Pecking Behavior Research Articles

Effects of age at first access to range area on pecking behaviour and plumage quality of free-range layer chickens

Abstract. The aim of this study was to investigate the effects of age on pecking behaviour and plumage quality of free-range laying hens during first access to range. Six hundred 16-week-old layer pullets obtained from a commercial company were housed in a experimental free-range house. The experimental house consisted of a slat-and-litter floor with range area and was divided into three similar pens. The pullets were randomly assigned to a control and two experimental groups according to age at first access to range area. The birds were allowed into the range area for the first time at 18, 20 and 22 weeks of age in the groups of treatment I, treatment II and control, respectively. Pecking behaviour and plumage quality of the birds were measured for 8-week intervals from 24 to 48 weeks of age. Total feather damage significantly increased with age in all groups (P < 0.040, P < 0.006, P < 0.001). Compared to the control group, birds allowed into the range area earlier had less feather damage. The feather score of the tail body region in all groups was significantly greater (more damage) than in the others (P < 0.001). There were no significant differences for the total pecking behaviour of the birds in the groups at 24, 32, 40 and 48 weeks of age. Incidents of gentle feather pecking in every period were more frequent, while aggressive pecking was less frequent (P < 0.026, P < 0.007, P < 0.001). It can be said that access to range area as early as possible at the beginning of the laying period may be useful to reduce the negative effect of feather pecking in free-range layer chickens.

A Kinect-based system for automatic recording of some pigeon behaviors.

Contact switches and touch screens are the state of the art for recording pigeons' pecking behavior. Recording other behavior, however, requires a different sensor for each behavior, and some behaviors cannot easily be recorded. We present a flexible and inexpensive image-based approach to detecting and counting pigeon behaviors that is based on the Kinect sensor from Microsoft. Although the system is as easy to set up and use as the standard approaches, it is more flexible because it can record behaviors in addition to key pecking. In this article, we show how both the fast, fine motion of key pecking and the gross body activity of feeding can be measured. Five pigeons were trained to peck at a lighted contact switch, a pigeon key, to obtain food reward. The timing of the pecks and the food reward signals were recorded in a log file using standard equipment. The Kinect-based system, called BehaviorWatch, also measured the pecking and feeding behavior and generated a different log file. For key pecking, BehaviorWatch had an average sensitivity of 95% and a precision of 91%, which were very similar to the pecking measurements from the standard equipment. For detecting feeding activity, BehaviorWatch had a sensitivity of 95% and a precision of 97%. These results allow us to demonstrate that an advantage of the Kinect-based approach is that it can also be reliably used to measure activity other than key pecking.

Chicks change their pecking behaviour towards stationary and mobile food sources over the first 12 weeks of life: improvement and discontinuities

Chicks (Gallus gallus domesticus) learn to peck soon after hatching and then peck in rapid bursts or bouts with intervals of non-pecking activity. The food sources may be static such as seeds and chick crumb, or mobile such as a mealworm. Here, changes with age in pecking toward chick crumb and a mealworm were measured.Chicks were reared in pairs and their pecking of crumb food was video recorded in their pair housed environment, from food presentation, every third day from day 8 (wk 2) to day 65 (wk 10). Peck rate at crumb food reached maximum levels at day 32 (wk 5), and then declined, fitting a quadratic model, with no sex, sex of cagemate, or box order effects. Within bouts the peck rate was higher and it increased to day 41 (wk 6) and then declined, and here males pecked faster than females. A change in dietary protein concentration from 22% to 18% at day 28 (wk 4) had no effect on subsequent peck rate.Pecking at and consumption of a mealworm in pair housed chicks were measured weekly from wks [5 to 12]. The latency to first worm peck and latency to swallow decreased to wk 8 and increased thereafter. The peck rate to first wormpeck and number of pecks to swallow increased to wk 8 and then declined paralleling the changes with crumb food. The increase in peck rate is coupled with an increase in efficiency in worm catching.The results are consistent with the view that the improvement in pecking ability and accuracy compliments change in nutritional requirement best served by an invertebrate food (IF) source requiring speed to achieve feeding success, especially with live prey. When this food source is no longer crucial these associated skill levels decline. An appreciation of the role of domestic fowl in controlling insect populations, at farm level, that are often vectors in disease spread is lacking.

Use of dynamic and rewarding environmental enrichment to alleviate feather pecking in non-cage laying hens

Feather pecking (FP) can cause feather loss, resulting in physical injuries, which may lead to cannibalism. FP appears to be a redirection of foraging behavior, which intensifies when hens have difficulty coping with stress and fear. Dynamic environmental enrichment (EE) may allow expression of natural foraging behavior thus reducing conspecific pecking behavior and alleviating hen injury. Three treatments (plastic box: BOX; hay bale: HAY; and no enrichment: CON) were randomly applied to 30 identical floor pens (10 hens/pen; 10 pens/trt). At the pen level, hen behavior, and the number of severe FP (SFP), gentle FP (GFP), aggressive pecks (AP), and enrichment pecks (EP) were recorded from video prior to (21wk) and after (24wk) treatment implementation, and when hens were 27, 32, and 37wk of age. A manual restraint test (MR) was performed immediately after behavioral observations and levels of blood serotonin (5-HT) and glucocorticoids (GC) measured. Short-term (ST) and long-term (LT) analyses identified the impact of EE over the ST (21 vs. 24wk of age) and LT (21 vs. all other ages) at the pen level. At the pen level, HAY (3.18±0.33) tended to reduce GFP compared to CON (4.10±0.34) over the ST (P=0.15) and LT (P=0.09), but did not impact the number of SFP, or AP over the ST or LT. More EP was observed in HAY (3.56±0.14) than BOX (1.61±0.18) throughout the study (P<0.0001). More HAY hens perched (P=0.05) at 24wk (0.28±0.12) compared to 21wk (0.19±0.11), and more HAY hens (3.69±0.25) performed dust bathing compared to CON (4.14±0.22, P=0.05) throughout the study. CON performed more struggles (1.13±0.04, P=0.04) and were quicker to vocalize (4.87±0.07s, P=0.05) during MR than HAY (latency to vocalize(s): 5.16±0.05; number of struggles: 0.96±0.05), counter-intuitively suggesting CON were less fearful. Treatment did not affect 5-HT or GC. HAY appears to be a promising EE for mitigating GFP in non-cage laying hens. Future studies should examine the impact of EE on individual, rather than group-level responses. These results suggest that the presence of a hay bale is stimulating and may reduce GFP while encouraging hens to redirect pecking towards a dynamic and manipulable EE.

Response to commentary on "Examples of overlooking common sense solutions: the domestication gene and selection against mortality".

In a commentary in Frontiers, Van Rooijen (2014) states: “Today the developments in genetics are exciting. Perhaps this explains why geneticists sometimes seem to overlook common sense solutions. One example of this is the selection experiment done by Bijma et al. (2007a,b). ……As a result their selection seemed not very efficient.” In those two papers, however, we do not report a selection experiment. The first paper presents general quantitative genetic theory, showing how interactions among individuals alter heritable variation in traits, and how this can affect response to selection. The second paper presents general methodology to estimate the quantitative genetic parameters for such traits, and illustrates this methodology using a population of laying hens showing high mortality due to pecking behavior. Neither of those papers report results of a selection experiment.

Persistent effect of broody hens on behaviour of chickens.

We reported previously that behavioral development of chicks was promoted remarkably by the presence of a broody hen. Here we report that these effects at an early age persist after maturity. A total of 60 female chicks were randomly assigned to one of two treatment groups: six pens with five chicks (brooded group) each were reared by a broody hen and six pens with five chicks (non-brooded group) each were provided with an infrared heating lamp. We evaluated the persistent effects of broody hens by measures of behavior, physical condition and production at 9, 16, 35 and 55 weeks of age. The numbers of threatening, aggressive pecking, fighting and severe feather pecking behaviors were higher in non-brooded than in brooded chickens (all P < 0.05). Egg production was lower in brooded than in non-brooded chickens (P < 0.05), while the number of brooding chickens was higher in the brooded than in the non-brooded group (P < 0.05). In conclusion, the presence of broody hens at an early stage of chicks' lives has a persistent effect on behavior. Although brooded chickens showed more brooding and lower egg production than non-brooded chickens, feather pecking and aggressive interaction were decreased in brooded hens.

Effect of substrate provision on performance and behaviour of laying hens in the pecking and scratching area of furnished cages

1. An experiment was set up to study the effects of substrate provision on performance and behaviour in the pecking and scratching area (PSA) of non-beak-trimmed hens housed in large furnished cages (60 hens/cage).2. Three layer hybrids (two brown and one white, ISA-Hendrix Genetics, France) and two substrate conditions (with or without wheat bran automatically distributed on the PSA) were compared in a 3 × 2 experimental design with 12 cages per treatment.3. Substrate distribution improved laying rate with no impact on the frequency of dirty or cracked eggs.4. Substrate distribution improved the viability and body integrity of hens, which were not beak-trimmed.5. Distribution of substrate tended to increase the number of hens in the PSA and enhanced their pecking and scratching behaviours but had a negative impact on the number of dust bath bouts per cage and encouraged dust bathing on the wire floor close to the feeder.6. The white hens laid more eggs in the nest than the brown birds and used the PSA more for pecking, scratching and dust bathing at the end of the day than the brown hens, underlining the necessity to adapt cage furnishing and rearing management to specific behaviours of each layer genotype.

The development of injurious pecking in a commercial turkey facility

Injurious pecking is considered a major economic concern and affects all sectors of commercial poultry production. Though extensive research has been performed examining feather pecking in layer chickens, little information exists regarding feather or head pecking behavior in domestic turkey flocks, and less still in commercial settings. The objective of the present field study was to examine the development of injurious feather and head pecking in tom turkeys raised in 2 different commercial environments. At a commercial facility, 49,332 beak-conditioned tom turkeys were placed in 8 barns (5,000–7,500 turkeys/barn) and studied through 16 wk of age. Approximately half were housed in control barns in March 2010; these barns were environmentally controlled (artificial light and tunnel ventilation) in both rearing and growing, with a density of 0.16 m2/bird for rearing through 4.5 wk and 0.39 m2/bird for growing through 16 wk. The remaining turkeys were housed in curtain-sided barns in April 2010; the 4 rearing barns were environmentally controlled with a density of 0.10 m2/bird, whereas the 4 growing barns had natural light and ventilation and a density of 0.36 to 0.38 m2/bird through 16 wk. Two barns from each growing environment were provided with multicolored plastic balls as enrichment. Each housing and enrichment combination had 2 replicate barns. Behavior, weights, and feather condition were assessed every 3 wk. Mortalities and culls were recorded as they occurred. Turkeys in curtain-sided barns had worse feather condition and more culls and mortalities with severe pecking injuries compared with those in control barns. In both environments, severe and gentle pecking was observed throughout production, and the majority of culls and mortalities had severe pecking injuries. More controlled studies are needed to parse the causal factors of injurious pecking in toms.

Microstructure of Woodpecker&amp;rsquo;s Cranial Bone Based on Micro-computed Tomography

The main purpose of this article is to research the microstructure of woodpeckers cranial bone on tempus, occiput and forehead. The great spotted woodpecker, the grey-headed woodpecker, the eurasian hoopoe, the titmouse and the lark bird were selected as research samples and the Eurasian hoopoe, the titmouse and the lark bird were chosen as control groups. Microstructure parameters including BV/TV, SMI, Tb.N, Tb.Th, Tb.Sp and BMD were measured based on the micro-computed tomography. After comparison with the control groups, it was found that the Tb.Th, BV/TV and Tb.N were significantly higher and the SMI was lower than that of control groups. These characteristics of woodpeckers cranial bone were developed during the evolutionary process in order to adapt to the pecking behaviours and it is an important reason why woodpeckers can resist head impact.

The phenotypic interrelationships between feather pecking, being feather pecked and fear criteria in White Leghorn lines selected for high and low severe feather pecking and their F2- crosses

Summary On the basis of observations that flocks of chickens with high incidence of feather pecking and feather damages show a high fear level, it is generally assumed that feather pecking and fear are positively correlated. This hypothesis was tested in two experiments using adult laying hens of lines selected for high (HFP) and low feather pecking behaviour (LFP) and their reciprocal crosses. A total of 60 adult birds, 30 HFP and 30 LFP, of the selection lines were used in part one of the experiment. The birds were first observed for the number of bouts of severe feather pecks delivered (FPD) and received (FPR) when kept in groups of equal numbers of both lines. Thereafter all birds were subjected to several fear tests: Tonic immobility test (TI), open- field test (OF), emerge box test (ET) and pencil test. In part two of the experiment a total of 967 birds of the F2- crosses of both lines were used. All birds were tested using the same fear tests as above at 7 days and 40 weeks of age. FPD and FPR were observed in adults only. The whole population was split for FPD in HFP and LFP using the threshold of ≥ 2 (HFP) and < 2 (LFP). HFP and LFP of the selection lines and the F2- crosses clearly differed in FPD. LFP of the selection lines received more feather pecks than HFP. There was no significant difference for FPR in HFP and LFP in the F2- crosses. In contrast to our expectation HFP from the selection lines showed a significant shorter duration of TI, shorter latency to move and to vocalize in the OF and a shorter latency to leave the emerge box, indicating lower fear. Similar results were found in the HFP and LFP of the F2- crosses for the duration of TI and latency of head appearance in the ET. Latency of the first step and to vocalize in the OF, however showed the opposite tendency. Line by age interactions appeared for the number of inductions in the TI and the latency of head emerge in the ET. There were no differences between HFP and LFP in the pencil test in both experiments. The phenotypic correlations between FPD and FPR with all fear criteria were low and not significant in both experiments. There is obviously no consistent relationship between feather pecking and fear in this population. Depending on type of fear test and age the HFP may show higher, lower or no difference in fear. Genotypes by age interactions further contribute to the variability of the results. The low phenotypic correlations among the criteria confirm this conclusion.

Serotonin release in the caudal nidopallium of adult laying hens genetically selected for high and low feather pecking behavior: An in vivo microdialysis study

Severe feather pecking (FP) is a detrimental behavior causing welfare problems in laying hens. Divergent genetic selection for FP in White Leghorns resulted in strong differences in FP incidences between lines. More recently, it was shown that the high FP (HFP) birds have increased locomotor activity as compared to hens of the low FP (LFP) line, but whether these lines differ in central serotonin (5-hydroxytryptamine, 5-HT) release is unknown. We compared baseline release levels of central 5-HT, and the metabolite 5-HIAA in the limbic and prefrontal subcomponents of the caudal nidopallium by in vivo microdialysis in adult HFP and LFP laying hens from the ninth generation of selection. A single subcutaneous d-fenfluramine injection (0.5 mg/kg) was given to release neuronal serotonin in order to investigate presynaptic storage capacity. The present study shows that HFP hens had higher baseline levels of 5-HT in the caudal nidopallium as compared to LFP laying hens. Remarkably, no differences in plasma tryptophan levels (precursor of 5-HT) between the lines were observed. d-fenfluramine increased 5-HT levels in both lines similarly indirectly suggesting that presynaptic storage capacity was the same. The present study shows that HFP hens release more 5-HT under baseline conditions in the caudal nidopallium as compared to the LFP birds. This suggests that HFP hens are characterized by a higher tonic 5-HT release.

Genetic parameters for feather pecking and aggressive behavior in a large F2-cross of laying hens using generalized linear mixed models

Feather pecking and aggressive pecking is a well-known problem in egg production. In the present study, genetic parameters for 4 feather-pecking-related traits were estimated using generalized linear mixed models. The traits were bouts of feather pecking delivered (FPD), bouts of feather pecking received (FPR), bouts of aggressive pecking delivered (APD), and bouts of aggressive pecking received (APR). An F2-design was established from 2 divergent selected founder lines. The lines were selected for low or high feather pecking for 10 generations. The number of F2 hens was 910. They were housed in pens with around 40 birds. Each pen was observed in 21 sessions of 20 min, distributed over 3 consecutive days. An animal model was applied that treated the bouts observed within 20 min as repeated observations. An over-dispersed Poisson distribution was assumed for observed counts and the link function was a log link. The model included a random animal effect, a random permanent environment effect, and a random day-by-hen effect. Residual variance was approximated on the link scale by the delta method. The results showed a heritability around 0.10 on the link scale for FPD and APD and of 0.04 for APR. The heritability of FPR was zero. For all behavior traits, substantial permanent environmental effects were observed. The approximate genetic correlation between FPD and APD (FPD and APR) was 0.81 (0.54). Egg production and feather eating records were collected on the same hens as well and were analyzed with a generalized linear mixed model, assuming a binomial distribution and using a probit link function. The heritability on the link scale for egg production was 0.40 and for feather eating 0.57. The approximate genetic correlation between FPD and egg production was 0.50 and between FPD and feather eating 0.73. Selection might help to reduce feather pecking, but this might result in an unfavorable correlated selection response reducing egg production. Feather eating and feather pecking are genetically correlated and this needs further investigation.

Modelling of feather pecking behavior in beak-trimmed and non-beak-trimmed crossbred laying hens: Variance component and trait-based approach

Because of a ban on the use of beak trimming in some European countries, feather pecking is becoming a substantial problem in the layer industry, both from animal welfare and economic points of view. The feather condition score (FCS) as a measure of feather damage has been shown to be closely related to feather pecking behavior in laying hens housed in groups. To obtain a better understanding of genetic and other biological mechanisms underlying feather pecking behavior, data on FCS of a population of 2,724 female offspring from crossing 50 male W1 and 907 female WB purebred lines were used. The offspring of 25 sires were beak-trimmed, and the offspring of another 25 sires were non-beak-trimmed. Titers of plasma natural antibody (NAb) isotypes IgM and IgG binding keyhole limpet hemocyanin at 24 wk of age were measured. Feather condition was scored at 53 wk of age. In the first part of the present study, we estimated genetic parameters for FCS with 2 variance components models: a traditional linear animal model and a model combining direct and associative genetic effects. In the second part of the present study, a trait-based analysis for FCS was conducted to investigate whether NAb isotype titers can explain variation in FCS among individuals, by fitting a linear mixed model. Though the estimated associative genetic variance was substantial, associative effects for FCS were not statistically significant in both populations (P = 0.09 in beak-trimmed birds, and P = 0.08 in non-beak-trimmed birds). This suggests an insufficient number of records on FCS. Individual's NAb isotypes titers did not show direct effect for FCS of itself, but individual's IgG titers showed a suggestive effect on the FCS of cage mates (associative effect) in beak-trimmed laying hens, which need further confirmation.

The choice of litter material to promote pecking, scratching and dustbathing behaviours in laying hens housed in furnished cages

Since 2012 in the EU, cages for the housing of laying hens must provide nests, perches and a pecking and scratching area to promote natural behaviours and enhance animal welfare. Previous studies highlighted the difficulty of finding adequate materials for pecking and scratching areas in such cages, mainly due to hygiene problems and technical constraints. This study investigates whether alternative materials could stimulate dustbathing (DB), pecking, and scratching behaviours and examines if hens show any preferences for these materials compared to other well-known litter materials such as sand, peat and artificial turf. We set up two separate experiments: one to simultaneously compare four litter materials (wheat bran, sand, shell sand and peat) and one to simultaneously compare four alternative non-litter, pad-type solutions (plastic mat, artificial turf mat, a slightly friable experimental block made of wood and oyster shells, and a slightly friable experimental sand block). For each experiment, 15 groups of four hens were observed over four days in a multiple choice test. Wheat bran was found to promote pecking and scratching behaviours better than the other litters. Peat induced more dustbaths than wheat bran but duration of DB bouts was similar for both materials. However, the number of dustbaths in wheat bran increased throughout the test, while the duration of DB bouts decreased in peat, showing an increasing preference for wheat bran. The shell sand was found to be the least preferred for pecking, scratching and DB. In the second experiment, pads were found to be less attractive than litters for pecking, scratching, and DB. The plastic mat was very rarely used for DB compared to other solutions in the pad choice test. As hens rarely pecked or scratched any of the pads, no significant differences were noted between the four different types. However, experimental blocks stimulate DB as much as artificial turf mats and seem promising, as their use for DB increased throughout the test. This study shows that wheat bran could be an optimal litter for use in furnished cages to improve hen welfare. In addition, research on new experimental blocks is worth being developed, as it has the advantage of not needing to be renewed during a laying period.

Evaluation of plumage condition and foot pad health in laying hens kept in a small group housing system

Summary Laying hen husbandry, especially conventional cages, have been a target of public criticism for a long time. The search for alternative housing systems, that are more animal-friendly, without losing high egg production standards, led to the development of small group housing systems. Equipment of these housing systems with perches, dust baths and nest boxes offers laying hens the possibility to perform a wider repertoire of their natural behaviour. The purpose of the present study was to evaluate the welfare status of hens kept in the small group housing system Eurovent German. Therefore, plumage condition and foot pad health were recorded during four consecutive trials. The analysis of variance showed a highly significant effect of the laying month, the layer line and the trial on almost all examined parameters. The effect of group size was solely significant for the plumage of tail. Feathering of head, neck and wings was significantly worse and sole pad lesions were more common in hens from the third tier of the housing system compared to layers of the lower tiers. Although the furnished elements of the small group housing system may improve the welfare of hens, these elements further may force feather pecking behaviour by giving the hens an incentive to peck. Apart from a number of causative factors influencing feather damage and foot pad alterations, the interaction between the individual laying hen and its environment plays a decisive role.

Can substrate in early rearing prevent feather pecking in adult laying hens?

AbstractIn The Netherlands, laying hen chicks are often reared without litter on the raised slatted area of a barn system or confined in the aviary system during the first two to five weeks after hatching, with chick paper or chicken wire on the floor. In the absence of a suitable pecking substrate, chicks may redirect their pecking behaviour to other birds, which possibly increases the risk of developing feather-pecking behaviour. The aim of this study was to determine whether housing on wood-shavings (WS treatment; n = 15 groups) as compared to housing on chicken wire (CW treatment; n = 15 groups) between day 1-20 could reduce feather pecking in adult birds. After day 20, all chickens were allowed wood-shavings as litter. Behavioural observations showed that CW chicks performed significantly less ground-pecking behaviour compared with WS chicks up to day 20. More CW chicks showed gentle feather pecking at day 7 and 14 as compared to WS chicks, and more CW chicks pecked at the feeder or drinker than WS chicks up to day 20. CW chicks showed rebound behaviour: the day after they were introduced to wood-shavings they displayed more ground-pecking behaviour compared to the WS chicks. Later on in the rearing period no noticeable differences between treatments were found in frequency of gentle and severe feather-pecking bouts. During laying, more gentle feather-pecking bouts were observed in CW than in WS groups but no differences in severe feather-pecking bouts were observed, nor in feather damage at the end of the trial. The results indicate that hens can display substantial flexibility in their pecking behaviour and that, despite more gentle feather pecking in CW hens in laying, the absence of substrate in early rearing does not increase the risk of developing severe feather-pecking behaviour when adult.

Effects of feather pecking phenotype (severe feather peckers, victims and non-peckers) on serotonergic and dopaminergic activity in four brain areas of laying hens (Gallus gallus domesticus)

Severe feather pecking (SFP) in laying hens is a detrimental behavior causing loss of feathers, skin damage and cannibalism. Previously, we have associated changes in frontal brain serotonin (5-HT) turnover and dopamine (DA) turnover with alterations in feather pecking behavior in young pullets (28–60days). Here, brain monoamine levels were measured in adult laying hens; focusing on four brain areas that are involved in emotional behavior or are part of the basal ganglia-thalamopallial circuit, which is involved in obsessive compulsive disorders. Three behavioral phenotypes were studied: Severe Feather Peckers (SFPs), Victims of SFP, and Non-Peckers (NPs). Hens (33weeks old) were sacrificed after a 5-min manual restraint test. SFPs had higher 5-HIAA levels and a higher serotonin turnover (5-HIAA/5-HT) in the dorsal thalamus than NPs, with intermediate levels in victims. NPs had higher 5-HT levels in the medial striatum than victims, with levels of SFPs in between. 5-HT turnover levels did not differ between phenotypes in medial striatum, arcopallium and hippocampus. DA turnover levels were not affected by feather pecking phenotype.These findings indicate that serotonergic neurotransmission in the dorsal thalamus and striatum of adult laying hens depends on differences in behavioral feather pecking phenotype, with, compared to non-pecking hens, changes in both SFP and their victims. Further identification of different SFP phenotypes is needed to elucidate the role of brain monoamines in SFP.

Puffer smells tetrodotoxin

Behavioral observation was conducted to test whether olfaction is functional to detect tetrodotoxin (TTX) in tiger puffer Takifugu rubripes using Y-maze. We placed either agarose carrier or one agarose and one agarose containing TTX (200 MU) at each head of the channel of Y-maze. Then three non-toxic hatchery-reared juveniles (body length, 5.6 ± 0.4 cm; n = 18) were released into the Y-maze and pecking behavior to carrier was observed for 3 h. The same procedure was tested for olfactory-ablated juveniles and for juveniles taht received sham operation. Juveniles showed significant selectivity to TTX, except for olfactory-ablated juveniles. These results indicate that pufferfish detects TTX by olfactory organ.

Investigating gene expression differences in two chicken groups with variable propensity to feather pecking

Feather pecking is a major welfare problem in egg production. It may be caused by genetic, physiological and environmental factors. The main aim of this study was to uncover gene expression variability in brain tissue between individuals from high feather pecking and low feather pecking groups using the Chicken Gene Expression Microarray. In total, 313 signals were initially identified as significant (P≤0.05) for the fold change higher than two. A subset of functional candidate genes including downregulated (GLUL, TSPO, MAOA) and upregulated (HTR1B, SIP1, PSEN1) transcripts was subjected to quantitative PCR validation. The significance level and direction of the fold change in gene expression observed by the microarray analysis were confirmed for four genes (HTR1B, SIP1, PSEN1 and GLUL). Newly identified candidate genes play an important role in neurotransmission and psychopathological disorders and can be considered as potential genetic components involved in complex feather pecking behavior. It can be concluded that this study has revealed some interesting differences in gene expression between high and low feather pecking groups and helped to approach elucidation of the genetic foundations of feather pecking.

Familiarity perception call elicited under restricted sensory cues in peer-social interactions of the domestic chick.

Social cognitive mechanisms are central to understanding developmental abnormalities, such as autistic spectrum disorder. Peer relations besides parent-infant or pair-bonding interactions are pivotal social relationships that are especially well developed in humans. Cognition of familiarity forms the basis of peer socialization. Domestic chick (Gallus gallus) studies have contributed to our understanding of the developmental process in sensory-motor cognition but many processes remain unknown. In this report, we used chicks, as they are precocial birds, and we could therefore focus on peer interaction without having to consider parenting. The subject chick behavior towards familiar and unfamiliar reference peers was video-recorded, where the subject and the reference were separated by either an opaque or transparent wall. Spectrogram and behavior correlation analyses based on principal component analysis, revealed that chicks elicited an intermediate contact call and a morphologically different distress call, more frequently towards familiar versus unfamiliar chicks in acoustic only conditions. When both visual and acoustic cues were present, subject chicks exhibited approaching and floor pecking behavior, while eliciting joyful (pleasant) calls, irrespective of whether reference peers were familiar or unfamiliar. Our result showed that chicks recognized familiarity using acoustic cues and expressed cognition through modified distress calls. These finding suggests that peer affiliation may be established by acoustic recognition, independent of visual face recognition, and that eventually, both forms of recognition are integrated, with modulation of acoustic recognition.