Pre-laying Behaviour Research Articles

Curtained nests facilitate settled nesting behaviour of laying hens in furnished cages

Egg location can be used to determine the nests that hens prefer, but it does not indicate whether the design of that nest satisfies a hen’s nesting motivation. Hens that are satisfied with the nest resources exhibit characteristic settled nesting behaviour including less activity and longer sitting phases during the hour pre-lay. The current experiment compared the nesting behaviour of hens housed in large furnished cages given two surfaces either enclosed with plastic curtains or open. We hypothesized that hens with curtained nests would be more settled in their pre-laying behaviour than hens only provided with plastic nest surfaces. Furthermore, we hypothesized nest-naïve hens would benefit from having an enclosed nest added, demonstrating more settled nesting behaviour. After being conventionally reared, 996 pullets were placed in 24 furnished cages at week 15 (large: 41,296 cm2; small: 20,880 cm2). Each FC had two nests, one with a plastic mesh surface and one with a smooth plastic surface (3368 cm2). Half of the FC had both nest surfaces enclosed with plastic red curtains (ENCL, n = 12) and half had two open surfaces (OPEN, n = 12). All FC were subsequently modified at week 28 to have one enclosed and one open surface. Egg location was recorded from the first egg to week 36. Focal hens were marked at week 20 and observed from week 22–24 and 31–33. Oviposition times were recorded during week 21, 27, 30, 36. Scan samples of sitting and aggressive behaviour were conducted during weeks 25–26 and 34–35. Hens with two curtained nests were less active (P = 0.0219), less aggressive (P = 0.0055), displaced less (P = 0.0269), and sat more (P < 0.0001) than hens with two OPEN nest surfaces. When hens from OPEN FCs were subsequently given an enclosed nest, the percentage of hens sitting increased (P < 0.0001) and the proportion of time spent active decreased (P = 0.02). Therefore, nest areas enclosed with simple plastic curtains facilitate the expression of more settled nesting behaviour, even for hens that had laid for three months without access to enclosed sites.

Rearing environment and laying location affect pre-laying behaviour in enriched cages

The number of eggs laid in a nest is often correlated with nest acceptance and therefore hen welfare. However, evaluating pre-laying behaviour may more accurately reflect welfare independent of egg location. Our objective was to compare the effect of rearing environment and laying location on the pre-laying behaviour of hens in furnished cages (FC). We hypothesized that hens reared conventionally would be less settled (more active, aggressive) during the pre-laying period than aviary-reared hens, and floor layers would be less settled than nest layers. LSL-Lite hens (n=1080) were housed in groups of 60 (N=12, Large FC, 41 296cm2) and 30 (N=12, Small FC, 20 880cm2). Half were reared in an aviary (litter access 7 weeks) and half in standard cages. Hens were housed in FC at week 16. Each FC had a nest area (red plastic curtains, yellow plastic mesh floor); a scratch area (smooth red plastic mat); and perches that ran parallel to the feeders. Egg location on the egg belt was recorded daily from 16 to 72 weeks. Four hens/LFC and two hens/SFC were wing-tagged at 18 weeks and observed at start of lay (week 22) and peak lay (week 32). Observers continuously scored prelaying behaviour of a single hen from lights-on (05:00h) until oviposition; behaviours performed in the final hour before oviposition were analyzed. Behavioural frequencies and durations were transformed before being analyzed with a Mixed model repeated measures ANOVA. Cage-reared hens laid more eggs in the nest (mean±SE: 89.6±0.4% vs. 81.7±0.6%; P<0.001) and fewer in the scratch (9.6±0.4% vs. 17.6±0.6%; P<0.001) than aviary-reared hens. At week 22, cage-reared hens entered the nest area more often (P=0.002) and were more active (P=0.0007) than aviary-reared hens with no difference at week 32 (P=0.5). Therefore, aviary-reared hens found the nest less attractive than cage-reared hens, but also expressed more settled pre-laying behaviour. Scratch layers sat for a longer duration (P=0.0015) and more frequently (P=0.04) than nest layers, but were also more aggressive (P=0.001). Neither the duration nor the frequency of activity differed between nest and scratch layers. Therefore, scratch layers were not more unsettled than nest layers in the hour before oviposition. These results suggest that both rearing environment and laying location affect pre-laying behaviour in large furnished cages.

Further observations on Black-breasted Buzzards Hamirostra melanosternon breeding near Alice Springs, Northern Territory

Parts of the breeding cycle of a pair of Black-breasted Buzzards Hamirostra melanosternon were observed near Alice Springs, Northern Territory, in 2014 and 2015, when the pair raised a single fledgling in each year. Supplementary information was obtained on pre-laying behaviour, vocalisations, nest defence and chick growth. Our study confirmed allopreening and use of the piping call in the pre-laying phase; male use of the wheezing call; and gender roles in defence at different stages; and highlighted further similarities with the Square-tailed Kite Lophoictinia isura .

Effects of variation in nest curtain design on pre-laying behaviour of domestic hens

Laying hens in loose-housing systems select a nest daily in which to lay their eggs among many identical looking nests, they often prefer corner nests. We investigated whether heterogeneity in nest curtain appearance – via colours and symbols – would influence nest selection and result in an even distribution of eggs among nests.We studied pre-laying behaviour in groups of 30 LSL hens across two consecutive trials with eight groups per trial. Half of the groups had access to six identical rollaway group-nests, while the others had access to six nests of the same type differing in outer appearance. Three colours (red, green, yellow) and three black symbols (cross, circle, rectangle) were used to create three different nest curtain designs per pen. Nest position and the side of entrance to the pens were changed at 28 and 30 weeks of age, respectively, whereby the order of changes was counterbalanced across trials. Nest positions were numbered 1–6, with nest position 1 representing the nest closest to the pen entrance. Eggs were counted per nest daily from week of age 18 to 33. Nest visits were recorded individually with an RFID system for the first 5h of light throughout weeks 24–33.Hens with access to nests differing in curtain appearance entered fewer nests daily than hens with identical nests throughout the study but both groups entered more nests with increasing age. We found no other evidence that curtain appearance affected nest choice and hens were inconsistent in their daily nest selection. A high proportion of eggs were laid in corner nests especially during the first three weeks of lay. The number of visits per egg depended upon nest position and age: it increased with age and was higher after the nest position change than before in nest position 1, whereas it stayed stable over time in nest position 6. At 24 weeks of age, gregarious nest visits (hens visiting an occupied nest when there was at least one unoccupied nest) and solitary nest visits (hens visiting an unoccupied nest when there was at least one occupied nest) accounted for a similar amount of nest visits, however, after the door switch, gregarious nest visits made up more than half of all nest visits, while the number of solitary nest visits had decreased. The visual cues were too subtle or inadequate for hens to develop individual preferences while nest position, entrance side, age and nest occupancy affected the quantity and type of nest visits.

The importance of pre-laying behaviour and nest boxes for laying hen welfare: a review

The housing of commercial laying hens in conventional cages is one of the most contentious animal welfare issues in animal production in Australia and other developed countries. The main issues are restriction of space and opportunity to perform ‘natural’ behaviours such as pre-laying behaviour, dust bathing and roosting. The provision of a nest box is argued by some to be essential for laying hen welfare. While the majority of hens (at least 70%) will lay in a nest box if provided, neither the lack of a nest box nor the sudden denial of access to a nest box, result in adverse welfare based on physiological stress response measured via corticosterone concentrations in either plasma or egg albumen. However, recent research suggests that hens that spent more time sitting during the 2 h before egg laying had lower plasma corticosterone concentrations, when sampled ~4–5 h post-egg laying. On the other hand, hens that displayed more bouts of sitting before egg laying, perhaps suggesting they were more frequently disturbed and thus less settled, had higher corticosterone concentrations. One function of nest boxes might be to provide those hens that choose to lay there with a location where they are less disturbed before egg laying. Further research on the effects of pre-laying behaviour and nest site selection on physiological stress in laying hens may provide important information regarding how to house commercial laying hens for good welfare.

Influence of nest seclusion and nesting material on pre-laying behaviour of laying hens

Provision of nest sites is beneficial for the welfare of laying hens in intensive production systems. The design of these nest sites has a direct effect on pre-laying behaviour. The aim of this study was to investigate the effects of screening off the entrances of the nest boxes with non-transparent flaps and providing nesting or flooring material on pre-laying behaviour. Eighteen individual Hisex brown laying hens and 18 groups of five hens were tested for 2 days in a test cage containing three nest boxes each with a different nesting material (peat, artificial turf and plastic-coated wire mesh). On one of the days the nest boxes were equipped with plastic flaps at the entrances. Pre-laying behaviour was analysed using focal sampling. Both degree of seclusion and nesting material had an effect on pre-laying behaviour of hens. Nest boxes with flaps were visited less frequently but for a longer duration per visit than nest boxes without flaps. Hens spent more time sitting and scratching, and less time standing and moving when flaps were present. Hens also received fewer pecks (group test) when nest boxes were equipped with flaps. Major differences were found between pre-laying behaviour on coated wire mesh compared to peat and artificial turf with shorter duration of nest visits (group test), more standing (group test) and moving (individual and group test), and less sitting (individual and group test) and object pecking (group test) on coated wire mesh. Differences in pre-laying behaviour on peat versus artificial turf were observed for the behaviours moving (less on peat), sitting (more on peat in the individual test) and object pecking (more on peat in the group test). It is concluded that hens show more settled pre-laying behaviour and more nest-building behaviour in the presence of flaps at the entrances of nest boxes. These results indicate that seclusion of nest boxes with non-transparent flaps is beneficial to laying hen welfare. Differences in pre-laying behaviour also suggest that plastic-coated wire mesh is less suitable as nesting material than peat and artificial turf.

Behavioural needs, priorities and preferences of laying hens

We review the behavioural needs, priorities and preferences of laying hens for increased space, perching, nesting, foraging and dustbathing behaviour. Hens make full use of and may work to gain access to perches, however it is not yet known how perching ranks in comparison with other behaviours. Laying hens appear to have an instinctive need to perform pre-laying (nest-building) behaviour and have a strong preference for a discrete, enclosed nest site, for which they will work hard to gain access as oviposition approaches. Access to a nest site is a high-ranking priority for laying hens, preferred over food at this time. Foraging is a behavioural need, with peat, sand and wood shavings preferred substrates in choice experiments. There is no reduction in time spent foraging when a cost is imposed, nor when feed is freely available. Dustbathing is currently viewed as a behavioural need, as the extent to which hens value dustbathing is not known. Bird preferences for space are complex and confounded by interactions between group size and stocking density. There is some evidence that priority for space varies during the day and increases when the total space available to a group of birds is restricted, and that greater priority is given to space than to small group size. The presence of apparently purposeless behaviour, of high levels of aggression or redirected behaviours such as feather pecking and cannibalism are indicators that the housing system is not meeting the behavioural needs of the hens and hence is not satisfactory for bird welfare.

Development of furnished cages for laying hens

1. A 3-year trial was carried out of cages for laying hens, occupying a full laying house. The main cage designs used were 5000 cm2 in area, 50 cm high at the rear and furnished with nests and perches. F cages had a front rollaway nest at the side, lined with artificial turf. FD cages also had a dust bath containing sand over the nest. H cages had two nest hollows at the side, one in front of the other. They were compared with conventional cages 2500 cm2 in area and 38 cm high at the rear. 2. Cages were stocked with from 4 to 8 ISA Brown hens per cage, resulting in varied allowances of area, feeder and perch per bird. No birds were beak trimmed. In F and FD cages two further treatments were applied: nests and dust baths were sometimes fitted with gates to exclude birds from dust baths in the morning and from both at night; elevated food troughs, with a lip 33 cm above the cage floor, were compared with standard troughs. 3. Management of the house was generally highly successful, with temperature control achieved by ventilation. Egg production was above breeders' standards and not significantly affected by cage design. More eggs per bird were collected when there were fewer birds per cage but food consumption also then tended to be higher. 4. The number of downgraded eggs was variable, with some tendency for more in furnished cages. Eggs laid in dust baths were often downgraded. Those laid at the back of the cage were frequently dirty because of accumulation of droppings. H nests were unsuccessful, with less than 50% of eggs laid in the nest hollows. However, up to 93% of eggs were laid in front rollaways, and few of these were downgraded. 5. Feather and foot damage were generally less in furnished than in conventional cages, greater where there were more birds per cage. With an elevated food trough there was less feather damage but more overgrowth of claws. In year 2, mortality was greater in cages with more birds. 6. Pre-laying behaviour was mostly settled in front rollaway nests. Dust baths were used more for pecking and scratching than for dust bathing. Comfort behaviour was more frequent in furnished cages than conventional, although still not frequent. Locomotion was strongly affected by number of birds per cage or by space per bird, being reduced by crowding. Most birds perched at night except in one treatment providing only 10.7 cm perch per bird. 7. Behaviour was more unrestricted and varied, and physical condition was better, in furnished than in conventional cages. However, egg production will cost more in furnished cages, partly because more eggs are downgraded. Dust baths must be fitted with gates that the birds cannot open from outside, but gates for nest boxes were found unnecessary. If a low perch is fitted it must be far enough from the back of the cage for birds to walk there. 8. Where there was less space per bird (more birds per cage) than the requirements in the 1999 European Commission Directive on laying hens, there were: fewer eggs per hen, but still above the breeders' target; lower food consumption; more feather and foot damage, but less than in conventional cages; higher mortality in one trial out of three; less freedom of movement. However, the results were still very good even with 8 birds per cage, and support the principle that furnished cages provide an acceptable way of protecting the welfare of laying hens.

Thwarting of behaviour in different contexts and the gakel-call in the laying hen

Earlier studies have shown that thwarting of feeding behaviour in the laying hen is expressed through a specific vocalisation, the gakel-call. The first aim of this study was to investigate whether the effect of deprivation per se on the occurrence of gakel-calls can be distinguished from the effect of the additional frustration. Frustration is defined as the state of an animal that results from nonreward in the expectancy of reward. The second aim was to investigate whether the occurrence of gakel-calls is restricted to a food context or whether it can be regarded as an expression of frustration in general. For this purpose, 20 hens were deprived of food, water and dustbath. After deprivation at a fixed time, a cue was given and the hens were rewarded with access to food, water or dust during a 15-min session on 4 consecutive days. On the fifth day, they were thwarted in the associated behaviours by blocking the access to these commodities, after the hens had been presented the signal that previously preceded the reward. We then recorded behaviours that might reflect the state of frustration in three 15-min periods. The period “Pre-Frustration” started 15 min before “Frustration”. This, in turn, was followed by the period “Post-frustration” in which the hens were rewarded again. Nesting behaviour was thwarted by blocking the access to the nest (Frustration) after a hen had reached the last stage of its prelaying behaviour. In the food, water and dustbath context, deprivation elicited gakel-calls. The additional frustration resulted in a higher number of gakel-calls in all contexts except the food context. However, together with the findings of previous experiments, the results of this study suggest that frustration, in general, is expressed through the gakel-call. Frustration in the nest context elicited more gakel-calls than the other contexts. This latter finding is discussed in the light of the occurrence of the gakel-call under natural circumstances.

Territorial intrusions and copulation patterns in red kites, Milvus milvus, in relation to breeding density

Two main paternity assurance strategies are generally found in birds: mate guarding and frequent copulations. The latter is expected particularly in species such as raptors that cannot guard their mates efficiently because of ecological constraints, such as frequent courtship feeding. I investigated the prelaying behaviour of red kites, in which the males courtship feed. I compared pair behaviour in situations of varying breeding density and simulated male territorial intrusions by presenting decoys. Males' certainty of paternity was likely to decrease with increasing breeding density, because of the proximity of other males and more frequent male territorial intrusions during the presumed fertile period. The percentage of time spent by males within their breeding territory during the prelaying period was positively related to the number of close breeding neighbours, suggesting territory surveillance and mate guarding. The kites copulated frequently and over a long period. Copulation frequency prior to and during laying increased with breeding density, and in isolated pairs in response to simulated male territorial intrusions. The results support the idea of paternity assurance through frequent copulations during the presumed fertile period of the female, and suggest that early copulation activity is related to functions other than fertilization, such as pair bonding or mate assessment.

Laying hens in large flocks in a perchery system: Influence of stocking density on location, use of resources and behaviour

1. ISA Brown laying hens (3000) were housed in a perchery in 10 pens, each with 300 birds. The pens varied in size to produce 4 different stocking densities: 9.9 birds/m2 (n =3), 13.5/m2 (n =2), 16.0/m2 (n =2) and 19.0/m2 (n =3). Observations began at 20 weeks of age and continued until 69 weeks to establish the spatial distribution of the birds, usage of the different resources and the expression of behaviour. 2. Overall, birds spent most time on the perch frame (47%), litter area (23%), slatted floor (17%) and nestbox area (9%). 3. There was no effect of density on the proportion of birds observed on the slatted floor or on the elevated perches but as density increased the proportion on the littered area decreased. 4. Space usage was determined vertically, horizontally and longitudinally . Individual birds were seen to use about 80% of the pen volume available to them. This value was similar for all densities and showed that individuals did not have separate home ranges. 5. Fewer vertical movements were made within the main perch frame at the upper than at the lower levels but movements between the perches of the main frame and the nestbox rails were relatively frequent. This may help birds move up and down through the main frame. 6. Behaviours which decreased in incidence with crowding included moving, foraging and dust-bathing. Behaviours which increased with crowding included standing. Behaviours which were unaffected included resting, preening, prelaying behaviour, comfort behaviour and the minor behaviours. 7. The proportion of birds engaged in feeding and drinking was unaffected by density, except each time the chain feeders (which operated intermittently) ran more hens were seen feeding at the lower densities. This suggests that food delivery stimulated feeding behaviour; there may have been some restriction at the higher densities on birds feeding when and where they wanted. 8. Stocking density had no effect on the frequency of agonistic interactions: threats, lunges, comb/head pecks, chases and fights. 9. The incidence of damaging pecking was low and not density dependent. 10. Increasing density within the range investigated inhibited the expression of a number of behaviours and limited the use of specific resources: bird welfare at 19 birds/m2 may have been very slightly impaired.

Identification of key nest site stimuli for Japanese quail ( Coturnix japonica)

For both egg production and laboratory research, Japanese quail ( Coturnix japonica) are typically housed in battery cages without nest boxes. In such cages the quail hens show symptoms of pre-laying restlessness. The inability to perform normal pre-laying behaviour is regarded as one of the most important problems for the welfare of caged laying hens. The present study aimed at identifying key nest site stimuli for quails, to enable nest boxes to be designed for alternative housing systems. Groups of hens were kept in pens containing litter, nest boxes and dustbathing boxes. The type of nest box was varied between pens, and the incidence of eggs laid outside the nest boxes (floor-eggs) was recorded over periods of 15 days. In experiment 1 (8 groups of 30 hens), both the nature of the top of the nest boxes (closed or with slits) and the type of substrate in the nest boxes (artificial turf or hay) had a significant effect on the percentage of floor-eggs. Nest boxes with a top with slits and filled with hay were best accepted for laying. Nest boxes situated in the corners of the pens were significantly selected more often for egg laying than more central nests. In experiment 2 (8 groups of 14 hens), neither the nature of the sides of the nest boxes (closed or with slits) nor the colour of the nest boxes (green or brown) had a significant effect on the incidence of floor-eggs. In experiment 3 (16 groups of 14 hens with 2 or 3 cocks), the percentage of floor-eggs was significantly lower in pens with high (170 lux) than with low (15 lux) light intensity. There was also a tendency for nest boxes filled with chaff to be better accepted than nest boxes filled with hay. In experiments 2 and 3, in pens with floors half litter and half of perforated plastic more floor-eggs were found on the litter. Few eggs were laid in the dustbathing boxes in any experiment. This study shows that Japanese quail lay up to 90% of eggs in nest boxes provided these are properly designed. It should therefore be feasible to develop housing systems with nests for Japanese quail which may replace conventional battery cages.

Effects of social interactions on pre-laying behaviour in hens

The aims of this study were to investigate the effects of social interactions on access to the nest site and pre-laying behaviour of hens in small groups. Nine groups of four hens were placed in a littered round pen. Aggressive pecks, together with the identity of the individuals involved, were recorded for 8 h of the day. Behaviour in the hour prior to oviposition was also recorded at 15 s intervals using a video camera and VCR. Records of pre-laying behaviour were divided into three categories: (1) dominant category, for hens whose pre-laying behaviour overlapped with that of subordinate pen-mates; (2) subordinate category, for hens whose pre-laying behaviour overlapped with that of dominant pen-mates; and (3) undisturbed category, for hens that showed pre-laying behaviour when no other hens were showing it. Dominant hens showed a pre-oviposition increase (median) interquartile range 13.0 (3.0–30.0)) in the number of pecks given in the hour before oviposition when compared to the hour after (1.0 (0.0–10.0), P < 0.05). Subordinate hens however, received more aggressive pecks in the hour before oviposition (21.5 (10.0–37.0)) than in the hour after (0.0 (0.0–5.0), P < 0.05). Undisturbed hens showed no changes in aggressive pecks either received or given between pre and post-oviposition time periods. Subordinate hens were also displaced more times from the nest (7.0 (4.3–12.5)) in the 30 min prior to oviposition than undisturbed hens (1.5 (0.8-2.3), P < 0.05). In the period 60-25 min before oviposition, subordinate hens walked more (163.5 (112.5–174.7) steps) than dominant (85.0 (43.0–221.5)) and undisturbed hens (59.0 (18.5–74.5)), P < 0.05). Subordinate hens also walked more (113.5 (50.3–281.2) steps) than dominant (14.0 (9.0–15.0)) and undisturbed hens (43.0 (20.0–59.5), P < 0.05) in the last 25 min before oviposition. For this time period, differences in the time spent sitting were also observed (subordinate 10.0 (4.1–14.6), dominant 19.3 (12.6–20.9) and undisturbed 13.8 (10.5–18.9) min, P < 0.05). Results suggested that hens compete for access to the nest site. Variations in pre-laying behaviour owing to social interactions were observed in both directions: subordinate hens showed an increased searching phase, whereas dominant hens remained nearer the nest site.

Motivational aspects of individual variation in response to nestboxes by laying hens

Laying hens,Gallus gallus domesticusshow individual variation in pre-laying behaviour including their ultimate choice of nest site. In housing systems with nestboxes, the majority of hens make a small number of long visits to nestboxes and lay their eggs therein, but some hens make many short visits and occasionally lay outside the nestbox. We investigated the motivational basis of this individual variation using six consistent hens which always laid in nestboxes and six inconsistent hens which sometimes laid outside nestboxes. Each hen was housed in a pen (containing either no nestbox, a semi-enclosed nestbox or an enclosed nestbox) with access to a ring-shaped tunnel which increased the opportunity to perform locomotor activity. Access to the tunnel could be restricted by narrowing the doorway to 140, 125, 110 or 95mm (compared with a mean hen width of 114mm). In trials with no nestbox, there was no difference in the pre-laying behaviour of consistent and inconsistent hens. Narrowing the doorway reduced the number of visits to the tunnel, but all hens persisted in visiting the tunnel and doorwidth had no effect on time spent therein. With both designs of nestbox, however, inconsistent hens visited the tunnel more often than consistent hens prior to oviposition, and continued to pass the narrowest doors to enter the tunnel, whilst consistent hens would not pass doors of 110 or 95mm. After oviposition, there was no difference in the two groups’ behaviour in any treatment and no hens would pass doors of either 110 or 95mm to visit the tunnel. Individual variation in nest-site choice, therefore, appeared to result from different perception of nestboxes rather than lower nesting motivation. Inconsistent hens worked as hard as consistent hens to perform pre-laying locomotion, but appeared to be less responsive to the cues provided by nestboxes than consistent hens, because they persisted with pre-laying locomotion when provided with either design of nestbox.

Assessment of pre-laying motivation in the domestic hen using social interaction

While much is known about the hormonal basis of pre-laying behaviour of domestic hens,Gallus gallus domesticuslittle is known about how the behaviour is initiated or how changes in this behaviour occur. An experiment was conducted in which hens had to overcome an aversive task, during the course of pre-laying behaviour, in order to reach a nest site. Twelve hens were tested in four treatments presented as a Latin square design. The test arena was arranged such that hens could approach the nestbox only along one corridor, and return to the home pen by another. The four treatments consisted of leaving the corridor leading to the nestbox empty, or placing a hen that was dominant, subordinate or unfamiliar to the test-bird in it. Hens took longer to enter the corridor leading to the nestbox when there was a dominant or unfamiliar stimulus-bird than with a subordinate or an empty corridor. They also made more attempts to find alternative routes to the nestbox during the searching phase of pre-laying behaviour when there was a dominant or unfamiliar stimulus-bird, than with a subordinate stimulus-bird or empty pen and made fewer entries into the corridor with an unfamiliar stimulus-bird, but not a dominant or subordinate stimulus-bird or an empty pen. We suggest that hens are weakly motivated to reach the nest site during the searching phase. However, the motivation to gain access to a nest site increases near the start of the sitting phase of pre-laying behaviour.

The Interaction Between Pre-Laying Behaviour and Feeding in Hens: Implications for Motivation

Abstract While considerable research has been undertaken on the hormonal basis of pre-laying behaviour of domestic hens (Gallus gallus domesticus), less is known about how the behaviour is initiated and about how changes in this behaviour occur. Two experiments were conducted to investigate aspects of the interaction of pre-laying behaviour with feeding motivation. Experiment 1 examined the effect of the absence of food. Pre-laying behaviour was observed in 20 laying hens either with or without food available. The duration of pre-laying behaviour was longer when deprived of food for short or long periods of time than for hens with access to food. The time of oviposition, however, appeared unchanged suggesting that motivation for pre-laying behaviour is initially increasing and that it competes with feeding behaviour for expression when food is available. Experiment 2 examined the effect of food in the absence of deprivation. The food of 17 hens was topped up at various intervals before oviposition. Contrary to expectation the delay in oviposition was greater (24 minutes) if food was presented closer to the expected oviposition (2 minutes) than if it was earlier (12 minutes before oviposition, which caused a delay of 12 minutes). When interrupted close to oviposition, most birds repeated part of the searching phase of pre-laying behaviour (7 minutes of searching as opposed to 3 minutes). It is concluded that a hypothesis based on competition between motivational systems offers a good predictor for the start of pre-laying behaviour, but not for the duration of interruption later in the pre-laying behaviour sequence.

Effects of nest quality and other cues for exploration on pre-laying behaviour

Persistence of searching behaviour during the pre-laying period in the presence of a suitable nest site may indicate that hens are strongly motivated to perform this behaviour. This was investigated by observing behaviour in environments with or without a suitable nest site and other cues for exploration. Eleven hens were tested individually in four environments using a 2 × 2 experimental design: presence or absence of litter and presence or absence of an exploratory walkway. Comparing pre-laying behaviour between environments with unlittered and littered nest box, longer durations of pre-laying behaviour (151(±20) vs. 110(±13) min, ANOVA, df = 1,27; P < 0.05) and searching phase (32(±6) vs. 19(±3) min; P < 0.05) were observed. Hens also showed more searching behaviour (26(±5) vs. 14(±4) min; P < 0.01) and performed more nest examinations (27(±8) vs. 10(±3); P < 0.01) in environments with a littered nest box. More entries were recorded into unlittered nest boxes (11(±2) vs. 7(±1); P < 0.05), though of a shorter mean duration (8(±2) vs. 16(±6) min; P < 0.01). The duration of the searching phase was longer in environments with than without the walkway (35(±6) and 16(±4) min respectively, P < 0.01). More searching behaviour (28(±5) vs. 13(±3) min; P < 0.001) and more nest examinations (8(±2) vs. 4(±1); P < 0.01) were recorded in environments with the walkway. It is suggested that in the absence of an appropriate nest site the motivation to perform searching behaviour remains high. However, when compared to barren environments, environments that provide cues for exploration result in the motivation to perform pre-laying behaviour being more fully expressed.

Individual variation in prelaying behaviour and the incidence of floor eggs.

1. Floor eggs are a problem in non-cage systems for laying hens, as they require secondary egg collecting. Failure to lay in a well-defined nest site may also be a welfare problem for the hens, but only if their nesting motivation has been thwarted. We investigated the relationships between a hen's prelaying behaviour and its tendency to lay on the floor by recording the behaviour of 20 hens housed individually in wire cages with single littered nest boxes. 3. Most floor eggs (80%) were laid by the same 6 hens. These 6 "floor-layers" performed more nest seeking behaviour, less nest-building behaviour and less sitting prior to oviposition than the 14 hens that consistently laid in nest boxes. 4. The incidence of floor eggs declined with age. Both nest and floor laying hens performed less nest seeking behaviour with age. Floor layers, however, increased their performance of nesting behaviour, whilst nest layers performed less nesting behaviour with age. 5. Floor laying hens behaved as if they found the nest box less attractive than nest-laying hens; perhaps because they had lower nesting motivation, or perhaps because their nesting motivation was as high, but they less readily perceived the nest box as an appropriate nest site.

Endogenous analgesia in the chicken

Endogenous analgesia has been identified in mammals, but little is known about suppression of tonic pain following trauma or disease. Birds suffer from gouty arthritis which can be induced experimentally by intra-articular injection of sodium urate (SU) crystals. SU injection into the ankle joint of the chicken tested in cages resulted in pain-coping behaviour (one-legged standing, sitting) together with severe lameness. Birds kept and tested in large pens showed significantly less pain-coping behaviour, while birds tested in novel pens showed either complete analgesia or marked hypoalgesia, together with a significant reduction in lameness. Complete analgesia was observed during pre-laying behaviour. These results demonstrate a remarkable ability of birds to suppress such severe tonic pain as SU arthritis.

Individual variation in hens' pre-laying behaviour and the incidence of floor eggs

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.