Pecking Behavior Research Articles

Pecking Behavior in Conventional Layer Hybrids and Dual-Purpose Hens Throughout the Laying Period.

To avoid the killing of surplus male layer chickens, dual-purpose hybrids are suggested as an alternative approach. These strains may offer additional advantages compared to conventional laying hens, for instance, a lower tendency to develop injurious pecking behavior. The aim of this study was to assess the behavior, with focus on pecking behavior, of conventional layers (Lohmann Brown plus, LB+) and dual-purpose hens (Lohmann Dual, LD). About 1,845 hens per strain with intact beaks were housed in four stable compartments in aviary systems. Video-based scan sampling of general behaviors and continuous observations of pecking behavior were carried out between 25 and 69 weeks of life. With the exception of “dustbathing” and “scratching,” hybrid × time during the laying period affected all of the observed general behaviors [F(2, 89) = 3.92–10.81, P < 0.001–0.05]. With increasing age, the LB+ hens performed more general pecking, more locomotion and less comfort and sitting behavior. General pecking and comfort behavior did not change over time in the LD hens, whereas inactive behaviors increased with age. During continuous observations, a significant hybrid x period interaction was found for all forms of pecking behavior [F(2, 89) = 4.55–14.80, P < 0.001–0.05]. The LB+ hens showed particularly more severe feather pecking (SFP), which increased with age. In contrast, SFP remained exceptionally low in the LD hens throughout production. Therefore, dual-purpose hybrids should be considered as an alternative to both avoid the killing of surplus male chickens and the development of SFP in laying hen production.

Prebiotics reduce feather pecking behavior, and improve trace element profile and redox balance in Mule ducks

The aim of this study was to evaluate the prebiotic effects of mannan-oligosaccharide (MOS) and β-glucan (BG) combination (MOS-BG prebiotics) on feather pecking behavior, some physiological aspects and brain histology in Mule ducks. A total of 48 Mule ducks (15 days of age) were assigned to 3 treatments; 4 control (C) groups of ducks fed a basal diet only, 4 low-dose AGRIMOSⓇ (LA) (1.5 g/kg diet) groups, and 4 high-dose AGRIMOSⓇ (HA) (3 g/kg diet) groups. The experiment lasted for 6 weeks. Feather pecking behavior was recorded by direct observation for altogether 1 hour/pen/week. Blood samples and brain tissues were collected from 2 ducks per pen (8 ducks per treatment group) at the end of the experiment. Feather pecking frequency and feather scores of the wings, back, and vent regions were significantly lower in HA compared to C groups, but higher in LA groups. Dopamine levels were highest in LA groups, followed by C and HA groups, and serotonin levels showed an opposite outcome pattern. Iron levels were highest in LA groups and vitamin C levels highest in HA groups. A dose-dependent increase in both magnesium level and superoxide dismutase activity was observed in LA and HA groups. Both LA and HA groups showed similarly increased zinc, copper and vitamin E levels, glutathione peroxidase activity and total antioxidant capacity as well as decreased total peroxide levels and oxidative stress indices were found. This, points to a possible welfare enhancing effect of MOS-BG prebiotics in ducks. However, no clear association between feather pecking behavior and antioxidant capacity was apparent. Additionally, the extent of feather pecking behavior was not reflected by any histological or cytological changes in the brain tissues or neurons, respectively. Considering the low sample size and the unexplainable result of more feather pecking when fed with low doses of prebiotics further investigations are needed. However, the study indicates that utilization of MOS-BG prebiotics at the high dose may attenuate feather pecking behavior and enhance the oxidative stability and trace element reserve.

Gut Microbial Composition and Predicted Functions Are Not Associated with Feather Pecking and Antagonistic Behavior in Laying Hens.

Background: Feather pecking is a well-known problem in layer flocks that causes animal welfare restrictions and contributes to economic losses. Birds’ gut microbiota has been linked to feather pecking. This study aims to characterize the microbial communities of two laying hen lines divergently selected for high (HFP) and low (LFP) feather pecking and investigates if the microbiota is associated with feather pecking or agonistic behavior. Methods: Besides phenotyping for the behavioral traits, microbial communities from the digesta and mucosa of the ileum and caeca were investigated using target amplicon sequencing and functional predictions. Microbiability was estimated with a microbial mixed linear model. Results: Ileum digesta showed an increase in the abundance of the genus Lactobacillus in LFP, while Escherichia was abundant in HFP hens. In the caeca digesta and mucosa of the LFP line were more abundant Faecalibacterium and Blautia. Tryptophan metabolism and lysine degradation were higher in both digesta and mucosa of the HFP hens. Linear models revealed that the two lines differ significantly in all behavior traits. Microbiabilities were close to zero and not significant in both lines and for all traits. Conclusions: Trait variation was not affected by the gut microbial composition in both selection lines.

Self- and conspecific-directed pecking behavior of commercial Pekin ducks

Injurious pecking behavior affects commercial Pekin duck welfare, but little information is available regarding the characteristics thereof. This study investigated self- and conspecific-directed pecking behavior of ducks, including 1) the prevalence, frequency and duration, 2) age-related changes in pecking and preening behavior, and body locations affected; 3) influence of time of day and location within the barn; and 4) occurrence of feather removal and feather eating. Behavior of two commercial flocks was video-recorded at 20–22 d (Period 1), 27–29 d (Period 2), and 34–36 d (Period 3) and analyzed using scan (n = 340 ± 91 ducks/flock per observation time point) and focal (n = 144 observation periods/flock) animal sampling. The percentage of ducks performing pecking behavior (gentle feather pecking (%GFP), severe feather pecking (SFP), aggressive pecking (AGGP) and self-picking (SELFP)) was determined every 30 min (09:00 h-15:00 h). Randomly selected focal ducks were observed for 30 min (09:45 h-10:15 h and 13:45 h-14:15 h) to determine durations and frequencies of pecking and preening behavior and the occurrence of feather removal and feather eating. Scan sampling data and focal behavioral durations were analyzed using PROC MIXED; behavioral frequencies were analyzed using PROC GLIMMIX (SAS 9.4). SFP, AGGP and SELFP were combined into one category, other pecking (OP), for analysis. GFP was observed most frequently, SFP and AGGP occurred less frequently, and SELFP was rarely observed. Feather removal (13 times) and feather eating (7 times) occurred infrequently. GFP frequency, duration and GFP% increased from Period 1 to 2 (P < 0.01), then declined from Period 2 to 3 (P < 0.01). Preening frequency and duration similarly changed with age (P < 0.01). OP frequency (P = 0.03) and duration (P = 0.03) were higher in Period 2 than Period 1. Body locations affected by GFP included the tail, wings and back. Little injurious pecking was observed; GFP between conspecifics was the most frequently observed behavior. Age was a major factor affecting the performance of pecking behavior, which peaked at Period 2 and was most frequently directed at the tail, wings and back. Further research is needed to examine seasonal effects and other factors influencing injurious pecking of ducks.

THE PECKING, RESTING AND FEEDING BEHAVIOUR OF FOUR BROILER STRAINS IN A HUMID TROPICAL ENVIRONMENT

An experiment to determine the pecking, resting and feeding behaviour of four strains of broilers (Anak, Hubbard, Luhman, and Hybro) was conducted with 120 day old chicks. The birds were housed 15 per replicate pen and there were two replicates pens for each of the four strains. The birds were fed with commercial broiler starter from 0-6 weeks and finisher from 7- 8 weeks. The criteria of measurements used were the number of birds pecking or resting, feed and water intakes and the weight gain of the birds from week one to 8 of age. Hubbard broilers pecked most following feed presentation at 8.00a.m. with mean values of 10.29+0.14 birds followed by Anak with 7.14+0.34, Hybro with 5.14+0.14 and Lohman with 1.57+0.53. Also the huhbard strains c‹›nsumed the largest quantity of feed and water and therefore gained most weight at eight weeks. The resting pattern of the birds was such that after two hours of introduction of feeds Hubbard had the largest number of bird resting followed by Anak, hybro and Lehman in that order.

Biological analysis of woodpecker’s brain after impact experiments

Woodpeckers can withstand a fierce impact during pecking. Previous studies have focused on the biomechanical analysis of the pecking process, the properties of the beak and hyoid bone of woodpecker; however, the biological characteristics of the woodpecker brain are also important in resisting impact injuries. We employed impact experiments and biological analysis in normal and injured brains to reveal the impact-resistant biological characteristics of woodpecker brains, as well as the impact energy’s biological effects on the woodpecker brain. The hoopoe, which has a similar size but only a slight pecking behavior, was selected as the control group to compare brain morphology and neuronal cells differences in normal brains between woodpecker and hoopoe by sectioning and staining. A loading device was designed to conduct a quantifiable impact energy to the woodpeckers’ head. Four groups of woodpeckers were impacted with the same energy on the forehead, beak, tempus and occiput, respectively. Biological changes in the injured brains were evaluated by Nissl staining and enzyme-linked immunosorbent assay. The results showed that: (1) woodpeckers had a larger cerebellum and a higher density of Nissl bodies than hoopoe; (2) Nissl apoptosis appeared in the brain samples after the forehead and the occiput impact experiments, but no obvious Nissl body apoptosis was observed after impact on the tempus and the beak; (3) β-amyloid protein accumulated in the normal status woodpecker brain. This study reveals that: woodpecker brain morphology is well-adapted to impact, woodpecker heads display location-dependent protective performance, with beak and tempus regions having a better protective performance than the forehead and occiput, Nissl apoptosis appears in injured woodpecker brains, and that the accumulation of β-amyloid protein does not show a direct relationship with the injury state of woodpecker’s brain tissue in our study.

Phenotypic and genomic analyses of agonistic interactions in laying hen lines divergently selected for feather pecking

In poultry, aggressive pecking and threatening are normal agonistic behavior patterns which serve to establish a social hierarchy. As agonistic behavior is a stressor for animals, its excessive occurrence is undesired in layer flocks. Feather pecking is a longstanding serious problem in layer flocks and its relationship to agonistic behavior is still not clear. Therefore, phenotypic and genomic analyses of the agonistic and feather pecking behavior of two laying hen lines divergently selected for high and low feather pecking were conducted. The hens were phenotyped for the active traits aggressive pecks delivered (APD)11Aggressive pecks delivered (APD), threats delivered (TD)22Threats delivered (TD), feather pecks delivered (FPD)33Feather pecks delivered (FPD) and the passive traits aggressive pecks received (APR)44Aggressive pecks received (APR), threats received (TR)55Threats received (TR) and feather pecks received (FPR)66Feather pecks received (FPR). Indices were built by subtracting the passive traits from the respective active traits to obtain the aggression index, the threat index, and the feather pecking index. As all three behavior patterns in their excessive manifestations are undesired, the index-traits Activity and Passivity were also defined by combining each the active and passive traits. The results showed that FPD is significantly positive correlated with APD and TD in both lines, but with higher coefficients in the high feather pecking line. The average amount of FPR in both lines is nearly the same and no correlation was found between FPR and FPD, APD or TD in any of the lines. The active traits and the feather pecking index showed medium heritabilities, whereas the heritability was negligibly small for the other traits. GWAS revealed four nominal significant (p ≤ 5*10−5) SNPs for APD on chromosome 6, the same four and three additional SNPs on chromosome 8 for Activity and three SNPs on chromosome 1 for the feather pecking index. It is concluded, that selection on high feather pecking leads to an increase of agonistic behavior. The correlation probably depends on the phase of establishing the social hierarchy in which the hens in a newly formed group are at the time of observation, and might disappear, after a stable ranking is established. The reception of feather pecking is similar in both lines. GWAS revealed that TD, APD, Activity and the feather pecking index seem to be typical quantitative traits with associated regions for the latter three which have slightly greater effects on these traits than other regions in the genome.

Causes of feather pecking and subsequent welfare issues for the laying hen: a review

When feather-pecking behaviour by hens becomes repetitive, plumage damage often results for the recipient of the pecks. The forceful removal of feathers and vigorous pecks directed at the skin may also cause pain, fear and even wounds. ‘Outbreaks’ of pecking behaviour have been reported in all housing systems in which poultry are managed. Pecking may progress to cannibalism and death, thus constituting significant hen welfare and farm economy problems. Farmers apply preventative management practices to minimise the risk of outbreaks. However, outbreaks are unpredictable and, once in progress, are difficult to control, especially in non-cage housing systems. For more than a century, research has been directed at trying to identify the causal factors underlying this problem, without success. The problem is multi-factorial and different studies often identify contradictory findings, such as, for example, in relation to the effects of adding forage to increase environmental enrichment, among others. The present review aims to provide background information about severe feather-pecking behaviour in laying hens, with mention of the resultant issues from repeated performance, such as, for example, on feather cover over the life of the laying hen. On-farm surveys, epidemiological studies and experimental trials have generated much information that has improved our general understanding of the significance of the problem, even though studies have typically been inconclusive due to its multi-factorial causes. While ‘Good Practice Guides’ are available and provide relevant advice for farmers to manage flocks to minimise the risk of outbreaks, we suggest significant progress towards identifying the root-cause(s) of the problem will more likely be achieved through controlled experimental trials using research models than through survey approaches. For example, using a stress-induction model, researchers should first focus on the impact of cumulative stressors in the flock that seem to predispose a hen to either become a feather pecker, or be the victim of pecking. Subsequent research should then investigate the affected hens for altered behavioural or (neuro-) physiological states, or physical stimuli on the skin and feathers, that may increase the motivation of hens to become feather peckers.

Effects of Dimethyl Anthranilate-Based Repellents on Behavior, Plumage Condition, Egg Quality, and Performance in Laying Hens.

Feather pecking is a behavior that occurs in order to cope with a constrained environment and is a serious problem in the egg production industry. This longitudinal study was conducted under commercial conditions to investigate whether the application of two repellent mixtures, previously suggested as aversive to wild birds, to the plumage of Prelux-R hybrid egg layers is a viable alternative to beak trimming as a solution to discourage feather pecking among laying hens. A total of 180 untrimmed hybrid layers was reared together in a floor pen. At 18 weeks of age they were allocated randomly to three treatments (repellent P, repellent T, control), each consisting of 6 replicated enriched cages with 10 hens in each cage. Hens were evenly sprayed once every 2 weeks for 54 weeks with solution P (dimethyl anthranilate and methyl phenylacetate), solution T (dimethyl anthranilate and geraniol), or distilled water (control). Body weight, plumage condition, behavior, feed intake, and egg quality measurements were taken at five time periods from 26 to 76 weeks of age. Egg production and mortality were recorded daily. The treatments did not affect feather pecking behavior. Hens treated with repellent T tended to perform less cage pecking than the control hens. The use of the repellents did not reduce feather pecking, the plumage was even more significantly damaged in the hens given the repellents compared to the control hens. This suggests the chemicals in the repellents worsened the plumage. No differences in feed intake and daily egg production between treatments were found. Raw and hard-boiled eggs were highly uniform in odor/flavor/taste and no offensive odor absorption related to the chemicals in the repellents was detected. In conclusion, in the present study we did not find any beneficial effect of dimethyl anthranilate-based repellents on feather pecking frequency and plumage/feather condition. Therefore, we do not encourage their use in wider commercial settings.

Effects of tryptophan and probiotic supplementation on growth and behavior in quail

In laying hens, a diet supplemented with tryptophan (Trp) has been shown to affect their pecking behavior. However, unlike this positive effect, Trp is also involved in negative effects on behavior and stress through indolic pathways. Indole production can be reduced by probiotics (Pro), thus we hypothesized that Pro may prevent negative effects of Trp and increase beneficial effects on behavior in birds. Combined effects of Pro and Trp were also expected. To investigate the effects on behavior in birds of supplementing with a high level of Trp with or without Pro, Japanese quail were used because their behavior can be influenced by Pediococcus acidilactici, and they can be highly aggressive. Quails (n = 120) were assigned to 4 groups in a 2 × 2 factorial design for 55 d: C-C (control diet with usual Trp level, 0.3%; without Pro; n = 30), Trp-C (Trp: 2%; without Pro; n = 30), C-Pro (control diet; with Pro: 1 x 109 CFU/L P. acidilactici in drinking water; n = 30), and Trp-Pro (Trp 2%; with Pro; n = 30). Body weight was measured every week, and different tests were conducted to investigate behavioral characteristics of each quail. Contrary to our hypothesis, there was almost no interaction between Trp and Pro treatments. Tryptophan supplementation significantly (P < 0.05) reduced live weight up to 27 d, whereas Pro treatment had no effect. There was no significant difference between groups for tonic immobility variables (P > 0.05). The birds fed the high Trp diet spent significantly less time in the periphery of the open field than those fed the control diet and moved less in the arena during the social isolation test. Interindividual distances were significantly lower in males fed with Trp 2% than with the control diet, whereas Trp and Pro supplements interacted in females. The treatments did not affect sexual motivation in males. These results indicate that a high level of Trp reduced growth and appeared to enhance emotional reactivity in quails and that supplementing with Pro did not reduce these effects. In conclusion, feeding high Trp for 55 d cannot be recommended as a strategy to improve social behavior unlike effects observed in laying hens.

The effect of an enriched laying environment on welfare, performance, and egg quality parameters of laying hens kept in a cage system

The aim of this study was to evaluate the welfare and performance of laying hens kept in a furnished cage system equipped with additional feeders. A total of 72 Lohmann Brown hens were randomly assigned to 4 experimental groups. Each group consisted of 6 cages housing 3 birds per cage (18 birds per group). Group I was a control group without an extra feeder in the cages. Experimental groups GII, GIII, and GIV contained one, 2, and 3 additional feeders in the cages, respectively. The assessment of bird welfare was based on production, physiological and behavioral parameters, as well as on the basis of external appearance. The experiment lasted 12 wk. The obtained results suggest that enriching laying hens’ cages with additional feeders improved the welfare of the hens. Enrichment of cages significantly reduced the number of feather pecking and aggressive behaviors in the GII and GIV groups (P < 0.01) and the GIII group (P < 0.05). Breast plumage was significantly (P < 0.05) better in the GII group compared with that in the control group. The control group also had the worst general plumage (P < 0.01). The GII and GIV groups were also characterized by significantly (P < 0.05) lower blood corticosterone concentrations compared with the control group. No negative changes in egg production and quality parameters were observed in the experimental groups. Only eggs from the GIV group had significantly (P < 0.05) lower breaking strength than those from the control and GII group. The results suggest that the best solution is to place 1 additional feeder in furnished laying hens’ cages.

Effect of various monochromatic light-emitting diode colours on the behaviour and welfare of broiler chickens

This study was conducted to evaluate the effect of different monochromatic light-emitting diode colours on the behaviour and welfare of broiler chicks. A total of 750 one-day-old chicks were used and lighting was set up as follows: pure blue (PB, 440–450 nm), bright blue (460–470 nm), sky blue (480–490 nm), greenish blue (500–510 nm), and green (530–540), while fluorescent white (400–700 nm) was used as a control. Birds were placed into 30 independent light proof pens and each light treatment was replicated five times with 25 birds in each pen. Video was recorded and behaviour was evaluated twice per day and observed five consecutive days in a week. Broiler welfare was evaluated using the characteristics of gait score, tibia dyschondroplasia, tonic immobility duration, and heterophil:lymphocyte ratio. In results, sitting, walking, and ground pecking behaviour were influenced by the light colour from 0 to 7 d. Extending the rearing period from 8 to 21 d resulted in increased sitting behaviour and decreased walking and pecking behaviour in chicks in the PB treatment (P &lt; 0.05). When the growth period was extended further (22–42 d), sitting behaviour increased when chicks were exposed to PB light (P &lt; 0.05). The effect of light colour did not significantly influence welfare of broiler chicks. Thus, the present results suggest that PB light colour decreased broiler chickens movement and thus increased duration of sitting behaviour. These results would be helpful to choose light colour for broiler producers.

Effect of fibrous diet and vitamin C inclusion on uniformity, carcass traits, skeletal strength, and behavior of broiler breeder pullets

This experiment studied the effect of broiler breeder nutritional strategies on uniformity, carcass traits, tibia parameters, and behavior during rearing and prebreeder periods (up to 22 wk of age). One-day-old pullets (n = 384) were randomly assigned to 4 treatments arranged as a 2 × 2 factorial, with 2 fiber levels (control vs. fibrous diet, 15% diluted in AMEn and nutrient content) and 2 vitamin C feed inclusions (0 vs. 200 mg/kg). At 6, 15, and 22 wk, blood sampling was carried out (4 birds/replicate) to determine serum alkaline phosphatase (ALP) levels, and behavior was observed by visual scan sampling. At 22 wk, carcass traits, tibia parameters, and intestinal morphology were assessed (2 birds/replicate), and tail- and wing-feather integrity of all birds were scored. Fibrous diet did not modify BW uniformity, mortality, or tibia growth when compared with control diet. Pullets fed the fibrous diet had lower tibia breaking strength, elastic modulus, and ash content values (P < 0.05). They also had lower ALP serum level at 6 and 22 wk (P < 0.05), their breast muscle was less developed (18.5 vs. 19.8%, P < 0.05), and their abdominal fat deposition was higher (1.14 vs. 0.87%, P < 0.05). At 15 and 22 wk, they performed, on average, 97% less grasping feather pecking and 45% less non–food object pecking behaviors, and their wing-feather score was lower (P < 0.05) at 22 wk. Tail- and wing-feather scores of the control treatments were reduced by vitamin C inclusion (tail: 0.30 vs. 1.15, P < 0.05; wing: 0.98 vs. 1.26, P < 0.05) at 22 wk. In conclusion, fibrous diet improves carcass traits (reduces breast muscle and increases abdominal fat deposition), deteriorates bone mineral deposition and thus skeletal strength, and reduces stereotypic behaviors, improving wing-feather integrity. Vitamin C inclusion improves tail- and wing-feather integrity of lower in feed allowance.

Effect of Production Systems and Dietary Interventions on Growth Performance, Morphometrics, Physiological Response and Behaviour of the Naked Neck Chickens

The present study was planned to evaluate the growth performance, morphometrics, physiological and behavioral response of Naked Neck chicken under different production systems and nutritional regimens. For this, a total of 900 Naked Neck chickens of 6-weeks of age were used; the birds were divided into 10 treatment groups consisting of 5 replicates of 18 birds each. A 2×5 factorial arrangement of treatment was employed under Completely Randomized Design. Treatments were consisted of two production systems (intensive and free range) and five nutritional regimens (100% commercial feed, 75% commercial feed +25% kitchen waste, 50% commercial feed +50% kitchen waste, 25% commercial feed +75% kitchen waste and 100% kitchen waste). Body weight, heartbeat and respiration rate were higher in birds reared under intensive system and spent most of their time sitting whereas higher feed intake and increased pecking behavior were noted in birds reared under free range system. Regarding feeding regimens, higher feed intake, cloacal temperature, body and neck length were observed in birds fed with 100% kitchen waste whereas higher drumstick, shank and wing spread were observed in birds fed under 100% commercial feed. Furthermore, higher shank and neck length were observed in birds fed 75% kitchen waste and higher body weight was observed in birds fed 50% kitchen waste. Significant interactions were also observed regarding feed intake, cloacal temperature, drumstick circumference, shank length, feeding, sitting and walking behavior. In conclusion, Naked Neck chicken perform better in free range system whereas feeding kitchen waste up to 50% may enhance growth, morphometric, physiological traits and improve behavioral response.

Live black soldier fly larvae (Hermetia illucens) for turkey poults

Black soldier fly larvae (BSFL;Hermetia illucens) are a suitable protein source for poultry. However the effect of live BSFL supplementation on growth performance and behaviour has never been demonstrated and quantified in turkeys. Wild turkeys eat insects during the first two weeks of life which is in contrast with commercially fed crumbs or pellets. Damaging pecking behaviour is a severe problem in turkeys. More lively diets may improve natural behaviour and decrease damaging pecking behaviour. The aim of the experiment was to stimulate natural behaviour of young non-beak treated turkeys by supply of live BSFL to avoid damaging pecking behaviour. Two treatments with seven replicates were studied in 14 floor pens (1.5 m2/pen and 20 turkeys per pen) from 0 to 35 days of age. Control groups were fed commercial diets and BSFL groups received live BSFL. The daily BSFL intake was calculated to be 10% of the expected daily feed intake (based on fresh weight) and dietary nutrient composition was adjusted in a way that control and BSFL groups were fed iso-nutritious. Daily feed intake and body weight gain of BSFL groups were significantly higher compared to control groups resulting in a significantly higher body weight at five weeks of age (2,190 vs 2,015 g;P=0.003) and a significantly lower feed conversion ratio. In the first week there was a tendency for more foraging related behaviour for the BSFL groups, but in the third and fifth week BSFL groups showed less foraging related behaviour compared to control groups. Provision of BSFL reduced aggressive pecking directed at the back and tail base at 5 weeks of age. Although the incidence of feather and skin damage was low, this type of damage tended to be lower in the BSFL groups.

Impact of light-emitting diode and compact fluorescent lighting type and cage tier on layers reared in an enriched cage system, part 2: some welfare traits

The aim of this study was to determine the effects of lighting type [light-emitting diode (LED) and compact fluorescent (FLO) light] and cage tier on welfare traits such as feather score, body and comb wounds, bumble foot and footpad dermatitis, beak damage, keel bone deformity, finger damage, aggressive pecking behavior, and the avoidance distance test (ADT) in laying hens reared in an enriched cage system. A total of 400 layers were used to determine these traits at 25 and 45 weeks of age. A total of 80 layers were used to determine tonic immobility (TI) duration and induction number. The dust accumulation rate (DAR I and DAR II) was recorded to determine the activity of layers under different lighting sources at 25, 35, and 45 weeks of age. The highest DAR I and DAR II were determined in the FLO group at 35 and 45 weeks of age (P < 0.05). The worst comb wound and highest ADT were found in the FLO group at 25 weeks of age (P < 0.05). In the FLO group the mean feather score, comb wound, and finger damage were worse than in the LED group (P < 0.01). In addition, aggressive pecking behavior (P < 0.01) was observed more in the FLO group at 45 weeks of age (P < 0.05). The breast and vent feather scores (P < 0.001), mean body feather score, comb wound, and footpad dermatitis of hens at 45 weeks of age (P < 0.05) were worse in lower cage tiers. In conclusion, using LED light in poultry houses helps to increase some of the welfare parameters. Cage tier significantly affects the welfare parameters, and this effect is clearer around 45 weeks of age in layers.

A Novel Model to Explain Extreme Feather Pecking Behavior in Laying Hens.

Feather pecking (FP) is a serious economic and welfare problem in the domestic fowl. It has recently been shown that the distribution of FP bouts within groups is heterogeneous and contains a sub-population of extreme feather peckers (EFP). The present study proposed a novel model to detect EFP hens. A mixture of two negative binomial distributions was fitted to FP data of a F2 cross of about 960 hens, and, based on the results, a calculation of the posterior probability for each hen belonging to the EFP subgroup (pEFP) was done. The fit of the mixture distribution revealed that the EFP subgroup made up a proportion of one third of the F2 cross. The EFP birds came more frequently into pecking mood and showed higher pecking intensities compared to the remaining birds. Tonic immobility and emerge box tests were conducted at juvenile and adult age of the hens to relate fearfulness to EFP. After dichotomization, all traits were analyzed in a multivariate threshold model and a genomewide association study was performed. The new trait pEFP has a medium heritability of 0.35 and is positively correlated with the fear traits. Breeding for this new trait could be an interesting option to reduce the proportion of extreme feather peckers. An index of fear related traits might serve as a proxy to breed indirectly for pEFP. GWAS revealed that all traits are typical quantitative traits with many genes and small effects contributing to the genetic variance.

Effects of Acute Tryptophan Depletion on Repetitive Behavior in Laying Hens.

Repetitive pecking at the feather cover of other birds (FP) is one of the most important welfare problems in domestic birds. It is not only characterized by motor symptoms, but also by an innate vulnerability of the serotonergic system. Moreover, the serotonergic system influences cognitive function. Acute tryptophan depletion (ATD) is a widely used method for studying serotonergic function in mammals and has been recently validated in birds. However, a tryptophan-deficient amino acid mixture has never been tested on groups of birds to impact their social behavior, including repetitive feather pecking, nor has it been given to potentially impact their cognition and motor performance. One hundred and sixty White Leghorn laying hens consisting of two genetic lines divergently selected to perform high (H) or low (L) levels of FP, and an unselected control line (UC), were kept in 10 groups consisting of 4 H, 3 L, and 9 UC genotypes. In a counterbalanced order, half of the groups were first subjected to an ATD treatment, while the other half were first given a balanced control (BC) treatment, and vice versa, after which their feather pecking behavior was observed. The effect of ATD/BC on repetitive pecking, motor performance, and cognition was investigated in a 5-s delayed reward task in an operant chamber with 10 phenotypic feather peckers, 10 recipients of feather pecking, and 10 bystanders (who neither performed nor received feather pecks). ATD given to groups of birds induced gentle, repetitive feather pecking in all genotypes. Following ATD, phenotypic feather peckers performed more poorly during the delayed reward task, as seen by their higher number of repetitive, non-rewarded key, and non-key pecks in the operant chamber. In conclusion, ATD impacted the hens' social behavior by increasing the number of repetitive gentle feather pecks at conspecifics. Furthermore, feather peckers were more likely to peck while waiting for a reward after ATD, suggesting a role for the serotonergic system on cognition in these birds.

Development of a Scoring System to Assess Feather Damage in Canadian Laying Hen Flocks.

Simple SummaryFeather damage is a continuous welfare challenge in the management of egg-laying hens. Canada is currently transitioning from conventional cages to alternative housing systems, where the risk of feather damage may increase due to larger group sizes. This change increases the need for continued and reliable assessment of flock feather condition, for which Canada does not have a standard method. Within this study, a feather damage scoring system and visual scoring guide were developed, with the ultimate goal of streamlining and increasing plumage assessment of laying flocks by farmers on Canadian commercial farms. Two differing feather scoring systems (LayWel and AssureWel) were compared based on user-friendliness and reliability. The AssureWel scoring system was easiest to use and achieved the most consistent outcomes among scorers for the back area of the body. This informed the design of a modified version with scoring levels from 0 to 2 for a sample of 50 birds per flock, along with an informational, visual guide for farmers. Training of farmers to use this simplified scoring system under commercial conditions can provide a benchmarking tool for feather damage levels, as well as a way to measure the success of management strategies to prevent and control feather damage.Feather damage (FD) due to feather pecking behavior is an ongoing welfare concern among commercial egg-laying hens. Canada’s current transition from conventional cage housing to alternative housing systems, where FD can spread easily within large flocks, underlines the need for frequent and accurate assessment of plumage condition. A standardized methodology for assessing FD in Canada does not yet exist. To improve FD assessment on commercial farms, a FD scoring system and visual scoring guide for farmers were developed. Two existing plumage scoring systems, LayWel and AssureWel, which differ in level of detail and bird handling, were assessed for ease of use, and intra- and inter-observer reliability. Practical application of the AssureWel scoring system was greatest, with strong intra- and inter-observer reliability for the back region of the body (weighted kappa = 0.88 for both measures) in small-scale flocks. This informed the creation of a modified version of the AssureWel system, which included three scoring levels and the visual assessment of 50 birds per flock. An accompanying guide was developed including sampling instructions and depictions of the scoring scheme, both written and visual. This simplified scoring system can serve as a benchmarking tool for FD prevalence, and can allow for future effectiveness assessments of management strategies to prevent and control FD; however, farmers should be trained to apply this system under commercial conditions.

The Role of Tryptophan-Kynurenine in Feather Pecking in Domestic Chicken Lines.

Research into the role of tryptophan (TRP) breakdown away from the serotonergic to the kynurenine (KYN) pathway by stimulating the brain-endocrine-immune axis system interaction has brought new insight into potential etiologies of certain human behavioral and mental disorders. TRP is involved in inappropriate social interactions, such as feather-destructive pecking behavior (FP) in birds selected for egg laying. Therefore, our goal was to determine the effect of social disruption stress on FP and the metabolism of the amino acids TRP, phenylalanine (PHE), tyrosine (TYR), their relevant ratios, and on large neutral amino acids which are competitors with regard to their transport across the blood-brain barriers, at least in the human system, in adolescent birds selected for and against FP behavior. We used 160 laying hens selected for high (HFP) or low (LFP) FP activity and an unselected control line (UC). Ten pens with 16 individuals each (4 HFP birds; 3 LFP birds; 9 UC birds) were used. At 16 weeks of age, we disrupted the groups twice in 5 pens by mixing individuals with unfamiliar birds to induce social stress. Blood plasma was collected before and after social disruption treatments, to measure amino acid concentrations. Birds FP behavior was recorded before and after social disruption treatments. HFP birds performed significantly more FP and had lower KYN/TRP ratios. We detected significantly higher FP activity and significantly lower plasma PHE/TYR ratios and a trend to lower KYN/TRP ratios in socially disrupted compared to control pens. This might indicate that activating insults for TRP catabolism along the KYN axis in laying hens differs compared to humans and points toward the need for a more detailed analysis of regulatory mechanisms to understand the role of TRP metabolism for laying hen immune system and brain function.