Joergen Kjaer

Hen welfare in different housing systems

Egg production systems have become subject to heightened levels of scrutiny. Multiple factors such as disease, skeletal and foot health, pest and parasite load, behavior, stress, affective states, nutrition, and genetics influence the level of welfare hens experience. Although the need to evaluate the influence of these factors on welfare is recognized, research is still in the early stages. We compared conventional cages, furnished cages, noncage systems, and outdoor systems. Specific attributes of each system are shown to affect welfare, and systems that have similar attributes are affected similarly. For instance, environments in which hens are exposed to litter and soil, such as noncage and outdoor systems, provide a greater opportunity for disease and parasites. The more complex the environment, the more difficult it is to clean, and the larger the group size, the more easily disease and parasites are able to spread. Environments such as conventional cages, which limit movement, can lead to osteoporosis, but environments that have increased complexity, such as noncage systems, expose hens to an increased incidence of bone fractures. More space allows for hens to perform a greater repertoire of behaviors, although some deleterious behaviors such as cannibalism and piling, which results in smothering, can occur in large groups. Less is understood about the stress that each system imposes on the hen, but it appears that each system has its unique challenges. Selective breeding for desired traits such as improved bone strength and decreased feather pecking and cannibalism may help to improve welfare. It appears that no single housing system is ideal from a hen welfare perspective. Although environmental complexity increases behavioral opportunities, it also introduces difficulties in terms of disease and pest control. In addition, environmental complexity can create opportunities for the hens to express behaviors that may be detrimental to their welfare. As a result, any attempt to evaluate the sustainability of a switch to an alternative housing system requires careful consideration of the merits and shortcomings of each housing system.

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.

Analysis of severe feather pecking behavior in a high feather pecking selection line

Even though feather pecking (FP) in laying hens has been extensively studied, a good solution to prevent chickens from this behavior under commercial circumstances has not been found. Selection against FP behavior is possible, but for a more effective selection across different populations, it is necessary to characterize the genetic mechanism associated with this behavior. In this study, we use a high FP selection line, which has been selected for 8 generations. We present evidence of the presence of a major dominant allele affecting the FP behavior by using an argument based on the presence of mixture in the distribution of the observed FP and by studying the evolution of the proportion of very high FP along the sequence of 8 generations. This hypothesis is further supported by the fact that the gene transcription profile of the birds performing high FP differs from the profile of the other birds performing FP (456 genes differentially expressed from a total of 14,077 investigated genes).

Litter lipid content affects dustbathing behavior in laying hens

Within the European Union, the provision of dustbathing material in layer housing systems will be compulsory beginning in 2012. In cage systems, food particles are mainly used as litter material and are provided on scratching mats by an automatic transporting system. However, because dustbathing is a means for hens to remove stale lipids from their plumage, lipid content of a substrate may be an important asset with regard to its adequacy. This study analyzes dustbathing behavior as affected by lipid content of feed used as litter material. A total of 72 laying hens of 2 genotypes (Lohmann Selected Leghorn, Lohmann Brown) were kept in 12 compartments (6 hens each). Compartments were equipped with a plastic grid floor (G) and additionally contained 3 different dustbathing trays (each 1,000 cm(2)/hen) holding low-lipid (0.82%; L), normal-lipid (4.2%; N), and high-lipid (15.7%; H) food particles. The experiment began at 20 wk of life, and video recordings were done at wk 23, 26, and 29. Number of dustbaths, time spent dustbathing, average dustbath duration, foraging, and single behaviors within dustbaths were analyzed during the light period over 2 d in each observation week. Dustbaths occurred most frequently in the L compared with the N, H, and G treatments (all P < 0.001). Total time spent dustbathing was longest in the L treatment compared with the N and H treatments (P < 0.001). No difference in the average duration of single dustbaths was found between the L, N, and H treatments. However, when dustbath interruptions (less than 10 min) were excluded, the duration of single dustbaths was longer in the H compared with the L (P = 0.009) and N (P = 0.024) treatments. Foraging was most frequently observed in the N compared with the L, H, and G treatments (all P < 0.001). More body wing shakes occurred in the L compared with the N treatment, and the number of vertical wing shakes was higher in the N compared with the H treatment (all P ≤ 0.05). Our results showed that preference for a dustbathing substrate increased with decreasing lipid content, implying that food particles may not be a suitable dustbathing substrate.

Analysis of landing behaviour of three layer lines on different perch designs.

Abstract 1. The prevalence of keel bone deformities in laying hens is high and is partly associated with unsuitable perch designs, which impose a risk of injury due to an unstable footing. 2. Over two experiments, 9 or 10 hens of each of three layer lines (Lohmann Selected Leghorn (LSL), Lohmann Tradition (LT) and Lohmann Brown (LB)) were filmed while landing on three different perch types, including steel perches of various diameters, a commercial mushroom-shaped plastic perch and a newly developed prototype perch with a soft surface material. 3. Data on landing behaviour (safe vs. unsafe or failed landing) following downward jumps were collected for 25, 50 and 60 cm vertical distances and 75 cm horizontal distance between a wooden start perch and the different destination perches. 4. The highest proportion of safe landings occurred on the prototype perch, whereas least safe landings were observed on steel perches, irrespective of their diameter. The mushroom-shaped perch was intermediate with regard to the safeness of landing. 5. A threshold of 50 cm vertical distance (34° slope) was identified as the optimum for downward jumps on perches in order to reduce the risk of unsafe or failed landings. Above this threshold, the proportion of safe landings declined significantly. 6. Brown shell layer types (LB and LT) had a lower proportion of safe landings compared to the white shell layer type (LSL), whereas no difference was found between LB and LT layer lines. 7. Although steel perches prevail in commercial housing, these perches were found to be least advantageous with regard to landing behaviour. The prototype perch provided the most stable footing on perching and is a promising alternative to replace commercial steel perches, thus helping to reduce the risk of perch-related keel bone injury.

Reducing stress during welfare inspection: validation of a non-intrusive version of the LayWel plumage scoring system for laying hens

1. The objectives of the present study were to validate a reduced, non-intrusive version (RLS) of the LayWel plumage scoring system in domestic laying hens with reference to complete, intrusive scoring (CLS) and to investigate the effect of these two scoring methods on corticosterone metabolite concentrations. 2. A total of 312 medium-heavy laying hens from 4 commercial hybrids kept in 24 floor pens were scored by two experienced teams. Another 150 hens from two hybrids kept in 6 pens were used for estimating scoring treatment effects on corticosterone metabolites in droppings. 3. Plumage scores were in general higher using the RLS method compared to the CLS method. The agreement between teams for plumage scores (CLS) were on a high (total score) to an excellent (single body part except breast and cloaca) level. 4. Birds subjected to CLS tended to have higher concentrations of corticosterone metabolites in droppings 2 h after scoring compared with birds in the control treatment (not scored). Birds subjected to RLS had intermediate concentrations. 5. It was concluded that a reduced version of the LayWel scoring system is a valid and reliable scoring method which tends to induce less stress to the subjects than the original procedure.

Feeding activity in groups of newly hatched broiler chicks: effects of strain and hatching time.

The feeding activity of 2 strains of broiler chickens was investigated during their first week of life in relation to their hatching time. Fast (Ross 308) and slow-growing (LB) strains were allocated to 1 of 3 (early, middle, or late hatch) single-strain groups of 80 to 100 as-hatched birds in 4 replicates divided into 2 time-separated blocks. Behavioral observations differed between blocks and were carried out at intervals on d 1 to 6, and the percentage of birds feeding (from trough or paper), drinking, or being otherwise active (block 2 only) were registered. A higher mortality caused by flip-over was seen among the late-hatching birds from the slow-growing strain. The percentage of birds engaged in feeding activity was similar for the 2 strains, but LB birds began to eat from the paper later and were observed eating from the trough less than Ross 308 birds, which in turn were less active than LB, especially in the early and middle hatch groups. Early hatch groups were observed feeding from the paper more than the middle and late hatch groups. Drinking behavior mirrored feeding from the trough, indicating that drinking was prandial. Within strain, no effect of hatch time was found on live weight at hatch, but the feeding behavior of early hatched birds led to a small, transient weight advantage on d 3 after hatch. The transition from feeding on paper to feeding only from the trough may have less effect on birds that feed from the trough sooner, such as the fast-growing strain.

Acute tryptophan depletion: the first method validation in an avian species (Gallus gallus domesticus)

ABSTRACT Acute tryptophan depletion (ATD) is a valuable non‐invasive nutritional tool in human and rodent research to study dysfunctions of the serotonergic system and related behavioral disorders. Serotonergic dysfunction is thought to be involved in the pathology of feather pecking behavior of laying hens, one of the most relevant welfare and production issues in modern intensive egg‐production systems. ATD temporarily compromises the influx of tryptophan (TRP) across the blood brain barrier which reduces central availability of TRP, the substrate for serotonin (5‐HT) synthesis. However, ATD has never before been developed and evaluated in birds. We hereby report that ATD in laying hens effectively depletes plasma levels of TRP to 50% of the baseline concentration, 4 hours after administration. Furthermore, ATD reduces the ratios of TRP towards aromatic amino acids (AAA) by 60% and the ratio of TRP towards large neutral amino acids (LNAA) by 70%, three hours after administration. Further studies will be needed to determine the effects of peripheral depletion on brain TRP and 5‐HT levels in birds. However, our study showed for the first time in an avian species that ATD causes lowering of plasma TRP and the ratio in plasma of TRP towards other AAA or LNAA.

Differences in cecal microbiome of selected high and low feather-pecking laying hens

ABSTRACT In mammals, it has become increasingly clear that the gut microbiota influences not only gastrointestinal physiology but also modulates behavior. In domestic birds, ceca have the greatest gastrointestinal microbial population. Feather‐pecking (FP) behavior in laying hens is one of the most important unsolved behavioral issues in modern agriculture. The aim of the present study was to assess the cecal microbial community of divergently selected high (HFP; n = 20) and low (LFP; n = 20) feather‐pecking birds at 60 wk of age. The cecal samples were subjected to community profiling of 16S rRNA and in silico metagenomics using a modified bar‐coded Illumina sequencing method on a MiSeq Illumina sequencer. Our results revealed that compared to HFP birds, LFP birds are characterized by an increased overall microbial diversity (beta diversity) shown by a difference in the Bray‐Curtis index (R2 = 0.171, P < 0.05). Furthermore, operational taxonomic unit comparisons showed an increased presence of Clostridiae and decreased presence of Lactobaccillacae in HFP birds when compared to LFP birds (False Discovery Rate < 0.05, Mann‐Whitney comparisons). Our data indicate that there may be differences in the cecal profile between these 2 lines of laying hens. More research, building on this first study using sequencing technology for profiling the chicken cecal microbiome, will be needed in order to reveal if and how there exists a functional link between the performance of FP and the cecal microbial community.