Relationship between welfare and individual ranging behaviour in commercial free-range laying hens

Laying hens housed in free-range systems have access to an outdoor range, and individual hens within a flock differ in their ranging behaviour. Whether there is a link between ranging and laying hen welfare remains unclear. We analysed the relationships between ranging by individual hens on a commercial free-range layer farm and behavioural, physiological and health measures of animal welfare. We hypothesised that hens that access the range more will be (1) less fearful in general and in response to novelty and humans, (2) have better health in terms of physical body condition and (3) have a reduced physiological stress response to behavioural tests of fear and health assessments than hens that use the range less. Using radio frequency identification tracking across two flocks, we recorded individual hens’ frequency, duration and consistency of ranging. We also assessed how far hens ventured into the range based on three zones: 0 to 2.4, 2.4 to 11.4 or >11.4 m from the shed. We assessed hen welfare using a variety of measures including: tonic immobility, open field, novel object, human approach, and human avoidance (HAV) behavioural tests; stress-induced plasma corticosterone response and faecal glucocorticoid metabolites; live weight, comb colour, and beak, plumage, footpad, and keel bone condition. Range use was positively correlated with plasma corticosterone response, faecal glucocorticoid metabolites, and greater flight distance during HAV. Hens that used the range more, moved towards rather than away from the novel object more often than hens that ranged less. Distance ranged from the shed was significantly associated with comb colour and beak condition, in that hens with darker combs and more intact beaks ranged further. Overall the findings suggest that there is no strong link between outdoor range usage and laying hen welfare. Alternatively, it may be that hens that differed in their ranging behaviour showed few differences in measures of welfare because free-range systems provide hens with adequate choice to cope with their environment. Further research into the relationship between individual range access and welfare is needed to test this possibility.     

Outdoor stocking density in free-range laying hens: radio-frequency identification of impacts on range use

The number and size of free-range laying hen (Gallus gallus domesticus) production systems are increasing within Australia in response to consumer demand for perceived improvement in hen welfare. However, variation in outdoor stocking density has generated consumer dissatisfaction leading to the development of a national information standard on free-range egg labelling by the Australian Consumer Affairs Ministers. The current Australian Model Code of Practice for Domestic Poultry states a guideline of 1500 hens/ha, but no maximum density is set. Radio-frequency identification (RFID) tracking technology was used to measure daily range usage by individual ISA Brown hens housed in six small flocks (150 hens/flock – 50% of hens tagged), each with access to one of three outdoor stocking density treatments (two replicates per treatment: 2000, 10 000, 20 000 hens/ha), from 22 to 26, 27 to 31 and 32 to 36 weeks of age. There was some variation in range usage across the sampling periods and by weeks 32 to 36 individual hens from the lowest stocking density on average used the range for longer each day (P<0.001), with fewer visits and longer maximum durations per visit (P<0.001). Individual hens within all stocking densities varied in the percentage of days they accessed the range with 2% of tagged hens in each treatment never venturing outdoors and a large proportion that accessed the range daily (2000 hens/ha: 80.5%; 10 000 hens/ha: 66.5%; 20 000 hens/ha: 71.4%). On average, 38% to 48% of hens were seen on the range simultaneously and used all available areas of all ranges. These results of experimental-sized flocks have implications for determining optimal outdoor stocking densities for commercial free-range laying hens but further research would be needed to determine the effects of increased range usage on hen welfare.     

Tissue-specific distribution of carotenoids and vitamin E in tissues of newly hatched chicks from various avian species

The aim of this study was to evaluate carotenoid and vitamin E distribution in egg and tissues of newly hatched chicks from wild mallard (Anas platyrhynchos), game pheasant (Phasianus colchicus), free-range guinea fowl (Numida meleagris), hen (Gallus domesticus) and domestic duck (Anas platyrhynchos) and intensively housed hens. Carotenoid concentrations in the egg yolk of free-range guinea fowl, pheasant and wild mallard were similar (61.3-79.2 microg/g). Egg yolks from ducks and intensively housed hens were characterised by the lowest carotenoid concentration comprising 11.2-14.8 microg/g. However, carotenoid concentration in eggs from free-range ducks and hens was less than half of that in free-range guinea fowl or pheasant. Depending on carotenoid concentration in the livers of species studied could be placed in the following descending order: free living pheasant>free-range guinea fowl>free-range hen>intensively housed hen>wild mallard>housed duck>free-range duck. The carotenoid concentrations in other tissues of free-range guinea fowl and pheasant were substantially higher than in the other species studied. Egg yolk of housed hens was characterised by the highest alpha- and gamma-tocopherol concentrations. In accordance with the alpha-tocopherol concentration in the egg yolk, the birds can be placed in the following descending order: intensively housed hen>wild mallard>free-living pheasant>free-range duck>free-range hen=free-range guinea fowl>housed duck. The main finding of this work is species- and tissue-specific differences in carotenoid and vitamin E distribution in the various avian species studied.     

The assessment of fear in domestic hens exposed to a looming human stimulus

The behavioural and physiological responses of hens exposed to a slowly approaching human being were assessed using remote observation and radio telemetry of heart rate. Forty isolated hens of two strains and from two rearing environments were used. The sequence of behavioural changes included looking around, ceasing feeding, head shaking or complete withdrawal and finally crouching or escape behaviour. The heart rate rose from a mean level of 303 beats/min when the birds were at rest, to 465 beats/min when the cage was opened and the bird caught and held at the conclusion of the approach. The light hybrid strain showed more pronounced behavioural responses and a greater proportional rise in heart rate in the course of the approach than the medium hybrid birds, consistent with the induction of a higher level of fear. An environmental effect was also observed, pen-reared birds were more disturbed than caged ones. The similarity of the time course of the physiological and behavioural measures supports the concept of fear as an intervening variable which has simultaneous effects on heart rate and behaviour. Both may be effective in assessing fear, and they should be regarded as complementary rather than alternative measures.     

Reaction of laying hens to humans in the home or a novel environment

Tests assessing the fear of humans by measuring avoidance or approach reactions of the test animals towards humans can be useful tools in welfare assessment schemes. In this study, we wanted to compare tests assessing the reactions of laying hens towards humans in the home environment to a test performed in a novel environment. As well we investigated inter-test correlations in the home environment. We performed several tests to assess the hens’ approach and avoidance reactions towards an unfamiliar human inside the home environment of laying hens in 14 caged flocks and 10 free-range flocks. We measured the reactions of hens to a stationary person and a moving person approaching individual hens in both systems, as well as reactions to a stationary person trying to touch individual hens in non-cage systems and reactions of caged hens to a person passing by. Additionally, a standardised arena test was performed outside the home environment to compare the birds’ avoidance reactions towards an approaching human in a novel environment. In caged hens no significant correlations of tests performed inside the home environment with the arena test could be found, but there were moderate to high correlations (r_s > 0.6) with one parameter of the arena test in non-caged hens. The different tests applied inside the home environment correlated significantly and moderately to highly with each other, supporting the validity of these tests to measure fear of humans. The caged laying hens in our study reacted differently in the novel environment from the non-caged birds, indicating that the birds’ reactions towards humans in an unfamiliar environment depend on the housing system. In summary, a comparison of the level of fear of humans between flocks in different housing systems by using an arena test outside the home environment seems difficult and was not possible in the present study.     

Outdoor stocking density in free-range laying hens: effects on behaviour and welfare

Free-range laying hen systems are increasing within Australia and research is needed to determine optimal outdoor stocking densities. Six small (n=150 hens) experimental flocks of ISA Brown laying hens were housed with access to ranges simulating one of three outdoor stocking densities with two pen replicates per density: 2000 hens/ha, 10 000 hens/ha or 20 000 hens/ha. Birds were provided daily range access from 21 to 36 weeks of age and the range usage of 50% of hens was tracked using radio-frequency identification technology. Throughout the study, basic external health assessments following a modified version of the Welfare Quality® protocol showed most birds were in visibly good condition (although keel damage was increasingly present with age) with few differences between stocking densities. Toenail length at 36 weeks of age was negatively correlated with hours spent ranging for all pens of birds (all r⩾−0.23, P⩽0.04). At 23 weeks of age, there were no differences between outdoor stocking densities in albumen corticosterone concentrations (P=0.44). At 35 weeks of age, density effects were significant (P<0.001) where the eggs from hens in the highest outdoor stocking density showed the highest albumen corticosterone concentrations, although eggs from hens in the 10 000 hens/ha density showed the lowest concentrations (P<0.017). Behavioural observations of hens both on the range and indoors showed more dust bathing and foraging (scratching followed by ground-pecking) was performed outdoors, but more resting indoors (all P<0.001). Hens from the 2000 hens/ha densities showed the least foraging on the range but the most resting outdoors, with hens from the 20 000 hens/ha densities showing the least amount of resting outdoors (all P<0.017). Proportions of dust bathing outdoors tended to differ between the stocking densities (P=0.08). For each of the health and behavioural measures there were differences between pen replicates within stocking densities. These data show outdoor stocking density has some effects on hen welfare, and it appears that consideration of both individual and group-level behaviour is necessary when developing optimal stocking density guidelines and free-range system management practices.     

Development of two inbred strains of rats and characteristics of their skin reactions.

Two inbred strains of rat (Donryu and Sprague-Dawley strains) were developed. The skin reactions of these strains immunized with M. tuberculosis, hen egg albumin (OVA) or hen egg lysozyme and challenged with the purified protein derivative (PPD) or each antigen were even and uniform. The Donryu strain showed a typical Arthus reaction with petechiae and edema and a negligible delayed skin reaction, whereas the Sprague-Dawley strain showed a poor Arthus reaction and a typical delayed skin reaction with central necrosis and induration. The Arthus reaction or delayed skin reaction could be passively transferred to recipient rats of each strain by immune sera or sensitized peritoneal exudate cells (PEC), respectively.     

Presence of Shiga toxin-producing Escherichia coli O157:H7 in living layer hens

AIMS: To evaluate the presence of Shiga toxin-producing strains of Escherichia coli (STEC) of the O157:H7 serotype in living layer hens so as to analyse the role of this avian species as potential reservoir. METHODS AND RESULTS: Cloacal swabs were collected between November 2004 and November 2005 from four intensive management layer hen farms and analysed for STEC O157:H7 by immunomagnetic separation methods and multiplex polymerase chain reaction for stx1 and/or stx2, the E. coli attaching and effacing (eae) and hly genes. STEC was detected in 26 of the 720 samples. CONCLUSIONS: The layer hens analysed were shown to carry STEC O157:H7. The presence of this bacterium in living layer hen farms investigated did not result in any detectable increase in gastrointestinal disease in this species. SIGNIFICANCE AND IMPACT OF THE STUDY: Living layer hens are a novel potential reservoir of E. coli O157:H7.     

Relationships between range access as monitored by radio frequency identification technology,fearfulness, and plumage damage in free-range laying hens

Severe feather-pecking (SFP), a particularly injurious behaviour in laying hens (Gallus gallus domesticus), is thought to be negatively correlated with range use in free-range systems. In turn, range use is thought to be inversely associated with fearfulness, where fearful birds may be less likely to venture outside. However, very few experiments have investigated the proposed association between range use and fearfulness. This experiment investigated associations between range use (time spent outside), fearfulness, plumage damage, and BW. Two pens of 50 ISA Brown laying hens (n=100) were fitted with radio frequency identification (RFID) transponders (contained within silicone leg rings) at 26 weeks of age. Data were then collected over 13 days. A total of 95% of birds accessed the outdoor run more than once per day. Birds spent an average duration of 6.1 h outside each day over 11 visits per bird per day (51.5 min per visit). The top 15 and bottom 15 range users (n=30), as determined by the total time spent on the range over 13 days, were selected for study. These birds were tonic immobility (TI) tested at the end of the trial and were feather-scored and weighed after TI testing. Birds with longer TI durations spent less time outside (P=0.01). Plumage damage was not associated with range use (P=0.68). The small group sizes used in this experiment may have been conducive to the high numbers of birds utilising the outdoor range area. The RFID technology collected a large amount of data on range access in the tagged birds, and provides a potential means for quantitatively assessing range access in laying hens. The present findings indicate a negative association between fearfulness and range use. However, the proposed negative association between plumage damage and range use was not supported. The relationships between range use, fearfulness, and SFP warrant further research.     

The sequential analysis of aggressive acts during hierarchy formation: an application of the ‘jigsaw puzzle’ approach

The ‘jigsaw puzzle’ approach is a general method for investigating how interactions among individuals cumulate to form the overall patterns of dominance behaviour in groups. Here, the model is used to discover how aggressive interactions between pairs of individuals modify subsequent interactions with bystanders or third parties. The model indicates that four sequences of successive, aggressive acts are possible in component triads of larger groups: two ensure transitive attack relationships and two can lead to either transitive or intransitive relationships. An application of the model to 14 groups of four hens demonstrates that the two sequences guaranteeing transitivity make up 77% of all sequences. More specifically, hens attacking one group member usually go on to attack a second member, and hens receiving one attack frequently receive a second attack from a bystander. In contrast, an attacked hen rarely ‘redirects’ an attack to a bystander, and a bystander rarely attacks a group member who has just attacked another individual. The application of the jigsaw puzzle approach to aggressive sequences in other species is discussed. Data available for several primate species corroborate the findings in hens and provide support for the method as a general tool for investigating the proximate mechanisms of hierarchy formation.     

Membrane mobility agents : V. Genetic variability in the fusibility of hen red cells

The membrane mobility agent, A₂C, promotes fusion of hen red cells from several strains of Leghorn hens with high efficiency. Cells from Cornish hens are also easily fused by the same procedure, but cells from Rhode Island Red hens fuse more slowly and to a lesser extent under the same conditions. Cells from several strains of White Rock hens do not fuse when treated in the same way. A potentially useful new parameter of the genetic control of the behavior of membrane (and/or cytoskeletal structure) is thus indicated.     

Use of perches and nestboxes by laying hens in relation to social status, based on examination of consistency of ranking orders and frequency of interaction

Four groups of 15-19 adult ISA Brown hens were studied in pens to assess the relationship between social status and use of perches and nestboxes. This was to test the hypothesis that subordinate hens use these resources more by day, for avoiding dominants, but that dominants use perches more at night, for roosting. The experiment consisted of a 5-week pre-treatment period, when no perches were present, and a 4-week treatment period, when each group was tested with different perch treatments (No, Low, Medium, High). All groups were observed systematically in each week, when all interactions of three types (aggressive peck, non-aggressive peck, approach/avoidance) in a group were recorded by noting the instigator and recipient (from numbered wing tags) onto a matrix. Proportions of time that each bird spent using perches and nestboxes, by day and at night, were also recorded. The results indicate that social status of individual laying hens is relatively stable across time and can be based reliably on counts of either aggressive pecks or approach/avoidances, but not non-aggressive pecks. Aggressive pecks were the most frequent type of interaction observed, and were reduced by the presence of perches. Use of nestboxes, but not perches, was greater at night than by day. There were weak tendencies for perches, and to a lesser extent nestboxes, to be used more by lower ranking birds by day, but not at night. There was some evidence of increased use of these resources by higher ranking birds at night. It is concluded that provision of perches reduces bird density on the floor (where nearly all interactions occurred), allows subordinates a means of avoiding dominants by day, reduces frequency of agonistic interactions, and should thus benefit laying hen welfare.     

Enterotoxigenicity and frequency of Campylobacter jejuni, C. coli and C. laridis in human and animal stool isolates from different countries

Campylobacter jejuni and C. coli strains were collected during three different years from adult patients with enterocolitis in Sweden (n = 372) from 49 patients in Kuwait, and Campylobacter strains from hens from Mexico, Pakistan and Sweden (n = 107) and Swedish pigs (n = 47). C. jejuni was the predominant species in human and hen isolates, and C. coli in pigs C. coli was significantly more common in human isolates from Sweden, and more common in hen isolates from Pakistan, than in hens from Sweden and Mexico. C. laridis was only isolated from pigs (17%) and was in no case enterotoxigenic. Both in human and hen isolates, C. jejuni strains were more enterotoxigenic than C. coli strains. C. jejuni strains from Swedish hens were less enterotoxigenic than those from Pakistan and Mexico (P less than 0.001), and strains from pigs were less enterotoxigenic than those from hens (P less than 0.001). We conclude that C. jejuni are more often enterotoxigenic and possibly more virulent than c. coli and C. laridis. The relative frequency of C. jejuni and C. coli in humans and animals differs from one country to another.     

Differences between spent hens of different genotype in performance,meat yield and suitability of the meat for sausage production

The valorization of spent hens via the food chain has some major limitations, which include low meat yield and tough meat. The latter issue can be overcome by producing convenience foods; the first may be alleviated by employing a genotype with higher meatiness. To quantitatively compare two common layer genotypes in production performance, meat yield and sausage quality, 2200 57 weeks old Institut de Sélection Animale (ISA) Warren and Dekalb White hens each were investigated during the last 60 days of egg laying. The hens were housed in an aviary system in 2×10 compartments (10 compartments/each genotype). Measurements included feed intake, laying performance, egg weight and feed conversion ratio as measured per compartment. BW was determined twice on 10 animals per compartment. Finally, two sub-groups of five hens per compartment were slaughtered, meat yield was recorded and bratwurst-type sausages were produced (n=20 per genotype). Fat proportion, cooking loss, connective tissue properties and Kramer shear energy were measured. After 1, 4, 7 and 10 months of frozen storage, oxidative stability (thiobarbituric acid reactive substances (TBARS)) and microbiological status were determined as shelf-life related criteria. ANOVA was performed considering genotype as the main effect. The ISA Warren hens were inferior in laying performance (−11%) and feed conversion ratio (+10%) compared with Dekalb White, but had the same feed intake. The ISA Warren had higher BW and carcass weight than the Dekalb White. Carcass yield was higher by 5.9%. There were 80 g (23%) more meat available for sausage production from ISA Warren compared with Dekalb White. Sausages prepared from meat of ISA Warren hens contained less fat than those from Dekalb White, but showed the same cooking loss. Although the collagen proportion of the sausages produced from ISA Warren was lower than from Dekalb White, collagen solubility was lower and shear energy was higher. During the 10 months of frozen storage, TBARS increased continuously, but not to an extent that would prevent its use as food. The sausages from the ISA Warren genotype had marginally higher TBARS levels during storage. Total colony counts decreased with storage time, with slightly lower values found in the non-spiced sausage material from the ISA Warren hens. In conclusion, when intending to use spent hens as food, ISA Warren are clearly superior to Dekalb White in meat and sausage yield. When processing the meat to sausages, the higher shear energy is probably advantageous.     

Implications for Welfare,Productivity and Sustainability of the Variation in Reported Levels of Mortality for Laying Hen Flocks Kept in Different Housing Systems: A Meta-Analysis of Ten Studies

Data from ten sources comprising 3,851 flocks were modelled to identify variation in levels of mortality in laying hens. The predicted increase with age was curvilinear with significant variation between the seven breed categories. Mortality was higher in loose housing systems than in cages and variable within system, confirming previous reports. Cumulative mortality (CM) was higher in flocks with intact beaks (χ2 = 6.03; df 1; p = 0.014) than in those with trimmed beaks. Most data were available for free-range systems (2,823 flocks), where producer recorded CM at 60–80 weeks of age averaged 10% but with a range from 0% to 69.3%. Life cycle assessment showed that the main effect of increased levels of hen mortality is to increase the relative contribution of breeding overheads, so increasing environmental burdens per unit of production. Reducing CM to levels currently achieved by the 1st quartile could reduce flock greenhouse gas emissions by as much as 25%. Concurrently this would enhance hen welfare and better meet the expectation of egg consumers. More research to understand the genetic x environment interaction and detailed records of the causes of mortality is required so that improved genotypes can be developed for different systems and different breeds can be better managed within systems.     

Happy Chickens Lay Tastier Eggs: Motivations for Buying Free-range Eggs in Australia

Recent public interest in so-called “ethical” food production, and in particular the welfare of intensively housed farm animals, has been linked to an increase in sales of free-range eggs in several countries including Australia. Animal activist groups around the world have campaigned for the abolition of caged-egg production, retailers and large food companies are now sourcing less of these products, and governments in various locales have placed restrictions on caged-egg production. In addition, the recent focus on food production and preparation in popular culture including books, films, and television has made these practices, including those associated with eggs, more transparent to mainstream audiences. Previous studies have examined consumers’ willingness-to-pay for free-range eggs, and community attitudes to animal welfare, but there has been little qualitative work that unpacks a key assumption which underlies much discussion of these issues: that free-range egg purchases are primarily or solely linked to consumers’ desires to have egg production systems changed from intensive to free-range. This paper analyses qualitative research undertaken in Australia that explores consumers’ motivations for buying free-range (or cage-free) eggs, which was part of a larger study examining ethical foods. Qualitative analysis of focus groups and interviews involving 73 participants revealed that free-range and cage-free eggs are perceived as being better quality, more nutritious, and safer, and having better sensory characteristics, than caged eggs. In response to open-ended questions, free-range and cage-free eggs were mentioned much more frequently than free-range meats, and were described as easy to identify and affordable, compared with other products with humane production claims. Several participants even had begun keeping their own hens in order to have an alternative to purchasing caged (or expensive free-range) eggs. Although caged-egg production was described by many participants as cruel, the desire to purchase free-range eggs was more often described in connection to efforts to avoid “industrialized” food than in relation to taking a stance on the issue of caged-hen welfare.     

Early rearing enrichments influenced nest use and egg quality in free-range laying hens

In Australia, free-range egg production pullets are typically reared indoors, but adult layers get outdoor access. This new environment may be challenging to adapt to, which could impair egg production and/or egg quality. Adaptation might be enhanced through rearing enrichments. We reared 1386 Hy-Line Brown® chicks indoors with three treatments across 16 weeks: (1) a control group with standard litter housing conditions, (2) a novelty group providing novel objects that changed weekly, and (3) a structural enrichment group with custom-designed structures to partially impair visibility across the pen and allow for vertical movement. Pullets were transferred to a free-range system at 16 weeks of age with daily outdoor access provided from 25 until 64 weeks. Daily egg production at different laying locations (large nests, small nests and floor), weekly egg weights and egg abnormalities were recorded from 18 to 64 weeks old. External and internal egg quality parameters of egg weight, shell reflectivity, albumen height, haugh unit, yolk colour score, shell weight and shell thickness were measured at 44, 52, 60 and 64 weeks. There was a significant interaction between rearing treatment and nest box use on hen-day production from weeks 18 to 25 (P < 0.0001) with the novelty hens laying the most eggs and the control hens the fewest eggs in the nest box. Similarly, from 26 to 64 weeks, the novelty hens laid more eggs in the large nest boxes and fewer eggs on the floor than both the structural and control hens (P < 0.0001). Egg weight and abnormalities increased with age (P < 0.0001), but rearing treatment had no effect on either measure (both P ≥ 0.19). Rearing treatment affected shell reflectivity and yolk colour with the control hens showing paler colours across time relative to the changes observed in the eggs from enriched hens. The novelty hens may have established nest box laying patterns as they were more accustomed to exploring new environments. The differences in egg quality could be related to stress adaptability or ranging behaviour. This study shows that enriching environments during rearing can have some impacts on production parameters in free-range hens.     

The Genome Sequence of the Highly Acetic Acid-Tolerant Zygosaccharomyces bailii-Derived Interspecies Hybrid Strain ISA1307, Isolated From a Sparkling Wine Plant

In this work, it is described the sequencing and annotation of the genome of the yeast strain ISA1307, isolated from a sparkling wine continuous production plant. This strain, formerly considered of the Zygosaccharomyces bailii species, has been used to study Z. bailii physiology, in particular, its extreme tolerance to acetic acid stress at low pH. The analysis of the genome sequence described in this work indicates that strain ISA1307 is an interspecies hybrid between Z. bailii and a closely related species. The genome sequence of ISA1307 is distributed through 154 scaffolds and has a size of around 21.2 Mb, corresponding to 96% of the genome size estimated by flow cytometry. Annotation of ISA1307 genome includes 4385 duplicated genes (∼90% of the total number of predicted genes) and 1155 predicted single-copy genes. The functional categories including a higher number of genes are ‘Metabolism and generation of energy’, ‘Protein folding, modification and targeting’ and ‘Biogenesis of cellular components’. The knowledge of the genome sequence of the ISA1307 strain is expected to contribute to accelerate systems-level understanding of stress resistance mechanisms in Z. bailii and to inspire and guide novel biotechnological applications of this yeast species/strain in fermentation processes, given its high resilience to acidic stress. The availability of the ISA1307 genome sequence also paves the way to a better understanding of the genetic mechanisms underlying the generation and selection of more robust hybrid yeast strains in the stressful environment of wine fermentations.     

Complete genome sequence of Gallibacterium anatis strain UMN179, isolated from a laying hen with peritonitis

Gallibacterium anatis is a member of the normal flora of avian hosts and an important causative agent of peritonitis and salpingitis in laying hens. Here we report the availability of the first completed G. anatis genome sequence of strain UMN179, isolated from an Iowa laying hen with peritonitis.     

The individual nest box as a super-stimulus for domestic hens

Following reports of inconsistent nest choice by hens in groups, choice of nest boxes by solitary hens was investigated. Thirty-two hens of a White Leghorn strain were each isolated with six nest boxes while they laid six eggs. From 16 hens, eggs were collected daily. Only one of these birds laid all her eggs in one nest box, and others used up to four boxes. The other 16 were allowed to accumulate eggs, and these were significantly more consistent in nest choice. Five used only one box. However, the other 11 of this group showed incomplete consistency.An explanation for inconsistent nest choice was suggested by a second experiment. The importance of enclosure in nest-site selection was tested in hens of White Leghorn and Rhode Island Red strains. Individuals about to lay their first egg were isolated with a choice of two types of nest box, selected from five types of different enclosure. Exposed nests, of similar dimensions to natural nests, were rarely used by either strain. By contrast, more enclosed nests were strongly selected. These results indicate that enclosure is an important stimulus in nest-site selection, and that artificial nest boxes, which are more enclosed than natural sites, act as super-normal stimuli (or “super-stimuli”). Choices between super-stimuli are likely to be equivocal, which accounts for inconsistency in the use of nest boxes and other features of the nesting behaviour of domestic hens.