For the purposes of farm animal welfare assessment, Farm Assurance Schemes and enforcement of animal welfare legislation, a requirement arises for a unitary welfare score which may be the amalgamation of several animal welfare measures. In amalgamating measures, weighting to reflect the importance of the individual measures for animal welfare is desirable. A study is described in which conjoint analysis was used to collect and evaluate expert opinion to weight a number of welfare assessment measures for the importance of each to broiler welfare in UK husbandry systems. The statistically combined opinion of the experts consulted revealed the weighting factors of the welfare assessment measures selected, with respect to the importance for bird welfare, to be: 0.26 for mortality levels on the growing unit; 0.24 for the level of leg weakness; 0.16 for the level of hock burn; 0.14 for stocking density; 0.10 for enrichment provision; and, 0.10 for the level of emergency provision. Criteria for selection of welfare assessment measures for use in the field, and level of agreement between experts consulted for the study, are discussed. It is concluded that weightings of welfare assessment measures by expert opinion, using conjoint analysis, might be used in the construction of a welfare index for assessment of broiler welfare on-farm. Such an index should not be considered as a ‘gold standard’ for welfare measurement but as an evolving standard for welfare assessment, based on current knowledge.

Broiler chickens are the most numerous terrestrial farmed animals on earth. These birds can suffer a range of pathologies which result in lameness, and one technique for assessing the impact of lameness on the individual bird, and on the flock has been gait scoring. This paper describes a study where the results of the same training programme for validated gait scoring are compared for groups of assessors in Thailand, Brazil and New Zealand. A uniform course of training carried out in the classroom, through video assessment and through on-farm training was carried out in the countries named; a total of 95 persons being trained overall. A measure of agreement with the reference scale for the assessors' numerical responses was carried out using a Cohen's Kappa test, and the results indicated significant differences in the ‘origin position’ ie the view taken by the assessors of the impact of lameness on the bird before training had taken place, but a high degree of consistency in the response to training. The study demonstrated that gait scoring can be learned by assessors from different geographical and social backgrounds, and that the ‘rate of learning’ – the improvement in performance in relation to a standard, was similar between the countries studied. The ‘origin’ and ‘final’ position of the assessors pre- and post-training, from the different countries in relation to the reference standard is discussed.

A case study is described in which a high incidence of lameness in broiler chickens (Gallus gallus domesticus) is associated with rearing to 84 days of age; broilers are normally slaughtered at less than 50 days of age. A sample of 185 birds was scored for walking ability, and 24 birds from this group were assessed for dehydration by measuring plasma osmolality. The proportion of the group having gait abnormalities was compared with that recorded during a recent survey of Danish flocks and was found to be higher. A relationship is established between the degree of gait impairment and the level of dehydration. The degree of dehydration is related to the findings for plasma osmolality from previous research, and the results indicate that some of the birds in this case may have been deprived of access to water for periods in excess of 60 hours.

There is continuing debate about the space needs and requirements of broiler chickens, The aims of this study were to measure the amount of floor area a six-week-old broiler occupies for different behaviours and to use the obtained results in two models to estimate the number of birds that can be kept per m2 in large flocks simulating different levels of behavioural synchronisation. Photographs were taken of overhead projections of broilers (2.468 kg on average) kept in floor pens of 1 m2 with either eight (low density) or 16 birds (high density) per pen. Individual body space was measured from these photographs for seven behaviours. Posture and density affected body space of the behaviours idle, drinking, and ground pecking. The first model, computing space needed per bird performing a behaviour in relation to flock size, showed that 15.3-15.7 birds m−2 (37.8-38.7 kg m−2) can be housed maximally, based on low density measurements and 18.5-19.4 birds m−2 (45.7-47.9 kg m−2) based on high density measurements. The second model, computing stocking density based on synchronisation of behaviour and body space, showed that 13.7-15.9 birds m−2 (33.8-39.2 kg m−2) can be housed maximally based on low density measurements and 15.4-18.6 birds m−2 (38.0-45.9 kg m−2) based on high density measurements. Results based on high density measurements implied that birds are compressed. Given the restrictions of a limited number of behaviours and no inclusion of movement and social interactions in the models of this study, stocking density in large flocks should not exceed 16 birds m−2 (39.4 kg) because that would lead to compression of birds which will suppress opportunities for behavioural expression and therefore impair welfare.

EU legislation stipulates that unfit broilers may not be transported, but no guidelines for fitness-for-transport assessment are provided. Moreover, the impact of pre-slaughter conditions (eg crate stocking density) may depend on broiler fitness. We aimed to evaluate a fitness-assessment method and test physiological responses to the pre-slaughter phase with different stocking densities. Broilers (41 days; n = 1,939) were transported for 45 min at ‘high’ (160 cm2 per kg), ‘medium’ (190 cm2 per kg) or ‘low’ (220 cm2 per kg) stocking density, and were subjected to a commercially representative pre-slaughter phase duration of ≈ 16 h. Pre-loading, lameness, illness, hock burns, foot-pad dermatitis, lesions, physical defects, cleanliness and cachexia were scored on a sample, for categorisation as fit (n = 49) or unfit (n = 25). Blood was collected before and after the pre-slaughter phase for determination of plasma levels of corticosterone (CORT), lactate, glucose and thiobarbituric acid-reactive substances (TBARS). Lameness, foot-pad dermatitis, lesions, illness, defects, and cachexia scores were, or tended to be, correlated with ≥ 1 physiological stress indicators. Unfit chickens tended to show or showed lower pre-transport glucose and lactate levels than fit chickens. Post-lairage, unfit chickens had higher TBARS and lower lactate levels compared to fit chickens. At high and low stocking densities, unfit chickens showed higher CORT levels than fit chickens. Furthermore, CORT levels of unfit chickens increased more at low stocking density. The results show that our method potentially identifies chickens experiencing additional stress during the pre-slaughter phase, due to poor physical condition. High and low stocking density proved a stressor for all, and especially for unfit chickens, with detrimental implications for their welfare.

Lame broiler chickens perform poorly in standardised mobility tests and have nociceptive thresholds that differ from those of nonlame birds, even when confounding factors such as differences in bodyweight are accounted for. This study investigated whether these altered responses could be due to pain, by comparing performance in a Group Obstacle test and a Latency to Lie (LTL) test of lame (Gait Score [GS] 2.5-4) and non-lame (GS 0-1) broilers administered analgesia or a saline control. We used exploratory subcutaneous doses of the non-steroidal anti-inflammatory drugs (NSAIDs), meloxicam (5 mg kg−1) or carprofen (35 mg kg−1) or the opioid butorphanol tartrate (4 mg kg−1). We included butorphanol to explore the possibility that NSAIDs could improve mobility by reducing inflammation without necessarily invoking an analgesic effect. Lameness was a significant predictor in all analyses. Neither the number of obstacle crossings nor latency to cross an obstacle was significantly changed by either NSAID, but LTL was longer in lame birds given carprofen and meloxicam than in lame birds given saline. LTL was associated with foot-pad dermatitis and ameliorated by both NSAIDs. Butorphanol did not affect LTL but appeared soporific in the obstacle test, increasing latency to cross and, in non-lame birds, reducing the number of crossings. Combined with data from other studies, the results suggest carprofen and meloxicam had some analgesic effect on lame birds, lending further support to concerns that lameness compromises broiler welfare. Further investigation of opioid treatments and lameness types is needed to disentangle effects on mobility and on pain.

Leg problems are highly prevalent in modern broiler production and provision of environmental enrichment could be a strategy to improve leg health. Different types of environmental enrichment have undergone evaluation. Our objective was to conduct a systematic review of the effect of environmental enrichment on leg health in broiler chickens. The evaluation of leg health included measures of the entire leg and foot, and behavioural, pathological and physical measures. Six types of environmental enrichment were selected for inclusion: light programme, intensity of light, stocking density, perches, straw bales and separation of resources. For each type, a systematic literature search was performed. The review included 62 studies; 56 randomised trials and six cross-sectional studies. An assessment of the methodological quality of all 56 randomised trials was performed with some reporting deficits regarding occurrence of blinding, randomisation and reliability of measures. Provision of perches and increased intensity of light only displayed limited effectiveness in improving leg health and both mainly affected contact dermatitis. In contrast, there was evidence that a lowered stocking density and a dark/light schedule could improve leg health. Few studies have been carried out on the effect of straw bales and separation of resources. The few studies done have, however, shown that both types of enrichment can be effective in improving leg health. In conclusion, identifying and providing the optimal types of enrichment for broilers will reduce leg problems and increase mobility, thereby improving the welfare of the birds.

Campylobacter is the leading cause of foodborne bacterial gastroenteritis in humans worldwide, often associated with the consumption of undercooked poultry. In Jordan, the majority of broiler chicken production occurs in semi-commercial farms, where poor housing conditions and low bio-security are likely to promote campylobacter colonisation. While several studies provided estimates of the key parameters describing the within-flock transmission dynamics of campylobacter in typical high-income countries settings, these data are not available for Jordan and Middle-East in general. A Bayesian model framework was applied to a longitudinal dataset on Campylobacter jejuni infection in a Jordan flock to quantify the transmission rate of C. jejuni in broilers within the farm, the day when the flock first became infected, and the within-flock prevalence (WFP) at clearance. Infection with C. jejuni is most likely to have occurred during the first 8 days of the production cycle, followed by a transmission rate value of 0.13 new infections caused by one infected bird/day (95% CI 0.11–0.17), and a WFP at clearance of 34% (95% CI 0.24–0.47). Our results differ from published studies conducted in intensive poultry production systems in high-income countries but are well aligned with the expectations obtained by means of structured questionnaires submitted to academics with expertise on campylobacter in Jordan. This study provides for the first time the most likely estimates and credible intervals of key epidemiological parameters driving the dynamics of C. jejuni infection in broiler production systems commonly found in Jordan and the Middle-East and could be used to inform Quantitative Microbial Risk Assessment models aimed to assess the risk of human exposure/infection to campylobacter through consumption of poultry meat.

The objective of the current experiment was to determine the effects of high-concentration phytase (5000 FTU/kg) feeding to diverse lines of chickens fed phosphorus (P) adequate maize–soybean meal diets (4.5 g/kg non-phytate P) on the performance and intestinal immune function. Performance was measured for outbred broiler (Ross 308) and inbred Fayoumi lines over 0–21 days, and duodenum and ileum were harvested for the determination of mucin-2, interleukin (IL)-1β and IgA mRNA by quantitative reverse transcription polymerase chain reaction. Over the 0–7-day period, there was a significant line × diet interaction, as high phytase supplementation increased broiler average daily gain (ADG), but had no effect on Fayoumi ADG. Treatment of diets with phytase increased expression of the mucin-2 gene in the duodenum mucosa. There were significant interactions between line and age, and line, diet and age on duodenal expression of the IL-1β gene as phytase supplementation of the broiler line reduced IL-1β in comparison to control fed broilers without change in the Fayoumi line. Overall, the addition of a high concentration of phytase to broilers fed adequate concentrations of non-phytate P resulted in improved growth performance early with a reduction in this effect over time. Mucosal mucin-2 expression was increased with high-concentration phytase feeding across both lines, but IL-1β mRNA expression was reduced in the duodenum of broilers fed high concentrations of phytase, suggesting that the increased performance noted might be related to decreased inflammation.

Provision of an appropriate dustbathing substrate may allow broiler chickens to satisfy a natural motivation and give them an opportunity to exercise. The main aim of this study was to evaluate the extent to which different substrates promote dustbathing behaviour in broilers. The trial was replicated over three production cycles in one commercial broiler house, with ~22 000 Ross broilers housed per cycle. The birds were provided with access to five experimental substrates from day 10 of the 6-week production cycle. The substrates included the following: (1) peat (P), (2) oat hulls (OH), (3) straw pellets (SP), (4) clean wood shavings (WS), and (5) litter control (C). The substrates were provided in 15 steel rings (1.1 m in diameter, three rings per substrate) dispersed throughout the house. The level of occupancy of the rings, behaviours performed in each substrate, and the effect of ring position (central or edge of house) were assessed in weeks 3, 4, 5 and 6 using scan sampling from video footage. Where substrates successfully promoted dustbathing, the length and components of the bouts (including number of vertical wing shakes and ground pecks) were also assessed. Results showed that birds used P significantly more than the remaining substrates for dustbathing (P<0.001). Oat hulls were the second most preferred substrate for dustbathing, with significantly more birds dustbathing in the OH compared with SP, WS and C (P<0.001). The least sitting inactive was also seen in the P and OH rings compared with the SP, WS and C (P<0.001). The highest levels of foraging were recorded in the P, OH and WS compared with SP and the C. Position of the rings did not affect the types of behaviours performed in any substrate, although overall more birds were counted in the central compared with edge rings (P=0.001). More detailed information on dustbathing behaviour was only recorded in the P and OH treatments, and there were no differences in the length of dustbathing bout, or components of the bout between them (P>0.05). The use of OH is likely to be more environmentally sustainable than that of P, and our results suggest that this substrate is relatively successful in promoting dustbathing. However, a preference was still observed for P and further work should investigate whether other suitable substrates could better reflect its qualities.

Vitamin D plays many important functions in the animal, as it is necessary for proper calcium (Ca) absorption and use in different biological processes. The aim of several recent experiments with poultry was to evaluate the efficacy of different forms and levels of vitamin D3 in the diets for broiler chickens and laying hens. The results of these studies are presented and discussed in this review paper. Based on these results, the modern high-performing poultry requirement for supplemental vitamin D to maximise mineral digestibility, performance and immunity indices, bone health, and eggshell quality is about 3,000 IU/kg, i.e. much higher than NRC (1994) recommendations. The results of several recent poultry studies have shown that 25-hydroxycholecalciferol (25-OH-D3) is more efficient in commercial poultry nutrition than the basic form of vitamin D3 (cholecalciferol).

Resin acid composition (RAC) has previously been shown to inhibit the growth of the Gram-positive bacterial species Clostridium perfringens in vitro and to modulate the ileal microbiota of broiler chickens. The following trials examined the effect of RAC on broiler chickens in two experiments. In experiment 1, 1400 one-day-old Ross 308 broilers were divided into two coccidiostat treatments: chemical (CC) and ionophore (IC), which were further divided into two RAC dosages: 0 and 0.5 g/kg. All diets were supplemented with xylanase, β-glucanase and phytase feed enzymes. The birds were raised in a commercial-type environment without additional microbial challenge during the 42-day trial. RAC improved the body weight gain by 3.3% and feed conversion ratio by 5.7% with CC, and improved footpad lesion scores with IC but had no effect on the litter quality. Experiment 2 was a 35-day subclinical necrotic enteritis (NE) challenge trial with 510 male Ross 308 chickens. The dietary treatments included a non-challenged, non-supplemented control and four NE challenged treatments with dietary RAC supplementation at 0, 1, 2, and 3 g/kg. The birds were challenged with Eimeria maxima on day nine and C. perfringens on day 14. While RAC at 1 g/kg significantly increased bird weight gain during the challenge, it did not affect the microbial or short chain fatty acid (SCFA) profiles. In contrast, RAC at 3 g/kg reduced the abundance of the Lactobacillus group and tended to reduce the abundance of genus Bifidobacterium and the total numbers of eubacteria. These experiments suggest that dietary RAC at a moderate dose positively affected broiler performance. However, changes in caecal microbiota populations may not have influenced the observed performance effects of RAC.

Campylobacter is the leading cause of bacterial diarrhoeal disease worldwide, with raw and undercooked poultry meat and products the primary source of infection. Colonization of broiler chicken flocks with Campylobacter has proved difficult to prevent, even with high levels of biosecurity. Dipteran flies are proven carriers of Campylobacter and their ingress into broiler houses may contribute to its transmission to broiler chickens. However, this has not been investigated in the UK. Campylobacter was cultured from 2195 flies collected from four UK broiler farms. Of flies cultured individually, 0·22% [2/902, 95% confidence interval (CI) 0–0·53] were positive by culture for Campylobacter spp. Additionally, 1293 flies were grouped by family and cultured in 127 batches: 4/127 (3·15%, 95% CI 0·11-6·19) from three broiler farms were positive for Campylobacter. Multilocus sequence typing of isolates demonstrated that the flies were carrying broiler-associated sequence types, responsible for human enteric illness. Malaise traps were used to survey the dipteran species diversity on study farms and also revealed up to 612 flies present around broiler-house ventilation inlets over a 2-h period. Therefore, despite the low prevalence of Campylobacter cultured from flies, the risk of transmission by this route may be high, particularly during summer when fly populations are greatest.

There is a large demand for holistic welfare assessment systems that result in a singular balanced summary of welfare. The Welfare Quality® (WQ) broiler protocol summarizes 18 welfare measures into four principles (‘good feeding’, ‘good housing’, ‘good health’ and ‘appropriate behaviour’), which are then integrated into one overall category (‘excellent’, ‘enhanced’, ‘acceptable’ or ‘not classified’). But the protocol is time consuming which hampers implementation. Furthermore, WQ’s aim to assess animal welfare in a wide range of husbandry systems may decrease its ability to discriminate between flocks from the same system. We applied the protocol in the context of intensive indoor rearing to assess whether it discriminated sufficiently between flocks, could be shortened without losing essential information, and provided a balanced summary of welfare. The vast majority of the flocks (88%) received the same overall classification (acceptable) whilst all other flocks received an adjacent classification (enhanced), suggesting poor discriminative capacity. For 95% of the flocks overall classification was explained by two measures only (‘drinker space’ and ‘stocking density’). A system based on these two measures would reduce assessment time from 3.5 h to a few minutes. However, both measures’ validity can be questioned as they are risk factors for poor welfare rather than animal-based outcome measures and they suffer from methodological weaknesses. Furthermore, the possibility for such an extreme simplification raises doubts on whether the overall classification reflects a balanced summary of different welfare aspects. In line with this, overall classification was not affected by replacing single measures within the ‘good health’ and ‘appropriate behaviour’ principles with realistically attainable minima or maxima for intensively reared flocks. Even replacing either of these two principles entirely with their realistically obtainable minimum or maximum did not affect classification. Such insensitivity to change may discourage attempts to improve the welfare of intensively reared flocks when assessments are made based on the overall classification. This calls for an adjustment of the classification system, which is currently being developed by the Welfare Quality Network.

Addition of butyrate or its salt has been reported to have a positive impact on growth performance in broilers due to its bactericidal and bacteriostatic properties. This study investigated the effect of enterically coated dietary sodium butyrate (SB) on broiler performance. In experiment 1, 408 day-old male Ross 308 chicks were used in a 2 × 2 factorial design. Factors were dietary energy (standard or minus 50 kcal/kg relative to standard diet) and coated SB level (0 and 1 g/kg). In experiment 2, 2160 day-old male Cobb 500 birds were used in a 2 × 2 × 2 factorial plus one arrangement of treatments. Factors included grain source (corn or wheat); protein level (standard or high); coated SB level (0 and 1 g/kg) plus a treatment using 2 kg SB in a high protein wheat-based diet. The results from the experiments showed no effect of coated SB on performance at 1 g/kg inclusion in feed across the ME range or across basal diet type (grain) or protein level (P > 0.05). However, birds fed the high protein wheat diet with 2 g/kg SB had higher body weights than the control birds at 10 and 24 days old. Birds fed high protein diets had lower body weight gain (WG) than those fed standard protein diets (P < 0.05), whereas birds fed corn based diets had higher WG than those fed wheat based diets (P < 0.05). Birds fed high dietary protein or wheat based diet showed decreased pH of caecal contents. The results indicated that dietary coated SB had no effect on broiler performance, the concentration of caecal and ileal short chain fatty acids (SCFA) or intestinal pH. Higher inclusion levels may play a beneficial role but this warrants further investigation.

Protein sources other than soybean for the diets of poultry are needed for agricultural systems in temperate regions to help avoid some negative social and ecological impacts of large-scale soybean imports from overseas. The aim of the present study was to test the suitability of alternative protein sources in diets for slow-growing organic broiler chicken. Four experimental broiler diets were tested against a commercial feed for organic broiler chicken fattening (control), containing 255 g kg−1 soybean cake. Each experimental diet was based on the control diet, but 130 g kg−1 of soybean cake was replaced with alternative feeds. The diet ‘HermAlf’ contained 78 g kg−1 Hermetia meal (dried larvae of the black soldier fly, Hermetia illucens) and 52 g kg−1 alfalfa (Medicago sativa) meal. Diet ‘HermPea’ contained 78 g kg−1 Hermetia meal and 52 g kg−1 pea (Pisum sativum) groats. Diet ‘AlfPea’ contained 78 g kg−1 alfalfa meal and 52 g kg−1 pea groats. Diet ‘PeaAlf’ contained 78 g kg−1 pea groats and 52 g kg−1 alfalfa meal. Both diets containing Hermetia meal had the same amount of crude protein (CP) concentration as the control, while CP concentration was lower in diet AlfPea (by 2.7%) and in diet PeaAlf (by 3.5%) compared with the control. Over the course of the experiment, 15 broilers each (slow-growing Hubbard S757) were fattened with one of the five diets ad libitum from days 7 to 82. Additionally, all broilers received water and wheat grains (Triticum aestivum) ad libitum. Feed intake was measured by group. Daily gains, live weights, carcass weights and meat quality were analyzed individually. Compared with the control, feed intake, daily weight gain, carcass weights and feed efficiency were equivalent for all experimental diets. Regarding quality parameters, only cooking loss was increased with the HermPea diet compared with the control. The results indicate that the alternative feeds tested could replace part of the soybean products in broiler diets while achieving equivalent feed efficiency and product quality.

The European Union (EU) Broiler Directive (2007/43/EC) is unique amongst current EU Directives, which address animal welfare, in that it uses outcome data collected at abattoirs and on farm to monitor on-farm broiler welfare and vary the maximum permitted stocking density on farm. In this study, we describe how, by bringing together personnel from the competent authorities in 22 member states (MSs) who have responsibility for implementing the Directive, and engaging in exchange of information and technical methods regarding the Broiler Directive, it has been possible to identify differences in approach with regard to ‘what data is being collected, and by whom’ across EU MSs. Online questionnaires and workshop exercises enabled us to identify priority areas for knowledge transfer and training. For example, foot pad dermatitis, hock burn, dead on arrival and total rejections (birds rejected as unfit for human consumption by the meat inspection staff at slaughter) were identified by the MSs as measures of medium-to-low priority in terms of knowledge transfer because there are assessment methods for these conditions that are already well accepted by competent authorities. On the other hand, breast lesions, cellulitis, emaciation, joint lesions, respiratory problems, scratches, wing fractures and a number of environmental measures were identified as having high priority in terms of knowledge transfer. The study identified that there is significant variability in the stage of implementation between MSs, and responses from the participating MSs indicated that sharing of guidance and technical information between MSs may be of value in the future set-up process for those MSs engaged in implementation of the Directive.

In this study, we describe the monitoring of young broiler chicken vocalisation, with sound recorded and assessed at regular intervals throughout the life of the birds from day 1 to day 38, with a focus on the first week of life. We assess whether there are recognisable, and even predictable, vocalisation patterns based on frequency and sound spectrum analysis, which can be observed in birds at different ages and stages of growth within the relatively short life of the birds in commercial broiler production cycles. The experimental trials were carried out in a farm where the broiler where reared indoor, and audio recording procedures carried out over 38 days. The recordings were made using two microphones connected to a digital recorder, and the sonic data was collected in situations without disturbance of the animals beyond that created by the routine activities of the farmer. Digital files of 1 h duration were cut into short files of 10 min duration, and these sound recordings were analysed and labelled using audio analysis software. Analysis of these short sound files showed that the key vocalisation frequency and patterns changed in relation to increasing age and the weight of the broilers. Statistical analysis showed a significant correlation (P<0.001) between the frequency of vocalisation and the age of the birds. Based on the identification of specific frequencies of the sounds emitted, in relation to age and weight, it is proposed that there is potential for audio monitoring and comparison with ‘anticipated’ sound patterns to be used to evaluate the status of farmed broiler chicken.

Boron (B) is a trace element that plays an important role in mineral and hormonal metabolism, cell membrane function, and enzymatic reactions. The current evidence supports the hypothesis that boron has an important biological role that affects the mineral metabolism of both humans and animals by interacting with Ca, Mg, P and cholecalciferol (vitamin D), all of which are important in bone metabolism. This implies that B can play a vital role in bone development and normal growth. However, the use of B occasionally results in apparently inconsistent responses in terms of performance in broiler chickens and layer hens. Although some studies have reported the effectiveness of B, no clear mode of action has been proposed. There are many potential reasons for the inconsistent results of B in eliciting beneficial responses. Available data obtained from relevant studies suggest that there are several concurrent factors involved. Of these, nutritional variables predominate. The purpose of this paper is to review the available studies examining the nutritional role of B on the production performance in broiler chickens and laying hens.

This study aimed to assess the effect of the number of straw bales (SBs) provided on the behaviour and leg health of commercial broiler chickens. Houses containing ~23 000 broiler chickens were assigned to one of two treatments: (1) access to 30 SBs per house, ‘30SB’ or (2) access to 45 SB per house, ‘45SB’. This equated to bale densities of 1 bale/44 m2 and 1 bale/29 m2 of floor space within houses, respectively. Treatments were applied in one of two houses on a commercial farm, and were replicated over six production cycles. Both houses had windows and were also artificially lit. Behaviour was observed in weeks 3 to5 of the cycle. This involved observations of general behaviour and activity, gait scores (0: perfect to 5: unable to walk) and latency to lie (measured in seconds from when a bird had been encouraged to stand). Production performance and environmental parameters were also measured. SB density had no significant effect on activity levels (P>0.05) or walking ability (P>0.05). However, the average latency to lie was greater in 30SB birds compared with 45SB birds (P<0.05). The incidence of hock burn and podo dermatitis, average BW at slaughter and levels of mortality and culling were unaffected by SB density (P>0.05). The results from this study suggest that increasing SB levels from 1 bale/44 m2 to 1 bale/29 m2 floor space does not lead to significant improvements in the welfare of commercial broiler chickens in windowed houses.