Space and density effects on group size preferences in laying hens

1. T‐maze preference tests were used to study group size and space preferences in laying hens kept on deep litter. The first experiment revealed a non‐significant tendency to prefer a larger group (120 hens) in a large space (9 m²) over a smaller group (5 hens) in a small space (1 m³), but when the space was constant and large, a strong preference for the smaller group in a large space emerged.

2. In experiment 2, 5 different group size/space options were tested using a T‐maze and test hens were non‐randomly selected, choosing more aggressive ‘peckers’ and more subordinate ‘receivers’. Chi‐squared tests showed preferences for (1) a larger group (70 over 4 or 0 hens), (2) a larger space (9 m² over 1 m²) and (3) 4 hens rather than an empty space. Although both peckers and receivers preferred the same size companion hen groups, receivers were more consistent in their choice than peckers.

3. The results have important implications for hens in all group sizes and suggest that while smaller group sizes may be important, they need to be combined with sufficient space. Furthermore, the ‘ideal group size’ may differ depending on the individual hen's dominance status.     

The preference of domestic hens for different types of battery cage floor

Hens were presented with four different types of floor in two‐choice situations; they were generally indifferent to the nature of the floor but showed a significant preference for fine hexagonal mesh over coarse rectangular mesh and over perforated steel sheet. Oviposition preferences mirrored standing preferences. Gauge of wire seemed to have little influence; we suggest that an important factor is the number of points at which the bird's foot is supported. The hens preferred the hexagonal mesh in spite of its gauge being so fine that wires parted during the experiment, resulting in potentially damaging holes. The findings indicated that welfare considerations are not necessarily incompatible with cage floor designs which minimise egg breakage; a very light floor may be as comfortable as a heavy, solid one.     

Incidence of non-laying in domestic hens.

1. Egg production records of 31,455 individually caged hens, 27 to 34 weeks of age and of 4 genotypes, were examined. 2. Sixty-nine non-layers were identified in the 30 to 40 week age group, and examined post mortem; an incidence of 2.1 per 1000. 3. Some of the 69 individuals had more than one abnormality. Forty-two percent were internal layers, 34% had some form of neoplasia, 24% had an abnormal or diseased oviduct, 18% were sex reversals, 16% had a diseased ovary, 8% were of poor condition and considered culls, and 7% were in good condition, but with small, immature ovaries. 4. Of 54 birds not in lay at 27 weeks, 43 (80%) had come into lay by 34 weeks of age. 5. Genotype influenced the incidence of neoplasia and, in turn, the number of non-layers.     

Effect of cage height and area on the behaviour of hens housed in battery cages

Medium hybrid hens were housed as pairs and observed at three cage heights: 30.0, 42.5 and 55.0 cm, and at three area allowances per bird: 570, 807 and 1045 cm2. With increased height, head stretching, head scratching and body shaking were performed at a higher rate and feeding and cage pecking at a lower rate. There was also an increase in the time spent sitting. With increased area, head scratching, body shaking and feather raising were performed at a higher rate and cage pecking at a lower rate. It is concluded that spatial restriction may increase the cost of performing certain 'comfort' activities, resulting in the reductions in performance rate observed in the above experiments. Welfare implications are briefly discussed and considered to depend on the motivational state of the birds.     

Group size and plumage damage in laying hens

1. Ninety‐one Shaver 288 laying hens were kept in groups of 1, 2, 4 or 6 birds per cage and were provided with a floor space of 1300 cm² for the single birds and 650 cm²/bird for the groups. The overall damage to the plumage of each bird was assessed at monthly intervals from 18 to 72 weeks of age.

2. Most of the plumage damage occurred during the first 24 weeks after caging and was attributed mainly to mechanical abrasion between the birds’ bodies and their cages. Little additional deterioration in feather cover occurred between 45 and 72 weeks of age.

3. The plumage damage of single birds was always less than that of birds kept in groups.     

Alterations in uterine contractility during the oviposition cycle in domestic hens

1. The potencies of several neurohypophysial hormones were examined at different times during the oviposition cycle in an in vitro fowl oxytocic assay.

2. Uterine tissues were removed 2 h before (—2h‐OP), immediately after (Oh‐OP) and 5 h after (+5h‐OP) spontaneous oviposition. In addition, uterine tissue was removed immediately after oviposition was induced, by administering prostaglandin E₂ 2 h before an expected oviposition (Induced‐OP).

3. The rank order of oxytocic potencies for the peptides was arginine vasotocin=vasopressin>oxytocin>mesotocin. The sensitivity of the uterus to the hormones was Oh‐OP = Induced‐OP> — 2h‐OP= +5‐OP.

4. These results suggest that uterine sensitivity to neurohypophysial hormones changes during the oviposition cycle in domestic fowls.     

Bacterial growth in albumen taken from the eggs of domestic hens and waterfowl

Gram‐negative bacteria formed small populations in albumen taken from the eggs of domestic hens. Adding yeast extract (final concentration 100 mg/ml) to the albumen did not increase the extent of microbial growth. Large populations were formed in albumen containing FeSO₄.₇H₂O (final concentration 9.95 mg/ml) or this sulphate and yeast extract and the organisms utilised the glucose of the egg white with a concomitant increase in the CO₂ released to the atmosphere. The rate of glucose utilisation, as judged by the rate and extent of the change in pH, was slow in albumen of the eggs of domestic hens to which had been added a heavy suspension of a fermentative bacterium. The retardation of glucose fermentation was a feature also of the albumen of eggs of several species of waterfowl. Both the rate and extent of glucose fermentation was increased when yeast extract (final concentration 100 mg/ml) was added to heavily seeded albumen but ferrous sulphate did not have a significant influence on the rate of glucose utilisation.     

Effects of single caging and cage size on behavior and stress level of domestic neutered cats housed in an animal shelter

Cats need a minimum amount of space even in animal shelters. In this study the effects of single caging and cage size on the behavior and stress level of domestic cats were investigated. Six neutered cats (2–15 years old) that had been housed in a group for at least 7 months were moved to three kinds of single cages (small, medium and large) by rotation on a Latin square design. They experienced each cage size for 6 days. Cats could use vertical dimensions when housed in a group room and the large cage. Behavioral observation was conducted for 3 h in the evening, and stress levels were assessed by urine cortisol‐to‐creatinine ratios. The amounts (estimated proportions) of time spent in locomotion and social/solitary play were lower even in large cages than in group housing (both P < 0.05). Conversely, the amount of time spent resting tended to increase when housed singly (P = 0.104). The urine cortisol‐to‐creatinine ratios of singly housed cats tended to be higher than that of group‐housed cats (P = 0.086). The results indicate that cats become less active when they are housed singly in cages regardless of the cage size. Cats seem to feel no undue stress even in small cages if the stay is short.     

Progesterone and testosterone elicit increases in the duration of shell formation in domestic hens

Injection of progesterone or testosterone in hens 4 and 10 h after ovulation increased the intervals between ovipositions and shell weights. The effects were dose-dependent. Expulsion of the egg from treated hens at the expected time of oviposition suppressed the increase in shell weight and deposition of the cuticle. The duration of shell formation had therefore been increased by the injections of progesterone or testosterone. Injections of progesterone 16 h or of testosterone 15 h after ovulation advanced oviposition and reduced shell weight. Testosterone propionate was more efficient than testosterone in its action on the duration of shell formation. Oestradiol was ineffective. Indomethacin delayed oviposition but did not change the duration of shell formation. These results suggest that the duration of shell formation is under the control of hormonal factors and that the larger follicles of the ovary, may be involved in its control.     

Effect of cage area,cage height and perches on feather condition,bone breakage and mortality of laying hens

1. The health of 2 flocks of 896 ISA Brown laying hens were studied successively over the years 1995 and 1996 under different caging conditions. Hens were kept in groups of 4 in a total of 224 cages. The treatments (7 different types of cages) differed in area per hen (450, 600 or 800 cm2) and height (40 or 60 cm). In the large (800 cm2/hen) and high (60 cm cage) treatment, half of the cages were equipped with perches (20 cm/hen). Each study lasted 48 weeks. 2. Feather condition was found to be independent of cage type. 3. No differences were apparent between the 7 treatments in tibia breaking strength (using the 3-point breakage technique). A significant increase in humerus breaking strength was observed in the high cages. The frequency of broken wings recorded after slaughter was lower in high cages (23%) than in low ones (36%). 4. Mortality was different between treatments. This was explained by a higher proportion of birds killed by 'body cannibalism' in the 60 cm high cages, and by a higher proportion of birds killed by 'vent cannibalism' in the cages with perches.     

Nesting and floor laying by domestic hens in a commercial flock

1. The nesting behaviour of broiler breeders was studied in a commercial flock of nearly 4000 birds kept on deep litter by tagging a sample of 200 hens. Use of nest boxes by tagged birds was recorded on 52 d over 34 weeks.

2. Forty hens were never observed in nest boxes and 33 others were recorded only in ground‐level boxes. These 73 birds were recorded significantly less often in nest boxes and more often apparently laying on the floor than others. Fewer of them perched during observations and they started doing so later than birds which used raised nest boxes.

3. These results suggested that there were consistent floor layers, which had difficulty reaching raised nest boxes, as found previously in experimental conditions. Many or all floor layers may, however, have used ground‐level boxes sometimes.

4. Hens were inconsistent in their use of particular nest boxes, and some even nested in two distinct areas.

5. Most individuals were, however, consistent in their reaction to one or more features of the nest boxes, including height, aspect and area. Individual choices for these features varied, so no boxes were used particularly heavily, with the exception of those at ground level.     

Relationships between fear of humans, productivity and cage position of laying hens

1. The productivity and behavioural responses of laying hens to humans were examined in relation to the effects of tier, row and position of the cage along the row over three consecutive 4-week periods. 2. Birds from the top tier had lower hen-day production, lower egg mass output and poorer efficiency of food utilisation than birds from the bottom tier in the third period. 3. Birds from the top tier showed greater avoidance of an approaching experimenter when in their cage or when on a table. 4. The production variables were significantly correlated with a number of behavioural responses to humans and a novel object, and with the corticosteroid response to handling/blood sampling. 5. The data suggest that birds from the top tier were more fearful of humans and that this higher level of fear may have been responsible for their lower productivity.     

Effect of lipopolysaccharide on sickness behaviour in hens kept in cage and free range environments

The aim of this study was to assess whether environmental enrichment and environmental conditions can influence the expression of sickness behaviour. The behaviour in response to injection of lipopolysaccharide or saline was examined in a total of 96 62-weeks old hatchmate hens kept in a free range or cage environment. There were eight experimental treatments, each with 12 birds. Half the birds were sourced from a commercial cage layer unit (C/-) and half from a commercial free range unit (FR/-). After intraperitoneal injection with either lipopolysaccharide or saline (as a control), the hens were placed in either a cage (-/C) or free range (-/FR) environment. Lipopolysaccharide caused greater suppression of activity in free range (FR/FR) than in caged hens, including less walking (53% reduction), roosting (−86%) and preening (−60%) (p < 0.05). Those responses were not observed in caged birds released into free range, nor in free range birds introduced to cages, suggesting that both the presence of and the familiarity with an environment affected sickness behaviour patterns. Increased sleeping was the most consistent response (+147%; p < 0.001), and it was least influenced by environment. It was concluded that free range layer hens can express a greater range of sickness behaviours than caged hens, and this may make it more difficult to recognise disease expression in the caged environment.     

The frequency of neck movements in laying hens and the improbability of cage abrasion causing feather wear

1. Three types of movement were recognised: Neck Through, Neck Up and Neck Shake.

2. Neck Shake was the only movement frequent enough to be capable of producing severe abrasion of the neck feathers.

3. Patterns of damage to neck feathers in individually‐caged hens were such that most could not be satisfactorily accounted for by abrasion against the cage front.

4. Removal of feathers by neighbouring birds was postulated as the most probable cause of feather loss.     

Effects of timing and size of daylength change on brown egg laying domestic hens: Plasma luteinising hormone concentration and sexual maturity

1. Brown egg laying pullets were transferred from an 8‐h photoperiod to an 8‐, 10‐, 13‐ or 16‐h photoperiod at 6, 9, 12, 15, 18 or 20–3 weeks of age. Plasma luteinising hormone (LH) concentrations were measured at transfer and 7 and 14 d afterwards.

2. Significant increases in plasma LH occurred following light stimulations at 6, 9 and 12 weeks of age.

3. Changes in LH concentration 7 d after a light increase from 8 h to 8, 10, 13, 16 h were highly correlated with photoperiod length at 9 and 12 weeks of age.

4. Changes in LH were generally poorly correlated with age at sexual maturity, although the reduced influence on age at first egg of a light increase given close to sexual maturity was reflected in minimal LH responses at 18 and 20.3 weeks.     

Hormonal changes associated with ageing and induced moulting of domestic hens

1. The effect of age on ovarian function was studied in 245-, 350-, 500-, 700- and 800-d-old Lohmann hens. The effect of three different methods for moult induction on ovarian function and corticosterone concentration was studied in 500-d-old hens. 2. No significant reductions in ovarian weight or in number of follicles before the age of 700 d were found. The ability to produce progesterone and oestradiol-17beta was unchanged up to the age of 700 d and the circadian secretion of these two steroids was identical in young (225 d) and old hens (600 d). 3. The effects of induced moulting by feed withdrawal (FW) and a high Zn (HZn) diet on body weight and ovarian function were very similar; those of a moderate Zn with low Ca (MZn/LCa) diet were smaller. 4. The first significant effect of moulting was a decrease in oestradiol-17beta plasma concentration (d 2). Plasma progesterone decreased more gradually than oestradiol-17beta, and reached a nadir on d 6 in FW- and HZn-treated hens and on d 9 in MZn/LCa-treated ones. 5. Hens treated with either FW or the MZn/LCa, but not those with the HZn diet, showed a very sharp rise in corticosterone concentration on d 2 of treatment. Thus the MZn/LCa diet was less efficient than the other treatments in induction of ovarian involution, but had a similar effect on stress induction, as indicated by increases in plasma corticosterone.     

Normal sexual maturation and reproductive function in domestic hens following unilateral adrenalectomy

The ovulation-inducing properties of adrenal hormones and the anatomical juxtaposition of the left adrenal gland and the ovary suggest that a functional relationship exists between these two endocrine organs. To test this hypothesis, the effect of unilateral adrenalectomy on sexual maturation and reproductive function was examined in left and right adrenalectomized SCWL pullets. Between 9 and 13 weeks of age, 24 and 12 pullets were either left or right adrenalectomized, respectively; 12 birds were sham operated and 7 birds served as unoperated controls. Blood samples were obtained immediately before and after surgery, 48h after surgery and at 14, 19 and 23 weeks of age. All samples were analyzed for plasma corticosterone by radioimmunoassay. At 20 weeks of age all birds were weighed and the photoschedule was changed from 8L:16D to 16L:8D. During the first 52 days following photostimulation the age at first egg and the distribution of ovipositions within the 24h photoschedule were recorded.Mean plasma corticosterone levels of the unilaterally adrenalectomized hens were not significantly different (P > .05) from those of control birds 48h after surgery or at 14, 19 and 23 weeks of age. Unilateral adrenalectomy had no effect on body weight at 20 weeks, average age at first egg, or percent hen-day production. In addition, 95% of the eggs laid in the first 52 days after photostimulation were restricted to a 10 hour period of the day regardless of the surgical treatment. These observations indicate that the removal of either the left or the right adrenal gland does not affect plasma levels of corticosterone, sexual maturation, or the open period for LH release as evidenced by the times of oviposition and fail to support the hypothesis of a localized functional relationship between the left adrenal gland and the ovary.     

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

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

Diurnal patterns of feeding and activity in laying hens in relation to dietary restriction and cage shape

1. The diurnal feeding pattern and motor activity of medium‐weight hybrid hens housed in groups of four were observed. Cages of two shapes were compared: conventional deep cages (406 × 457 mm) and shallow cages (610 × 305 mm).

2. Birds in conventional deep cages were more active than those in shallow cages in each of four different periods of day. Activity reached a peak between 11.00 and 13.00 h irrespective of cage shape.

3. Mean feeding activity was greater in the shallow (45.6%) than in the conventional deep cages (39.9%).

4. Mean feeding activity was greater in birds fed ad libitum (43.3%) than in those fed on a restricted diet (40.4%).

5. Although restricted birds in shallow cages showed more feeding activity than those in conventional deep cages they consumed less food (56% against 67%) in the 7 h between supply of their daily ration and the onset of the dark period.

6. Feather damage was greater in the conventional deep cages than in the shallow cages.

7. The more efficient utilisation of food by hens in shallow cages is probably due largely to three factors: reduced levels of motor activity and general disturbance, a more leisurely eating pattern and better feather cover.