Browsing by Subject "Feather pecking"

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Genetic analyses of feather pecking and related behavior traits of laying hens
(2016) Lutz, Vanessa; Bennewitz, Jörn
The main objective of the present study was to study the genetic foundation of behaviour traits, especially feather pecking behaviour, and to infer ethological interrelationship between certain traits of laying hens. The data of two divergently selected lines for feather pecking behaviour was available, and additionally a large F2-cross, set up from these divergently selected lines, was established. Chickens of a White Leghorn layer line were divergently selected for high and low feather pecking for 11 generations. The selection started in the Danish Institute of Animal Sciences, Foulum, Denmark, for the first six generations (0-5). Thereafter, five rounds of selection took place at the Institute of Animal Science, University of Hohenheim, Germany. The large F2-cross was established from the 10th selection generation, and a comprehensive data collection of behaviour and performance traits of 960 hens was performed. These two data sets were used for the following five research chapters. In chapter one, a quantitative genetic analysis of fear traits and feather pecking as well as aggressive pecking using data from the large F2-cross was performed. Fear was recorded by the tonic immobility test, the open field activity and the emergence box test. These were recorded at a juvenile and adult age. Behavior traits as feather pecking and aggressive pecking were recorded in groups of 36 to 40 animals at the age of 27 weeks. The genetic parameters were estimated using a linear mixed model. Aggressive pecking showed the highest heritability (0.27) followed by feather pecking (0.14). The fear test traits showed heritabilities in the range of 0.07 to 0.14. The appreciable genetic correlation between fear traits and feather pecking was tonic immobility at juvenile age (rg=0.27). In chapter two we used dispersed Poisson models to estimate variance components, heritabilities of feather and aggressive pecking of different observation periods. The short period included the number of feather pecks in 20 min and the medium period was the summed bouts within one day. The results showed that modelling the data as repeated observations (short and medium period) and analysing them with a dispersed Poisson model is a suitable option to separate the important permanent environment effects from the additive animal effects and to account for the non-normal distribution of the data. The objective of chapter three was to analyze the interrelationship between feather pecking and feather eating as well as general locomotor activity using structural equation models. The estimated heritabilities of feather eating, general locomotor activity and feather pecking were 0.36, 0.29 and 0.20, respectively. The genetic correlation between feather pecking and feather eating (general locomotor activity) was 0.17 (0.04). A high genetic correlation of 0.47 was estimated between feather eating and general locomotor activity. The recursive effect from feather eating to feather pecking was λ ̂_(FP,FE)= 0.258, and from general locomotor activity to feather pecking λ ̂_(FP,GLA)= 0.046. These results imply that an increase of feather eating leads to an increased feather pecking behavior and that an increase in general locomotor activity results in a higher feather pecking value. The objective of chapter four was to perform a quantitative genetic analysis and to map signatures of selection in two divergent laying hen lines selected for feather pecking behaviour. In the selection experiment, lines were selected for low or high feather pecking for 11 generations. Pedigree and phenotypic data were available for the last six generations of both lines for the statistical analysis with a standard mixed linear model and a Poisson model. The mixed linear model failed to analyse the low feather pecker data because of the large number of 0s in the observation vector. The Poisson model fitted the data well and revealed a small but continuous genetic trend in both lines. From the 11th generation 75 birds, 41 high feather peckers and 34 low feather peckers were genotyped using the Illumina 60K chicken Infinium iSelect chip. An FST-based approach was used to map selection signature. We detected 17 genome-wide significant SNPs with a FST-value of 1, i.e. alleles were divergently fixed in the two lines, which are mostly located on chromosome 3 and 4, and a number of additional significant SNPs with a p-value of ≤ 5x10-4 and ≤ 5x10-5, respectively. Based on the assumption that selection affects several consecutive SNPs, 13 clusters were identified. In chapter five, we used the data from the large F2-cross experiment to perform a genome-wide association study for feather pecking and aggressive pecking behaviour, to combine the results of this GWAS with the results from the selection experiment (chapter four) in a meta-analysis, and to link the results to those obtained from a differential gene expression study. 817 F2-hens were genotyped with the Illumina 60K chicken Infinium iSelect chip. We used single marker association analysis and a Poisson model. We detected four genome-wide significant SNPs for aggressive pecking delivered, but none for feather pecking and aggressive pecking received. However, a number of significant SNPs at p≤5x10-5 were mapped for feather pecking and aggressive pecking received. In the meta analysis we identified nine genome-wide significant SNPs for feather pecking delivered, which were localized in chromosomal clusters (3 Mb). A previously conducted differential gene expression analysis provided eight significantly differential expressed genes within the feather pecking associated chromosomal clusters. The thesis ends with a general discussion.
Untersuchungen zu den Beziehungen von Federpicken, Exploration und Nahrungsaufnahme bei Legehennen
(2008) Benda, Isabel; Bessei, Werner
First documented in 1873 by Oettel (1873), the problem of feather pecking and feather eating remains a major issue in modern laying hen husbandry. Various motivational models developed in the past years interpret feather pecking as redirected foraging behaviour, pecking while sand bathing or as misdirected exploratory behaviour. The laying hens, however, only show exploratory curiosity in these diverse materials for a short time. It has been shown that diet-related deficiencies elicit increased exploratory behaviour and feather pecking. In the first section of this experiment, we attempted to redirect the exploratory pecking activity of the laying hens to an alternative object (pecking block) for a sustained period of time through offering the animals food and calcium separately. Less feather pecking behaviour was expected to result. Investigations carried out in recent years indicate an association between feather pecking and feather eating. Although almost indigestible, both wood shavings (cellulose) and feathers are eaten by laying hens. Hence, the influence of feathers and cellulose in food on the behaviour of laying hens was tested in the second section of this experiment. The inclusion of feathers or cellulose in food was expected to reduce feather pecking behaviour, since the animals? requirement for these substrates was adequately covered in the food. The goal of the third section of the experiment was to determine if the ingestion of feathers or wood shavings has an underlying physiological background, which consequently initiates a need for these substrates. The effect of substrate ingestion was tested in two different lines. The first experiment comprised three feeding treatments. Group 1 received a calcium-poor ration (0.67% Ca) whereas groups 2 and 3 received a calcium-balanced ration (3.45% Ca). An additional pecking block containing molasses and bran was available to birds in groups 1 and 2. The pecking block available to birds in group 1 had a calcium content of 31%. Each of the 3 treatments was repeated 10 times with 8 laying hens per treatment. Half of the animals were brown, the other half white laying hybrids. The three groups did not differ in their propensity to feather peck. However, animals in group 1 showed a better feather condition than those in groups 2 and 3. Breed origin had a significant effect on pecking activity, whereby brown laying hybrids displayed aggressive and vigorous feather pecking more frequently than their white counterparts. The second section of the investigation likewise comprised three feeding treatments. The first group received pellets with 10% feather grit, the second group pellets with 10% cellulose and the third group received additive-free pellets. Each treatment was repeated 4 times on 15 hens (white laying hybrid). Feed preference with respect to the different pellet variations available was examined and feather eating behaviour was tested after the test rations were discontinued. Birds in both the feather grit and cellulose groups showed less feather pecking behaviour than control animals throughout the entire experiment. Likewise, birds in the feather grit group had a significantly better plumage condition than those in the control group. Animals in the feather grit group also ate more pellets and ingested significantly more feathers than those in both the control and cellulose groups. The third section of the experiment was conducted with animal selected on high (HFP) and low (LFP) feather pecking activity (KJAER et al., 2001); three different feeding treatments were tested. Birds in the first group were offered 70 feathers per week (HF and LF), birds in the second group had access to wood shavings ad libitum (HSp and LSp), and birds in the third group were not offered any additional substrates (H0 and L0). The intestinal passage rate of each group was investigated, whereby animals receiving additional substrates were selected for comparison when the amount of substrate (feathers or wood shavings) ingested was comparable. Animals in the HF group showed the fastest intestinal passage rate, followed by LF and H0 birds. The L0 animals had the slowest marker excretion. Although feather intake in HF and LF groups was similar, only the HF birds had a significantly faster passage rate. HFP birds which had access to wood shavings showed faster marker excretion as LFP birds in comparison. This experiment demonstrates that misdirected exploratory behaviour does not seem to be the primary cause of feather pecking. Rather the ingestion of feathers or wood shavings / cellulose plays a meaningful role in this behaviour. The results of this study show that feather pecking can be classified as feeding behaviour. This is in accordance with previous literature in which feather pecking is identified as feather eating. Furthermore, genetic discrepancies between HFP and LFP animals seem to exist, since the ingestion of a similar amount of feathers or wood shavings had different effects on the intestinal tracts of the animals in the two lines. Further research is necessary to validate the results of this study.
Untersuchungen zur Motivation zum Federfressen bei Legehennen
(2007) Häusler, Kirsten; Bessei, Werner
The focus of this thesis is to unveil the dependency of feather pecking as an expression of explorative behaviour (foraging and activity) and the actual ingestion of feathers. The survey of motivation ratio was realized through conduction a preference test. This was performed by two substrate variations (feathers and feed) at three different grades of accessibility within the trial location. In addition the strength of motivation was measured by force records of pecking impacts vial corresponding gratification in a facility for operant conditioning (Skinner Box). The trials have been conducted with White Leghorn hens, which were selected over six generations on performing high (HFP) and low (LFP) feather pecking activity. At first 20 HFP and 20 LFP individuals were tested in the preference test. The choice presented was displayed as loose feathers (for ingestion), affixed feathers (activity), feed and an empty alternative. Each substrate was provided in equal quantity and frequency at all three grades of accessibility. The findings confirm the HFP type to peck a distinct higher degree of feathers than the LFP. Even affixed feathers were found to be atorn for ingestion mainly by the HFP. The highest grade of substrates displayed by transparent plastic foil remained untouched. 28 individual hens (14 HFP and14 LFP) were selected from the group of hens which were tested in the preference test. The strength of motivation was revealed by the operant conditioning method. The hens were taught tit peck at a pecking device for food and mealworms. They were tested with a fixed (FR)-reinforcement schedule. By using the FR the hens had to peck in the pecking device for a determinate number (1, 5, 10, ...). The number of pecks with had to be fulfilled by the hens where increased after each testing period until twenty by the increments of five. The described experiments were succeeded by a progressive ratio (PR = reinforcement schedule, which includes a successive increase of pecking impacts within a testing period (3x1, 3x3, 3x5, etc.) Mealworms were used to validate the system. Pecking without a reward was checked to pose as reward itself for the conditioned hens. In contrast to the LFP, the HFP (positive and negative evidence) performed a higher motivation expressed by the pecking frequency for feathers. This meets the results of the first preference test. For the second preference test 23 remaining hens (12 HFP and 11 LFP) were tested. Since affixed festhers were ingested and substrate underneath the transparent foil remained unattended in the first preference test, the dispositions of the choises were modified. Affixed feathers were removed and transparent foil was changed into non transparent plastic foil. Visual examination of the covered substrate was disqualified. Furthermore the social partner was moved from the nearby compartment to a place where contact was reduced to an audio exposure. The results of the second preference test provided no further evidence of feather pecking motivation of the conditioned individuals. HFP and LFP results showed no further discrepancy. The results of the present experiments are in contrast to the exisiting hypothesis that describes the motivation of feather pecking mainly as driven by foraging and exploration behaviour, as well as boredom. It is assumed that ingestion of feathers is a relevant issue of the motivation for feather pecking.