Organ weight and serum triglyceride responses of older (80 week) commercial laying hens fed an alfalfa meal molt diet

Since one of the costs in the commercial egg industry is that of replacement pullets, commercial egg layer managers have opted to induce molt older hens in order to extend their productive life for additional egg laying cycles. Conventional molt induction involves the complete removal of feed for several days. However, this management practice can lead to deleterious physiological responses by the hen and subsequent susceptibility to infection by pathogens. Consequently less stressful molting regimens involving the feeding of low energy diets such as alfalfa have been developed. In this study, 80 week old laying hens that were deprived of feed or fed alfalfa meal during a nine day induced molt. Full fed hens were used as the control. On day 8 serum triglycerides were quantified and on day 9 hens were euthanized and the liver, spleen, heart, intestine, pancreas, ovary, and kidney were collected and weighed. Intestinal weight were highest in the non-molted hens, lower in the hens fed alfalfa, and lower still in the hens deprived of feed. Molted hens exhibited reduced weights of liver, heart, ovary, and pancreas compared to the non-molted hens. Serum triglycerides were highest in the non-molted hens, less in feed deprived hens, and the lowest in alfalfa fed hens. These results suggest that a comparable molt could be achieved with feeding alfalfa meal to 80 week hens compared to feed deprivation.     

Potential of alfalfa as an alternative molt induction diet for laying hens: egg quality and consumer acceptability

Dietary molt induction to initiate additional egg laying cycles in commercial laying hen flocks is a wide spread practice in the United States. Feed deprivation is the most commonly used method but this practice has generated several concerns which has lead to research for viable alternative approaches. From a management standpoint a single ingredient molting diet consisting of high fiber-low energy represents an easily adaptable diet for large laying hen production units. Alfalfa meal is readily available in most commercial locations and possesses many of the desirable properties of an ideal laying hen molt diet. In the current study hens at a commercial laying facility were molted by both alfalfa and feed deprivation. After the hens had reentered post-molt commercial egg production, eggs were examined for egg quality performance. Egg shell strength, albumen height, yolk height, weight, length, and yolk color were all tested using various mechanical techniques. The eggs were also sampled for testing by consumer sensory panels that assessed the desirability of the eggs' color and flavor/texture. Eggs laid by hens molted by alfalfa had a significantly lower (p<0.05) "a*" level of colorimetry. Eggs laid by hens molted with alfalfa also exhibited significantly higher (p<0.05) egg weights and length. In the consumer sensory test, there was no significant difference (p>0.05) in color or flavor/texture scores in eggs from either feed deprived or alfalfa molted hens. The consumer sensory and mechanical quality attributes indicates that alfalfa shows promise as an alternative molt induction diet by providing a single diet option for extending egg production into a second egg laying cycle.     

Effect of alfalfa meal in diets of laying quails on performance, egg quality and some serum parameters

This study was conducted to investigate the effects of increasing levels of alfalfa meal in the diet of laying quails on egg production, feed consumption, feed efficiency, egg quality, egg yolk cholesterol and selected serum parameters. In this study, 192, 10-week old quails (Coturnix coturnix japonica) were evenly distributed to four groups with four replicates of 12 quails each. The control group was fed a basal diet containing 0% alfalfa meal and the remaining groups received 3, 6 or 9% alfalfa meal for 12 weeks. Live weight, feed consumption, and egg production were recorded and feed efficiency were calculated. Eggs were examined for interior and exterior quality and egg yolk cholesterol content. At the end of the experiment, blood samples were collected and sera were analysed for serum Ca, inorganic P (P(i)), Mg, triglycerides and total cholesterol. Any level of alfalfa meal had no effect on live weight, egg production, feed consumption, feed efficiency, egg weight, and egg yolk index. Six percent and 9% alfalfa meal increased specific gravity of whole egg and eggshell thickness as well as serum P(i) levels. Nine percent alfalfa meal reduced serum triglycerides, total cholesterol levels and egg yolk cholesterol content. The results of this experiment indicated that addition of 9% alfalfa meal into the laying quail diet may improve eggshell quality and reduced serum triglycerides and serum and egg yolk cholesterol without any adverse effect on performance.     

Using a feed-grade zinc propionate to achieve molt induction in laying hens and retain postmolt egg production and quality

A commercial-feed-grade form of zinc propionate was examined as a potential feed amendment at a concentration of 1% zinc to induce molt in 90-wk-old hens. Dietary treatments consisted, of 4 treatment groups of 28 birds each randomly assigned to either (1) molted conventionally by feed withdrawal, (2) 1% zinc as Zn acetate, (3) 1% zinc as Zn propionate, or (4) nonmolted control for 9 d. Ovary weights of hens fed Zn acetate or Zn propionate were not significantly different from each other, but hens fed Zn acetate or Zn propionate were significantly (p<0.05) lighter than the ovary weight of nonmolted control hens. Zinc concentrations in the kidney and liver were significantly (p<0.05) increased in both Zn acetate- and Zn propionate-molted hens when compared to either nonmolted control-fed hens or feed-withdrawal molted hens. Over the entire 3-mo postmolt period, there were no significant differences in interior or exterior egg qualities among the four treatments Egg production of hens fed Zn acetate was significantly lower than feed-withdrawal hens, Zn propionate-fed hens, or nonmolted control hens (p<0.05). The data of the current study demonstrated that feeding a feed grade of Zn propionate (1% Zn)-supplemented diet can induce molt and retain postmolt egg quality and production comparable to hens molted by feed withdrawal.     

A functional study on L-type calcium channels in granulosa cells of small follicles in laying and forced molt hens

To investigate Ca(2+) dynamics in earlier phases of follicular development we compared the resting [Ca(2+)](i) and tested the functional responses to agonist/antagonist of L-type voltage-operated calcium channels (VOCCs) in small follicles GCs from hens during oviposition (O-GCs) and forced molt (M-GCs), using the microspectrofluorimetric [Ca(2+)](i) imaging. O-GCs were obtained from prehierarchical follicles (F(6)-F(5)-F(4)<8mm). In basal and agonist/antagonist stimulated M-GCs we did not observe a change in the [Ca(2+)](i) under any of condition in all cells analyzed. Based on basal measurements we can distinguish three different patterns reflecting cells variability within O-GCs group: (a) 39% cells showed small oscillations and [Ca(2+)](i) was 108±11nM; (b) 36% cells displayed yet small oscillations and [Ca(2+)](i) was 167±14nM; (c) 25% were cells with repetitive irregular oscillations that peaked until 2 fold basal value and [Ca(2+)](i) very variable, was 248±41nM. In O-GCs L-type VOCCs stimuli displayed different effects on [Ca(2+)](i) for both treatment in three basal patterns. In our study we demonstrated: (1) at resting the [Ca(2+)](i) is low (111±5nM) in M-GCs and tend to increasing in prehierarchical O-GCs; (2) L-type Ca(2+) channels are functionally expressed in the major part of O-GCs whereas they are not activated nor inhibited in M-GCs and in a percentage of O-GCs; (3) there are three different cellular types in prehierarchical O-GCs that may be associated with increasing stages of follicular development, based on their Ca(2+) pathway. Therefore, the functional response of L-type Ca(2+) channels in cultured laying hen prehierarchical GCs may be correlated with the functional maturation phase of laying hens ovarian. We hypothesize that the L-type Ca(2+)-dependent signaling could have a critical role in the regulatory mechanisms hormone mediated in hen ovarian cycle.     

Detection of QTL for immune response to sheep red blood cells in laying hens

The aim of this study is to detect quantitative trait loci (QTL) involved in the regulation of the primary and the secondary immune response to sheep red blood cells (SRBC) in a resource population using microsatellite DNA markers. The F2 resource population originates from a cross of two divergently selected lines for either high (H line) or low (L line) primary antibody response to SRBC. The F2 population consisted of six half-sib families, three families per each of reciprocal crosses. Total antibody titres to SRBC were determined by agglutination in serum from all birds. F2, F1 and F0 generations were genotyped for 170 microsatellite markers, using a whole-genome scan approach. The half-sib and the line-cross analyses were performed to determine QTL regions associated with regulation of the immune response. In the half-sib analysis, four QTL for SRBC primary response have been identified: on GGA3, GGA5, GGA16 and GGA23. No QTL was identified for SRBC secondary response under the half-sib model. In the line-cross analysis, three QTL were identified on GGA10, GGA16 and GGA27 for SRBC primary response and five QTL were identified on GGA6, GGA9, GGA15, GGA16 and GGA27 for SRBC secondary response. Subsequently, the family contribution of individual families to the QTL was analysed. The family with the largest contribution was genotyped with additional microsatellite markers in the QTL region on GGA5. The extended half-sib analysis with additional genotype information results in narrowing down the QTL region on GGA5.     

Reaction to frustration in high and low feather pecking lines of laying hens from commercial or semi-natural rearing conditions

The effect of rearing conditions on feather pecking and reaction to frustration was studied in two lines of laying hens. From commercial rearing conditions (large group, no mother hen), seven birds from a high feather pecking line (HC birds) and eight birds from a low feather pecking line (LC birds) were used. From semi-natural rearing conditions (small group, mother hen present) seven birds from the high feather pecking line (HN birds) were used. Feather pecking behaviour of HC, LC, and HN groups was recorded for 30 min. After that, each bird was food deprived and trained to peck a key for a food reward in a Skinnerbox. After training, each bird was subjected to a frustration session in a Skinnerbox, where the feeder was covered with Perspex. Three HC birds showed severe feather pecking, compared with one HN bird and zero LC birds. Differences in reaction to frustration were found between birds from different lines, but not in birds from different rearing conditions. LC birds tended to put their head in the feeder more frequently than HC birds over all sessions. Although limited, this study indicates that rearing conditions influence feather pecking, but not reaction to frustration.     

Across-line SNP association study of innate and adaptive immune response in laying hens

The aim of the present study was to detect quantitative trait loci (QTL) for innate and adaptive immunity in laying hens. For this purpose, the associations between 1022 single nucleotide polymorphism (SNP) markers and immune traits were studied in 583 hens from nine different layer lines. Immune traits were natural antibodies for keyhole limpet haemocyanin (KLH) and lipopolysaccharide (LPS) at 20, 40 and 65 weeks, acquired antibodies to the vaccinal virus of Newcastle disease at 20 weeks, and complement activity measured on sheep and bovine red blood cells at 20, 40 and 65 weeks. We adopted a novel approach based on across-line analysis and testing of the SNP-by-line interaction. Among lines, linkage disequilibrium is conserved at shorter distances than in individual lines; therefore, SNPs significantly associated with immune traits across lines are expected to be near the functional mutations. In the analysis, the SNPs that had a significant across-line effect but did not show significant SNP-by-line interaction were identified to test whether the association was consistent in the individual lines. Ultimately, 59 significant associations between SNPs and immune traits were detected. Our results confirmed some previously identified QTL and identified new QTL potentially involved in the immune function. We found evidence for a role of IL17A (chromosome 3) in natural and acquired antibody titres and in the classical and alternative pathways of complement activation. The major histocompatibility genes on chromosome 16 showed significant association with natural and acquired antibody titres and classical complement activity. The IL12B gene on chromosome 13 was associated with natural antibody titres.     

Spatial distribution and behaviour of laying hens housed in an alternative system

The spatial distribution and behaviour of perchery housed laying hens were compared at a constant stocking density (18.5 birds/m(2)) in eight pens with colonies of five different sizes (323 birds (N=1), 374 birds (N=2), 431 birds (N=2), 572 birds (N=1) and 912 birds (N=2)). The birds were placed in the perchery when they were 12 weeks old. Observations began when they were 26 weeks old and continued at 8 week intervals until 61 weeks of age. Colony size did not appear to affect the spatial distribution of birds, but more standing behaviour and less feeding behaviour were observed in the smallest and largest colony sizes. Older birds spent more time on the floor areas and less time on perches. Young birds (26-28 weeks) spent more time feeding, foraging, drinking and preening, and less time standing idle than older birds. In the afternoons, there were fewer birds on the perches and more on the floor levels, corresponding with less time spent resting and more time spent performing active behaviours. Birds did not distribute themselves evenly throughout their pens: within specific areas of pens densities varied between 9 and 41 birds/m(2). This variation, which reflects the flux of birds from one part of the pen to another, was greatest for the larger colony sizes, and may have adverse implications for welfare in terms of crowding and hysteria.     

Early enrichment in free-range laying hens: effects on ranging behaviour,welfare and response to stressors

Free-range laying hen systems are increasing within Australia. The pullets for these systems are typically reared indoors before being provided first range access around 21 to 26 weeks of age. Thus, the rearing and laying environments are disparate and hens may not adapt well to free-range housing. In this study, we reared 290 Hy-Line® Brown day-old chicks divided into two rooms each with feed, water and litter. In the enriched room, multiple structural, manipulable, visual and auditory stimuli were also provided from 4 to 21 days, the non-enriched room had no additional objects or stimuli. Pullets were transferred to the laying facility at 12 weeks of age and divided into six pens (three enriched-reared, three non-enriched-reared) with identical indoor resources and outdoor range area. All birds were first provided range access at 21 weeks of age. Video observations of natural disturbance behaviours on the range at 22 to 23 and 33 to 34 weeks of age showed no differences in frequency of disturbance occurrences between treatment groups (P=0.09) but a decrease in disturbance occurrences over time (P<0.0001). Radio-frequency identification tracking of individually tagged birds from 21 to 37 weeks of age showed enriched birds on average, spent less time on the range each day (P<0.04) but with a higher number of range visits than non-enriched birds from 21 to 24 weeks of age (P=0.01). Enriched birds accessed the range on more days (P=0.03) but over time, most birds in both treatment groups accessed the range daily. Basic external health scoring showed minimal differences between treatment groups with most birds in visibly good condition. At 38 weeks of age all birds were locked inside for 2 days and from 40 to 42 weeks of age the outdoor range was reduced to 20% of its original size to simulate stressful events. The eggs from non-enriched birds had higher corticosterone concentrations following lock-in and 2 weeks following range reduction compared with the concentrations within eggs from enriched birds (P<0.0001). Correspondingly, the enriched hens showing a greater increase in the number of visits following range area reduction compared to non-enriched hens (P=0.02). Only one rearing room per treatment was used but these preliminary data indicate 3 weeks of early enrichment had some long-term effects on hen ranging behaviour and enhanced hen’s adaptability to environmental stressors.     

Changes in plasma thyroid hormones, luteinizing hormone (LH), estradiol, progesterone and corticosterone of laying hens during a forced molt

1. Circulating concentrations of iodothyronines, luteinizing hormone(LH), estradiol(E2), progesterone and corticosterone were measured in hens before, during, and after a forced molt induced by fasting. 2. Corticosterone increased at the onset of molt, peaked at the maximal molt and returned to pre- and post-molt levels. LH, E2 and progesterone declined during the molt, and the decline was coincident with the cessation of egg production. 3. Thyroxine(T4), triiodothyronine (T3) and reverse triiodothyronine(rT3) increased during the molt. The increases of T4 and T3 were not abolished even if the forced molt was conducted in mild weather.     

Dietary supplementation of pyrroloquinoline quinone disodium protects against oxidative stress and liver damage in laying hens fed an oxidized sunflower oil-added diet

The protective effects of dietary pyrroloquinoline quinone disodium (PQQ.Na₂) supplementation against oxidized sunflower oil-induced oxidative stress and liver injury in laying hens were examined. Three hundred and sixty 53-week-old Hy-Line Gray laying hens were randomly allocated into one of the five dietary treatments. The treatments included: (1) a diet containing 2% fresh sunflower oil; (2) a diet containing 2% thermally oxidized sunflower oil; (3) an oxidized sunflower oil diet with 100 mg/kg of added vitamin E; (4) an oxidized sunflower oil diet with 0.08 mg/kg of PQQ.Na₂; and (5) an oxidized sunflower oil diet with 0.12 mg/kg of PQQ.Na₂. Birds fed the oxidized sunflower oil diet showed a lower feed intake compared to birds fed the fresh oil diet or oxidized oil diet supplemented with vitamin E (P=0.009). Exposure to oxidized sunflower oil increased plasma malondialdehyde (P<0.001), hepatic reactive oxygen species (P<0.05) and carbonyl group levels (P<0.001), but decreased plasma glutathione levels (P=0.006) in laying hens. These unfavorable changes induced by the oxidized sunflower oil diet were modulated by dietary vitamin E or PQQ.Na₂ supplementation to levels comparable to the fresh oil group. Dietary supplementation with PQQ.Na₂ or vitamin E increased the activities of total superoxide dismutase and glutathione peroxidase in plasma and the liver, when compared with the oxidized sunflower oil group (P<0.05). PQQ.Na₂ or vitamin E diminished the oxidized sunflower oil diet induced elevation of liver weight (P=0.026), liver to BW ratio (P=0.001) and plasma activities of alanine aminotransferase (P=0.001) and aspartate aminotransferase (P<0.001) and maintained these indices at the similar levels to the fresh oil diet. Furthermore, oxidized sunflower oil increased hepatic DNA tail length (P<0.05) and tail moment (P<0.05) compared with the fresh oil group. Dietary supplementation of PQQ.Na₂ or vitamin E decreased the oxidized oil diet induced DNA tail length and tail moment to the basal levels in fresh oil diet. These results indicate that PQQ.Na₂ is a potential antioxidant and is as effective against oxidized oil-related liver injury in laying hens as vitamin E. The protective effects of PQQ.Na₂ against liver damage induced by oxidized oil may be partially due to its role in the scavenging of free radicals, inhibiting of lipid peroxidation and enhancing of antioxidant defense systems.     

Effects of ambient temperature and methionine supplementation of a low protein diet on the performance of laying hens

The effects of ambient temperature and the supplementation of methionine to a low protein diet on egg production, egg quality, blood constituents and nitrogen excretion of laying hens were studied. The objective was to derive an environmental friendly feed formulation for warm climate. Seventy-two 29-week-old commercial White Leghorn hens of Babcock ISA white strain were used in this trial. The design is a completely randomized design with a 2×3 factors arrangement of treatments. Two constant ambient temperatures were 24±1°C and 34±1°C with 85% relative humidity. The three dietary treatments were 170 g kg⁻¹ crude protein, 140 g kg⁻¹ crude protein and 140 g kg⁻¹ crude protein supplemented with methionine 1.4 g kg⁻¹. Hens were allotted into six groups according to egg production and body weight. Birds were raised in individual wire cages for the experimental feeding period of five weeks. At the end of the feeding trial, one replicate of laying hens (four birds) from each treatment were selected for a four-day metabolic study for the daily collection of the excreta. The blood samples were withdrawn from the wing vein for analysis of hematocrit, blood glucose, sodium, potassium, magnesium, calcium, phosphorus and uric acid. Experimental results indicate that increases in ambient temperature significantly depress feed intake, egg production, egg weight and live weight of laying hens. High ambient temperature also caused inferior egg quality, including shell weight, shell thickness, shell breaking strength and specific gravity. Ambient temperature also changes the egg components with heavier egg albumin and yolk in the low-temperature group. Increasing ambient temperature also caused an increase in pH value in the plasma. This increase revealed a trend of depressed glucose (P<0.05) in the plasma of the laying hens. The dietary treatments, however, did not significantly influence feed intakes. Except egg weight, laying hens that were fed with the low protein (140 g kg⁻¹) with methionine supplemented diet produced similar numbers of egg and feed conversion as the layers fed with the high protein diet. The low protein with methionine supplemented diet produced significantly lighter eggs than the high dietary protein diet under the high ambient temperature, but produced heavier egg under the low ambient temperature. The concentration of uric acid in the plasma and nitrogen in the excreta of the high protein group was significantly higher than the other two low protein dietary groups (P<0.05).     

Feather eating and its associations with plumage damage and feathers on the floor in commercial farms of laying hens

Feather eating has been associated with feather pecking, which continues to pose economic and welfare problems in egg production. Knowledge on feather eating is limited and studies of feather eating in commercial flocks of laying hens have not been performed previously. Therefore, the main objective was to investigate feather eating and its association with plumage damage and floor feather characteristics in commercial flocks of layers in barn and organic production systems. The study was performed in 13 flocks of barn layers and 17 flocks of organic layers. Each flock was visited at around 32 and 62 weeks of age. During both visits, the plumage condition was assessed and the density of floor feathers recorded. In week 62, droppings and floor feathers were collected. Droppings were examined for presence of feather content, whereas length, downiness and pecking damage were recorded for each floor feather. In week 62, a higher prevalence of hens with poor plumage condition was found in barn (22.2%) compared with organic production systems (7.4%; P<0.001), but the prevalence of droppings with feather content did not differ between the two production systems (8.5% in barn v. 4.3% in organic; P=0.99). Our hypothesis about a positive correlation between feather eating and plumage damage was not supported as no correlation was found between the prevalence of poor plumage condition and the prevalence of droppings with feather content. However, the prevalence of pecking damaged floor feathers was positively correlated both with prevalence of droppings with feather content (P<0.05) and poor plumage condition (P<0.01), indicating a possible association between feather eating and feather pecking. In conclusion, it was confirmed that feather eating occurs on-farm, but feather eating was only found to be positively correlated to the number of floor feathers with pecking damage and not as expected to the prevalence of plumage damage. More research is needed into the sources from where feathers are selected for ingestion, that is, whether they are picked from the floor litter, plucked directly from other hens or dislodged during preening of own feathers.     

Motivation to dust-bathe of laying hens housed in cages and in aviaries

New housing systems for commercial egg production, furnished cages and non-cage systems, should improve the welfare of laying hens. In particular, thanks to the presence of a litter area, these new housing systems are thought to satisfy the dust-bathing motivation of hens more than in conventional cages, in which no litter area is present. However, although apparently obvious, there is no concrete evidence that non-cage systems, particularly aviaries, satisfy hens' motivation to dust-bathe and thus improve hens' welfare in terms of dust-bathing behaviour. The aim of this study was to compare hens' dust-bathing motivation when housed for a long time under similar conditions to commercial conditions in laying aviaries (with litter) and in conventional cages (without litter). Three treatments were compared: hens reared in floor pens then housed in conventional cages, hens reared in furnished floor pens then housed in a laying aviary, and hens reared in rearing aviaries then housed in a laying aviary. All three treatments provided access to litter during the rearing period. After transfer to the laying systems, access to litter was maintained for the aviary hens but stopped for the cage hens. Twelve groups of four hens per treatment were tested 36 to 43 weeks after transfer. The hens were placed in sawdust-filled testing arenas, and latency to dust-bathe, duration and number of dust baths, and number of hens dust-bathing were recorded. Latency to dust-bathe was shorter, dust baths were longer and more numerous and more hens dust-bathed among cage hens than among aviary hens. Our results indicate that hens' motivation to dust-bathe was more satisfied in laying aviaries than in conventional cages. Thus, laying aviaries improve hens' welfare in term of dust-bathing behaviour compared with conventional cages.     

Impact of an energy- and nutrient-reduced diet containing 10% lignocellulose on animal performance,body composition and egg quality of dual purpose laying hens

In response to ethical concerns regarding the killing of day-old male chicks of layer breeds, the use of dual purpose chickens is increasingly discussed in public while data on nutritional requirements of dual purpose laying hens are not available. The present study examined the impact of an energy- and nutrient-reduced diet containing lignocellulose on performance, body composition and egg quality of dual purpose hens. Female Lohmann Dual chicks were allocated to 12 pens and fed two different diets for 52 weeks: a control (CON) and a treatment diet (LC), based on CON but diluted with 10% lignocellulose. During the trial, animal performance, whole-body composition and egg quality parameters of hens were consistently ascertained. The results showed that LC-fed hens had lower body weights compared to those receiving CON (p < 0.05). During the laying period, feed intake was increased in LC-fed hens (p < 0.001). LC-fed hens showed a higher egg production and egg mass resulting in an improved feed efficiency (p < 0.05) and laid smaller eggs compared to CON-fed hens (p < 0.001). At 52 weeks of age, bodies of LC-fed hens had higher protein and lower fat contents than those fed with CON diet (p ≤ 0.001). Mean body weight was positively correlated to the body fat content (p = 0.004) and body fat content was negatively correlated to the egg production (p = 0.043). Analyses of the egg quality showed that yolk mass at all sampling points and albumen mass at 27 and 42 weeks were lower in hens fed with diet LC compared to those fed with diet CON (p< 0.05). In conclusion, the feeding of energy- and nutrient-reduced diets containing 10% lignocellulose reduced the body fat content and simultaneously improved the laying performance in dual purpose hens.     

Night-time roosting in laying hens and the effect of thwarting access to perches

Free-living hens roost on branches in trees at night, and laying hens in aviary systems or cages provided with perches also make extensive use of these for night-time roosting. It is therefore suggested that roosting on perches is important to the hens and that domestic hens should be provided with perches in order to promote welfare. However, no study has addressed the question of motivation for roosting. In the present experiment, we studied undisturbed roosting behaviour and the reaction of commercial laying hens when roosting on perches was thwarted. Fifty-two adult hens (Lohmann Selected Leghorn, LSL) were kept in two groups of 26 hens in litter pens with perches at heights of 23, 43 and 63 cm. Behaviour was observed for 60 min starting at lights-off, registering the number of hens on each perch level. The hens started to get onto the perch immediately and within 10 min after lights-off, more than 90% of the hens were on the perch. All hens roosted close together on the top perch. In a second experiment, 24 hens were kept in eight groups of three birds each in experimental pens equipped with perches. Birds were tested in four different situations: (1) the pen unchanged (Base), (2) the perch covered with plexiglass (PCov), (3) the perch removed (PRem) and (4) the unchanged pen (Post). The order of PCov and PRem alternated between groups in a balanced manner and all groups of birds experienced all four treatments. The hens were observed for 60 min from lights-off using focal sampling. For comparisons, the Post treatment served as the control. In the treatments where perching was not possible, the hens spent less time sitting (p=0.042), and also tended to spend more time standing (p=0.06), than in the control. Furthermore, the hens moved more (p=0.042) when the perch was inaccessible, and when the perch was visible but inaccessible they also showed more attempts to take off (p=0.042). These findings can be interpreted as increased frustration and/or exploration, probably to find an alternative roosting site. Together with the high use of perches for night-time roosting under undisturbed conditions, these results indicate that laying hens are motivated to perch and imply that hens kept under conditions where perching is not possible may experience reduced welfare.     

The humoral immune response and the productivity of laying hens kept on the ground or in cages

The effects of two different keeping systems on the humoral immune response and productivity were compared for 80 laying hens, divided into four groups. Two groups each of 20 hens were kept on the ground and two were kept in cages. All the birds were immunised subcutaneously with human serum immunoglobulin G (IgG) at a dose of 100(microg per injection. The immunisations were performed twice at 4-week intervals. The lipopeptide Pam(3)Cys-Ser-(Lys)(4) was used as an adjuvant at a dose of 0.25mg per injection in one group from each housing system. In the second group from each housing system, the hens were immunised without any adjuvant (antigen control groups). The mean egg yield was significantly higher in both the antigen control group and the adjuvant group, when laying hens were kept in cages. Total egg weight remained constant in both of the housing systems. Keeping hens in cages resulted in higher mean specific antibody titres and mean immunoglobulin Y concentrations in the egg yolk.