Detection of jumping and landing force in laying hens using wireless wearable sensors.

Increased mobility of hens in noncaged housing presents possibilities for bone breakage due to crash landings from jumps or flights between perches or housing infrastructure. Because bone breakage is a welfare and economic concern, understanding how movement from different heights affects hen landing impact is important. By tracking 3-dimensional bird movement, an automated sensor technology could facilitate understanding regarding the interaction between noncage laying hens and their housing. A method for detecting jumps and flight trajectories could help explain how jumps from different heights affect hen landing impact. In this study, a wearable sensor-based jump detection mechanism for egg-laying hens was designed and implemented. Hens were fitted with a lightweight (10 g) wireless body-mounted sensor to remotely sample accelerometer data. Postprocessed data could detect occurrence of jumps from a perch to the ground, time of jump initiation, time of landing, and force of landing. Additionally, the developed technology could estimate the approximate height of the jump. Hens jumping from heights of 41 and 61 cm were found to land with an average force of 81.0 ± 2.7 N and 106.9 ± 2.6 N, respectively, assuming zero initial velocity (P < 0.001). This paper establishes the technological feasibility of using body-mounted sensor technology for jump detection by hens in different noncage housing configurations.

Comb size, shape complexity and laterality of laying hens reared in environments varying in resource choice.

The comb is an ornament involved in signalling condition in domestic fowl. We hypothesised that comb size, comb shape complexity (i.e., rugosity, the comb perimeter jaggedness), and comb laterality of laying hens would be influenced by the degree of environmental enrichment experienced during juvenile development in the form of resource choice. We conducted a 2 × 2 factorial crossover experiment with pullets reared in pens containing four perches of equal length and four litter areas of equal size. Pullets were exposed to a single choice vs multiple choices of perch and litter types (i.e., all the same vs all different) during Weeks 1-4 (Period 1) and/or Weeks 5-15 (Period 2) of rearing (n = 4 pens/treatment combination) prior to transfer to standard adult laying pens for Weeks 16-27 (Period 3). In Week 27, combs were photographed, and comb laterality (hanging on left or right side) was noted. Using a custom-made image analysis programme, we captured comb area (mm2), perimeter length (mm), and rugosity ((perimeter length - horizontal length) / horizontal length) from comb photographs of 6-7 randomly selected hens/pen. We predicted that hens reared in the multi-choice environment during Periods 1 and 2 would have larger, more complex, and left-side-biased combs than those in the other treatment groups, reflecting lower allostatic load. The predicted comb side bias was based on a possible bias in head posture/movements associated with greater right eye/ear use and left-brain hemispheric dominance. Contrary to our predictions, we detected an overall right-side bias in comb laterality, and no associations between resource choice treatment in Period 1 or Period 2 and comb area, perimeter length, rugosity, or laterality of the adult hens. Thus, variation in allostatic load resulting from the rearing treatments was insufficient to modify the trajectory of comb morphological development, possibly due to a ceiling effect when comparing environmental treatments on the positive end of the welfare spectrum. We found that left-lopping combs had shorter perimeters than right-lopping combs. However, among hens with left-lopping combs, those with larger combs were heavier and had less feather damage, while among hens with right-lopping combs, those with longer-perimeter combs were heavier and tended to have less comb damage. In conclusion, comb characteristics were related to physical condition at the individual level but did not serve as sensitive integrated indicators of hen welfare in response to basic vs enhanced resource choice during rearing.

Enhancing their quality of life: environmental enrichment for poultry.

Providing environmental enrichments that increase environmental complexity can benefit poultry welfare. This Poultry Science Association symposium paper is structured around four themes on 1) poultry preferences and affective states 2) species-specific behavior, including play behavior and the relationship between behavior, activity level and walking ability, 3) environmental enrichment and its relationship with indicators of welfare, and 4) a case study focusing on the application of enrichments in commercial broiler chicken production. For effective enrichment strategies, the birds' perspective matters most, and we need to consider individual variation, social dynamics, and previous experience when assessing these strategies. Play behavior can be a valuable indicator of positive affect, and while we do not yet know how much play would be optimal, absence of play suggests a welfare deficit. Activity levels and behavior can be improved by environmental modifications and prior research has shown that the activity level of broilers can be increased, at least temporarily, by increasing the environmental complexity. However, more research on impacts of enrichments on birds' resilience, on birds in commercial conditions, and on slow(er)-growing strains is needed. Finally, incorporating farmers' expertise can greatly benefit enrichment design and implementation on commercial farms.

The effect of cage and house design on egg production and egg weight of White Leghorn hens: an epidemiological study.

Hen performance can be affected by many interacting variables related to cage design, such as floor area, height, tier arrangement, and feeder and drinker type and placement within the cage. Likewise, features of house design such as waste management and lighting can also affect hen productivity. The influence of these design aspects on hen performance has not been fully assessed. Determining the effects of numerous, interacting variables is impractical in a traditional experiment; therefore, an epidemiological approach, using variability in cage and house design among and within commercial producers, was employed to identify features that affect egg production and egg weight. A universal cage measurement system was created to calculate cage design variables. A database for recording information on cage design, resource location, waste management, environmental conditions, and hen productivity was developed. Production outcomes were assessed from placement to 60 wk of age in White Leghorns (n = 165-168 houses). Using GLM, a statistical model was identified that best described the variance in egg traits. Eggs/hen-housed increased with greater feeder space allocation (P = 0.031); taller cages (P = 0.029); rear (vs. front) drinker location in vertical cages (P = 0.026); and regular removal of manure from the house (P = 0.005). Case weight of eggs was greater in A-frame houses where manure was removed regularly instead of being left in the house (P < 0.001); with increasing cage floor slope (P = 0.001); in cages where drinkers were placed more toward the front or back of the cage as compared with the middle of the cage (P < 0.001); with more space/hen (P = 0.024); and with higher caloric intake (P < 0.001). Perhaps because of its negative correlation with egg production, case weight of eggs increased with less feeder space allocation (P = 0.004) and shorter cage heights (P < 0.001). These results reveal important effects of feeder space, floor space, cage height, drinker position, and waste management on hen productivity.

Hen welfare in different housing systems.

Egg production systems have become subject to heightened levels of scrutiny. Multiple factors such as disease, skeletal and foot health, pest and parasite load, behavior, stress, affective states, nutrition, and genetics influence the level of welfare hens experience. Although the need to evaluate the influence of these factors on welfare is recognized, research is still in the early stages. We compared conventional cages, furnished cages, noncage systems, and outdoor systems. Specific attributes of each system are shown to affect welfare, and systems that have similar attributes are affected similarly. For instance, environments in which hens are exposed to litter and soil, such as noncage and outdoor systems, provide a greater opportunity for disease and parasites. The more complex the environment, the more difficult it is to clean, and the larger the group size, the more easily disease and parasites are able to spread. Environments such as conventional cages, which limit movement, can lead to osteoporosis, but environments that have increased complexity, such as noncage systems, expose hens to an increased incidence of bone fractures. More space allows for hens to perform a greater repertoire of behaviors, although some deleterious behaviors such as cannibalism and piling, which results in smothering, can occur in large groups. Less is understood about the stress that each system imposes on the hen, but it appears that each system has its unique challenges. Selective breeding for desired traits such as improved bone strength and decreased feather pecking and cannibalism may help to improve welfare. It appears that no single housing system is ideal from a hen welfare perspective. Although environmental complexity increases behavioral opportunities, it also introduces difficulties in terms of disease and pest control. In addition, environmental complexity can create opportunities for the hens to express behaviors that may be detrimental to their welfare. As a result, any attempt to evaluate the sustainability of a switch to an alternative housing system requires careful consideration of the merits and shortcomings of each housing system.

The effect of feeder space allocation on behavior of Hy-Line W-36 hens housed in conventional cages.

Insufficient feeder space for laying hens could increase competition at the feed trough, resulting in exclusion of low-ranking hens from the feeder. To test this hypothesis, the effects of feeder space allocation (FSA) on feeding behavior, aggression, feather scores, BW, and mortality were evaluated in a common commercial strain of egg-laying chickens. Beak-trimmed Hy-Line W-36 hens (n = 480) were obtained as pullets at 16.5 wk of age and housed in conventional cages on 4 tiers. Five pullets/cage were housed at a stocking density of 434 cm(2)/pullet and an FSA of 12.2 cm/pullet. After 1.5 wk of acclimation, baseline measurements were taken for 2 wk and then pullets were given either 5.8, 7.1, 8.4, 9.7, 10.9, or 12.2 cm of feeder space/hen (16 cages/treatment). Feeding behavior was evaluated in each cage over a 24-h period each month. For each hen, percentage of time spent feeding and synchrony (mean number of additional hens feeding at the same time) were determined and scores were averaged for each cage. For each cage, feeder switching (number of observations in which hens changed from feeding to not feeding) and feeder sharing (probability that feeder access was equally distributed among all hens) were calculated. At monthly intervals, individual hens were weighed and their feathers scored using a 5-point scale on 8 body regions. Data were analyzed using a repeated measures GLM incorporating cage, tier, FSA, and age of the hen. Hens with reduced feeder space spent less time feeding (P < 0.001), synchronized their feeding bouts to a lesser extent (P < 0.001), made fewer switches at the feeder (P < 0.001), and shared the feeder less (P < 0.001). However, feather scores, BW, and BW uniformity were not affected by FSA. There was almost no aggressive behavior and little mortality. These results demonstrate that Hy-Line W-36 hens did not respond to reduced feeder space by aggressively excluding cage-mates from the feeder but instead desynchronized their feeding behavior.

The effect of feeder space allocation on productivity and physiology of Hy-Line W-36 hens housed in conventional cages.

Insufficient feeder space for laying hens could increase competition at the feed trough, leading to disrupted feeding, inadequate nutrient intake, stress, and reduced productivity. The effects of feeder space allocation (FSA) on physiology and productivity were evaluated in beak-trimmed Hy-Line W-36 hens (n=480). They were obtained at 16.5 wk of age and housed on 4 tiers of shallow conventional cages. Five pullets/cage were housed at a stocking density of 434 cm2/hen and a feeder space of 12.2 cm/hen. After 1.5 wk of acclimation, baseline measurements were taken for feed utilization, bone mineralization, and heterophil:lymphocyte ratios. At 20 wk of age, pullets were given 5.8, 7.1, 8.4, 9.7, 10.9, or 12.2 cm of feeder space/bird (16 cages/treatment). Physiological and production measures were calculated monthly or twice a month for 12 mo. The heart, spleen, and right adrenal gland were collected from each hen at the end of the study. Data were analyzed using a repeated measures GLM incorporating cage, tier, FSA, and hen age. There were no effects of FSA on total egg production, bone mineral density, bone mineral content, heterophil:lymphocyte ratios, or organ weights. Hens with reduced FSA utilized more feed (P<0.001), had poorer feed conversion (P<0.001), and laid eggs with slightly thicker and heavier shells (P<0.001). There were effects of FSA on total egg weight (P<0.001) and hen-day egg production (P<0.001), but they were of low magnitude and not linear (P>0.05). Because BW was similar among FSA treatments, the results suggest that reduced feeder space did not limit feed intake. In addition, reduced FSA did not lower bone mineralization or cause physiological stress in W-36 hens housed in shallow cages, suggesting that it did not impair hen welfare. However, it did result in poorer feed efficiency, possibly related to greater feed wastage, predictive of an adverse economic effect from reducing feeder space.

Appearance matters: artificial marking alters aggression and stress.

Artificial marking of animals for identification is frequently employed by researchers in the behavioral, biomedical, agricultural, and environmental sciences. The impact of artificial marking on experimental results is rarely explicitly considered despite evidence demonstrating that changes in phenotypic appearance can modify animal behavior and reproductive success. Here we present evidence that artificial marking of individuals within a social group has frequency-dependent effects on the behavior and physiology of domestic fowl (Gallus gallus domesticus). We demonstrate that when only 20 or 50% of individuals within a group were artificially marked, the marked birds received more aggression and had lesser body mass than the unmarked individuals within the same group. Furthermore, in groups in which only a small proportion of the individuals were marked, we report altered plasma epinephrine and dopamine levels in marked individuals. These effects of marking were imperceptible when all birds in a group were marked. This finding has important implications for animal research because, when only a subset of group members is artificially marked and used for data collection, the results obtained may not be representative of the population.

Avian vitreous humor concentrations of inosine, hypoxanthine, xanthine, uric acid, uracil and uridine as influenced by age and sex: their relevance as indicators of ante-mortem hypoxia.

An investigation was made to determine the effects of age and sex on postmortem concentrations (mumol/l) of inosine, hypoxanthine, xanthine, uric acid, uracil and uridine in the vitreous humor of chickens (Gallus domesticus). Five male and 5 female chickens were sampled each week from 0-10 weeks of age. Samples were collected at 0 and 24 h postmortem and analysed by HPLC. Hypoxanthine, uric acid and uridine were detected at both 0 and 24 h postmortem whereas inosine, xanthine and uracil were detected only at 24 h postmortem. Neither sex nor the sex X age interaction influenced the concentrations of the compounds investigated (P greater than 0.01). Age had a significant influence on the concentrations of all compounds at 24 h postmortem (P less than 0.0001). At 0 h postmortem, age significantly affected the levels of hypoxanthine and uridine (P less than 0.0001) but not uric acid (P = 0.014). All compounds occurred at higher concentrations at 24 than 0 h postmortem with the exception of uridine at 0 and 1 week of age. Previous studies using data confounded by age and postmortem sampling time have concluded that postmortem vitreous humor hypoxanthine concentration is a useful indicator of antemortem hypoxia. The results of this study cast doubt on that conclusion. Age and postmortem sampling time should be rigorously controlled when conducting quantitative analyses of these compounds in vitreous humor.

Effect of group size on tonic immobility in laying hens.

It has been shown that duration of tonic immobility (TI) reflects predation risk and levels of fearfulness. Since the chances of escaping predation are higher in larger groups, birds from these groups should have shorter TI duration. On the other hand, increased competition between birds in larger groups might lead to greater fearfulness and longer TI in larger groups. The aim of this study was to test these two hypotheses. Laying hens raised in floor pens in group sizes of 15, 30, 60 and 120, each with four replicates, were used. Tonic immobility tests were performed on adult birds, either directly 'in' their home pen or 'out' in a separate room. In the test 'in', duration of TI increased with group size, with a significant difference between group sizes 15 and 120 (P=0.012). In the test performed 'out', there was a trend for TI to be longer in larger groups. The duration of TI in groups tested 'in', was significantly shorter than in groups tested 'out' (P<0.00l). The results of this study suggest that although the ultimate function of TI is to reduce predation, the social environment is a proximate factor affecting TI duration in domestic hens.

Playful behaviour of piglets.

Domestic piglets living in multi-litter groups with their dams and other pigs in a large, socially and ecologically rich outdoor enclosure were observed, to obtain a quantitative description of the frequencies and sequences of behaviour patterns performed during play. Focal animal sampling was used to collect data on the playful behaviour of 14 male and 21 female piglets from birth to 14 weeks of age. The "play markers" hop, scamper, pivot, toss head, shake object and carry object were used to identify playful behaviour sequences. The variety of different behaviour patterns performed in first order transitions with play markers was highest in the first 6 weeks and declined thereafter with increasing age. Behaviour patterns occurring in transitions with play markers significantly more often than expected included stand, walk, trot, gallop, freeze, shove and circle. The overall frequency of play markers was significantly affected by age, with a peak frequency occurring between 2 and 6 weeks of age. Male and female piglets performed play markers at similar rates. Results are discussed with reference to the welfare of piglets kept in housing systems which limit playful behaviour.

Subjective and objective measurements of postoperative pain in cats.

OBJECTIVE: To evaluate the ability of various subjective and objective measurements to determine the presence and degree of postoperative pain in cats. DESIGN: Randomized controlled prospective clinical study. ANIMALS: 18 healthy client-owned cats. PROCEDURE: Cats were randomly assigned to 3 groups of 6: control, tenectomy, and onychectomy. Jugular catheters were placed the day prior to surgery. All surgeries were performed by the same surgeon, and all observations were made by the same blinded trained observer. One hour prior to surgery and at assigned intervals for 36 hours after surgery, heart rate, respiratory rate, and rectal temperature were measured. Scores were assigned for 3 interaction responses, including response to palpation, by use of simple descriptive scales, and to 2 pain assessments by use of visual analogue scales. Blood was collected to measure plasma beta-endorphin and cortisol concentrations. Butorphanol was administered to all cats before surgery and to any cat subjectively assessed to be experiencing pain after surgery. RESULTS: Only visual analogue scale scores and response to palpation scores differed significantly between control and surgical groups. CONCLUSIONS AND CLINICAL RELEVANCE: Determination of the presence of pain in cats can be made on the basis of observation and interaction by a trained observer. Physiologic measurements, including plasma cortisol and beta-endorphin concentrations, did not differentiate between control cats and cats that underwent surgery.

Influence of increasing photoperiod and toe clipping on breast buttons of turkeys.

Two 17-wk experiments compared the effects of an increasing photoperiod treatment (INC) versus a constant photoperiod treatment (23H), and intact toes versus clipped toes, on the breast button incidence and performance of heavy tom turkeys. Under INC, the photoperiod was increased gradually from 8 to 23 h between 4 and 16 wk. Under 23H, the photoperiod remained constant at 23 h. Use of INC versus 23H resulted in a significant reduction in breast button incidence at 17 wk in both experiments (P less than .05). Toe clipping had no effect on breast button incidence. The presence of breast buttons was positively correlated with body weight at 12 wk, and area of unfeathered skin over the keel at 17 wk. In Experiment 1, the photoperiod treatments had no significant effect on 17-wk body weight or mortality, but the INC treatment had an adverse effect on feed efficiency (P less than .05). In Experiment 2, turkeys reared under INC were heavier at 17 wk (P less than .05), with similar feed efficiencies. Mortality was significantly lower on INC than 23H up to 12 wk in Experiment 2 (P less than .05). Turkeys with intact toes were .44 kg heavier than turkeys with clipped toes at 17 wk in both experiments (P less than .05) and had similar feed efficiencies. Mortality to 4 wk was lower for turkeys with intact than clipped toes in Experiment 2 (P less than .05). Increasing photoperiod treatments have potential for improving turkey performance, survival, and carcass quality.(ABSTRACT TRUNCATED AT 250 WORDS)

Behavioral responses of broiler chickens to handling: effects of dietary tryptophan and two lighting regimens.

In three 2 x 2 factorial experiments, effects of added dietary Trp (0 or .2%, Experiments 1 and 2; 0 or .4%, Experiment 3) and two lighting regimens [1) constant 23-h photoperiod (23H); or 2) increasing photoperiod (INC)] on behavioral responses of broilers to handling were assessed. In Week 6 of Experiment 1, and Weeks 3 and 6 of Experiments 2 and 3, 32 chickens from each treatment were picked up and held by both legs for 30 s, carried for 60 s, and induced into tonic immobility (TI). In all experiments, chickens reared under INC were more likely to flap when carried, and flapped longer, than chickens reared under 23H (P < .01). In Experiments 2 and 3, INC chickens were more likely to curl the body ventrally when handled and were more susceptible to TI induction than 23H chickens (P < .05). The duration of TI was shorter on INC than 23H in Experiment 2 (P < .05), and longer in Experiment 3 (P < .001). Dietary Trp supplementation resulted in a lower flapping duration and higher incidence of body curling in Experiment 2 (P < .05), and a shorter TI duration in Experiment 3 (P < .05). Flapping, body curling, and TI responses of chickens varied between handlers (P < .05). Vocalization and flapping rates were lower, and flapping incidence and duration of flapping and TI higher, in Week 6 than in Week 3 (P < .05). Chickens reared under INC may be at greater risk of injury during preslaughter handling than chickens reared under 23H.(ABSTRACT TRUNCATED AT 250 WORDS)

Effects of lighting pattern and dietary tryptophan supplementation on growth and mortality in broilers.

The effect of lighting pattern and supplementation of the diet with Trp on growth and mortality of male broiler chickens was evaluated in three experiments using 2,392, 2,608, and 2,400 chickens, respectively. There were two lighting treatments, either a constant 23 h of continuous light/24-h period or an increasing photoperiod lighting system, i.e., 0 to 3 days, 23 h light (L):1 h dark (D); 4 to 14 days, 6L:18D; 15 to 21 days, 10L:14D; 22 to 28 days, 14L:10D; 29 to 35 days, 18L:6D; 36 to 42 days, 23L:1D. The design was a completely randomized 2 x 2 factorial, with four replicates per treatment. In the first two experiments, a starter diet with or without .2% supplemental L-Trp (feed grade) was fed from 0 to 3 wk of age and a finisher diet with or without .2% supplemental Trp was fed from 3 to 6 wk of age. In the third experiment, the level of supplemental Trp was .4% in the starter and finisher diet. Birds raised on the increasing light pattern consumed less feed during the first 3 wk, were lighter in weight at 3 wk, and had lower feed:gain ratios (P < .001) than their counterparts on constant light. By market age (6 wk) they had similar body weight but feed intake was significantly (P < .05) lower in all experiments, and feed:gain ratio was significantly lower in these birds in Experiment 3 (P < .05) than in their counterparts on constant light.(ABSTRACT TRUNCATED AT 250 WORDS)

Behavior of chickens prior to death from sudden death syndrome.

A study was made to determine if chickens dying from sudden death syndrome (SDS) showed any unusual behavioral characteristics during the final 12 h preceding death. Continuous video recordings were made of floor pens of 50 to 120 individually marked male broiler chickens between 3 and 10 wk of age. Behavioral data were obtained from video tapes played back following death of chickens from SDS. Analysis of the video tapes revealed no significant differences between 10 SDS chickens and their matched controls in the frequencies or proportions of time spent in each of 19 different behavioral activities. All SDS chickens exhibited a sudden attack prior to death lasting an average of 53 s and characterized by loss of balance, violent flapping, and strong muscular contractions. There was no evidence that death was preceded by a particular environmental or behavioral event. It was concluded that there were no consistent behavioral symptoms which could be used to identify SDS chickens prior to death.

Fatty acid composition of hepatic and cardiac tissue from chickens dying of sudden death syndrome.

Gas chromatographic analysis of tissue lipids from broiler chickens dying from sudden death syndrome (SDS) were carried out to determine if anomalies in fatty acid composition could be linked to the disease. Crude extracts of lipids from hearts and livers of chickens dying from SDS and their matched controls (matched for pen number, sex and time of death) were fractionated by thin layer chromatography and the phospholipid, triacylglycerol (TG) and nonesterified aliphatic carboxylic acid [C14-C22] (FA) fractions were transmethylated and analysed by capillary gas chromatography. A number of significant (P less than .05) differences in fatty acid composition were found to exist between males dying of SDS and their controls, the most notable being elevated levels of arachidonic acid in the hepatic TG and cardiac FA fractions of SDS males. Few significant differences were found between SDS females and their controls. There was a trend toward increased desaturation of cardiac and hepatic tissue lipids of male SDS chickens, although this was significant only for the hepatic TG fraction. The results did not support the hypothesis that a lack of arachidonic acid as a precursor of prostaglandin synthesis was a causative factor in the disease.

Effect of estradiol-17 beta-monopalmitate on the incidence of sudden death syndrome in male broiler chickens.

One-thousand male broiler crossbred chickens were implanted subcutaneously with 15 mg of estradiol-17 beta-monopalmitate at 2 wk of age; another 1,000 chickens served as untreated controls. Each of the treatments consisted of 8 pens of 125 chickens each. All chickens that died during the 9-wk experiment were necropsied and the incidence of sudden death syndrome (SDS), determined. There was no significant difference between treated and control groups in total mortality or in mortality attributed to SDS. Treated birds had higher feed-to-gain ratios and drank more water than controls.

Influence of light intensity on behavior and performance of broiler chickens.

The influence of two light intensity treatments, 180 and 6 lx, on behavior and performance of broiler chickens was examined in two experiments. The first experiment tested male chickens reared to 9 wk of age and the second experiment tested both sexes reared separately to 6 wk. Behavioral data were collected by scan sampling of behavior recorded on video tape. Standing, walking, and total activity were higher under the 180 lx than the 6-lx treatment (P less than .01), whereas feeding and drinking were not significantly affected by light intensity. Body weight, feed and water consumption, and feed conversion were unaffected by light intensity. Incidence of leg disorders at 6 wk and the percentage of bruised carcasses at 64 days were significantly lower under the higher light intensity treatment in the first experiment, as was mortality to 3 and 6 wk in the second experiment. No significant light intensity X sex interactions were detected. Results did not support the hypothesis that brighter lighting reduces performance due to increased chicken activity. Use of brighter lighting had no adverse effects on performance and there was some evidence that it may have a beneficial effect on welfare by reducing bruising.

Effect of alternating lights and strain on behavior and leg disorders of roaster chickens.

The effects of light treatment and strain on movement, spacial distribution, activity, and incidence of leg disorders of 4 to 10-week-old male chickens were examined in two experiments. In both, an alternating light treatment, in which high-intensity light alternated from one side of the barn to the other against a background of low intensity light, was compared with a control light treatment of continuous low intensity light supplied to both sides of the barn. Two strains were tested in each experiment. In Experiment 1, chickens responded to the alternating light between 4 and 7 weeks of age, although not between 7 and 10 weeks of age, by moving into areas of relatively high intensity light. In Experiment 2, chickens responded during both periods by moving into areas of relatively low intensity light. Bird distribution was also affected by a geographical side preference. In both experiments, activity was higher in areas of high vs. low light intensity, higher under alternating than control light, and higher for younger than older birds (P less than .05). Activity was also influenced by strain (P less than .01). Incidence of leg disorders was influenced by strain (P less than .01) but not light treatment.