Effect of manipulating feathers of laying hens on the incidence of feather pecking and cannibalism

Feather pecking is a problem in commercial laying hens, particularly in loose-housing systems, where many hens can be affected by only a few feather peckers. In addition, feather pecking can become an even larger problem if it spreads throughout the flock. There are several possible ways that feather pecking may spread. The simplest way is that one hen may damage the feathers of a hen, and another hen may find the damaged feathers an attractive pecking target. The aim of this experiment was to determine if damaged feathers were feather-pecked more than undamaged feathers on the same body area, and to determine whether some types of feather-body area manipulations were preferred over others as pecking stimuli. Manipulations involved damaging the feathers on the rump, tail or belly of different hens, with two or three levels of severity of manipulation at each body area. Sixteen groups of 11 Lohmann Brown hens between 26 and 28 weeks were observed with the recipient, the feather pecker and the body area that was pecked all being recorded. The feather pecks were classified separately as either gentle or severe. Damaged feathers received significantly more severe feather pecks than undamaged feathers. There were also more gentle feather pecks to damaged feathers, although this did not reach statistical significance. The feather-body area manipulations that received the greatest number of severe feather pecks were the tail feathers when they were cut very short, the rump feathers when they were trimmed, and the rump when feathers were removed. These results support the suggestion that feather pecking does indeed spread through flocks by damaged feathers becoming an attractive target for feather-pecking behaviour. An unexpected result of performing the feather manipulations was an outbreak of cannibalism in half of the experimental groups. Even though there was no visible damage to the skin of the hens after having the feathers manipulated, 13 of the 16 attacked hens were wounded on the part of the body where the feathers had been damaged in some way.     

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.     

Selection method and early-life history affect behavioural development, feather pecking and cannibalism in laying hens: A review

The aim of this review is to discuss the effects of selection method and early-life history on the behavioural development of laying hens. Especially in larger groups, laying hens often develop damaging behaviours, such as feather pecking and cannibalism, leading to impaired animal welfare. We hypothesise that the propensity to develop feather pecking and cannibalism is affected by a bird's genetic background and by its early-life history. The genetic background can be influenced by genetic selection. Laying hens are traditionally selected on individual performance, which may lead to co-selection of feather pecking and cannibalism. For hens kept in small groups, it has recently been demonstrated that a novel group selection method, focusing on group performance, can help to reduce cannibalism. However, the biological background behind the success of group selection is unknown. It is also not known whether these results from small groups can be translated to larger groups of laying hens. Regarding early-life history, laying, brooding and rearing conditions have been shown to have major effects on behavioural development and on feather pecking and cannibalism. The presence of a hen during rearing has been shown to improve foraging- and social behaviour, to decrease feather pecking and to decrease fearfulness in chicks. Applying group selection and rearing laying hens in a more natural environment may be key factors in solving the problems caused by feather pecking and cannibalism, especially if the promising results of group selection from small groups in experimental settings can be translated to large-group housing systems.     

Plumage condition in laying hens: genetic parameters for direct and indirect effects in two purebred layer lines

Background

Feather pecking is a major welfare issue in laying hen industry that leads to mortality. Due to a ban on conventional cages in the EU and on beak trimming in some countries of the EU, feather pecking will become an even bigger problem. Its severity depends both on the victim receiving pecking and on its group mates inflicting pecking (indirect effects), which together determine plumage condition of the victim. Plumage condition may depend, therefore, on both the direct genetic effect of an individual itself and on the indirect genetic effects of its group mates. Here, we present estimated genetic parameters for direct and indirect effects on plumage condition of different body regions in two purebred layer lines, and estimates of genetic correlations between body regions.

Methods

Feather condition scores (FCS) were recorded at 40 weeks of age for neck, back, rump and belly and these four scores were added-up into a total FCS. A classical animal model and a direct–indirect effects model were used to estimate genetic parameters for FCS. In addition, a bivariate model with mortality (0/1) was used to account for mortality before recording FCS. Due to mortality during the first 23 weeks of laying, 5363 (for W1) and 5089 (for WB) FCS records were available.

Results

Total heritable variance for FCS ranged from 1.5% to 9.8% and from 9.8% to 53.6% when estimated respectively with the classical animal and the direct–indirect effects model. The direct–indirect effects model had a significantly higher likelihood. In both lines, 70% to 94% of the estimated total heritable variation in FCS was due to indirect effects. Using bivariate analysis of FCS and mortality did not affect estimates of genetic parameters. Genetic correlations were high between adjacent regions for FCS on neck, back, and rump but moderate to low for belly with other regions.

Conclusion

Our results show that 70% to 94% of the heritable variation in FCS relates to indirect effects, indicating that methods of genetic selection that include indirect genetic effects offer perspectives to improve plumage condition in laying hens. This, in turn could reduce a major welfare problem.     

Are genetic differences in foraging behaviour of laying hen chicks paralleled by hybrid-specific differences in feather pecking?

Feather pecking is a behavioural disorder in laying hens which consists of pecking the feathers of conspecifics, causing feather damage or even injuries to the skin. Its development can be explained by redirection of foraging behaviour. While the occurrence of feather pecking strongly depends on the kind of housing condition, it is also known that there are strain differences in the tendency to feather peck. From the inverse relation between feather pecking and foraging behaviour found earlier, we hypothesised that genetically determined differences in foraging behaviour could be responsible for the observed differences in feather pecking between strains.In a first experiment we tested whether there are differences in the foraging behaviour of two hybrids. As hybrids, we used Lohman selected leghorn (LSL) and Dekalb; eight groups of 20 1-day old chicks each. They were kept in enriched pens (265cmx90cm) with a litter area (200cmx90cm) consisting of wood-shavings, chaff, straw, polystyrene blocks, sand area (65cmx90cm) and elevated perches. Behavioural observations were carried out in week 4. In a subsequent experiment with the same birds we tested how the foraging behaviour of the two hybrids differed when housing conditions were changed from enriched to restricted and to what extent they developed feather pecking. A 2x2 factorial design with hybrid (LSL, Dekalb) and housing condition (restricted, enriched) as factors and with four replicates of each factor combination was used. Half of the pens of each hybrid were changed from enriched to restricted housing conditions by covering the litter area with slats. Behavioural observations were carried out in weeks 5 and 6.In experiment 1, LSL and Dekalb spent the same amount of time foraging, but Dekalb spent significantly more of that time with pecking and hacking at the polystyrene blocks. On the other hand, LSL spent significantly more time at the feeding troughs and rested significantly less than Dekalb. In the restricted environment of experiment 2, again, the total foraging time did not differ between hybrids, but LSL chicks spent significantly less time scratching, while Dekalb spent significantly more time moving. Both hybrids developed feather pecking but LSL showed significantly higher rates than Dekalb.Our results demonstrate genetic differences in the foraging behaviour and in the way hybrids cope with the change in housing condition from enriched to an environment that is restricted in relation to foraging possibilities. We conclude that the results support the hypothesis put forward that genetic differences in foraging behaviour could be the basis for the genetic influence in the development of feather pecking.     

Effect of rearing density on pecking behaviour and plumage condition of laying hens in two types of aviary

The objective of this experiment was to investigate the effect of rearing density on pecking behaviour and plumage during rearing and throughout the laying period in aviaries. Chicks were reared on sand at high (H; 13 m⁻²) or low (L; 6.5 m⁻²) density, in four rearing pens of 390 chicks and eight pens of 195 chicks, respectively, each pen measuring 30 m². Proportions of chicks per pen performing various types of pecking behaviour were recorded by scan sampling during 16 observation bouts in each rearing pen at 6 weeks of age and during 24 observation bouts at 12 weeks. Individual body weights and plumage condition were recorded. Later, these pullets were housed at 17 hens m⁻² in Tiered Wire Floor (TWF; 3 H and 3 L pens of 275 hens) and Laco-Volétage (2 H and 2 L pens of 275 hens) aviaries. At 35 weeks, two samples of eight hens from each aviary pen were observed for pecking behaviour in a test pen. Throughout the laying period, additional records were collected on pecking behaviour, body weight, plumage condition, egg production, and mortality. The L birds had better plumage condition at 6 weeks of age and throughout the laying period. These birds also ground pecked more frequently than H birds during rearing and the laying period. At 12 weeks, L birds feather pecked less than H birds, but no relationship was found between rearing density and feather-pecking behaviour during the laying period. Although TWF hens feather pecked more frequently than Volétage hens, there was no interaction between rearing density and type of aviary for the various pecking behaviours.     

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

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

The association between plumage damage and feather-eating in free-range laying hens

Severe feather-pecking (SFP) persists as a highly prevalent and detrimental behavioural problem in laying hens (Gallus gallus domesticus) worldwide. The present experiment investigated the association between feather-eating and plumage damage, a consequence of SFP, in groups of free-range, ISA Brown laying hens. Single feathers were placed on the floor of the home pens. Feathers were sourced from seven different birds. A total of 50 birds in six pens with extensive plumage damage were compared with birds in six control pens with little plumage damage at 41 to 43 weeks of age (n=12 pens, 600 hens). Birds in pens with extensive plumage damage ingested more feathers (F=8.1, DF=1, 8, P=0.02), and also showed shorter latencies to peck at (χ²=54.5, DF=1, P<0.001), and ingest feathers (χ²=55.6, DF=1, P<0.001). Birds ingested feathers from a bird in the free-range facility, in which the testing took place, more quickly than from a bird housed in a separate cage facility (χ² = 39.0, DF=6, P<0.001). A second experiment investigated the predictive relationship between feather-eating and plumage damage. Feathers were presented to 16 pens of 50 pullets prior to the development of plumage damage, at 15 weeks of age, and then to the same hens after plumage damage had become prominent, at 40 weeks of age. Birds had a higher probability of ingesting feathers (F=142.0, DF=1, 231, P<0.001), pecked feathers more times (F=11.24, DF=1, 239, P<0.001), and also pecked (χ² = 127.3, DF=1, P<0.001) and ingested (χ²=189.3, DF=1, P<0.001) the feathers more quickly at 40 than 15 weeks of age. There was a trend for an interaction, where birds pecked feathers from the rump more times than feathers from the back at 40 weeks of age (F=3.46, DF=1, 237, P=0.06). However, a lack of variability in plumage damage between pens in this experiment precluded investigation of the predictive relationship. The results from the present study confirm the association between feather-eating and plumage damage, and suggest that birds may prefer feathers from particular body areas and from particular hens. Future experiments should focus on elucidating whether feather-eating may act as a predictor of SFP.     

Pharmacokinetics of Repeated Sodium Salicylate Administration to Laying Hens: Evidence for Time Dependent Increase in Drug Elimination from Plasma and Eggs

Salicylates were the first non-steroid anti-inflammatory drugs (NSAIDs) to be used in any species and are still widely used in humans and livestock. However, the data on their pharmacokinetics in animals is limited, especially after repeated administration. Evidence exist that in chickens (Gallus gallus) salicylate (SA) may induce its own elimination. The aim of this study was to investigate salicylate pharmacokinetics and egg residues during repeated administration of sodium salicylate (SS) to laying hens. Pharmacokinetics of SA was assessed during 14 d oral administration of SS at daily doses of 50 mg/kg and 200 mg/kg body weight to laying hens. On the 1^st, 7^th and 14^th d a 24 h-long pharmacokinetic study was carried out, whereas eggs were collected daily. Salicylate concentrations in plasma and eggs were determined using high-performance liquid chromatography with ultraviolet detection and pharmacokinetic variables were calculated using a non-compartmental model. Mean residence time (MRT), minimal plasma concentration (C_min, C_16h) and elimination half-life (T_1/2el) of SA showed gradual decrease in layers administered with a lower dose. Total body clearance (Cl_B) increased. Layers administered with the higher dose showed a decrease only in the T_1/2el. In the low dose group, SA was found only in the egg white and was low throughout the experiment. Egg whites from the higher dose group showed initially high SA levels which significantly decreased during the experiment. Yolk SA levels were lower and showed longer periods of accumulation and elimination. Repeated administration of SS induces SA elimination, although this effect may differ depending on the dose and production type of a chicken. Decreased plasma drug concentration may have clinical implications during prolonged SS treatment.     

Is there social transmission of feather pecking in groups of laying hen chicks?

Feather pecking is an abnormal behaviour where laying hens peck the feathers of conspecifics, damaging the plumage or even injuring the skin. If it occurs in a flock, more and more birds show it within a short period of time. A possible mechanism is social transmission. Several studies have shown that laying hen chicks, Gallus gallus domesticus, are able to modify their own behaviour when observing the behaviour of other chicks, for example, when feeding and foraging. As there is good experimental evidence that feather pecking originates from foraging behaviour, we hypothesized that feather pecking could also be socially transmitted. To test this, we reared 16 groups of 30 chicks. After week 4, the birds were regrouped into 16 groups of 20 chicks into each of which we introduced either five chicks that showed high frequencies of feather pecking or, as controls, five chicks that had not developed feather pecking. We then determined the feather-pecking rate and the frequency of foraging, dustbathing, feeding, drinking, preening, moving, standing and resting of all birds in a group. Data from the introduced birds were analysed separately and excluded from the group data. Chicks in groups with introduced feather-pecking chicks had a significantly higher feather-pecking rate than chicks in the control groups. In addition, birds in groups with introduced feather peckers showed significantly lower foraging frequencies than those in the control groups, although the housing conditions were identical and there were no differences in either the number or the quality of the stimuli relevant to foraging behaviour. The study therefore suggests that feather pecking is socially transmitted in groups of laying hen chicks. Copyright 2000 The Association for the Study of Animal Behaviour.     

Losing the last feather: feather loss as an antipredator adaptation in birds

Birds often lose feathers during predation attempts, and thisability has evolved as a means of escape. Because predatorsare more likely to grab feathers on the rump and the back thanon the ventral side of an escaping bird, we predicted that theformer feathers would have evolved to be relatively looselyattached as an antipredator strategy in species that frequentlydie from predation. We estimated the force required to removefeathers from the rump, back, and breast by pulling featherswith a spring balance from a range of European bird speciesin an attempt to investigate ecological factors associated withease of feather loss during predation attempts. The force requiredto loosen a feather from the rump was less than that requiredto loosen a feather from back, which in turn was less than thatrequired to loosen a feather from the breast. The relative forceneeded to loosen rump feathers compared with feathers from theback and the breast was smaller for prey species preferred bythe most common predator of small passerine birds, the sparrowhawkAccipiter nisus. Likewise, the relative force was also smallerin species with a high frequency of complete tail loss amongfree-living birds, which we used as an index of the frequencyof failed predation attempts. The relative force required toremove feathers from the rump was smaller in species with ahigh frequency of fear screams, another measure of the relativeimportance of predation as a cause of death. Feather loss requiredparticularly little force among solitarily breeding bird speciesthat suffer the highest degree of predation. Antipredator defensein terms of force required to remove feathers from the rumpwas larger in species with a strong antiparasite defense interms of T-cell–mediated immune response. These findingsare consistent with the hypothesis that different defenses areantagonistic and that they are traded off against each other.     

Prebasic molt initiation and progress in northern fulmars of the High Arctic: do molt and breeding overlap?

We examined feather molt progress of northern fulmars (Fulmarus glacialis) at Cape Vera in the Canadian High Arctic through opportunistic observation of individuals in flight from 2003 to 2006, and examination of bodies and wings of 127 individuals collected at the site, from 2003 to 2005. We found no evidence suggesting that fulmars shed primary feathers during breeding. Prebasic molt was initiated in the head, neck, sides, belly and back approximately 1 week before hatch. We failed to detect a sex effect on molt progress, but molt among breeders was delayed compared to molt in non- or failed breeders. This study constitutes a baseline we feel may be useful to: (1) researchers interested in feather replacement chronology, wherein feathers are used as sources of biological information; and (2) researchers interested in eventual assessment of relationships among large-scale environmental processes and molt progress in this species, especially in light of predicted changes to Arctic regions.     

Heritability of body surface temperature in hens estimated by infrared thermography at normal or hot temperatures and genetic correlations with egg and feather quality

Exposure of laying hens to chronic heat stress results in loss of egg production. It should be possible to improve hen resilience to chronic heat stress by genetic selection but measuring their sensitivity through internal temperature is time consuming and is not very precise. In this study we used infrared thermography to measure the hen’s capacity to dissipate heat, in a commercial line of laying hens subjected to cycles of neutral (N, 19.6°C) or high (H, 28.4°C) ambient temperatures. Mean body temperatures (BT) were estimated from 9355 infrared images of wing, comb and shank taken from 1200 hens. Genetic parameters were estimated separately for N and H temperatures. Correlations between BT and plumage condition were also investigated. Wing temperature had low heritability (0.00 to 0.09), consistent with the fact that wing temperature mainly reflects the environmental temperature and is not a zone of heat dissipation. The heritability of comb temperature was higher, from 0.15 to 0.19 in N and H conditions, respectively. Finally, the shank temperature provided the highest heritability estimates, with values of 0.20 to 0.22 in H and N conditions, respectively. Taken together, these results show that heat dissipation is partly under genetic control. Interestingly, the genetic correlation between plumage condition and shank and comb temperatures indicated that birds with poor condition plumage also had the possibility to dissipate heat through featherless areas. Genetic correlations of temperature measurements with egg quality showed that temperatures were correlated with egg width and weight, yolk brightness and yellowness and Haugh units only under H conditions. In contrast, shell colour was correlated with leg temperature only at thermo-neutrality.     

Thermoregulatory,behavioral and productive responses of laying hens supplemented with different types and dosages of phytases raised in a hot environment: An integrative approach

This study had the following objectives: (i) to evaluate the thermoregulatory and behavioral responses of light laying hens supplemented with different types and dosages of phytases in the two day shifts; and (ii) to integrate the thermoregulatory and behavioral responses with performance of these birds raised in a hot environment. 270 light laying hens of the Hy-Line White lineage, with a body weight of 1.60 ± 0.092 kg were distributed in a completely randomized design in a 2 × 2 + 1 factorial model with two types of phytases (bacterial and fungal) and two dosages (450 and 900 FTU), and a control diet. The day shift (morning and afternoon) was considered as a fixed effect in the factorial arrangement. Principal component analysis (P_CA), correspondence analysis (C_A) and canonical discriminant analysis (C_DA) were used. There was no interaction (P > 0.05) between phytases and dosages for thermoregulatory responses. Respiratory rate (R_R), cloacal temperature (C_T), and surface temperature with feathers (S_TWF) and featherless (S_TF) were higher (P < 0.001) in the afternoon. Birds show different thermoregulatory and behavioral responses in the two shifts of the day. We also observed that birds supplemented with bacterial and fungal phytase showed similar thermoregulatory and behavioral responses to the control group in both day shifts. Expression of the “eating” activity was greater in the morning, while the birds remained sitting longer in the afternoon. Egg production was higher (P < 0.001) in birds supplemented with bacterial phytase. The phytase dosages had no effect on thermoregulatory, behavioral or performance responses. Egg production, feed conversion per dozen eggs corresponded to 81.1% of the differences between bacterial and fungal phytase supplementation and group control. Thus, we conclude that: (i) phytase dietary supplementation has no effect on the thermoregulatory responses of laying hens reared in a hot environment; (ii) birds supplemented with bacterial phytase showed higher egg production; and (iii) phytases (450 and 900 FTU) do not interfere with productive, behavioral and thermoregulatory responses.     

Reducing feather pecking when raising laying hen chicks in aviary systems

Aviary systems for laying hens offer several advantages over battery cages. However, pecking the feathers of conspecifics remains a serious problem that negatively affects the welfare of the birds as well as the economy of a farm. From experimental studies with small groups, it has been shown that feather pecking and foraging behaviour are related and that both behaviour are influenced by early access to litter substrate. We, therefore, hypothesised, that feather pecking in aviaries can be reduced with an adequate management in the first 2 weeks of life.Each of seven pens on six commercial poultry farms, was divided into two identical compartments (matched pair design). In one of the compartments (experimental compartment) chicks were reared for the first 2 weeks of life with access to litter (wood shavings, in one case with additional straw), while the chicks in the other compartment (control) were kept on a plastic grid. Thereafter, all chicks had unrestricted access to litter and there were no differences between the two compartments neither in housing conditions nor in management procedures.Chicks in the experimental compartments spent significantly more time foraging (week 5), showed significantly less feather pecking (weeks 5 and 14) and significantly fewer birds had damaged tail feathers (weeks 5 and 14).The study demonstrates that in aviaries, under commercial conditions, early access to litter substrate has a significant effect on the development of feather pecking. In order to reduce feather pecking and to increase foraging behaviour, it is recommended that laying hen chicks raised in aviary systems do get access to litter from day 1 on.     

Causes of mortality in laying hens in different housing systems in 2001 to 2004

Background  

The husbandry systems for laying hens were changed in Sweden during the years 2001 – 2004, and an increase in the number of submissions for necropsy from laying hen farms was noted. Hence, this study was initiated to compare causes of mortality in different housing systems for commercial laying hens during this change.     

Relationship between feather pecking and ground pecking in laying hens and the effect of group size

The aim of this experiment was to study the relationship between feather pecking and ground pecking in laying hens and the effect of group size on feather pecking behaviour. Hisex White hens were kept in floor pens in group sizes of 15, 30, 60 and 120 birds, each with four replicates. Behavioural observations were performed at four different ages and focused on the number of feather pecks and aggressive pecks, both given and received. The part of the body pecked and the location of the bird was recorded as well as the number of pecks made to the floor, feeder and drinker.The results showed that most feather pecking activity occurred in the largest group size (120 birds) and there was some evidence of an increasing frequency of aggressive pecks with increasing group size. The parts of the body which were targets for feather pecking varied depending on the location of the bird giving the peck and the bird receiving it. When looking at the behaviour of individuals, birds doing a lot of feather pecking also showed more ground pecking.     

Possible risk factors for keel bone damage in organic laying hens

Keel bone damage (KBD) in laying hens is an important welfare problem in both conventional and organic egg production systems. We aimed to identify possible risk factors for KBD in organic hens by analysing cross-sectional data of 107 flocks assessed in eight European countries. Due to partly missing data, the final multiple regression model was based on data from 50 flocks. Keel bone damage included fractures and/or deviations, and was recorded, alongside with other animal based measures, by palpation and visual inspection of at least 50 randomly collected hens per flock between 52 and 73 weeks of age. Management and housing data were obtained by interviews, inspection and by feed analysis. Keel bone damage flock prevalences ranged from 3% to 88%. Compiled on the basis of literature and practical experience, 26 potential associative factors of KBD went into an univariable selection by Spearman correlation analysis or Mann–Whitney U test (with P<0.1 level). The resulting nine factors were presented to stepwise forward linear regression modelling. Aviary v. floor systems, absence of natural daylight in the hen house, a higher proportion of underweight birds, as well as a higher laying performance were found to be significantly associated with a higher percentage of hens with KBD. The final model explained 32% of the variation in KBD between farms. The moderate explanatory value of the model underlines the multifactorial nature of KBD. Based on the results increased attention should be paid to an adequate housing design and lighting that allows the birds easy orientation and safe manoeuvring in the system. Furthermore, feeding management should aim at sufficient bird live weights that fulfil breeder weight standards. In order to achieve a better understanding of the relationships between laying performance, feed management and KBD further investigations are needed.     

COLOR EVOLUTION IN THE HUMMINGBIRD GENUS COELIGENA

The remarkable diversity of coloration and species present in hummingbirds has been considered the result of sexual selection. I evaluate if color differences among species in the genus Coeligena are consistent with expectations from sexual selection theory. If sexual selection on color is important for speciation, closely related species should be markedly different in the colors of feather patches associated with aggression and breeding. I evaluate this prediction through a statistical assessment of the phylogenetic signal of colors from five feather patches: crown, gorget, belly, upper back, and rump. The first two are associated with aggressive and courtship displays and are expected to be under sexual selection, whereas the others are not. Contrary to expectations, the crown and gorget were the only patches with significant phylogenetic signal. Furthermore, I assess if populations of dichromatic species are more divergent in coloration and therefore have reduced gene flow. Color distances among dichromatic subspecies were larger than among monochromatic subspecies, but the magnitude of phenotypic differentiation was not related to levels of gene flow. These results support a role for sexual selection in shaping color variation among populations, but these differences alone are not sufficient to explain speciation.     

Interactive effects of vitamins A and K3 on laying performance,egg quality,tibia attributes and antioxidative status of aged Roman Pink laying hens

Extending laying cycle is a tendency in hen breeding, but egg quality declines as laying hens age. The present study was conducted to investigate the interactive effects of vitamins A and K₃ on laying performance, egg and tibia quality, and antioxidative status of aged Roman Pink laying hens. In a 3 × 3 factorial arrangement, 1 080 87-week-old laying hens were allocated to nine groups with eight replicates in each group. Deficient, adequate and excess vitamins A (0, 7 000 and 14 000 IU/kg) and K₃ (0, 2.0 and 4.0 mg/kg) were supplemented into a basal diet with 1 320 IU/kg of vitamin A and 0.5 mg/kg of vitamin K₃. After 2 weeks of adaption to basal diet, hens were fed corresponding diets for 8 weeks. Vitamins A and K₃ did not significantly affect the laying performance. However, they showed interactive effects on yolk ratio at week 93 as well as tibia weight and diameter (P < 0.05), and hens fed deficient vitamins A and K₃ had the highest yolk ratio and tibia weight, but the lowest tibia diameter. Compared with deficient addition, adequate or excess vitamins A and K₃ increased yolk color at weeks 93 and 97 (P < 0.05). Compared with hens fed deficient or excess vitamins, hens fed adequate vitamins A and K₃ had higher eggshell strength at week 93 or 97 (P < 0.05). Increasing vitamin A elevated plasma total superoxide dismutase (T-SOD) activity and decreased hepatic glutathione peroxidase (GSH-Px) activity (P < 0.05). Excess vitamin K₃ increased hepatic T-SOD activity (P < 0.05). Vitamins A and K₃ exhibited interaction on the activities of antioxidative enzymes in eggshell gland (P < 0.05), and adequate or excess vitamins A and K₃ increased the activities of GSH-Px, T-SOD and catalase (CAT). Adequate and excess vitamin A up-regulated the mRNA expression of GSH-Px1, GSH-Px3 and SOD1 in eggshell gland (P < 0.05). Vitamins A and K₃ showed interactive effects on CAT mRNA expression in eggshell gland (P < 0.05) and hens fed adequate vitamins A and K₃ had the highest CAT mRNA levels. In conclusion, dietary addition of vitamins A and K₃ improved the eggshell quality and yolk color as well as antioxidative status in eggshell gland of aged laying hens. Adequate vitamins A and K₃ showed beneficial effects and excess levels did not exhibit superior effects.