Lohmann Selected Leghorn Hens Research Articles

The potential of a light spot, heat area, and novel object to attract laying hens and induce piling behaviour

Piling behaviour of laying hens often results in smothering or death due to suffocation. Mechanisms leading to piling are not yet understood though various potential factors have been suggested. In this experimental study, we predicted that the presence of a light spot, a novel object (metal foil), or a heat area within animal pens would increase animal numbers around the stimulus leading to piling behaviour. We presented the cues in a 4 × 2 Latin-square design in eight identical experimental pens including each 55 Lohmann Selected Leghorn hens. The cues were presented in two test areas per pen, at two bouts per day in the morning, consecutively for 5 days, over four periods (age: 20, 22, 24, 26 weeks). Each pen received a cue and control condition simultaneously (test areas without cue presentation) once. For a bout, each cue was presented for 35 min except for the light spot where the duration was 10 min. Birds’ responses to the cues during bout and non-bout times were video recorded and analysed for the first bout of each period. To assess the cues’ attractiveness, the number of hens during bout times was counted at predefined times within the test and control areas. To assess the cues’ effects on piling, we described piling behaviour (pile number, duration, animal numbers, trigger) in control and test areas during bout times. Furthermore, we described piling behaviour during bout times and non-bout times on the first day of the first period and fourth period. The best model explaining the number of hens included the interactions of treatment and bout time, and treatment and area. Over the bout’s time course, more hens were attracted to the light spot compared to the control condition, and more to test areas compared to control areas. In the novel object condition, more hens were drawn to the test areas compared to the control areas. Hens were not attracted to the heat area. Piling in bout times was observed twice when hens pecked at the novel object. During non-bout times, piling behaviour occurred frequently at midday and in the late morning compared to the afternoon, mostly in corners and mainly preceded by the mutual attraction of hens. Overall, hens were attracted to light spots and less so to the novel object though neither reliably induced piling behaviour. The occurrence of piling behaviour in non-bout times shows that more work is needed to understand mechanisms eliciting piling behaviour.

Feather Pecking in Non-Beak-Trimmed and Beak-Trimmed Laying Hens on Commercial Farms with Aviaries.

Simple SummarySevere feather pecking (SFP) is a major animal welfare problem in layers. It results in pain and injuries in the affected animal. SFP is a behavioral disorder and should not be confused with aggressive pecking. The aim of our study was to observe the pecking behavior of layers on farms with flock sizes common in practice and to identify possible influencing factors. We found that SFP occurred in all flocks, but the pecking rate varied widely between flocks. A low stocking density and the provision of a winter garden or free range (or both) had a positive effect and reduced SFP. Keeping mixed flocks of brown and white layers was a risk factor for SFP. SFP occurred mainly in the litter area and only rarely on perches. This finding emphasizes the importance of providing enough litter, litter areas and environmental enrichment. Aggressive pecking and SFP were correlated, which may indicate a higher stress level in the flock. Beak trimming reduced pecking rates but did not entirely prevent SFP. Instead of subjecting chicks to this potentially painful procedure, reasons for SFP should be addressed. SFP remains a multifactorial problem, but in recent years, many risk factors have been identified and included in best-practice recommendations, allowing the housing of non-beak-trimmed layers.Severe feather pecking (SFP) is a major animal welfare problem in layers. It results in pain and injuries in the affected animal. It was the aim of this study to gain insight into the actual pecking behavior of laying hens kept on commercial farms with flock sizes common in practice. We observed aggressive pecking and SFP in non-beak-trimmed and beak-trimmed flocks of laying hens and investigated possible influencing factors. The study took place on eight conventional farms in Germany with aviaries, including three farms with a free range and a winter garden, one with a free range and one with a winter garden. Pecking behavior was observed during three observational periods (OPs): OP 1, at the peak of the laying period between the 28th and 33rd week of life; OP 2, in the middle of the laying period between the 42nd and 48th week of life; and OP 3, at the end of the laying period between the 63rd and 68th week of life in one laying period. Videos were analyzed using behavior sampling and continuous recording. We found that SFP occurred in all flocks, but the pecking rate differed significantly between the flocks. SFP correlated positively with the number of hens per square meter of usable area, with statistical significance in the litter area (r = 0.564; p = 0.045). The multivariate analysis revealed that access to a winter garden or free range significantly reduced the SFP rate on perches (p = 0.001). The stocking density (number of birds per usable square meter) had a significant influence on the SPF rate in the nest-box area (p = 0.001). The hybrid line had a significant effect on the SFP rate on perches and in the nest-box area (p = 0.001 each). Lohmann Brown hens in mixed flocks had a higher SFP rate (significant in OP 2) than those in homogeneous flocks, indicating that mixed flocks may be a risk factor for SFP. Lohmann Brown hens pecked significantly less than Dekalb White hens in the litter area (p = 0.010) and in the nest-box area (p = 0.025) and less than Lohmann Selected Leghorn hens in the litter area (p = 0.010). Lohmann Brown and Lohmann Selected Leghorn hens showed increasing SFP rates during the laying period. All hybrid lines had significantly higher SFP rates in the litter area, followed by the nest-box area and perches. These findings emphasize the importance of providing enough litter, litter areas and environmental enrichment. We found a significant positive correlation between aggressive pecking and SFP—in OP 1: rho (Spearman) = 0.580, p < 0.001; OP 2: rho = 0.486, p = 0.002; and OP 3: rho = 0.482, p = 0.002 (n = 39) —indicating that SFP may lead to a higher stress level in the flock. Beak trimming reduced pecking rates but did not entirely prevent SFP. Instead of subjecting chicks to this potentially painful procedure, reasons for SFP should be addressed. In conclusion, our data suggest a positive influence of a lower stocking density and the provision of a winter garden or free range for additional space. The hybrid line had a significant influence on the feather-pecking rate on perches and the nest-box area. Aggressive pecking and severe feather pecking correlated positively. We assume that vigorous and painful AP were an additional stress factor, especially in non-beak-trimmed flocks, leading to more SFP in due course. Beak trimming had a reducing effect on SFP. However, our results showed that non-beak-trimmed flocks could be kept without major outbreaks of SFP.

Transcriptional responses in jejunum of two layer chicken strains following variations in dietary calcium and phosphorus levels

BackgroundCalcium (Ca) and phosphorus (P) are essential nutrients that are linked to a large array of biological processes. Disturbances in Ca and P homeostasis in chickens are associated with a decline in growth and egg laying performance and environmental burden due to excessive P excretion rates. Improved utilization of minerals in particular of P sources contributes to healthy growth while preserving the finite resource of mineral P and mitigating environmental pollution. In the current study, high performance Lohmann Selected Leghorn (LSL) and Lohmann Brown (LB) hens at peak laying performance were examined to approximate the consequences of variable dietary Ca and P supply. The experimental design comprised four dietary groups with standard or reduced levels of either Ca or P or both (n = 10 birds per treatment group and strain) in order to stimulate intrinsic mechanisms to maintain homeostasis. Jejunal transcriptome profiles and the systemic endocrine regulation of mineral homeostasis were assessed (n = 80).ResultsEndogenous mechanisms to maintain mineral homeostasis in response to variations in the supply of Ca and P were effective in both laying hen strains. However, the LSL and LB appeared to adopt different molecular pathways, as shown by circulating vitamin D levels and strain-specific transcriptome patterns. Responses in LSL indicated altered proliferation rates of intestinal cells as well as adaptive responses at the level of paracellular transport and immunocompetence. Endogenous mechanisms in LB appeared to involve a restructuring of the epithelium, which may allow adaptation of absorption capacity via improved micro-anatomical characteristics.ConclusionsThe results suggest that LSL and LB hens may exhibit different Ca, P, and vitamin D requirements, which have so far been neglected in the supply recommendations. There is a demand for trial data showing the mechanisms of endogenous factors of Ca and P homeostasis, such as vitamin D, at local and systemic levels in laying hens.

Daily energy expenditure and water turnover in two breeds of laying hens kept in floor housing

Laying hens are increasingly kept in barn or free-range systems, which not only allows birds to move freely but also potentially entails higher energy expenditures due to higher locomotor activity. Therefore, the aim of our study was to quantify the daily energy expenditure (DEE) and water turnover in freely moving laying hens. For that purpose, 10 Lohmann Selected Leghorn (LSL) and 10 Lohmann Brown (LB) hens were obtained from a conventional breeding company at 17 weeks of age. The trial started when birds reached an age of 34 weeks. All 20 birds were kept together in the same littered floor pen (12.1 m2). The pen was equipped with perches, a nest box, feeding and nipple drinkers. The DEE was determined individually for all experimental birds (n = 20) for a total of nine days using the doubly labelled water (DLW) method. Lohmann Brown hens were heavier than LSL hens, but laying rate did not differ between the two breeds, that is, one egg per hen and day during the study period. Average egg mass was 63.1 ± 0.20 g in LB and 61.7 ± 0.12 g in LSL hens, which converted to an egg energy content of 420 and 410 kJ/egg, respectively. Dilution spaces for oxygen and hydrogen differed between the breeds but not the respective turnover rates. Total body water as a percentage of body mass (LB: 54.4%, LSL: 53.8%; SEM = 0.7, F1,18 = 0.41, P = 0.513) and total water intake (TWI) per day (LB: 275 ml/day, LSL: 276 ml/day; SEM = 20, F1,17 = 0, P = 0.994) did not differ between LB and LSL hens. Individual DEE increased with body mass in LB but not in LSL hens. Average DEE did not differ between the two breeds (LB: 1501 kJ/day; LSL: 1520 kJ/day; SEM = 32.1, F1,17 = 2.54, P = 0.131). However, when comparing the DEE on a metabolic mass basis, LSL hens expended with 984 kJ/kg0.75 on average significantly more energy per day than LB hens (895 kJ/kg0.75; SEM = 20.3, F1,18 = 10.1, P = 0.005). Our results suggest that the DLW technique is a viable method to measure the energy expenditure and water turnover over several days in laying hens. Furthermore, we show that laying hens kept in floor pens fit into the general pattern of DEE among wild birds.

Feasibility of artificial light regimes to increase the vitamin D content in indoor-laid eggs

Vitamin D insufficiency is prevalent worldwide. Recently, we showed that exposure of laying hens to sunlight or artificial ultraviolet B (UVB) light is an efficient strategy to increase the vitamin D content in eggs. In the current study, using 2 different chicken genotypes and stocking densities, we addressed the question of whether different UVB-emitting regimes work under real indoor housing conditions in a floor system or in furnished cages. Here, we found a 3.7-fold increase in the egg vitamin D content in Lohmann Selected Leghorn hens and a 4.2-fold increase in Lohmann Brown hens after UVB exposure for 6 h/d. The data further reveal that UVB exposure under high stocking density is equally effective compared to that at low stocking density. The different light regimes were not associated with changes in the behavior of these animals. To conclude, artificial UVB-emitting light regimes are a practical strategy to increase the vitamin D content in indoor-laid eggs.

Keel bone fractures are associated with individual mobility of laying hens in an aviary system

Keel bone fractures (KBF) in laying hens have been shown to cause pain and impair mobility under experimental conditions. However, it is not known how KBF relates to the mobility of individual hens housed in aviary systems. For the current study, 120 focal hens (60 Lohmann Brown (LB) and 60 Lohmann Selected Leghorn (LSL)) were kept in six identical pens equipped with a commercially relevant aviary system (20 LSL focal hens + 205 LB or 20 LB focal hens + 205 LSL per pen, respectively). Data on hen mobility were recorded at 21, 24, 27, 31, 35, 39, 44, 48, 52, 57 and 61 weeks of age. Infrared receivers were attached to the legs of focal hens. They recorded zone-specific codes between five zones (litter, lower tier, nest boxes, top tier, and wintergarden) at a frequency of 1 Hz for six consecutive days per week of age. At the end of each data collection period, hens were radiographed to assess keel bone fracture severity. Data were analysed using (generalized) linear mixed effect models. With increasing KBF severity, LB hens spent more time in the top tier (p = 0.005) and less time in the litter zone (p < 0.0001) and in the lower tier (p = 0.001). Independent of KBF, LB hens spent less time in the wintergarden (p = 0.011) and in the lower tier (p = 0.002) and more time in the top tier (p = 0.009) with increasing age. The likelihood of crossing more than one zone within a movement (e.g., jumping from the top tier to the litter directly) increased with increasing KBF severity (p = 0.036). Lohmann Selected Leghorn hens spent most time in the nest box zone and top tier and had few transitions between zones. With increasing age, LSL hens spent less time in the nest box zone (p = 0.018) and more time in the top tier (p = 0.006). Irrespective of strain, hens crossed fewer zones with increasing age (LB: p = 0.009, LSL: p = 0.002). Our findings indicate that hens having KBF prioritized paths among the upper tiers (i.e., mostly between nest box zone and top tier) over paths among the mid and lower tiers (i.e., between litter, lower tier and nest box zone). We conclude that behavioural adaptation to pain, the accessibility of resources as well as social factors might be important mechanisms driving individual mobility in response to KBF.

Influence of a Sustained Release Deslorelin Acetate Implant on Reproductive Physiology and Associated Traits in Laying Hens.

The aim of this study was to develop an animal model with non-laying hens which would allow for investigation of the relationship between egg production and common diseases in hens. A total of 40 Lohmann Selected Leghorn hens were kept for 20 weeks in a floor housing system in two groups: group “Adult” (21 weeks of age) and group “Juvenile” (14 weeks of age). In each group, 10 hens were administered a 4.7 mg sustained release deslorelin acetate implant subcutaneously; in group “Adult” after, in group “Juvenile” before the onset of lay. In both groups, the remaining hens served as control hens. An examination of each hen was performed weekly, including ultrasonography to check for ovarian follicles, analysis of estradiol-17ß plasma concentration, and assessment of comb size. Digital radiographs of the keel bone were taken in experimental weeks 7 and 15. No follicles were detected on the ovary of treated hens for a certain time period which varied between individuals (between 8 weeks and until the end of the experiment). Estradiol-17ß concentrations were significantly higher in control hens. The comb was significantly smaller in treated hens. A lower prevalence of keel bone damage (group “Adult”) and foot pad dermatitis (FPD) (both groups) was found in treated compared to control hens. These results show that a model with laying and non-laying hens can be achieved by administering a deslorelin acetate implant. Furthermore, they indicate a relationship between egg production and keel bone damage as well as FPD.

Feeder space affects access to the feeder, aggression, and feed conversion in laying hens in an aviary system

In laying hens, minimal requirements for feeder space (cm per bird) are based primarily on data from small groups of hens (n<10) housed in battery cages. The aim of the present study was to determine the effects of feeder space on agonistic behaviour, access to the feeder, and production in laying hens housed in an aviary system. The experiment was conducted in a quasi-commercial barn that contained 20 pens with 200 Lohmann Selected Leghorn hens housed in each. Five levels of feeder space (3.8, 6.0, 8.0, 9.0, and 10.0cm/hen) were systematically allocated to four pens each from 21 weeks of age onwards. Behavioural assessments from video recordings at 21, 32, 39, and 45 weeks of age included: aggression, jostling followed by either feeding or other behaviour, duration of feeding bouts, and the number of hens feeding from the perch above the feeder as well as simultaneously from the platform at the feeder. Production parameters were measured daily and included: egg production, floor eggs, feed disappearance, and feed conversion ratio. Our results show that more feeder space was associated with less aggression (z-value=−4.06, p<0.001) and less jostling (followed by feeding: z-value=−3.74, p<0.001; followed by other behaviour: z-value=4.24, p<0.001), as well as more simultaneous feeding from the platform at the feeder (z-value=−5.36, p<0.001) and longer feeding bouts (z-value=4.68, p<0.001). Feed disappearance (t-value=3.08, df=18, p=0.006) increased and feed conversion decreased with feeder space (t-value=2.245, df=18, p=0.038). The results indicate positive effects of increased feeder space on laying hen behaviour at the cost of relatively minor production losses. Thus, competition at the feeder decreased with increasing feeder space, allowing more birds to feed simultaneously, while feed conversion decreased only slightly. By combining measures of behaviour and production, our results can facilitate decisions on feeder space for laying hens in view of optimal trade-offs between agonistic behaviour, access to the feeder, and feed conversion.

Dust-bathing behavior of laying hens in enriched colony housing systems and an aviary system

The dust-bathing behavior of Lohmann Selected Leghorn hens was compared in 4 enriched colony housing systems and in an aviary system. The enriched colony housing systems differed especially in the alignment and division of the functional areas dust bath, nest, and perches. Forty-eight-hour video recordings were performed at 3 time-points during the laying period, and focal animal sampling and behavior sampling methods were used to analyze the dust-bathing behavior. Focal animal data included the relative fractions of dust-bathing hens overall, of hens bathing in the dust-bath area, and of those bathing on the wire floor throughout the day. Behavior data included the number of dust-bathing bouts within a predefined time range, the duration of 1 bout, the number of and reasons for interruptions, and the number of and reasons for the termination of dust-bathing bouts. Results showed that the average duration of dust bathing varied between the 4 enriched colony housing systems compared with the aviary system. The duration of dust-bathing bouts was shorter than reported under natural conditions. A positive correlation between dust-bathing activity and size of the dust-bath area was observed. Frequently, dust baths were interrupted and terminated by disturbing influences such as pecking by other hens. This was especially observed in the enriched colony housing systems. In none of the observed systems, neither in the enriched colony housing nor in the aviary system, were all of the observed dust baths terminated “normally.” Dust bathing behavior on the wire mesh rather than in the provided dust-bath area generally was observed at different frequencies in all enriched colony housing systems during all observation periods, but never in the aviary system. The size and design of the dust-bath area influenced the prevalence of dust-bathing behavior in that small and subdivided dust-bath areas reduced the number of dust-bathing bouts but increased the incidence of sham dust bathing on the wire mesh.

Welfare indicators in laying hens in relation to nest exclusion

Consumer concerns about the welfare of laying hens are increasing, leading to increased interest in identifying reliable ways to assess welfare. The present study evaluated invasive and non-invasive welfare indicators in relation to a stressful challenge. The study included 126 Lohmann Selected Leghorn hens housed in furnished cages. Welfare indicators were measured between 61 and 70 wk of age in birds excluded from their nests for 5 consecutive d and control birds that had continuous access to nests. Baseline recordings were carried out in both groups prior to and post exclusion period. The assessed indicators were: corticosterone metabolites in droppings (FCM), corticosterone concentration in yolk, corticosterone concentration in plasma, irregularities of eggshells, heterophil to lymphocyte (H:L) ratio, tonic immobility duration, and feather cover. Behavioral observations showed that the birds had a clear preference for using the secluded nest sites, confirming that they were likely to perceive nest exclusion as an undesirable experience. Further, elevated levels of FCM in droppings, yolk corticosterone concentrations, H:L ratios and irregular eggshells were detected in both nest deprived and control birds during the exclusion. This suggests that these indicators were able to detect an increased stress response arising from nest deprivation, and it is hypothesized that the stress spread to birds in adjacent cages with access to nests. There was a positive and consistent correlation between FCM in droppings and eggshell irregularities, also supporting the use of eggshell irregularities as a potential non-invasive welfare indicator. However, the pattern of the stress response varied between indicators and correlations were generally few and inconsistent, highlighting the complexity of the relationship among welfare indicators.

Spatial requirements of poultry assessed by using a colour-contrast method (KobaPlan)

Sufficient floor space is a fundamental precondition for poultry to perform normal behavioural patterns. To calculate and determine stocking densities, it is essential to know the absolute minimum surface area required by any given animal (body space). Additional space is required for characteristic behaviours (behavioural space) and for adequate inter-individual distances, group sizes and room to perform social interactions have to be taken into account.To calculate body space, planimetric measurements were carried out by the colour contrast method “KobaPlan” in various poultry species in standing and sitting positions and at a number of different ages. They included laying hens (Lohmann brown (LB), Lohmann selected Leghorn (LSL)), broiler breeders (Ross, both genders), broiler chickens (Ross 308, both genders), turkeys (BUT 6, males), Peking ducks (Cherry Valley, both genders) and Muscovy ducks (Canedins R51, males).Depending on live weight, age, plumage condition and body position, LB hens occupied an average area between 401 cm2 and 542 cm2, LSL hens between 353 cm2 and 445 cm2, broiler breeder females between 440 cm2 and 537 cm2, broiler breeder males 623 cm2 up to 945 cm2, broiler chickens up to 434 cm2, male fattening turkeys up to 1808 cm2, Muscovy drakes up to 873 cm2 and Peking ducks up to 627 cm2.The values can be regarded as necessary minimum spatial requirements for the measured poultry species and genotype.The current method offers the potential to record the area occupied by animals exhibiting species-specific behavioural patterns.

Nesting behaviour – a comparison of single nest boxes and family nests

Summary From an evolutionary point of view, the laying behaviour hardly has changed and is an important behaviour trait for layers. Nesting behaviour is of special interest with increasing consumer demand for eggs produced in cage free systems. Good nesting behaviour is crucial for the economic success of table egg production. The aim of the study was to evaluate the nesting behaviour of two layer strains in a single and a family nest. Two different nest systems equipped with electronic animal identification and data recording were used to capture behaviour traits routinely over the entire laying period. The Weihenstephan funnel nest box (FNB), a single nest box, and the high frequency family nest (HFGN) were used. Hens of similar age from the strains Lohmann Brown (LB) and Lohmann Selected Leghorn (LSL) were blended for this study and housed in pens equipped with one of the two nest systems, either FNB or HFGN, at the experimental station Thalhausen of the Technische Universität München. The hens of each flock changed the nest system after six months and stayed then for further four months in the second nest system. So each group of hens was tested in both nest systems, either first in the FNB (flock 1) or first in the HFGN (flock 2). In flock 1, the median for the trait number of nest visits per hen and day was 1.2 for the LB and 1.3 for the LSL hens in the FNB, when being housed in the FNB first. In flock 2, the median was 1.2 for both strains. The median for the number of nest visits per hen and day was 1.2 in the HFGN for the LB and 1.4 for the LSL layers regardless in which nest system being housed first. In the FNB the median for the trait overall duration of stay in nest per hen and day was 23Â min in flock 1 and 28Â min in flock 2 for the LB. In the FNB the median of duration of stay in a nest of the LSL hens was 65Â min in flock 1 and 42Â min in flock 2. LB hens stayed in the HFGN on average 27Â min in flock 1 and 30Â min in flock 2. When being housed in the FNB first, the median for duration in the nest decreased from 69Â min in flock 2 to 54Â min in flock 1 for the LSL hens in the HFGN. The results of this study show clearly differences in the nesting behaviour between white and brown layers as well as between the nest systems. Additionally the hen’s age and their familiarisation to a specific nest system have an important impact on the number of nest visits as well as the time spent in a nest.

Corticosterone metabolites in laying hen droppings—Effects of fiber enrichment, genotype, and daily variations

There is growing interest and concern for animal welfare in commercial poultry production. To evaluate stress and welfare in an objective and noninvasive way, fecal corticosterone metabolites (FCM) in droppings can be analyzed. However, the influence of diet, genotype, and daily variations in FCM and production of droppings in laying hens has been poorly investigated. This study examined the effect of insoluble fiber by adding 3% ground straw pellets to the feed to Lohmann Selected Leghorn (LSL) and Lohmann Brown (LB) hens housed in furnished cages between 20 and 40 wk of age. In total, 960 hens were included in the study. Droppings were collected 4 times per day for 3 consecutive days and analyzed by corticosterone immunoassay. Biological validation confirmed the ability of the assay to detect changes in FCM levels. Inclusion of straw pellets in the feed increased FCM concentration in both hen genotypes and increased excretion rate of FCM in LB hens. The LB hens also produced greater amounts of droppings than LSL hens. Both FCM levels and production of droppings varied during the day, although no distinct diurnal rhythm was found. These findings demonstrate that when using FCM to evaluate stress and welfare in laying hens, many factors (e.g., diet, genotype used, and so on) need to be taken into account to allow accurate interpretation of the results. In addition, under certain conditions, excretion rate of FCM might be more appropriate to use compared with FCM concentration.

Evaluation of bone strength, keel bone status, plumage condition and egg quality of two layer lines kept in small group housing systems

1. The aim of the present study was to determine the influence of large (54 or 60) and small (36 or 40) group sizes and tiers of the small group housing system “Eurovent German” on tibia and humerus bone breaking strength, keel bone status, plumage condition and egg quality for two commercial layer lines, Lohmann Selected Leghorn (LSL) and Lohmann Brown (LB), at the same stocking density (890 or 830 cm2/bird). 2. In 4 consecutive trials, 4752 hens were recorded for keel bone status. Evaluation of plumage condition was made for 1440 hens and bone breaking strength was recorded for 1200 hens. A total of 4962 eggs were analysed for internal and external egg quality traits. Analyses involved 30 small group compartments per trial. 3. The layer line had a much more pronounced influence on humerus breaking strength than on tibia breaking strength. 4. Plumage condition, particularly on the neck, was positively correlated with humerus breaking strength in both layer lines. 5. An average of 34% of LB and 23% of LSL hens showed keel bone deformities, with higher proportions of slight deformities. 6. Slight keel bone deformities, rather than moderate to severe, increased significantly during the laying period. 7. Stocking density had no influence on bone breaking strength, keel bone status and egg quality traits. 8. LB layers had a 1.4-fold higher humerus, but only a 1.06-fold higher tibia breaking strength compared to LSL layers. 9. Tibia breaking strength was significantly affected by the interaction of group size and layer line. LSL layers in small groups had lower tibia breaking strengths than those of the large groups.

Influence of nest site on the behaviour of laying hens

Low rates of nest acceptance by laying hens are a major problem in commercial poultry farming operations with aviary systems, leading to costly manual collection and cleaning of mislaid eggs. To gain knowledge about factors affecting nest use, laying hens’ preferences for different nest locations were tested. Nests are normally installed at one of two sites: against a wall of the hen house or integrated into one tier of the aviary rack. The preferences of laying hens for different nest sites have never been examined under commercial conditions. The aim of this study is to investigate whether behavioural differences can be detected between the different nest sites. The study consists of two consecutive trials involving 5027 Lohmann Selected Leghorn hens (LSL) and 601 layer hybrids selected for extensive housing conditions (EXT). The hens were randomly assigned to eight compartments per trial in groups of 355–360 LSL or 300 EXT in a laying hen house. Four compartments were equipped with a Volito Voletage ® aviary system (VV), and four were equipped with a Rihs Bolegg ®II aviary system (RB), both of which contained either integrated or wall-placed nests when the experiments started. A strongly balanced crossover design with four periods was used. At 36, 44 and 52 weeks of age, the nest site in four out of the eight compartments was switched. Before each change, the fronts of half of the nests were videotaped during the light period, and the behaviour throughout the main laying period was analysed. Furthermore, the numbers of nest eggs and mislaid eggs in each compartment were recorded every day. No differences in the number of mislaid eggs between the two nest sites could be detected, except at the age of 20/21 weeks when hens in VV aviaries mislaid more eggs when nests were integrated ( P = 0.0012). More hens stood simultaneously in front of the integrated nests than in front of wall-placed nests ( P = 0.015). Activity of the laying hens increased ( P = 0.0073), and stationary behavioural patterns declined ( P = 0.0093), when the nests were placed by the wall. Hens inspected integrated nests for a longer duration than wall-placed nests, but wall-placed nests were visited more frequently. In addition to the nest site, the width of the platform in front of the nest influenced laying hen behaviour. Compared with narrower platforms, balance movements decreased on wider ones. Additionally, the platform design had to be taken into account as well, given that hens could not stand or walk as securely on wooden slats as on a grid floor.

Effects of housing, perches, genetics, and 25-hydroxycholecalciferol on keel bone deformities in laying hens

Several studies have shown a high prevalence of keel bone deformities in commercial laying hens. The aim of this project was to assess the effects of perch material, a vitamin D feed additive (25-hydroxyvitamin D(3); HyD, DSM Nutritional Products, Basel, Switzerland), and genetics on keel bone pathology. The study consisted of 2 experiments. In the first experiment, 4,000 Lohmann Selected Leghorn hens were raised in aviary systems until 18 wk of age. Two factors were investigated: perch material (plastic or rubber-coated metal) and feed (with and without HyD). Afterward, the hens were moved to a layer house with 8 pens with 2 aviary systems. Daily feed consumption, egg production, mortality, and feather condition were evaluated. Every 6 wk, the keel bones of 10 randomly selected birds per pen were palpated and scored. In the second experiment, 2,000 Lohmann Brown (LB) hens and 2,000 Lohmann Brown parent stock (LBPS) hens were raised in a manner identical to the first experiment. During the laying period, the hens were kept in 24 identical floor pens but equipped with different perch material (plastic or rubber-coated metal). The same variables were investigated as in the first experiment. No keel bone deformities were found during the rearing period in either experiment. During the laying period, deformities gradually appeared and reached a prevalence of 35% in the first experiment and 43.8% in the second experiment at the age of 65 and 62 wk, respectively. In the first experiment, neither HyD nor the aviary system had any significant effect on the prevalence of keel bone deformities. In the second experiment, LBPS had significantly fewer moderate and severe deformities than LB, and rubber-coated metal perches were associated with a higher prevalence of keel bone deformities compared with plastic perches. The LBPS laid more but smaller eggs than the LB. Again, HyD did not affect the prevalence of keel bone deformities. However, the significant effect of breed affiliation strongly indicates a sizeable genetic component that may provide a basis for targeted selection.

Roosting behaviour in laying hens on perches of different temperatures: Trade-offs between thermoregulation, energy budget, vigilance and resting

Laying hens usually select an elevated position for resting at night-time. A previous study showed that the position a hen takes during resting was affected by perch material, most probably due to its thermal conductivity. The aim of the present study was to analyse the effect of perch surface temperature on resting behaviour and resting comfort in laying hens. In each of two identical trials, three groups of five Lohmann Selected Leghorn hens were housed in each of three compartments in turn ( n = 30 birds in six groups). Compartments were equally equipped with one smooth, round galvanised steel perch of 34 mm external diameter. The surface temperatures of perches were controlled by passing water through them, giving temperatures of 15 °C, 18 °C (room temperature) and 28 °C respectively in the three compartments. Hen behaviour was observed at night-time by investigating the proportion of active behavioural patterns and resting (standing or sitting), either with ‘head forward motionless and neck withdrawn’ or ‘head tucked backwards into feathers above wing base or behind a wing.’ The number of hens perching and the time spent perching were unaffected by perch temperature. Hens’ resting postures, however, were strongly influenced. On the warmest perch, hens rested more with their head forward in a standing position and showed more active behavioural patterns compared to both cooler perches ( P < 0.001). On the cooler perches, hens rested more with their head covered by feathers in a sitting and standing position ( P < 0.05). Our data show that perch temperature strongly affects laying hens’ resting behaviour. In this context, hens are confronted with arising trade-offs between thermoregulatory adjustment of behaviour, optimisation of energy budget, restful roosting and vigilance behaviour.

Genetic resistance to natural helminth infections in two chicken layer lines

Groups of Lohmann Brown (LB) and Lohmann Selected Leghorn (LSL) hens were reared under helminth-free conditions and kept afterwards together in a free range system. Mortality rate, body weight development, laying performance and faecal egg counts (FEC) were recorded during a 12 month laying period. At the end of the laying period, 246 LSL and 197 LB hens were necropsied and worms counted following the World Association for the Advancement of Veterinary Parasitology (W.A.A.V.P.) guidelines. In addition adult Heterakis gallinarum and Ascaridia galli were sexed and measured for length.Significant (P<0.01) differences were observed in mortality rates between LSL and LB animals (12.9 vs. 5.7%). LSL hens showed significantly (P<0.05) higher FEC when compared with LB hens at almost all dates of monitoring. Almost all animals became infected with at least one helminth species. The most prevalent species were H. gallinarum, Capillaria spp. and A. galli. LB hens showed a significantly (P<0.05) higher average number of adult H. gallinarum, Capillaria spp. and tapeworms when compared with LSL animals. However, number of adult A. galli was in tendency lower in these animals. In total, LB had a significantly (P<0.05) higher worm burden than LSL (192.3 vs. 94.3). The estimated heritabilities for total worm burden were 0.23 (SE±0.12) in LSL and 0.75 (SE±0.21) in LB, respectively. The number of all different helminth species were positively correlated.The sex ratio of H. gallinarum and A. galli and the average worm lengths were not significantly (P>0.05) different between the genotypes.There was no significant phenotypic correlation between body weight and worm burden in LSL, whereas it was the case in LB (r=0.17, P<0.05).Based on the estimated heritabilities it is possible to select for helminth resistance in both genotypes.

Effects of calcium diet supplements on egg strength in conventional and furnished cages, and effects of 2 different nest floor materials

Several studies have demonstrated a greater incidence of cracked eggs in furnished than in conventional cages. Hens kept in furnished cages may have greater bone strength, so they may lay eggs with weaker shells because they may utilize more calcium for bone mineralization and less for shell formation. The effects of increased dietary calcium content were therefore studied in 3-hen conventional and 8-hen furnished cages. In addition, the effects of 2 different nest floor materials were studied in furnished cages. A total of 1,216 Lohmann Selected Leghorn hens were housed in either furnished or conventional cages and offered either the normal calcium supplementation used in commercial diets (37 to 40 g of calcium/kg) or increased calcium supplementation (44 to 50 g of calcium/kg) consisting of added limestone for 3 consecutive feeding phases of 20, 16, and 16 wk. Dietary calcium had similar effects in both cage systems. Greater limestone supplementation increased the laying rate (P < 0.05). Increased dietary limestone had no significant effects on egg quality, and no effects on tibia-breaking strength or specific gravity were observed. The laying rate was higher in conventional than in furnished cages (P < 0.05), but there was no significant difference between the cage types in terms of total egg mass produced. The cage type had no effect on tibia-breaking strength. However, the specific gravity and ash content of tibias were higher in hens kept in furnished than in conventional cages (P < 0.001). Based on this study, the weakening of eggshells in furnished cages is not caused by a possible calcium shortage resulting from high bone mineralization.

Perch material and diameter affects particular perching behaviours in laying hens

Resting on perches is an important behaviour for laying hens. However, perches in laying hen husbandry systems are associated with health problems which may result from inadequate perch designs. The aim of this study was to focus on particular behavioural patterns shown by laying hens on different perches during night-time in order to test whether perching behaviour may provide information on the suitability of a particular perch design. A total of 60 Lohmann Selected Leghorn hens were kept in six compartments over two identical trials. Hens were randomly offered nine round perches, which differed in material (wood, steel, rubber cover) and diameter (27, 34, 45 mm) for one week each. Duration of resting, standing, preening and frequencies of balance movements and comfort behaviours shown by individual hens on each perch were recorded throughout one night (10.5 h) on day six of each observation week. Balance movements decreased with increasing perch diameter ( P < 0.001) and appeared less on rubber perches compared to wood and steel ( P < 0.05). On steel perches, hens rested longer with their heads tucked backwards into their feathers ( P < 0.001) and less with their heads forward with neck pulled back compared to wood and rubber perches ( P < 0.001) irrespective of perch diameter. Standing was shown less often on steel compared to wood or rubber perches ( P < 0.001). Our data provide evidence that a detailed analysis of hens’ perching behaviour can give important information on the suitability of a perch design related to diameter and material. In this context, balance movements may be the most sensitive indicator of the suitability of a perch design with respect to stable footing on perch, whereas resting position and standing on perches are likely to be related to thermoregulatory adjustment in behaviour.