube feeders, which allowed the pullets the appropriate feeder space.

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ANDERSON AND ADAMS TABLE 1. Effects of cage vs floor rearing environments on age at 50% production, egg production, egg weight, egg quality, feed consumption, and mortality Rearing environment

Variables

Cage

Floor

Pooled SEM

Age at 50% production, wk Eggs produced, no. Hen-day production, % Egg weight, g A Grade, % B Grade, % Bloods, % Body checks, % Cracks, % Feed consumption, kg/100 hens/d Feed conversion, g egg:g feed Mortality, %

21.7 262 77.9 57.0*** 95.3*** 1.0 .1 2.2 1.4 12.04 .413 6.2

22.4*** 266 79.1 56.3 94.2 1.0 .1 3.1*** 1.6 12.06 .416 8.3

.09 1.55 .45 .15 .31 .14 .05 .21 .15 .09 .005 2.57

until reduced to mineral form. After cooling, bone ash was measured by w e i g h t (Association of A n a l y t i c a l Chemists, 1984). The 2 x 2 x 3 factorial arrangement of welded wire cage floor, floor, or cage rearing, and feeder spaces was a randomized block design. Arc sine transformation was used on percentage mortality prior to analysis. Data were analyzed with individual cages as the experimental unit, using the General Linear Models (GLM) procedure of SAS® (SAS Institute, 1985) to allow for unequal sample sizes. Means detected to be significantly different by GLM were separated using Duncan's (1955) multiple range test. RESULTS AND DISCUSSION Rearing Floor Rearing pullets in cages reduced (P < .001) the age at 50% production compared to the age at 50% production observed for pullets reared in floor pens, 21.7 vs 22.4 wk (Table 1). The number of eggs produced and hen-day production were not affected by the rearing environment. These findings are consistent with those of Stockland and Blaylock (1974) and Jin and Craig (1988). However, hens reared in cages produced (P < .001) heavier eggs than those reared in floor pens, 57.0 and 56.3 g, respectively. In addition, the percentage of eggs that graded

A was (P < .001) improved by 1.1%, and the percentage of body checks was reduced by .9 for hens reared in cages compared with hens reared in floor pens. Throughout the laying period, no differences were apparent for feed consumption, feed conversion, or mortality due to the rearing environment. Hens reared in floor pens were significantly heavier than those reared in cages at 68 wk of age (Table 2). A similar observation was noted by Stockland and Blaylock (1974), who found a 30-g difference at 62 wk of age. In addition, similar responses were reported by Reece et al. (1971) in broilers and Bond et al. (1989) in turkeys. That work, taken together with the present study, indicates that weight differences at the end of the rearing period are carried over throughout the production cycle. The weight gains for the hens from both rearing environments in this study were not different (Table 2). Moving pullets from rearing cages to laying cages results in less fearful hens than moving pullets from floor pens to cages. The hens reared in floor pens had higher (P < .001) tearfulness scores at 68 wk of age compared with hens in cages (Table 2). However, Okpokho and Craig (1987) failed to find a relationship between the rearing environment and the fear response of layers. This may have been due to the limited sample size they used. Bond et al. (1989) found that the bones of the leg were longer in turkeys reared on the floor.

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*P < .001.

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CAGE FLOOR AND REARING ENVIRONMENT ON LEGHORN PRODUCTION TABLE 2. Effects of cage vs floor rearing environments on body weight, tearfulness, and bone structure Rearing environment Variables

Cage

Floor

SEM

Ending body weight, g Body weight gain, % Fearfulness score1 Femur length, mm Tibia length, mm Shank length, mm Tibia breaking strength, kg/cm 2 Tibia ash, %

1,536 19.0 .52 82.0 118.9 98.3 29.2 49.7

1,576* 21.1 .93*** 83.5 120.4 99.1 25.1 51.7

12.63 1.02 .06 .54 .69 .37 3.44 .88

tearfulness scores from 0 to 4, the lower the number the less fearful. *P < .05. ***P < .001.

other experiments. Rowland et al. (1971) showed no difference in bone strength or percentage ash between cage- and floorreared broilers when they increased dietary phosphorus to .8%. Rearing Feeder Space Rearing feeder space had no effect on the age at 50% production, eggs produced, or hen-day production (Table 3). This is consistent with the findings of McCluskey and Johnson (1958) and Anderson and Adams (1992), who reported no carry-over effect of rearing feeder space on the subsequent

TABLE 3. Effects of rearing feeder space on age at 50% production, egg production, egg quality, feed consumption, and mortality Rearing feeder space per bird Variables

2.7 cm

4.0 cm

5.4 cm

Pooled SEM

Age at 50% production, wk Eggs produced, no. Hen-day production, % Egg weight, g A Grade, % B Grade, % Bloods, % Body checks, % Cracks, % Feed consumption, kg/100 hens/d Feed conversion, g egg:g feed Mortality, %

21.1 261 78.1 56.5AB 95.1 .8 .1 2.3" 1.6 12.04 .416 4.7

22.1 264 78.2 57.1A 94.4 .9 .1 3.2a 1.5 11.97 .414 6.3

22.0 267 78.2 56.3B 94.8 1.3 .1 2.4b 1.4 12.15 .415 10.9

.16 2.93 .87 .26 .51 .25 .08 .34 .25 .15 .008 3.13

a b

- Means in a row with no common superscript differ significantly (P < .05). - Means in a row with no common superscript differ significantly (P < .01).

A B

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However, in our study, the femur, tibia, and shank lengths were similar for both rearing environments at 68 wk of age (Table 2). In addition, breaking strength and tibia ash were not different for hens reared in cages or in floor pens, which is contradictory of previous work (Rowland et ah, 1968; Rowland and Harms, 1970). Dietary Ca and P levels were approximately 3.00 and .73%, respectively, which could have resulted in changes in bone mineralization over the course of a production cycle. In addition, the hens in this experiment were maintained in production to 68 wk of age, which was 28 wk longer than that indicated in

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TABLE 4. Effects of rearing feeder space on body weight, tearfulness, and bone structure Rearing feeder space per bird Variables Ending body weight, g Body weight gain, % Fearfulness score 1 Femur length, mm Tibia length, mm Shank length, mm Tibia breaking strength, kg/cm 2 Tibia ash, %

2.7 cm

4.0 cm ab

1,535b 22.0" .69 83.0 120.7 98.6 22.8 50.4

l,555 20.5*» .78 83.0 119.6 98.5 31.6 50.1

5.4 cm

SEM

1,579* 17.7b .73 82.3 118.7 99.0 27.0 51.7

15.06 1.18 .09 .69 .85 .46 3.79 1.09

ab

' Means in a row with no common superscript differ significantly (P < .05). tearfulness scores from 0 to 4, the lower the number the less fearful.

of 1,555 g. Body weight gain also decreased as final BW increased and followed the same pattern. This follows the same trends found by Anderson and Adams (1992) (i.e., that BW differences manifested at the end of the rearing period remained through the production cycle). The rearing feeder space had no carry-over effects on the fearfulness, bone length, or tibia breaking strength of hens. Layer Cage Floor Tauson (1980) indicated that the type of flooring used in layer cages has the potential of affecting the production and welfare of the hens. As shown in Table 5, the age at

TABLE 5. Effect of mesh size of layer cage floor on age at 50% production, egg production, egg quality, feed consumption, and mortality Layer cage flooring Variables

2.5 x 2.5 cm Welded wire

2.5 x 5.0 cm Welded wire

Pooled SEM

Age at 50% production, wk Eggs produced, no. Hen-day production, % Egg weight, g A Grade, % B Grade, % Bloods, % Body checks, % Cracks, % Feed consumption, kg/100 hens/d Feed conversion, g egg:g feed Mortality, %

22.0 265 78.8 56.7 94.4 1.1 .1 2.5 1.9*" 12.08 .414 9.4

22.1 263 78.2 56.6 95.1 1.0 .1 2.8 1.1 12.02 .415 12.02

.13 .52 .47 .15 .30 .13 .05 .21 .15 .09 .005 1.52

>P < . 0 0 1 .

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performance of the birds. Egg weight was found to be significantly higher when the hens were reared with 4.0 cm rather than 5.4 cm of feeder space and due to the increased egg size the percentage body checks was also significantly higher. The percentage body checks was not different for either 2.7 or 5.4 cm of rearing feeder space. The remaining egg quality variables, feed consumption, and mortality were similar among feeder space allotments. Body weight at the end of the production period was heavier (P < .05) when the birds were reared with 5.4 cm rather than 2.7 cm of feeder space, 1,579 and 1,535 g, respectively (Table 4). Those hens reared with 4.0 cm of feeder space had an intermediate BW

CAGE FLOOR AND REARING ENVIRONMENT ON LEGHORN PRODUCTION

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TABLE 6. Effect of mesh size of layer cage floor on body weight fearfulness, and bone structure Layer cage flooring Variables

2.5 x 2.5 cm Welded wire

2.5 x 5.0 cm Welded wire

Pooled SEM

Ending body weight, g Body weight gain, % Fearfulness score 1 Femur length, mm Tibia length, mm Shank length, mm 2 Tibia breaking strength, kg/cm Tibia ash, %

1,565 19.9 .76 82.5 119.4 98.3 28.1 50.7

1,547 20.2 .78 83.0 119.9 99.1 26.1 50.7

13.13 1.05 .26 .55 .70 .37 3.48 .89

tearfulness scores from 0 to 4, the lower the number the less fearful.

laying house. However, no clear advantage of floor over cage rearing was observed; any advantages that one rearing environment holds ultimately negate advantages of the other. This is also true for the carry-over effects of rearing feeder space. The significant effects of feeder space allotments during the rearing period and floor vs cage rearing on BW at 18 wk persisted through-' out the production cycle. However, the BW did not affect the performance of the birds when the economic traits of egg production and feed conversion were examined. This is consistent with findings of Meunier-Salaun et al. (1984), who reported that the rearing environment had no significant effects on hen performance. These two rearing environments provide no clear advantages or disadvantages. REFERENCES Association of Official Analytical Chemists, 1984. Official Methods of Analysis. 14th ed. Association of Official Analytical Chemists, Washington, DC. Anderson, K. E., and A. W. Adams, 1992. Effects of rearing density and feeder and waterer spaces on the productivity and fearful behavior of layers. Poultry Sci. 71:53-58. Anderson, J. O., R. E. Warnick, and N. Nakhata, 1979. Effect of cage and floor rearing; dietary calcium, phosphorus, fluoride, and energy levels; and temperature on growing turkey performance, the incidence of broken bones and bone weight, and ash. Poultry Sci. 58:1175-1182. Bell, D., 1969. Crowding in cage rearing affects pullet weights. Poult. Trib. Jan:18, 19, 28. Bond, P. L., T. W. Sullivan, J. H. Douglas, L. Robeson, and J. Baier, 1989. Influence of age and sex on bone development of broilers. Poultry Sci. 68(Suppl. l):15.(Abstr.)

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50% production, eggs produced, hen-day production, and feed consumption were not affected by changing from the conventional 2.5 x 5.0 cm welded wire floor to one with 2.5 x 2.5 cm spacing. The percentage of cracked eggs increased (P < .001) by .8% when the hens were housed on the 2.5 x 2.5 cm wire floors. This may have been due to the floor being much suffer, with the additional wires causing eggs to crack when they hit the floor after being laid. The flooring material had no effects on other egg quality factors, feed consumption, or mortality. Ending BW and BW gain were not affected by the type of flooring material (Table 6). The hens responded in similar fashion to the fearfulness test conducted at 68 wk of age. Increasing the foot support by replacing the 2.5 x 5.0 cm welded wire floor to one with 2.5 x 2.5 cm spacing resulted in no benefit in bone structure or strength. Researchers have proposed that hens are under additional stress if the foot is not allowed to rest on firm support during their productive life. The supposition presented by Tauson (1980) that smaller wire spacings in the layer cage floor may improve the foot and, thus, the leg structure, ultimately resulting in lower mortality and higher production, are not borne out in this study. Either floor type will provide the hen with adequate foot and leg support. The keys to maintaining acceptable production are maintenance and repair of the cage and the physical environment. Apparently, the rearing floor environment does have effects that carry into the

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ANDERSON AND ADAMS environment, age, and habituation. Poultry Sci. 66:376-377. Reece, F. N., J. W. Deaton, J. D. May, and K. N. May, 1971. Cage versus floor rearing of broiler chickens. Poultry Sci. 50:1786-1790. Rowland, L. O., Jr., B. L. Damron, E. Ross, and R. H. Harms, 1971. Comparisons of bone characteristics between floor and battery grown broilers. Poultry Sci. 50:1121-1124. Rowland, L. O., Jr., and R. H. Harms, 1970. The effect of wire pens and cages on bone characteristics of laying hens. Poultry Sci. 49:1223-1225. Rowland, L. O., Jr., H. R. Wilson, J. L. Fry, and R. H. Harms, 1968. A comparison of bone strength of caged and floor layers and roosters. Poultry Sci. 47:2013-2015. Simonsen, H. B., K. Vestergaard, and P. Willeberg, 1980. Effect of floor type and density on the integument of egg-layers. Poultry Sci. 59: 2202-2206. Simpson, G. D., and H. S. Nakaue, 1987. Performance and carcass quality .of broilers reared on wire flooring, plastic inserts, wood slats, or plasticcoated expanded metal flooring each with or without padded roosts. Poultry Sci. 66:1624-1628. Singsen, E. P., C. Riddell, L. D. Matterson, and J. J. Tlustohowicz, 1969. Phosphorus in the nutrition of the adult hen. 3. The influence of phosphorus source and level on cage layer osteoporosis (cage layer fatigue). Poultry Sci. 48:394-401. SAS Institute, 1985. SAS® User's Guide: Statistics. Version 5 Edition. SAS Institute Inc., Cary, NC. Stockland, W. L., and L. G. Blaylock, 1974. The influence of ration protein level on the performance of floor reared and cage reared replacement pullets. Poultry Sci. 53:790-800. Tauson, R., 1980. Cages: How could they be improved? The Laying Hen and It's Environment. Pages 269-304 in: Current Topics in Veterinary Medicine and Animal Science. Vol. 8: R. Moss, ed. Martinus Nijhoff Publishers, The Hague, The Netherlands.

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Consortium, 1988. Guide for the Care and Use of Agricultural Animals in Agricultural Research and Teaching. Consortium for Developing a Guide for the Care and Use of Agricultural Animals in Agricultural Research and Teaching. Association Headquarters, Champaign, IL. Crenshaw, T. D., E. R. Peo, Jr., A. J. Lewis, B. D. Moser, and D. Olsen, 1981. Influence of age, sex and calcium and phosphorus levels on the mechanical properties of various bones in swine. J. Anim. Sci. 52:1319-1329. Davami, A., M. J. Wineland, W. T. Jones, R. L. Ilardi, and R. A. Peterson, 1987. Effects of population size, floor space and feeder space upon productive performance, external appearance and plasma corticosterone concentration of laying hens. Poultry Sci. 66:251-257. Deaton, J. W., S. L. Branton, B. D. Lott, and J. D. Brake, 1985. Noted difference in the digestive system in cage and floor-reared commercial egg-type pullets. Poultry Sci. 64:1035-1037. Duncan, D. B., 1955. Multiple range and multiple F tests. Biometrics 11:1-42. Hansen, R. S., 1976. Nervousness and hysteria of mature female chickens. Poultry Sci. 55:531-543. Jin, L., and J. V. Craig, 1988. Some effects of cage and floor rearing on commercial white leghorn pullets during growth and the first year of egg production. Poultry Sci. 67:1400-1406. King, D. F., 1965. Effects of cage size on cage layer fatigue. Poultry Sci. 44:898-900. Kujiyat, S. K., and J. V. Craig, 1983. Duration of tonic immobility affected by housing environment in white leghorn hens. Poultry Sci. 62:2280-2282. McCluskey, W. H., and L. E. Johnson, 1958. The influence of feeder space upon chick growth. Poultry Sci. 37:889-892. Meunier-Salaun, M. C, F. Huon, and J. M. Faure, 1984. Lack of influence of pullet rearing conditions on the hen's performance. Br. Poult. Sci. 25:541-546. Okpokho, N. A., and J. V. Craig, 1987. Fear-related behavior of hens in cages: Effects of rearing