Litter lipid content affects dustbathing behavior in laying hens

Effects of dustbathing environment on gut microbiota and expression of intestinal barrier and immune-related genes of adult laying hens housed individually in modified traditional cage

Litters, the composition of sand and peat rich in microbiota, are essential to trigger the dustbathing behavior of chickens. To investigate the effects of a dustbathing environment (DE) on the intestinal health, gut microbiota, and immune responses of laying hens, a total of 72 healthy Hy-Line Brown laying hens at 69 wk of age (WOA) were housed individually in modified traditional cages and randomly divided into 2 groups: one group had free access to litters (CT), while the other one was restricted from litters (CC). The experiment lasted for 42 d. At the end of the experiment, the intestinal histomorphology and immune status of laying hens were determined, and the 16S rRNA sequencing method was used to assess the composition of the intestinal microbial community of birds. Intestinal histomorphology changed, including villus height and villus-to-crypt ratio significantly increased in the CT group (P < 0.01). DE reshaped the microbial community and increased the microbial richness with the higher indicators of Chao1 and observed species and the comparatively abundant beta diversity (P < 0.05). Ten genera, including Faecalibacterium and Coprococcus, declined in laying hens from the CT group (P < 0.05), while Alistipes increased in CT hens (P < 0.05) compared to those hens from the CC group. The expression levels of intestinal barrier-related genes of claudin-1, claudin-4, occludin, ZO-1, and ZO-2 and immune-related genes of IL-4, IL-6, IL-8, IFN-γ, IgA, TLR-2, and TLR-4 were significantly upregulated in the intestine of laying hens in CT group (P < 0.05). DE also increased the serum levels of IL-4, IL-6, IL-8, IFN-γ, and IgA (P < 0.01). The alteration of the gut microbiota by DE is closely related to host immune responses, including Lactobacillus positively correlated with IL-4 and IgA. Thus, a dustbathing environment can improve the welfare of laying hens by changing the intestinal histomorphology, immune response, and the gut microbial community.

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.

Floor Substrate Preferences of Chickens: A Meta-Analysis

Environmental enrichment promotes sensory and motor stimulation for species-typical behaviors, which in turn enhance animal well-being. For farmed Galliformes, housing systems often limit enrichment to bedding and litter, that simultaneously act as material for dustbathing and foraging. Therefore, this meta-analysis sought to systematically review and synthesize the substrate preference test literature for Galliformes. Data based on the following four welfare-related behaviors were extracted for analysis: (1) dustbathing, (2) foraging, (3) pecking, and (4) time spent on a given substrate. Literature searches in CAB Direct, Web of Science, and Google Scholar yielded 239 articles, and hand searching yielded an additional five articles. Ten publications that used different chicken strains as test subjects, met the criteria to be included in the systematic review. The effects of bedding type, the number of days birds had access to tested substrates, enclosure area, and substrate area, on the examined behaviors were determined. We found that birds preferred dustbathing in sand and peat moss more than on any other substrates. The bedding type, size of the enclosure, and size of the substrate area affected the amount of time that birds spent on the tested substrates. When provided the choice between bedding materials, birds spent more time on sand or peat moss than on any other substrate or on no substrate. Notably, most studies did not report relevant physical or chemical characteristics of substrate that may influence birds' preferences, such as grain size, moisture content and the level of soiling. Focusing future studies on identifying substrate characteristics that influence preferences can lead to the discovery of new, practical, enriching beddings that can be easily implemented in housing systems for Galliformes.

Dust bathing in laying hens: strain, proximity to, and number of conspecifics matter

As housing laying hens in aviaries becomes more common, understanding relationships between social context and performance of key behaviors, such as dust bathing (DB), is important. Expression of behaviors may be increased or repressed by the presence of conspecifics, and degree of behavioral synchrony can affect per hen resource allocation. We investigated relationships between number of hens on litter, number of hens simultaneously DB, and interbird distances (IBD) on space used to DB and duration of DB bouts across 4 laying hen strains (Hy-Line Brown [HB], Bovan Brown [BB], DeKalb White [DW], and Hy-Line [W36]) at 28 wk of age. Brown hens needed more space to DB than white hens (HB 1125.26; BB 1146.51 vs. DW 962.65; W36 943.39 cm²; P < 0.01). More white hens occupied litter at once (43 DW, 41 W36 vs. 28 HB, 31 BB; P < 0.01), and more white hens DB simultaneously than brown hens (11 DW, 19 W36 vs. 4 HB, 4 BB; P < 0.01). Brown hens had larger average IBD (HB 13.99, BB 15.11 vs. DW 8.39, W36 7.85 cm; P < 0.01) and larger minimum IBD (HB 6.76, BB 7.35 vs. DW 1.63, W36 1.79 cm; P < 0.01) but shorter DB durations than white hens (HB 7.37, BB 9.00 vs. DW 13.91, W36 15.16 min; P < 0.01). White hens' DB area decreased if number of hens on litter increased (DW 0.85; W36 0.79 cm; P < 0.05) or minimum IBD decreased (DW 3.66, W36 2.98 cm; P < 0.01). Brown hens' DB bout duration decreased as number of hens on litter increased (HB 0.87, BB 0.95 min; P < 0.01), number of other hens DB increased (HB 0.75, BB 0.69 min; P ≤ 0.02), or minimum IBD decreased (HB 2.39, BB 2.31 min; P < 0.01). In response to smaller IBD and more hens on litter simultaneously, DW and W36 hens minimize DB area while BB and HB hens shorten DB bouts, potentially terminating bouts before fulfilling their needs. Variations in DB behavior among strains should be considered when planning and stocking laying hen aviaries.

How does the presence of excreta affect the behavior of laying hens on scratch pads?

Enriched cages for laying hens provide scratch pads for foraging on the wire mesh floors. Apart from foraging on scratch pads, hens also defecate on these pads, causing them to become soiled with excreta. This study was conducted to determine the relative preference of laying hens for foraging on clean (C) scratch pads or scratch pads soiled with excreta (E), and to study the behaviors performed by hens on such pads. A total of 288 laying hens was housed in 16 enriched cages (18 hens/cage), each divided into 2 compartments. On a daily basis, half of the scratch pads (one in each compartment) were removed and cleaned, while the other half were cleaned and then covered with 550 g (0.35 g/cm2) of conspecific excreta. The C and E scratch pads were then put back into the cages in a systematic order to avoid side bias. Feed was delivered automatically onto the scratch pads as a litter substrate. The frequency of visits and the total time spent performing different behaviors on C and E pads were video-recorded [the time of video recording was relative to litter (feed) delivery on the scratch pads] for a total of 10 min/d, 3 times/wk, over a period of 4 weeks. Overall, the allocation of the time budget for different behaviors was found to be-in order of greatest to least amount of time-resting, locomotor behaviors (walking and running), foraging, and dust bathing. Laying hens showed a relative preference for E scratch pads by visiting them more frequently (P = 0.001), and spent more time (P = 0.035) foraging on them, whereas they rested for more time (P < 0.001) on C scratch pads. The relative preference for E scratch pads during foraging signifies the innate importance of foraging substrates in enriched cages for laying hens. Similarly, the longer use of C scratch pads for resting indicates the need for an ideal and clean resting surface in enriched cages.

Behavioral Differences of Laying Hens with Fractured Keel Bones within Furnished Cages

High prevalence of keel bone fractures in laying hens is reported in all housing systems. Keel fractures have been associated with pain and restricted mobility in hens in loose housing. The objective was to determine whether keel fractures were associated with activity of hens in furnished cages. Thirty-six pairs of LSL-Lite hens (72 weeks) were enrolled in the study. One hen with a fractured keel and one hen without were identified by palpation in each of 36 groups of hens housed in either 30- or 60-bird cages stocked at 750 cm²/hen. Behavioral activity of each hen was recorded by four observers blind to keel status using focal animal sampling for 10 min within a 2-h period in the morning (08:00–10:00), afternoon (12:00–14:00), and evening (17:00–19:00). All hens were observed during each of the three sample periods for 3 days totaling 90 min, and individual hen data were summed for analysis. Hens were euthanized 48 h after final observations, dissected, and classified by keel status: F₀ (no fracture, N = 24), F₁ (single fracture, N = 17), and F₂ (multiple fractures, N = 31). The percentages of time hens performed each behavior were analyzed using a mixed procedure in SAS with fracture severity, body weight, cage size, rearing environment, and tier in the model. Fracture severity affected the duration of perching (P = 0.04) and standing (P = 0.001), bout length of standing (P < 0.0001), and location (floor vs. perch) of resting behaviors (P = 0.01). F₂ hens perched longer than F₀ hens, 20.0 ± 2.9 and 11.6 ± 3.2%. F₂ hens spent less time standing, 15.2 ± 1.5%, than F₀ and F₁ hens, 20.7 ± 1.6 and 21.6 ± 1.8%. F₂ hens had shorter standing bouts (22.0 ± 4.2 s) than both F₀ and F₁ hens, 33.1 ± 4.3 and 27.4 ± 4.4 s. Non-fractured hens spent 80.0 ± 6.9% of total resting time on the floor, whereas F₁ and F₂ hens spent 56.9 ± 12.4 and 51.5 ± 7.7% resting on the floor. Behavioral differences reported here provide insight into possible causes of keel damage, or alternatively, indicate a coping strategy used to offset pain or restricted mobility caused by keel fractures.

Dust-bathing behavior of laying hens in enriched colony housing systems and an aviary system

The dust-bathing behavior of Lohmann Selected Leghorn hens was compared in 4 enriched colony housing systems and in an aviary system. The enriched colony housing systems differed especially in the alignment and division of the functional areas dust bath, nest, and perches. Forty-eight-hour video recordings were performed at 3 time-points during the laying period, and focal animal sampling and behavior sampling methods were used to analyze the dust-bathing behavior. Focal animal data included the relative fractions of dust-bathing hens overall, of hens bathing in the dust-bath area, and of those bathing on the wire floor throughout the day. Behavior data included the number of dust-bathing bouts within a predefined time range, the duration of 1 bout, the number of and reasons for interruptions, and the number of and reasons for the termination of dust-bathing bouts. Results showed that the average duration of dust bathing varied between the 4 enriched colony housing systems compared with the aviary system. The duration of dust-bathing bouts was shorter than reported under natural conditions. A positive correlation between dust-bathing activity and size of the dust-bath area was observed. Frequently, dust baths were interrupted and terminated by disturbing influences such as pecking by other hens. This was especially observed in the enriched colony housing systems. In none of the observed systems, neither in the enriched colony housing nor in the aviary system, were all of the observed dust baths terminated “normally.” Dust bathing behavior on the wire mesh rather than in the provided dust-bath area generally was observed at different frequencies in all enriched colony housing systems during all observation periods, but never in the aviary system. The size and design of the dust-bath area influenced the prevalence of dust-bathing behavior in that small and subdivided dust-bath areas reduced the number of dust-bathing bouts but increased the incidence of sham dust bathing on the wire mesh.

Effect of substrate provision on performance and behaviour of laying hens in the pecking and scratching area of furnished cages

1. An experiment was set up to study the effects of substrate provision on performance and behaviour in the pecking and scratching area (PSA) of non-beak-trimmed hens housed in large furnished cages (60 hens/cage). 2. Three layer hybrids (two brown and one white, ISA-Hendrix Genetics, France) and two substrate conditions (with or without wheat bran automatically distributed on the PSA) were compared in a 3 × 2 experimental design with 12 cages per treatment. 3. Substrate distribution improved laying rate with no impact on the frequency of dirty or cracked eggs. 4. Substrate distribution improved the viability and body integrity of hens, which were not beak-trimmed. 5. Distribution of substrate tended to increase the number of hens in the PSA and enhanced their pecking and scratching behaviours but had a negative impact on the number of dust bath bouts per cage and encouraged dust bathing on the wire floor close to the feeder. 6. The white hens laid more eggs in the nest than the brown birds and used the PSA more for pecking, scratching and dust bathing at the end of the day than the brown hens, underlining the necessity to adapt cage furnishing and rearing management to specific behaviours of each layer genotype.

Dustbathing in food particles does not remove feather lipids

Within the European Union, dustbathing material in cage-housing systems for laying hens became compulsory in 2012. In practice, most producers use food particles as litter substrate. The feed is dropped in small amounts on scratching mats by an automatic transporting system. However, because dustbathing behavior is meant to remove stale lipids from hens' plumage, food particles may not be a suitable substrate due to their fat content. This study analyzes feather lipid concentration (FLC) of laying hens with access to food particles (F) or lignocellulose (L) as litter substrates. In each of 2 identical trials, 84 laying hens of 2 genotypes (Lohmann Selected Leghorn, Lohmann Brown) were kept in 12 compartments (7 hens each). Compartments were equipped with a grid floor and additionally contained a closed dustbathing tray holding F or L. Feather samples (150 feathers) were taken 2 times throughout the experiment. At 23 wk of age, 4 hens per compartment were sampled after they were allowed pair-wise access to a dustbath for 2.5 h and 3 hens were sampled without access to a dustbathing tray (control). After 10 wk of free access to the dustbathing trays, all hens were sampled again. In trial 2, an additional third sampling was made after dustbaths had been closed again for 6 wk. Here, 6 hens per compartment were sampled immediately before and after a dustbath. Dustbathing in F resulted in higher FLC compared with L and control (P < 0.001), whereas no significant difference was found between L and control (P = 0.103). When open access to litter was provided, hens had higher FLC in F compared with L (P < 0.001). The FLC immediately after dustbathing in F was higher compared with the level before dustbathing (P < 0.001), whereas it was lower after dustbathing in L (P = 0.006). These results show that F are not suitable litter material for laying hens because they lead to lipid accumulation on the plumage.