Assessment of Welfare Problems in Broilers: Focus on Musculoskeletal Problems Associated with Their Rapid Growth

The growth of the broiler industry has been accompanied with concerns over the environmental and social impacts on intensive production systems, as well as the welfare of the animals themselves. As a result, since the 2000s, there has been growing interest in alternative production systems that improve animal welfare and sustainability. In this context, it is important to prioritize the welfare of broilers in commercial production systems and to use reliable welfare indicators to provide consumers with information about the welfare of the animals they consume. Resource-based measures (RBM) are based on assessing the resources available to the birds in terms of their housing, environment, and management practices, such as stocking density, litter quality, lighting and air quality, etc. Outcome-based measures (OBM), also known as animal-based measures, focus on assessing the actual welfare outcomes for the birds, such as footpad dermatitis, hock burn, contamination or damage to feathers, gait score, mortality, etc. These OBM-based measures are one of the more direct indicators of welfare and can help identify any welfare issues. The present review highlighted the factors that affect animal welfare indicators focused on OBMs which can be used in the commercial broiler farms.

Research Note: Welfare and stress responses of broiler chickens raised in conventional and animal welfare-certified broiler farms

The present study was conducted to assess the animal welfare status of broiler chickens raised in conventional and welfare-certified farms. One conventional farm (30,000 birds/house, 1,488 m2/house, 2 houses) and one animal welfare-certified farm (32,000 birds/house, 1,920 m2/house, 2 houses) were selected to measure productivity, stress responses, and animal welfare indicators in 3 broiler flocks (2 farms/season, n = 6 flocks/farm type) during summer, autumn, and spring. Upon farm visits, body weight, uniformity, and animal welfare indicators (i.e., fecal and feather corticosterone, footpad dermatitis, hock burn, feather dirtiness, and gait score) were measured at 26 d posthatch. Also, moisture, nitrogen, and pH of litter, light intensity, ammonia concentration, and body surface temperature of head, chest, and legs were measured. There was no difference in body weight and uniformity between farm types. Fecal corticosterone concentrations were higher (P = 0.021) in welfare-certified vs. conventional farm, but no significant difference was found in feather corticosterone. Welfare-certified vs. conventional farm had lower percentages of hock burn (P = 0.018), feather dirtiness scores (P = 0.009), and gait score (P = 0.040), and there was no difference in footpad dermatitis. Nitrogen content in litter samples tended to be higher in conventional vs. welfare-certified farms (P = 0.094), and there was no difference in moisture and pH between farm types. Ammonia concentration within the broiler houses was not different between 2 farms. However, animal welfare farm was found to be brighter than conventional farm (P < 0.001). The body surface temperature of head, chest, and legs was not different between farm types. In conclusion, the welfare-certified farm had higher welfare measures, including lower hock burn, feather dirtiness, and gait score, confirming an overall improvement in welfare indicators. However, the observation on the elevated feather corticosterone noted in welfare vs. conventionally raised chickens warrants further studies.

Measuring Chronic Stress in Broiler Chickens: Effects of Environmental Complexity and Stocking Density on Immunoglobulin-A Levels

Commercial housing conditions may contribute to chronic negative stress in broiler chickens, reducing their animal welfare. The objective of this study was to determine how secretory (fecal) and plasma immunoglobulin-A (IgA) levels in fast-growing broilers respond to positive and negative housing conditions. In three replicated experiments, male Ross 708 broilers (n = 1650/experiment) were housed in a 2 × 2 factorial study of high or low environmental complexity and high or low stocking density. In experiments 1 and 3 but not in experiment 2, high complexity tended to positively impact day 48 plasma IgA concentrations. When three experiments were combined, high complexity positively impacted day 48 plasma IgA concentrations. Stocking density and the complexity × density interaction did not impact day 48 plasma IgA concentrations. Environmental complexity and the complexity × density interaction did not impact day 48 secretory IgA concentrations. A high stocking density negatively impacted day 48 secretory IgA concentrations overall but not in individual experiments. These results suggest that environmental complexity decreased chronic stress, while a high stocking density increased chronic stress. Thus, plasma IgA levels increased under high-complexity housing conditions (at day 48), and secretory IgA levels (at day 48) decreased under high-density conditions, suggesting that chronic stress differed among treatments. Therefore, these measures may be useful for quantifying chronic stress but only if the statistical power is high. Future research should replicate these findings under similar and different housing conditions to confirm the suitability of IgA as a measure of chronic stress in broiler chickens.

Fast- and slower-growing broilers respond similarly to a reduction in stocking density with regard to gait, hock burn, skin lesions, cleanliness and performance

There is an increasing trend toward broiler production systems with higher welfare requirements. Breed and stocking density are considered key factors for broiler welfare that are often specified as criteria for such higher welfare systems. However, it remains unknown how slower-growing broilers respond to a reduction in stocking density with regard to their welfare and performance, and whether this response differs from fast-growing broilers. Therefore, we compared fast- (F) and slower-growing broilers (S) housed at 4 different stocking densities (24, 30, 36, and 42 kg/m², based on slaughter weight) and measured their welfare scores (i.e., gait, footpad dermatitis, hock burn, skin lesions and cleanliness), litter quality and performance. The experiment had a 2 × 4 factorial design with 4 replicates (pens) per treatment (32 pens in total). Thinning (15%) was done in a 50/50 male/female ratio at 38 (F) and 44 (S) d of age (estimated body weight of 2.2 kg). We hypothesized that breeds would respond differently to a reduction in stocking density. Contrary to our hypothesis, only one interaction between breed and stocking density was found on footpad dermatitis, indicating that fast- and slower-growing broilers generally showed similar responses to a reduction in stocking density. F broilers showed a steeper decline in the prevalence of footpad dermatitis with reducing stocking density compared to S broilers. Broilers housed at lower stocking densities (24 and/or 30 kg/m²) showed improved welfare measures, litter quality and performance compared to those housed at higher stocking densities (36 and/or 42 kg/m²). S broilers had better welfare scores (gait, footpad dermatitis and skin lesions), litter quality and lower performance compared to F broilers. In conclusion, reducing stocking density improved welfare of both F and S broilers, but more for F broilers in case of footpad dermatitis, and using S broilers improved welfare compared to F broilers. Reducing stocking density and using slower-growing broilers benefits broiler welfare, where combining both would further improve broiler welfare.

Welfare of broilers on farm

This Scientific Opinion considers the welfare of domestic fowl (Gallus gallus) related to the production of meat (broilers) and includes the keeping of day-old chicks, broiler breeders, and broiler chickens. Currently used husbandry systems in the EU are described. Overall, 19 highly relevant welfare consequences (WCs) were identified based on severity, duration and frequency of occurrence: 'bone lesions', 'cold stress', 'gastro-enteric disorders', 'group stress', 'handling stress', 'heat stress', 'isolation stress', 'inability to perform comfort behaviour', 'inability to perform exploratory or foraging behaviour', 'inability to avoid unwanted sexual behaviour', 'locomotory disorders', 'prolonged hunger', 'prolonged thirst', 'predation stress', 'restriction of movement', 'resting problems', 'sensory under- and overstimulation', 'soft tissue and integument damage' and 'umbilical disorders'. These WCs and their animal-based measures (ABMs) that can identify them are described in detail. A variety of hazards related to the different husbandry systems were identified as well as ABMs for assessing the different WCs. Measures to prevent or correct the hazards and/or mitigate each of the WCs are listed. Recommendations are provided on quantitative or qualitative criteria to answer specific questions on the welfare of broilers and related to genetic selection, temperature, feed and water restriction, use of cages, light, air quality and mutilations in breeders such as beak trimming, de-toeing and comb dubbing. In addition, minimal requirements (e.g. stocking density, group size, nests, provision of litter, perches and platforms, drinkers and feeders, of covered veranda and outdoor range) for an enclosure for keeping broiler chickens (fast-growing, slower-growing and broiler breeders) are recommended. Finally, 'total mortality', 'wounds', 'carcass condemnation' and 'footpad dermatitis' are proposed as indicators for monitoring at slaughter the welfare of broilers on-farm.

Undergraduate student attitudes to current poultry industry issues over four semesters: surveying an introductory poultry science course

Individual background and demographics affect student perceptions of animal production. Understanding how science-based education alters these opinions is a critical aspect of improving university instruction as well as increasing consumer engagement in the poultry industry. The study objectives were to quantify the effects of student background, career interests, and science-based instruction on opinions regarding current issues in the poultry industry. Undergraduate students enrolled in a one semester poultry science course at Iowa State University between 2018 and 2021 were anonymously surveyed at the start and end of the semester as part of a 4-yr study. Students who opted to take the survey answered three demographic questions indicating their 1) livestock experience, 2) sex, and 3) career goals. The body of the survey consisted of 16 "poultry issue statements" where students were directed to mark a vertical dash on a 130 mm horizontal line indicating their level of agreement with each statement. Post-survey collection, the line was separated into 5 sections for discussion: responses within 0%-20% indicated strongly disagree, 21%-40% disagree, 41%-60% neutral, 61%-80% agree, and 81%-100% indicated strongly agree. Responses were analyzed using Proc Mixed in SAS Version 9.4 with a Tukey-Kramer adjustment for all pairwise comparisons using main effects including demographic categories, education (pre- or post-instruction), and year the survey was taken. Responses to various issue statements were affected by students' livestock experience (P < 0.05; 6 out of 16 statements affected), sex (P < 0.05; 5 out of 16 statements), and ultimate career goals (P < 0.05; 4 out of 16 statements). Pre- vs. post-education responses differed significantly in 6 out of 16 statements (P < 0.05), and in 2 out of 16 poultry issue statements, the year of instruction affected student response (P < 0.05). These data indicate that individual student background, sex, and differing career interests impact opinions of current topics in the broiler and layer industries. Further, science-based education as well as the year the course was taken over consecutive semesters significantly altered student opinions.

Bird Welfare in Zoos and Aquariums: General Insights across Industries

Animal welfare is a priority across accredited zoological institutions; however, historically, research has been prioritized for mammals. Bird-focused studies accounted for less than 10% of welfare research in zoos and aquariums over the last ten years. Due to the lack of scientific publications on bird welfare, zoo scientists and animal practitioners can look to other industries such as agriculture, laboratories, and companion animal research for insight. This qualitative review highlights findings across industries to inform animal care staff and scientists on the welfare needs of birds within zoos and aquariums. Specifically, the review includes an overview of research on different topics and a summary of key findings across nine resources that affect bird welfare. We also highlight areas where additional research is necessary. Future welfare research in zoos and aquariums should prioritize studies that consider a diversity of bird species across topics and work to identify animal-based measures with empirical evidence. Moving forward, research from other industries can help develop innovative research on bird welfare within zoos and aquariums.

A comparison of fast growing broiler chickens with a slower-growing breed type reared on Higher Welfare commercial farms

Slowing the growth of modern broiler chickens can have a positive effect on a number of welfare outcomes. However, relatively few studies have compared fast and slower growing broiler chickens reared under the same commercial conditions. The main aim of this study was to evaluate a slower growing breed and standard fast growing broilers on commercial farms. Ross 308 broilers and slower growing Hubbard Redbro broilers were housed on six farms for 17 production cycles. Production data were available for all cycles. Behaviour and environmental measures were taken over one cycle on each of two farms. The farms were visited during weeks 3-6 for both breeds and week 7 for Redbros. We found that breed had a significant effect on a number of measures, including gait score, latency to lie, feather cover, avoidance distances, perch use and play behaviour (p < 0.05). Gait scores were consistently lower among the Redbro flocks during weeks 4, 5, 6 and 7. Redbro broilers generally had longer latency to lie times, better feather cover, and were more reactive to approaching observers. They also showed higher levels of perch use and play. Despite these indications of improved locomotion and physical ability, we found little difference in their general behaviour. However, Redbro broilers did perform longer activity bouts in week 7 than Ross 308s in their final week. There was no effect of breed on dust levels, ammonia concentration or litter condition. Redbro broilers were slaughtered 5.5 days later than Ross 308 birds at a lower average weight (2.32 vs 2.52kg) and had lower mortality, fewer culls and fewer carcasses downgraded at the abattoir. Our results suggest that the slower growing strain was healthier throughout the cycle and more capable of displaying some natural behaviours.

Potential impact of stocking density on growth, carcass traits, indicators of biochemical and oxidative stress and meat quality of different broiler breeds

The aim of the current study to investigate the potential impact of different stocking densities on growth performance, carcass traits, indicators of biochemical and oxidative stress and meat quality of Arbor Acres and Ross-308 broiler breeds to recommend the better stocking density with low production cost simultaneously with high quality. A total of 312 one-day old of each Arbor Acres broiler and Ross-308 were randomly classified into 3 experimental groups with different stocking density, each of 6 replicates. The first group (SD1) was 14 birds/m2 (28 kg/m2), while the second group (SD2) was 18 birds/m2 (36 kg/m2) and the third group (SD3) was 20 birds/m2 (40 kg/m2). The growth performance, carcass traits, meat quality hematological and biochemical parameters were measured. SD3 group possessed the lowest body weight. Alanine transaminase in Arbor Acres was 15 and 14% higher in SD3 when compared with SD1 and SD2, respectively. While, was 21 and 20% of Ross-308, respectively. SD3 revealed the highest values of cholesterol, TG, MDA, and LDL of both breeds when compared with SD1 and SD2, with the lowest levels of HDL, GPX, and IGG. Birds of SD3 was the nastiest carcass weight 873 (P = 0.000) and 1,411.60 g (P = 0.000); dressing percentage 63.07 (P = 0.000) and 75.83% (P = 0.000); breast weight 513.10 g (P = 0.000) and 885.50g (P = 0.000); thigh weight 359.90 g (P = 0.000) and 526.08 g (P = 0.000) when compared with SD1 and SD2 of Arbor Acres and Ross-308, respectively. The dressing % of SD1 and SD2 was approximately 19% better than that of SD3 of Arbor Acres, while it was 4% of Ross-308. The cooking loss and drip loss of breast and thigh muscles were higher in SD3 of both breeds. Moreover, SD3 possessed the highest bacterial count. In conclusion birds reared in medium stocking density revealed better performance and welfare than high density but similar to low density. Therefore, from the economic point, medium density was the best.

Effect of stocking density on performance, infection by Eimeria spp., intestinal lesions and foot pad injuries in broilers with outdoor access under tropical conditions

1. The study was carried out to evaluate the effect of stocking density on performance, litter moisture, Eimeria oocyst shedding, intestinal and foot lesions in broilers.2. A total of 192 1-d-old male Cobb broilers were distributed with three different stocking densities (6, 8 or 10 chickens/m²) with outdoor access and eight replicates in a completely randomised design over two periods. Productive parameters were measured from 3 to 7 weeks of age.3. Oocyst counts (OPG) in both excreta and litter were performed at 3, 4 and 5 weeks of age. Intestinal and foot pad lesions were evaluated at 7 weeks old. The stocking density of 6 birds/m² had the highest body weights (P < 0.05) (2129 ± 37.67, 2759 ± 50.82 and 3167 ± 75.64 g at weeks 5, 6 and 7 of age, respectively).4. Feed intake decreased with increasing stocking density at week 3 (r = -0.57), 4 (r = -0.48), 5 (r = -0.84), 6 (r = -0.68) and 7 (r = -0.65) of age (P < 0.05). Birds with stocking densities of 8 and 10/m² consumed, respectively, up to 11% and 19.5% less feed than the lower stocking density groups.5. Stocking density affected (P < 0.05) feed conversion (1.61, 1.49 and 1.46) and litter moisture (40.88, 52.60 and 56.19%) at 3 weeks of age. Neither carcase yield nor mortality was different between densities (P > 0.05). Likewise, there was no effect of stocking density on OPG neither in excreta nor in litter, intestinal lesions, or foot pad and hock injuries (P > 0.05).6. In conclusion, the higher stocking density decreased both the feed intake and the live weight in broilers, but there were no effects in the number of Eimeria OPG in excreta or litter, neither intestinal lesions nor in foot pad injuries.

Effect of Environmental Complexity and Stocking Density on Fear and Anxiety in Broiler Chickens

Barren housing and high stocking densities may contribute to negative affective states in broiler chickens, reducing their welfare. We investigated the effects of environmental complexity and stocking density on broilers' attention bias (measure of anxiety) and tonic immobility (measure of fear). In Experiment 1, individual birds were tested for attention bias (n = 60) and in Experiment 2, groups of three birds were tested (n = 144). Tonic immobility testing was performed on days 12 and 26 (n = 36) in Experiment 1, and on day 19 (n = 72) in Experiment 2. In Experiment 1, no differences were observed in the attention bias test. In Experiment 2, birds from high-complexity pens began feeding faster and more birds resumed feeding than from low-complexity pens following playback of an alarm call, suggesting that birds housed in the complex environment were less anxious. Furthermore, birds housed in high-density or high-complexity pens had shorter tonic immobility durations on day 12 compared to day 26 in Experiment 1. In Experiment 2, birds from high-density pens had shorter tonic immobility durations than birds housed in low-density pens, which is contrary to expectations. Our results suggest that birds at 3 weeks of age were less fearful under high stocking density conditions than low density conditions. In addition, results indicated that the complex environment improved welfare of broilers through reduced anxiety.

Welfare of broiler chickens reared in two different industrial house types during the winter season in Southern Brazil

1. The following trial compared broiler chicken welfare in closed-sided (CS) versus open-sided (OS) industrial house types during the winter season in the South of Brazil.2. Ten flocks in each house type were evaluated as follows: a) bird health: contact dermatitis on the breast and abdominal areas (CDE), bird soiling (BSO), footpad dermatitis (FPD), hock burn (HBU), lameness (LAM), fractures (FRA), bruising (BRU), scratches (SCR), dead on arrival (DOA), and diseases (DIS); b) house environmental measurements: relative humidity (RHU), temperature (TEM), air velocity (AVE), illuminance (ILL), ammonia concentration (NH₃), and carbon dioxide concentration (CO₂), and c) bird behaviour and affective states: bird behaviour (BBE), touch test (TTE), and qualitative behaviour assessment (QBA).3. Statistical analyses were based on regression models for CDE, BSO, FPD, HBU, LAM and generalised linear models for DOA, FRA, BRU, SCR, and DIS. The Mann-Whitney test was used for RHU, TEM, AVE, ILL, NH₃, CO₂, and the t-test for TTE and LMO, with a specific regression model for BBE data and Principal Component Analysis for QBA.4. According to odds ratio for worse scores for CS relative to OS, birds were less likely to have severe scores for CDE (P = 0.040 and P = 0.007), BSO (P = 0.031, P = 0.016, and P = 0.038), and HBU (P = 0.017), and had higher median values for AVE (2.3, 0.0-7.8 m s^-1 vs. 0.0, 0.0-4.3 m s^-1), lower NH₃ concentration (9.0, 0.0-64.0 ppm vs. 12.0, 0.0-60.0 ppm) and TTE scores (98, 96-100 vs. 67, 25-100). Worse results were observed in CS houses for higher stocking density (13.8 ± 0.2 birds/m² vs. 12.0 ± 0.2 birds/m²), RHU (74.5, 50.7-99.9% vs 72.3, 47.4-99.9%), and TEM (23.9, 14.6-29.2°C vs. 21.7, 12.9-30.1°C), lower ILL (16.0, 1.0-60.0 lx vs. 161.0, 8.0-2380.0 lx), less drinking (P = 0.007), more inactive behaviour (P < 0.001) and lower positive emotions, according to QBA (P = 0.028).5. In the studied region and season, CS houses seemed to offer fewer welfare problems in terms of the health indicators; however, OS houses showed fewer behavioural restrictions and higher positive emotional states.

Effect of stocking density on performance, meat quality and cecal bacterial communities of yellow feather broilers

Totally, 315 42-day-old male Xueshan chickens were allocated into 3 caging densities, 14, 21 and 28 birds/m². Each treatment was represented by 5 replicates. The body weight (BW), slaughter performance, meat quality, behavioral assessment, and the cecal microorganisms were detected at the market age. The results showed that the BW of broilers in the low- and medium-density groups was significantly higher (p < 0.05) than that of the high-density group from the age of 10 weeks. Only the feather quality of the broilers in the low-density group improved significantly (p < 0.05) compared with those of the other two groups. And, the abdominal fat percentage and the fat content of thigh muscle of broilers in the low- and medium-density groups were higher (p < 0.05) than those in the high-density group. No significant difference (p > 0.05) was noted in the other traits. The abundance of some microbial like Akkermansiaceae, Lactobacillaceae and Faecalibacterium may be correlated with the BW and fat content of broilers. The findings of this study suggest that increasing the stocking density decreased the final BW, fat content and the feather quality, whereas no evidence was found that stocking density caused changes in other parameters.

Slow-growing broilers are healthier and express more behavioural indicators of positive welfare

Broiler chicken welfare is under increasing scrutiny due to welfare concerns regarding growth rate and stocking density. This farm-based study explored broiler welfare in four conditions representing commercial systems varying in breed and planned maximum stocking density: (1) Breed A, 30 kg/m²; (2) Breed B, 30 kg/m²; (3) Breed B, 34 kg/m²; (4) Breed C, 34 kg/m². Breeds A and B were ‘slow-growing’ breeds (< 50 g/day), and Breed C was a widely used ‘fast-growing’ breed. Indicators of negative welfare, behavioural indicators of positive welfare and environmental outcomes were assessed. Clear differences between conditions were detected. Birds in Condition 4 experienced the poorest health (highest mortality and post-mortem inspection rejections, poorest walking ability, most hock burn and pododermatitis) and litter quality. These birds also displayed lower levels of behaviours indicative of positive welfare (enrichment bale occupation, qualitative ‘happy/active’ scores, play, ground-scratching) than birds in Conditions 1–3. These findings provide farm-based evidence that significant welfare improvement can be achieved by utilising slow-growing breeds. There are suggested welfare benefits of a slightly lower planned maximum stocking density for Breed B and further health benefits of the slowest-growing breed, although these interventions do not offer the same magnitude of welfare improvement as moving away from fast-growing broilers.