Effects of pullet-stocking density on performance of laying hens

Cage-Free Pullets Minimally Affected by Stocking Density Stressors

Management choices during the pullet phase can affect behavior, welfare, and health later in life, but few studies have evaluated the pullet phase, particularly in extensive housing systems. This study was a 2 × 2 factorial randomized complete block design (RCBD) with two strains and two stocking densities. The Lohmann LB-Lite and Lohmann LSL-Lite were housed on the floor at high-stocking density (619-670 cm2/bird) and low-stocking density (1249-1352 cm2/bird), which changed with age from 2 to 16 weeks of age (WOA). Bird-based measures of appearance, blood parameters, organ measurements, and production values were evaluated. Stocking density alone affected (p < 0.05) only relative bursal weight (% of body weight)-3.32% in the low-density versus 3.08% in the high-density group. High-stocking density was correlated with decreased uniformity (high-89.33 ± 0.24%; low-90.41 ± 0.24; p < 0.02) and worse feather coverage in the brown strain. High-stocking density was correlated with greater uniformity (High-90.39 ± 0.24%; Low-88.47 ± 0.24%; p < 0.001) and better feather coverage in the white strain. This study's feed conversion ratio (FCR) was improved by 0.07 in the low-stocking density for both strains. The remaining parameters were affected by strain and age only. Thus, while stocking density effects vary slightly depending on the strain used, cage-free pullets had limited negative effects at both the high and low-stocking densities tested in this study; there were few to no changes in the numerous bird-based welfare parameters tested.

Development and evaluation of an animal health and welfare monitoring system for veterinary supervision of pullet farms

Regular welfare monitoring throughout rearing of pullets may help to identify problems early and take counteractions timely, which helps in guaranteeing good welfare. The aims of our observational study were (i) to establish and test a welfare monitoring system that can be used during (short) routine veterinary and technical staff visits for pullet flocks, (ii) to use the monitoring system to investigate variability between flocks and (iii) to analyse factors that potentially affect pullets' body weight, uniformity in body weight and mortality. The developed monitoring system tries to minimise the time required while not losing important information. Age-specific recording sheets comprise animal-based indicators of welfare and relevant environmental factors (housing, management, care) to allow for identifying causes of problems and targeted action. Finally, the system was implemented in a cross-sectional study and data collected in 100 flocks (67 organic, 33 conventional) on 28 rearing farms in Austria. Linear mixed models were used to identify factors influencing body weight, uniformity and mortality, both including all flocks (A) and only organic flocks (O) and a linear regression model with all flocks to investigate associations within animal-based indicators. High variability was found between flocks in animal-based indicators. Body weight was higher when the pre-rearing period was shorter (p ≤ 0.001, A&O), with higher intensities of light (p = 0.012, O), with only one compared to more stockpersons (p ≤ 0.007, A&O), with a higher number of flock visits per day (p ≤ 0.018, A&O), and a lower avoidance distance (p = 0.034, A). Body weight uniformity increased, with age and decreased with the duration of the light period (p = 0.046, A), and, amongst others, was higher on organic farms (farming type; p = 0.041). The latter may reflect a more uniform level of welfare due to a lower stocking density and lowered effects of social competition. Within organic flocks mortality was lower if pullets had access to a covered veranda (p = 0.025) resulting in an overall lower stocking density inside the barn, while in the model including all farms mortality was higher in cases where a disease had been diagnosed. We conclude that our monitoring system can easily be implemented in regular veterinary and technical staff visits, but could also be used by the farmers'. Several easy-to-record animal-based indicators of animal welfare could be analysed more frequently to increase early detection of problems. Implementation of such a routine-based monitoring system with easy-to-assess animal-based parameters and input measures can contribute to better animal health and welfare in pullets.

Effect of stocking density and age on physiological performance and dynamic gut bacterial and fungal communities in Langya hens

Background

The characterization of colonization and dynamic changes related to gut microorganisms might be vital, as it presents an opportunity to quantify the co-variation between stocking densities and gut microbiome of dynamic distribution. The objective of this study was to determine the stocking density on physiological performance and dynamic distribution of gut microbiome (including bacterial and fungal communities) of Langya laying hens in the two development stages.

Methods

A randomized design with 2 × 3 factorial controls consisting of two development stages (24, 43 weeks-old) with three different stocking densities was performed. Three different stocking densities were allocated to a total of 300 11-week-old Langya laying hens (450 cm²/bird, 675 cm²/bird, 900 cm²/bird). Three housing densities were accomplished by raising different chickens per cage with the same floor size. The dependent variables of stocking densities at each sampling point were; growth performance, organs index, egg quality and the changes of dynamic gut bacterial and fungal communities in the cecum.

Results

Results showed that the stocking density didn’t affect liver index, eggshell thickness, breaking shell strength and egg shape index. Hens from the highest stocking density had the lowest body weight, fallopian tube index, egg weight and yolk colour score. Except for the yolk colour score, the measurement changes caused by age followed the opposite pattern as stocking density. We observed a substantial rise in taxa linked with health threats when stocking density was increased, including Talaromyces, Oscillospiraceae_UCG-002, Oscillospira, and Dielma. The opposite was observed with Bacteroides, Bifidobacterium, Lachnoclostridium, Eisenbergiella, and Kurtzmaniella. Also, most taxa were linked to polymicrobial infection in clinical cases, especially species whose percentage declined as the hens aged, such as Terrisporobacter, Faecalicoccus, Dialister, Cylindrocarpon etc. Whereas Sellimonas, Mitsuokella, Eurotium, Wardomyces and Cephalotheca had the opposite trend.

Conclusion

We speculated that excessive high density drove the abundance of bacteria and fungi connected with health problems. Where the gut microecology gradually reach a mature and balance status with age. Overall, this study demonstrates gut microbiome ecological processes in Langya layers at various stocking densities and finds possible connections between stocking density, microbiome and production performance. Our study will contribute to new insights associating suitable density patterns and production performance in laying hens by harnessing such a relative microbiome.

Effects of Stocking Density in Group Cages on Egg Production, Profitability, and Aggressive Pecking of Hens

There is an increasing concern about welfare issues related to battery cages, which are commonly used in Vietnam, and requires a modified cage that improves hen welfare while retaining its economic and management advantages. We combined adjacent conventional cages to form group cages to examine the effects of stocking density on egg production, economic returns, and aggressive pecking of hens. The control group included triplicate conventional cages with four birds/single cage (12 hens per three cages) or 450 cm² area per hen. Three group cage treatments were set up with 10, 12, and 14 birds per group cage or 540, 450, and 386 cm² of floor area per hen, respectively. Compared to 14 birds per cage, hens housed at 10 birds per group cage had a higher hen-day production, consumed less feed, and thus had a better feed conversion ratio/dozen eggs. Reducing the stocking density to 10 birds per group cage resulted in additional production cost, but it was compensated for by a high egg income, and significantly decreased aggressive pecks. Group cages benefit hen performance, profitability, and welfare when decreasing the stocking density to 10 birds per cage with 540 cm²/hen.

Effect of dietary 25-hydroxycholecalciferol supplementation and high stocking density on performance, egg quality, and tibia quality in laying hens

This study was conducted to determine the effects of 25-hydroxycholecalciferol (25-OH-D₃) on performance, egg quality, tibia quality, and serum hormones concentration in laying hens reared under high stocking density. A total of 800 45-week-old Lohmann laying hens were randomly allotted into a 2 × 2 factorial design with 2 levels of dietary 25-OH-D₃ levels (0 and 69 μg/kg) and 2 rates of stocking densities [506 (low density) and 338 (high density) cm²/hen]. Laying hens were monitored for 16 wk. High stocking density decreased laying rate, egg weight, and feed intake compared with low stocking density (P < 0.01) during 1 to 8 wk and 1 to 16 wk. Overall, high stocking density increased eggshell lightness value and decreased shell redness and yellowness value, strength, thickness, and relative weight compared with low stocking density (P < 0.05). Dietary supplementation with 25-OH-D₃ reduced the value of the eggshell lightness and increased its yellowness and eggshells weight (P ≤ 0.05). The increase in eggshell thickness was more pronounced when 25-OH-D₃ was supplemented to layers under high stocking density (interaction, P < 0.05). Layers under high stocking density had lower ash content and calcium content in the tibia than layers under low stocking density (P = 0.04); dietary 25-OH-D₃ increased tibia strength compared with no addition (P = 0.05). Layers under high stocking density had higher serum concentrations of 25-OH-D₃, corticosterone (CORT), lipopolysaccharide (LPS), and osteocalcin (OC; P < 0.05), lower content of parathyroid hormone (PTH) compared with layers under low stocking density (P < 0.01). Dietary 25-OH-D₃ increased serum concentration of 25-OH-D₃, carbonic anhydrase (CA), and calcitonin (CT) (P < 0.01) and reduced corticosterone, lipopolysaccharide and osteocalcin concentration (P ≤ 0.05). The increase effect in PTH was more pronounced when 25-OH-D₃ was supplemented to layers under high stocking density (interaction, P = 0.05). Overall, the results gathered in this study indicate that high stocking density result in reducing production performance, shell color and quality, and tibia health, whereas dietary 25-OH-D₃ was able to maintain tibia health and to mitigate the negative impact of high stocking density on productive performance.

Laying hen production and welfare in enriched colony cages at different stocking densities

Many laying hen companies in the United States are pledging to move away from intensive conventional cages to extensive housing systems. Enriched colony cages (ECC) are a practical alternative to conventional cage systems. Scientific research is limited on the effects of ECC on hen production and welfare. Therefore, the objective of this study was to evaluate the effects of stocking density on welfare and performance with the overall outcome to provide guidance on stocking density for ECC. At 16 wk, W-36 pullets were placed into 2 commercial ECC housing systems. Within each ECC enclosure, hens were allocated into 1 of 6 stocking densities: A) 465 to 484 cm2/bird, B) 581 to 606 cm2/bird, C) 652 to 677 cm2/bird, D) 754 to 780 cm2/bird, E) 799 to 832 cm2/bird, and F) 923 to 955 cm2/bird. Body weight, egg production, mortality, and Welfare Quality data were collected each 28 d period from 17 to 68 wk. The 6 ECC stocking densities had several transient effects on production measures within age periods with no difference in hen-day production (P > 0.05). Body weight was affected by stocking density (P < 0.05) where hens raised at stocking density A (465 to 484 cm2/bird) weighed at least 25 g less than hens from other stocking densities. Stocking density differences for Welfare Quality assessments were only apparent for feather coverage. Hens raised at stocking density A (465 to 484 cm2) consistently had the poorest (P < 0.05) crop, keel, belly, back, and rump feather coverage. The keel, neck, and back body regions had poorer feather coverage when hens were raised at stocking densities B (581 to 606 cm2) and C (652 to 677 cm2) compared to hens from lower stocking densities (P < 0.05). Therefore, the minimum area per hen housed in commercial ECC systems should be 754 cm2 per bird for greater feather coverage.

The influence of environmental enrichment and stocking density on the plumage and health conditions of laying hen pullets

In this study, the effects of environmental enrichment, stocking density, and microclimate on feather condition, skin injuries, and other health parameters were investigated. During 2 rearing periods (RP), non-beak-trimmed Lohmann Brown hybrid pullets were housed in an aviary system for rearing with cages and from week 5 of age onwards with access to a litter area. All pullets were reared in the same barn and under practical conditions. In total, 9,187 (RP 1) and 9,090 (RP 2) pullets were distributed in 9 units, and each unit was assigned to 1 of 3 experimental groups (EG). In the control group (EG 1), the pullets were kept without environmental enrichment and at a commonly used stocking density (22 to 23 pullets per m²). Each unit of the 2 treatment groups was provided with 3 types of environmental enrichment simultaneously (pecking stones, pecking blocks, and lucerne bales), and the pullets were kept at a lower than usual (18 pullets per m²) (EG 2) or commonly used stocking density (EG 3). In each RP, the plumage condition, injuries and health of the pullets, and the microclimate of the housing system were examined 5 times. The statistical relationships of enrichment, stocking density, and microclimate with animal health were estimated via regression models. We found that the provision of environmental enrichment had a significant increasing effect on the plumage quality in week 17. Furthermore, significant relationships were found between several predictors (temperature in the housing system, dust concentration, and age of the pullets) and response variables (plumage condition, body injuries, head injuries, bodyweight, difference to the target weight and uniformity). The results of this study showed that increasing temperature in the housing system and increasing age of the pullets are significantly associated with the occurrence of feather damage and skin injuries during rearing. With stocking densities as high as we used (all > 17 pullets per m²), no significant positive effect of a reduced stocking density could be observed.

Stocking Density Affects Stress and Anxious Behavior in the Laying Hen Chick During Rearing

Simple Summary

‘Crowding’, keeping too many birds per m², is one of the largest welfare concerns in the poultry industry. It is therefore worrisome that there is a gap in research investigating the effects of high stocking densities during the rearing phase of laying hens. This study evaluated anxious behavior and corticosterone levels, a hormone involved in the stress response, during the first 10 weeks of laying hen chicks housed under three different crowding conditions: undercrowding, conventional crowding, and overcrowding. We found that overcrowded chicks displayed more anxious behavior compared to undercrowded chicks. Corticosterone levels were elevated in both extreme groups in week 3, but dropped to values of the conventional crowding group at week 10. We conclude that current conventional stocking densities do not seem to impair the welfare state of the laying hen chick, and that a three-fold in- or decrease of density influences stress and anxiety, but within the adaptive capacity of the chick. Important side-notes to this conclusion are that an increase of stocking density did result in a slower rate of adaptation, and that we currently do not know if there are long-term consequences of different crowding densities reaching into the laying period.

Abstract

The recent increases in stocking density, in extreme cases resulting in ‘crowding’, have a major impact on poultry welfare. In contrast to available research on adult laying hens, there is a gap in the literature studying the rearing phase. The present study investigated the effects of stocking density during the rearing period on the welfare of the laying hen chick. The chicks were housed under one of three crowding conditions, increasing with age: undercrowding (500-1000-1429 cm² per chick), conventional crowding (167-333-500 cm² per chick), or overcrowding (56-111-167 cm² per chick). The parameters evaluated encompassed behavioral and physiological factors related to anxiety and stress. We found that during the first 6 weeks, overcrowded chicks displayed more anxious behavior than undercrowded chicks, and both extreme densities induced higher corticosterone levels compared to chicks housed under conventional crowding. At 10 weeks of age, plasma corticosterone had dropped to the level of conventional crowding group in both groups, whereas feather corticosterone remained high only in the overcrowded group. We conclude that current conventional stocking densities do not seem to impair the welfare state of the laying hen chick, and that a three-fold increase or decrease of density influences corticosterone levels and anxious behavior, but within the adaptive capacity of the chick. Important side notes to this conclusion are that an increase of stocking density did result in a slower rate of adaptation, and that there could be long-term consequences of both the different stocking densities and/or increased costs of adaptation.

Effects of stock density on the laying performance, blood parameter, corticosterone, litter quality, gas emission and bone mineral density of laying hens in floor pens

The effects of stocking density on the performance, egg quality, leukocyte concentration, blood biochemistry, corticosterone levels, bone mineral density, and noxious gas emission of laying hens were investigated. Eight hundred 34-week-old Hy-Line Brown laying hens (Gallus gallus domesticus) were randomly assigned to one of 4 treatments, each of which was replicated 4 times. Four stocking densities, including 5, 6, 7, and 10 birds/m2, were compared. A commercial-type basal diet was formulated to meet or exceed nutrient recommendations for laying hens from the National Research Council. The diet was fed to the hens ad libitum for 8 wk. Results indicated that hen-day egg production, egg mass, and feed intake were less for (P < 0.01) 10 birds/m2 stock density than other stock densities. Production rate of floor and broken eggs and eggshell strength were greater (P < 0.01) for 10 birds/m2 stock density than other stock densities. There were no significant differences in the level of leukocytes among densities. However, heterophils and the H/L ratio were greater (P < 0.01) for 10 birds/m2 than in stock density of 6 or 7 birds/m2 Serum corticosterone was greater (P < 0.01) 10 birds/m2 than stock density than other stock densities. Litter moisture and gas emission (CO2 and NH3) were greater (P < 0.01) for 10 birds/m2 than stock density than 6 and 7 birds/m2 stock density. Bone mineral content was not influenced by increasing stock density. However, bone mineral density was less (P < 0.05) for 10 m2 stock density than other stock densities. These results indicate that increasing the density beyond 5 birds/m2 elicits some negative effects on laying performance of Hy-Line brown laying hens.

Review of rearing-related factors affecting the welfare of laying hens

Laying hens may face a number of welfare problems including: acute and chronic pain caused by beak trimming; exaggerated fearfulness that may cause stress and suffocation; difficulties in locating resources, resulting potentially in emaciation and dehydration; frustration and boredom, caused by an environment that is barren; feather pecking; cannibalism; foot lesions; and bone fractures. In Europe, a greater proportion of laying hens are housed in non-cage systems compared to the rest of the world. The extent of the different welfare problems may therefore vary between countries as the type of housing system influences the risk of suffering. More generally, many of these welfare problems are influenced by the rearing environment of the pullets. This article therefore focuses on welfare problems in laying hens that can be traced back to rearing. Factors that have been studied in relation to their effects on bird welfare include beak trimming, housing type, furnishing, enrichment, feeding, stocking density, flock size, sound and light levels, concentration of gasses, age at transfer from rearing to production facilities, similarity between rearing and production facilities, competence of staff, and interactions between bird strain and environment. The present review aims to summarize rearing-related risk factors of poor welfare in adult laying hens housed according to European Union legislation. It aims to identify gaps in current knowledge, and suggests strategies for improving bird welfare by improving rearing conditions. Two main conclusions of this work are that attempts should be made to use appropriate genetic material and that beak trimming should be limited where possible. In addition to this, the rearing system should provide constant access to appropriate substrates, perches, and mashed feed, and should be as similar as possible to the housing system used for the adult birds. Finally, young birds (pullets) should be moved to the production facilities before 16 weeks of age. The measures outlined in this review may be useful for improving the welfare of pullets and adult laying hens.

The influence of stocking density on body weight, egg weight, and feed intake of adult broiler breeder hens

The influence of stocking density on BW, egg weight (EW), and feed intake (FI) in Ross broiler breeder hens (n = 120) was investigated during the late medium egg production period (from 50 to 54 wk of age). Birds were randomly allocated to 6 pens in densities of 15, 20, and 25 birds/pen, giving rise to a floor space allowance of 5, 6.67, and 8.33 birds/m(2), respectively. Each density was replicated twice, and the order among the 6 pens was chosen at random. Data were analyzed using the repeated measures techniques of the Statistical Analysis System, considering the covariance structure of the observed data. There was a significant effect attributable to stocking density, time (in days), and their interaction for BW, EW, and FI. Birds in density of 6.67 per m(2) were lighter but had heavier eggs than birds in density of 5 per m(2); however, birds in density of 8.33 per m(2) had similar BW and EW with birds in the other 2 groups. The mean FI were statistically different among the 3 groups, with a reduction in FI as density increases. Total egg production within the 3 density groups and average egg production per bird were also analyzed using categorical data techniques. The results indicated that stocking density influenced egg production, with birds at higher density producing fewer eggs per bird. Although generous floor space allowances were allocated per bird in this experiment, stocking density influenced the performance of broiler breeder hens.

Laying performance of pearl gray guinea fowl hens as affected by caging density

The caging density required for optimal egg production by various avian species and varieties is highly variable. Even so, little is known of the required cage density for optimum performance of the laying guinea fowl (Numida meleagris). The objective of this study was to assess the effect of varying cage densities on production performance of pearl gray guinea fowl laying hens. In 3 replicates, 270 pearl gray guinea hens [28 wk of age (WOA)] were weighed individually and randomly assigned to laying cages at densities of 1, 2, and 3 birds/cage, equivalent to 1394, 697, and 465 cm2/bird, respectively. During the experiment, all birds received a 16-h lighting regimen and were fed the same diet, comprising 2800 kcal of ME/kg of diet and 16% CP (28 to 59 WOA) and 2800 kcal of ME/kg of diet and 14% CP (60 to 76 WOA). Feed and water were provided for ad libitum consumption. Experimental birds were observed for feed consumption (FC), hen-day egg production (HDEP), egg weight, egg mass (EM), feed conversion ratio, internal egg quality, and shell thickness at the end of each 28-d lay period for 11 consecutive periods. Mean FC and HDEP decreased significantly with increases in cage density, such that 1394 > 697 > 465 cm2/bird. Mean EM was also higher (P < 0.05) for birds reared in cages at 1394 cm2/bird than those reared in cages at 697 and 465 cm2/bird (24.8, 17.4, and 14 g/hen per d, respectively). Feed conversion, HDEP, and EM were negatively correlated with cage density (P < 0.05). Mean feed conversion ratio and percentage of mortality were also lower in birds reared in cages at 1394 cm2/bird than in other treatment groups. Therefore, laying guinea fowl hens exhibited superior performance when raised at a density of 1 bird/cage (1394 cm2/bird) than those reared at densities of 2 and 3 birds/cage (697 and 465 cm2/bird, respectively).

Reevaluation of nonphytate phosphorus requirement of growing pullets with and without phytase

An experiment was conducted to re-evaluate the nonphytate phosphorus (NPP) requirement of growing pullets and to determine to what extent this requirement could be reduced by phytase. Six diets in a 3 x 2 factorial design were used. The pullets of the control group (T1) were fed a sequence of 0.4-0.35-0.3% NPP for the age periods of 0 to 6, 6 to 12, and 12 to 18 wk, respectively, according to NRC (1994) recommendation. The NPP level was reduced by an increment of 0.1% in each phase in T2 and T3. The pullets of T4 to T6 were fed similar NPP levels to T1 to T3, respectively, with 300 units phytase/kg diet. From 18 to 30 wk of age, the pullets on all growing regimens were fed a layer diet with 0.4% NPP. Records were maintained for BW and feed intake during the growing period and for egg production during the laying period. Blood and tibia samples were taken at 6, 12, and 18 wk of age for determining plasma P, tibia weight, and tibia ash. Two digestion trials were conducted at Weeks 5 and 18 for determining total P excretion. Body weights at 18 wk and feed intake for the period of 0 to 18 wk were not different from the control for pullets fed the two lower NPP regimens (P > 0.05). Phytase had a favorable effect on BW at 18 wk (P = 0.0539) and feed intake for the period of 0 to 18 wk (P < 0.05). Plasma P was lower for pullets fed the least NPP than for those fed the control NPP regimen only at 6 wk of age (P < 0.05). Bone quality measurements at 6, 12, and 18 wk of age were not different for pullets fed various NPP regimens (P > 0.05). Phytase, for the most part did, not have an effect on plasma P and bone quality (P > 0.05). Total P intake and total P excretion (mg/bird per day) were reduced due to lowering the dietary NPP in both digestion trials (P < 0.05). Phytase did not have an effect on daily total P intake or excretion. Production and specific gravity were not influenced by NPP regimens used during the growing period. Specific gravity for the entire experiment was greater for pullets fed phytase (P < 0.05). The results indicated that the lowest NPP regimen in the absence of phytase was adequate to support performance of pullets, and due to this, it was not possible to determine the effect of phytase in diminishing the P need of growing pullets.

The effect of light regimen, floor space, and energy and protein levels during the growing period on body weight and early egg size

Two experiments (Exp.) were conducted to determine whether dietary manipulation of energy and protein, additional floor space, and the use of a step-down light regimen during the growing period can influence BW of the White Leghorn pullets at the age of housing (18 wk) and egg size during the early stages of egg production. The results of Exp. 1 indicated that BW at 18 wk of age was increased (P < 0.05) due to the use of high energy (3,036 vs 2,816 kcal ME/kg) or high protein (17.5 vs 14.5%) diets or providing the pullets with more floor space (346 vs 283 cm2 per pullet) from 8 to 18 wk of age. However, the extent of increases of BW due to these variables were not large enough to increase egg size during the early stages of the egg production cycle. The results of Exp. 2 indicated that 18-wk BW was increased (P < 0.05) only due to the use of a high protein sequence (22, 18, and 16% vs 18, 16, and 14% that were used during 0 to 6, 6 to 12, and 12 to 18 wk of age, respectively). Body weight at 18 wk of age was not influenced by the use of a higher energy diet (3,036 vs 2,816 kcal ME/kg) from day-old to 18 wk. Energy or protein levels did not have an effect on early egg size or overall performance up to 66 wk of age. Body weight of the pullets on the step-down light regimen (which were exposed to 23 h/d light at day-old and was gradually reduced to 8 h/d at 15 wk of age) were heavier than the pullets of the short-day light regimen (which were exposed to 8 h/d light during the growing period) during most parts of the growing and laying periods (P < 0.05). The step-down light regimen resulted in increased egg size and higher percentage of extra-large plus large-sized eggs for the entire experiment (P < 0.05), but reduced hen-day egg production and egg mass and impaired feed conversion (P < 0.05) for the entire experiment (18 to 66 wk of age).

Impact of cage density on pullet performance and blood parameters of stress

The effects of cage density on pullet live performance and blood indices of stress were evaluated in two commercial White Leghorn strains housed at 38, 32, 26, and 20 birds per cage from Day 1 to 6 wk of age, and 19, 16, 13, and 10 birds per cage from 6 to 18 wk. Cage densities of 26 and 13 birds per cage represent a U.S. standard of 142 and 284 cm2 per bird that is often applied in commercial pullet rearing. Cage density treatments include confounding cage, feeder, and drinker spaces per bird as might be encountered in commercial practice when growing more pullets per cage. Body weight was significantly reduced at greater bird densities in both strains; however, one strain was affected as early as 6 wk of age, whereas in the other strain, body weight was not reduced significantly until 18 wk. Feed intake was increased by more than 13% in both strains at the lowest density treatment (20 birds per cage) from Day 1 to 2 wk but reduced by more than 9% by higher cage densities during the remainder of the study. Feed conversion (FC) ratio was similarly improved (i.e., reduced) when more pullets were housed per cage, and increased when fewer birds were placed per cage compared to the standard. Despite a significant reduction in feed intake and a corresponding loss of body weight, cage density treatments had no significant affect on hemagglutinin titers to sheep red blood cell antigen, percentage heterophils (H), lymphocytes (L), or the H:L ratio. However, pullet age and strain differences were observed for all blood parameters. Overall, treatments allowing more cage, feeder, and drinker spaces per bird than the U.S. commercial standard provided no body weight advantage, and allowed for greater feed intake and poorer FC at several ages.