Movement of broiler chickens reared in commercial conditions

Large variation in the movement of individual broiler chickens tracked in a commercial house using ultra-wideband backpacks

Our understanding of the movement patterns of individual broiler chickens in large flocks is extremely limited. Here we report the use of a Real Time Locating System to track individual broilers in a house of 28 000 birds. Broilers were fitted with backpacks containing ultra-wideband tags on day 21 (N = 8 broilers) or day 24 (N = 9 broilers), with tags recording positioning and distance data until Day 38. Tagged birds were penned overnight on Day 31 to avoid 'thinning'. We found no clear evidence of broilers consistently creating similar sized "home ranges". Some broilers spent most time < 10 m from where they were originally found while others visited at least 90% of the house in the period before thinning. While some broilers rapidly returned to the area they were collected from at thinning, the majority did not. Movement data suggested that broilers that restricted themselves to smaller areas of the house were not necessarily less active. Although there was an average reduction in movement with age, this was not linear and there was individual variation. There was also no clear association between movement patterns and broiler weight or gait score, suggesting a more complicated relationship between activity, ranging and some welfare measures.

Broiler Chickens On-Farm Welfare Assessment: Estimating the Robustness of the Transect Sampling Method

Assessing commercial broiler chickens' welfare usually comes at the cost of reduced precision due to the large flock sizes and required time commitments. The transect method for on-farm welfare assessment is conducted by walking within delimited paths between feeder and drinker lines within the commercial house, referred to as transects. This non-invasive method is conducted by detecting birds with signs of impaired welfare indicators, which include leg problems, sickness, body wounds, and feather dirtiness. The transect method has been validated for commercial turkey flocks but not for broiler chickens due to the large flock sizes. The aim of this study was to evaluate the robustness of the transect method in broiler chicken flocks through a capture-recapture approach of a known subpopulation of 80 birds. Groups of 10 chickens were captured and individually marked in eight locations of the house. Two observers collected the number and position of the detected marked birds while walking along non-adjacent transects (four samplings/house/day) during the two following days. Detection and repetition rates per house, and within transects, were calculated, as well as the effects of flock density, transect number/house (six vs. eight), and sampling time (morning vs. afternoon). The number of traveled transects was calculated for birds detected more than once, and the population random distribution was tested by comparing the number of observed and expected birds/transect. Results showed more than 64% of detection rate with a repetition rate/house sampling of 24% and per transect of 1.66%. Higher repetition rates in six-transect houses and during morning samplings were detected. The number of traveled transects was higher in eight-transect houses and from birds first detected at walls, indicating longer traveled distances in wider houses. In addition, bootstrapping techniques were used to calculate the optimal sampling effort. Our findings indicate that the lowest repetition rates and optimal sampling can be achieved by assessing two transects, being one wall and one central, separated by three transects in between. Such sampling procedure would provide robust results for welfare assessment of commercial broiler chicken flocks.

Walking Behaviour and Spatial Use of Broiler Chickens

Modern broiler chickens are genetically selected for reaching higher weights in shorter life spans. In addition to this, they are raised in crowded housing conditions with less opportunity for movement. Understanding movement patterns, migration and use of space is essential in determining welfare of the birds in commercial farms. In this study, migration behaviour of broiler chickens in semi-commercial farms of 1800 chickens was studied. Observations were repeated in six growth periods each on 12 chickens once a day during their growth period of 42 days. It was seen that the activity of broilers was not decreasing during the growth period. Travelled distances of the chickens in total were not reduced in the last 3 weeks of their growth period (p > 0.05 in 89% of the observed birds, Mann-Whitney U test). Chickens preferred to be in the zones next to the wall farthest to the entrance of the house. The observed birds did not restrict themselves only around the feeders and the drinkers but used the whole surface area available during the whole growth period. The results of the study seem to be encouraging in achieving welfare of broiler chickens even in commercialised houses with high stocking density. Reported mobility of chickens is important for their survival and has therefore considerable impact on efficient production on farms.

Peck orders and group size in laying hens: `futures contracts' for non-aggression

We analyse a simple model of the establishment and maintenance of dominance hierarchies in hens. To be beneficial, dominance relationships require that the probability of meeting the same individual repeatedly is high, otherwise costs of establishing the dominance relation are never recouped. Winners and losers benefit from dominance relationships, not necessarily from changing the rate at which they acquire resources but by avoiding costly contests over them in future encounters. We show that so-called `loser effects', in which animals base their strategies for contesting resources solely upon their past experiences of winning or losing dominance fights and not upon who their opponent is, cannot work - these strategies (`pragmatists') must additionally involve either individual or status category recognition. As alternatives to dominance relationships, we show that signals of status or fighting ability that determine access to contested resources are expected to evolve in species with typically large groups because in such conditions the costs of establishing dominance relations are not recouped. Such signals do not depend upon recognizing others individually, but rather upon general category recognition. Status signals are not expected in small groups because dominance relationships are likely to be cheaper and just as effective. The results of the model have implications for the welfare of hens kept in large groups.

A comparison of transmission characteristics of Salmonella enterica serovar Enteritidis between pair-housed and group-housed laying hens

Human cases of bacterial gastro-enteritis are often caused by the consumption of eggs contaminated with Salmonella species, mainly Salmonella enterica serovar Enteriditis (Salmonella Enteritidis). To reduce human exposure, in several countries worldwide surveillance programmes are implemented to detect colonized layer flocks. The sampling schemes are based on the within-flock prevalence, and, as this changes over time, knowledge of the within-flock dynamics of Salmonella Enteritidis is required. Transmission of Salmonella Enteritidis has been quantified in pairs of layers, but the question is whether the dynamics in pairs is comparable to transmission in large groups, which are more representative for commercial layer flocks. The aim of this study was to compare results of transmission experiments between pairs and groups of laying hens. Experimental groups of either 2 or 200 hens were housed at similar densities, and 1 or 4 hens were inoculated with Salmonella Enteritidis, respectively. Excretion was monitored by regularly testing of fecal samples for the presence of Salmonella Enteritidis. Using mathematical modeling, the group experiments were simulated with transmission parameter estimates from the pairwise experiments. Transmission of the bacteria did not differ significantly between pairs or groups. This finding suggests that the transmission parameter estimates from small-scale experiments might be extrapolated to the field situation.

Effects of social rank and familiarity on dustbathing in domestic fowl

The objective of this study was to investigate the effects of social rank (Experiment 1) and familiarity (Experiment 2) on dust-bathing in domestic hens (Gallus gallus domesticus). We conducted choice tests between two conditions using actual birds as the stimuli and evaluated the effects in terms of quality and quantity of dustbathing performed. Twenty-four, medium-ranked hens were selected as test subjects. The stimuli presented were combinations of a high-ranked hen, a low-ranked hen, or no hen at all for Experiment 1, and a combination of a familiar hen, an unfamiliar hen, or no hen for Experiment 2. The number and duration of dustbaths, wing tosses as well as other behaviours were measured. For Experiment 1, the test hen performed dustbathing more frequently on the side of the hen, regardless of its social rank, when presented with a choice of a high- or low-ranked hen, or no hen. For Experiment 2, the test hen performed dustbathing more frequently on the side of the familiar hen when presented with a familiar hen or no hen, and more frequently on the side of no hen when presented with an unfamiliar hen and no hen. It was concluded that dustbathing was not affected by social rank, and that the quality and quantity of dustbathing was greater on the side of the familiar hen. However, dustbathing was restricted by the presence of an unfamiliar hen.

Campylobacter jejuni colonization and transmission in broiler chickens: a modelling perspective

Campylobacter jejuni is one of the most common causes of acute enteritis in the developed world. The consumption of contaminated poultry, where C. jejuni is believed to be a commensal organism, is a major risk factor. However, the dynamics of this colonization process in commercially reared chickens is still poorly understood. Quantification of these dynamics of infection at an individual level is vital to understand transmission within populations and formulate new control strategies. There are multiple potential routes of introduction of C. jejuni into a commercial flock. Introduction is followed by a rapid increase in environmental levels of C. jejuni and the level of colonization of individual broilers. Recent experimental and epidemiological evidence suggest that the celerity of this process could be masking a complex pattern of colonization and extinction of bacterial strains within individual hosts. Despite the rapidity of colonization, experimental transmission studies exhibit a highly variable and unexplained delay time in the initial stages of the process. We review past models of transmission of C. jejuni in broilers and consider simple modifications, motivated by the plausible biological mechanisms of clearance and latency, which could account for this delay. We show how simple mathematical models can be used to guide the focus of experimental studies by providing testable predictions based on our hypotheses. We conclude by suggesting that competition experiments could be used to further understand the dynamics and mechanisms underlying the colonization process. The population models for such competition processes have been extensively studied in other ecological and evolutionary contexts. However, C. jejuni can potentially adapt phenotypically through phase variation in gene expression, leading to unification of ecological and evolutionary time-scales. For a theoretician, the colonization dynamics of C. jejuni offer an experimental system to explore these 'phylodynamics', the synthesis of population dynamics and evolutionary biology.

Effects of heterogeneity in infection-exposure history and immunity on the dynamics of a protozoan parasite

Infection systems where traits of the host, such as acquired immunity, interact with the infection process can show complex dynamic behaviour with counter-intuitive results. In this study, we consider the traits ‘immune status’ and ‘exposure history’, and our aim is to assess the influence of acquired individual heterogeneity in these traits. We have built an individual-based model of Eimeria acervulina infections, a protozoan parasite with an environmental stage that causes coccidiosis in chickens. With the model, we simulate outbreaks of the disease under varying initial contaminations. Heterogeneity in the traits arises stochastically through differences in the dose and frequency of parasites that individuals pick up from the environment. We find that the relationship between the initial contamination and the severity of an outbreak has a non-monotonous ‘wave-like’ pattern. This pattern can be explained by an increased heterogeneity in the host population caused by the infection process at the most severe outbreaks. We conclude that when dealing with these types of infection systems, models that are used to develop or evaluate control measures cannot neglect acquired heterogeneity in the host population traits that interact with the infection process.

Evaluation of the effects of cage height and stocking density on the behaviour of laying hens in furnished cages

1. Limited information is available on how changes in horizontal and vertical space within enriched or furnished layer cages (as defined by Directive 1999/74/EC) influence hen behaviour. This study evaluated the effects of varying minimum cage heights and space allowances on the behaviour of laying hens housed in furnished cages. It was conducted on two flocks of medium brown hybrid hens housed in furnished cages with access to perches and nest boxes on a semi-commercial scale at ADAS Gleadthorpe. 2. Flock 1 consisted of two layer strains (ISA Brown and Babcock 380), housed at two minimum cage heights (38 and 45 cm) and 5 stocking densities between 609 and 870 cm2/bird, with 12 replicates of each of the 20 strain/cage height/stocking density treatment combinations. Stocking density was varied by varying the number of birds per cage from 10 to 7 in standard full-width cages or housing 7 hens in a narrower cage. As a consequence stocking density, group size and trough width per bird co-varied for 4 out of 5 stocking density treatments. 3. Behaviour of flock 1 was sampled at 33 to 36, 46 and 68 weeks of age. At each age one top-tier, one middle-tier and one bottom-tier cage was sampled for each treatment. 4. Few behavioural differences due to cage treatments were detected. Hens at 870 cm2 had shorter feeding bouts than hens at 609 and 762 cm2. Yawning was more common in the cages with greater cage height. 5. Video recordings of flock 1 examined cage height effects on hens' use of vertical space and provided additional data on stretching and self-maintenance activities. No differences in behaviour between 38 and 45 cm cages were found except that scratching head was more common in cages with greater cage height. 6. Flock 2 consisted of two layer strains (Shaver Brown and Hy-Line Brown), housed at 38 and 45 cm and 609, 762 and 1016 cm2/bird, with 18 replicates of each of the 12 strain/cage height/stocking density treatment combinations. Stocking density was varied by housing 10, 8 or 6 hens in standard full-width cages. Behaviour of flock 2 was sampled at 30, 48, 60 and 67 weeks from video recordings. Three cages per treatment from middle-tiers only were sampled at each age. 7. Hens housed at 609 cm2/hen had the longest mean feeding bout, greater than for hens at 762 cm2/hen but not hens at 1016 cm2/hen. More unsuccessful attempts to reach the feeder and sideways and backwards displacements from the feeder occurred at 762 and 609 cm2/hen than at 1016 cm2/hen. A maximum of 8 hens were observed feeding synchronously. 8. These results suggest that changes in horizontal and vertical space over the ranges we studied had little effect on behaviour other than feeding behaviour. Specifying a minimum useable trough space per hen, rather than calculating feeder space from total length of feeder per cage, irrespective of accessibility, might help avoid crowding at the feeder and associated disturbance of feeding bouts.

Stocking Density and Physiological Adaptive Responses of Broilers

Three trials were conducted to assess the effects of stocking density on physiological adaptive responses of broilers. Male broilers were reared in floor pens under conditions similar to those used commercially in the United States. Accepted indicators of adaptation to a stressor were measured on d 49 including plasma concentrations of corticosterone, glucose, cholesterol, and total nitrites as an indicator of nitric oxide, as well as heterophil:lymphocyte ratio. In trial 1, calculated stocking densities were 20, 25, 30, 35, 40, 45, 50, and 55 kg of BW/ m2 and in trials 2 and 3, stocking densities were 30, 35, 40, and 45 kg of BW/m2. Stocking densities were calculated based on a final BW of 3.3 kg. Linear trend analyses were used to assess the role of stocking density on each of the physiological parameters. Results indicate that stocking density did not cause physiological adaptive changes indicative of stress.

Quantifying transmission of Campylobacter spp. among broilers

Campylobacter species are frequently identified as a cause of human gastroenteritis, often from eating or mishandling contaminated poultry products. Quantitative knowledge of transmission of Campylobacter in broiler flocks is necessary, as this may help to determine the moment of introduction of Campylobacter in broiler flocks more precisely. The aim of this study was to determine the transmission rate parameter in broiler flocks. Four experiments were performed, each with four Campylobacter-inoculated chicks housed with 396 contact chicks per group. Colonization was monitored by regularly testing fecal samples for Campylobacter. A mathematical model was used to quantify the transmission rate, which was determined to be 1.04 new cases per colonized chick per day. This would imply that, for example, in a flock of 20,000 broilers, the prevalence of Campylobacter would increase from 5% to 95% within 6 days after Campylobacter introduction. The model and the estimated transmission rate parameter can be used to develop a suitable sampling scheme to determine transmission in commercial broiler flocks, to estimate whether control measures can reduce the transmission rate, or to estimate when Campylobacter was introduced into a colonized broiler flock on the basis of the time course of transmission in the flock.

Effects of the addition of sand and string to pens on use of space, activity, tarsal angulations and bone composition in broiler chickens

Fast-growing broiler chickens use pen-space heterogeneously and have low activity levels, related in part to leg problems. The aim of this study was to test the effects of the addition of string and sand trays to rearing pens on the use of space, levels of activity and leg problems. Broiler chickens were reared in 12 pens (40 birds per pen). Drinkers and feeders only were present in the six control pens (C group), whereas the six other pens were enriched (E group) with two sand trays and string. Behaviour was recorded by scan and focal sampling on days 2-3, 13-14, 23-24 and 34-35. Bodyweight, the occurrence of tarsal deformities and the composition of tibiotarsi were measured on day 37. Chickens from the E group spent more time and stood more often in the area enriched with sand than did the g group birds. ghickens in the E group foraged in the sand throughout the rearing period, and their foraging activities were greater than those of the C group birds. They had little interest in the strings. Locomotor activity during standing bouts was enhanced in the E group on days 2-3 only. Bodyweight at day 37, the occurrence of tarsal deformities and the composition of tibiotarsi were not significantly different between groups. These results indicate that sand could attract chickens into areas that are usually rarely used, which may reduce problems resulting from their heterogeneous distribution. However, the results also indicate the difficulty of stimulating locomotion.

Anticoccidial vaccines for broiler chickens: pathways to success

The use of live vaccines, either attenuated or non-attenuated, for the control of coccidiosis due to Eimeria infections in broiler breeder or layer chickens is well established. Use in broilers, however, has been slow to gain acceptance. This has been partly for economic reasons, but also because of perceived adverse effects on early chick growth, particularly with non-attenuated vaccines, and concerns about timely onset of protective immunity in such short-lived birds. This review describes advances in understanding of epidemiological factors and recent improvements of administration methods that have helped to allay these fears and to make the use of anticoccidial vaccines in broilers technically achievable. Topics discussed include: (1) types of commercially available vaccine, (2) vaccines in development, (3) vaccination methods and equipment, (4) basis of vaccine efficacy and immunogenic variation of parasites, (5) key factors in the survival, sporulation and dissemination of vaccinal oocysts, (6) descriptions and significance of patterns of litter oocyst accumulation and occurrence of intestinal lesions in vaccinated flocks, (7) rotation of anticoccidial vaccination and chemotherapy to restore drug sensitivity to resistant wild-type coccidia, (8) combinations of anticoccidial vaccination and chemotherapy, (9) interactions between coccidiosis and clostridiosis in broilers and compatibilities of potential control methods, (10) published performance data for live anticoccidial vaccines in broilers, (11) possible further developments of live vaccines.

Behavior of the domestic fowl in the presence of vertical panels

The effects of environmental complexity on the time budget of chickens were investigated. It was hypothesized that the provision of vertical panels to pen centers would generate additional protective areas within the pen, influencing the amount of time spent performing different behaviors. The experiment consisted of three cover treatments (mesh panels, frame panels, and no cover) and two group sizes (80 and 110). Vertical panels, constructed of polyvinyl chloride piping, were positioned in pen centers, whereas pen centers in the no-cover treatment were left empty. Drinking, dust bathing, feeding, foraging, movement, preening, resting, and standing were recorded during continuous focal sampling of 210 focal individuals from 5 to 44 d of age. Resting was the most frequent behavior accounting for over 64% of the chicken time budget. Resting time was influenced by the presence of cover (P < 0.01), and was higher in pens enriched with panels. Time spent moving and standing in the different pen regions was influenced by the presence of cover (P < 0.01) and age (P < 0.05). The presence of cover did not influence time spent feeding or drinking, but both behaviors were affected by age (P < 0.05). The presence of cover influenced time spent foraging, which occurred more often in the pens containing no panels (P = 0.05). Preening and dust bathing were the only behaviors influenced by group size (P < 0.05). These results suggest that incorporating enrichment into the environment does influence the time a chicken will spend performing different behaviors.

Influence of vertical panels on use of space by domestic fowl

In the wild, cover is used by animals to seek shelter from the elements, protection from predators and aggressive conspecifics and as a way to reduce inter-animal communication. Rearing environments for captive raised fowl often contain open areas that are lacking in complexity and that are greatly underused. As a result, use of space within pen-type enclosures is often not uniform. This paper investigates the effect of increased environmental complexity on the use of space by broilers. The experiment consisted of three cover treatments (mesh panels, frame panels and no cover) and three group sizes (80, 110 and 140). The vertical panels, constructed of PVC piping, were positioned in pen centers, while the pen centers in the no cover treatment were left empty. It was hypothesized that the provision of vertical panels to pen centers would attract birds into the central space and would lead to a more uniform distribution of birds. Using a grid-coordinate system set up in each pen, scan samples were taken on the use of space in each pen four times per day, 3 days per week from 5 to 44 days of age. Use of space in the central region for the two cover treatments was significantly higher than for the no cover treatment (P<0.0001). The effect of cover treatment on the mean percentage of birds using the central space was influenced by age (P<0.0001) and by group size (P<0.05). Differences in the use of space between the frame and mesh treatment were only found during week 1. In the side, end and middle regions surrounding the panels, use of space was influenced by cover treatment and age (P<0.0001). Over 80% of the use of pen center occurred at the ends and sides of the panels. These results support the hypothesis that the presence of vertical panels results in a more uniform distribution of birds within the pen by increasing the number of birds using the center.

The effect of a single or repeated period of high stocking density on the behavior and response to stimuli in broiler chickens

Broiler chickens are normally housed at a fixed number per unit area throughout their life, which reduces their opportunity for movement during the later stages of rearing. An experiment is described that exposed broilers to a high stocking density either once or twice in the rearing period, and investigated the effects on the birds' behavior, and the response to other birds and humans after the second exposure to high or low stocking density. The stocking density was increased from a low level (1.7 kg/m2) to a high level (14 kg/m2) for the 2nd and/or 4th wk of rearing, or left unchanged at the low level. When stocked at the low rate, the birds spent more time walking and sitting and less time dozing and sleeping. They pecked more at inanimate objects and interacted more with other birds, but this did not include aggressive interaction. The effects of stocking density on behavior were greater in Week 4 than in Week 2, but there was no evidence that exposure to a high stocking density in Week 2 influenced the birds' behavioral response to a high stocking density in Week 4. Where stocking density did affect behavior in both Weeks 2 and 4, there was evidence of the response being cumulative. The activity of birds in the presence of another bird restrained in an open field arena was greatest when they had been stocked at the low density throughout the experiment. When a familiar person was in the arena, the birds that had been stocked at the high density in Week 2 were most active, but these birds showed the longest tonic immobility when inverted in a cradle. It is concluded that a high stocking density reduces activity in broiler chickens, and that birds stocked at a high density early in the rearing period are most active in the presence of people and show the longest tonic immobility in response to a fearful stimulus.

Applications of behavior to poultry management

The application of poultry behavior to management is discussed with examples of behavior-management interactions relating to commercial poultry husbandry practices. Behaviors that are important for the adaptation of poultry to husbandry include: social behavior, aggression, sexual behavior, feeding, broodiness, cannibalism, nest site selection, and comfort behaviors.