Coup in the coop: Rank changes in chicken dominance hierarchies over maturation.

Chicken dominance hierarchies or pecking orders are established before maturation and maintained by consistent submissive responses of subordinate individuals, leading to stable ranks within unchanged groups. We observed interactions of 418 laying hens (Gallus gallus domesticus) distributed across three small (20) and three large (~120) groups. The observations were performed before sexual maturation (young period) and additionally after onset of maturation (mature period) to confirm stability of ranks. Dominance ranks were estimated via the Elo rating system across both observation periods. Diagnostics of the ranks revealed unexpected uncertainty and rank instability for the full dataset, although sampling appeared to be adequate. Subsequent evaluations of ranks based on the mature period only, showed more reliable ranks than across both observation periods. Furthermore, winning success during the young period did not directly predict high rank during the mature period. These results indicated rank changes between observation periods. The current study design could not discern whether ranks were stable in all pens before maturation. However, our data rather suggested active rank mobility after hierarchy establishment to be the cause for our findings. Once thought to be stable, chicken hierarchies may provide an excellent system to study causes and implications of active rank mobility

Grouping of breeding rabbit does at different time points: effects on fertility, mortality and weight

[EN] Semi-group housing in breeding does has been shown to reduce production and breeding success in comparison to single-housed animals. One reason for this reduction could be stress and aggression when grouping does only 2 d after artificial insemination. The aim of this study was to test different time points of grouping on fertility of does, body weight of both kits and does, and mortality rates. Hence, does were separated and housed individually one day before giving birth to their kits. The does were then artificially inseminated on day 10 postpartum (dpp) and regrouped according to the treatment (time point) on 12 (TG12), 18 (TG18), or 22 (TG22) dpp, respectively. In total, five trials with three groups pertaining to the three treatments (eight does per treatment group) were conducted. Non-pregnant does were replaced with pregnant does before each new trial (57 different does needed). Data were analysed with (generalised) linear mixed effect models and survival analysis. There were no significant differences in fertility, body weight or mortality of does among the treatments. The average fertility rate (number of kindling events/number of artificial inseminations×100) was low (40.92%) and seasonal effects may have partially masked treatment effects, as most trials took place during winter. Likewise, the survival rate of kits was not influenced by the treatment (survival test: χ2=2.3, df = 2, P = 0.3). Body weight of the kits was also not affected by the time point of grouping (average weight: 447.70±46.42 g (TG12), 452.20±55.30 g (TG18) and 460.06±89.23 g (TG22); P = 0.33). In conclusion, grouping does at a later time point in the reproductive cycle did not show any significant improvement in the breeding or productive success in a Swiss semi-group housing system. An elongated separation from conspecifics did not enhance the welfare of semi-group housed rabbits.We thank the Federal Food Safety and Veterinary Office (BLV, Project No. 2.18.04) for the financial support for this study. Also many thanks to Felix Näf, Frans Köhlen and the team of KaniSwiss for the professional support throughout the experiment.Braconnier, M.; Munari, C.; Gómez, Y.; Gebhardt-Henrich, S. (2020). Grouping of breeding rabbit does at different time points: effects on fertility, mortality and weight. World Rabbit Science. 28(2):73-80. https://doi.org/10.4995/wrs.2020.13107OJS7380282Albers P.C.H., de Vries H. 2001. Elo-rating as a tool in the sequential estimation of dominance strengths. Anim. Behav., 61: 489-495. https://doi.org/10.1006/anbe.2000.1571Al-Saef A.M., Khalil M.H., Al-Homidan A.H., Al-Dobaib S.N., Al-Sobayil K.A., García M.L., Baselga M. 2008. 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One clutch or two clutches? Fitness correlates of coexisting alternative female life-histories in the European earwig

Whether to reproduce once or multiple times (semelparity vs. iteroparity) is a major life-history decision that organisms have to take. Mode of parity is usually considered a species characteristic. However, recent models suggested that population properties or condition-dependent fitness payoffs could help to maintain both life-history tactics within populations. In arthropods, semelparity was also hypothesised to be a critical pre-adaptation for the evolution of maternal care, semelparous females being predicted to provide more care due to the absence of costs on future reproduction. The aim of this study was to characterize potential fitness payoffs and levels of maternal care in semel- and itero-parous females of the European earwig Forficula auricularia. Based on 15 traits measured in 494 females and their nymphs, our results revealed that iteroparous females laid their first clutch earlier, had more eggs in their first clutch, gained more weight during the 2weeks following hatching of the first clutch, but produced eggs that developed more slowly than semelparous females. Among iteroparous females, the sizes of first and second clutches were significantly and positively correlated, indicating no investment trade-off between reproductive events. Iteroparous females also provided more food than semelparous ones, a result contrasting with predictions that iteroparity is incompatible with the evolution of maternal care. Finally, a controlled breeding experiment reported full mating compatibility among offspring from females of the two modes of parity, confirming that both types of females belong to one single species. Overall, these results indicate that alternative modes of parity represent coexisting life-history tactics that are likely to be condition-dependent and associated with offspring development and specific levels of maternal care in earwig

Tracking performance in poultry is affected by data cleaning method and housing system

Sensor-based behavioural observation methods improve our understanding of individual behaviour and welfare in large commercial groups, including poultry. Validating automatically generated data is essential to account for potential sources of error. Our study aimed to validate a sensor-based tracking system for broiler breeders (BB) and laying hens (LH) in commercially relevant housing systems. The BB study was conducted in 10 pens with 33 females and three males (Ross 308) per pen. Half of the pens contained a raised slatted area and two raised group nests (Raised), while in the remaining five pens, the nests and slats were on the floor (Floor). For the LH study, six pens with a commercial aviary were used, with 225 Dekalb White hens housed per pen (Aviary). Focal hens (BB, 10/pen; LH, 18/pen) were equipped with backpacks containing tracking devices that registered transitions between four (BB) or five (LH) resource-related zones covering all accessible areas within each housing system. The tracking data was compared against video observations for 20 focal BB on two days and 18 focal LH on three days (3 × 20 min/day). Three data cleaning methods tested with 30 values of a duration parameter were evaluated for reliability and stability with a cross-validation approach. Initial and post-cleaning performance were assessed with accuracy, precision, and sensitivity of recorded transitions and by calculating the reliability for two aspects of movement: total transitions (Lin’s Concordance Correlation Coefficient) and locations (mean proportion of matching duration). A mixed model was applied to evaluate the duration of stay after false and true tracking registrations. Initial location reliability was high (> 0.949) in all housing systems, while reliability of total transitions was low ( 0.832) while reliability of locations remained high (> 0.949) in Aviary and Raised. The duration between registrations was affected by housing system (p < 0.001) and was longer for true compared to false registrations (p < 0.001). Initial tracking performance varied between movement aspects and housing systems. The difference in duration between true and false registrations allowed for the application of simple yet effective data cleaning in Aviary and Raised, ensuring that the generated data better represented the animal's actual movement with reduced error associated with the tracking system

Evaluation of an Active LF Tracking System and Data Processing Methods for Livestock Precision Farming in the Poultry Sector

Tracking technologies offer a way to monitor movement of many individuals over long time periods with minimal disturbances and could become a helpful tool for a variety of uses in animal agriculture, including health monitoring or selection of breeding traits that benefit welfare within intensive cage-free poultry farming. Herein, we present an active, low-frequency tracking system that distinguishes between five predefined zones within a commercial aviary. We aimed to evaluate both the processed and unprocessed datasets against a “ground truth” based on video observations. The two data processing methods aimed to filter false registrations, one with a simple deterministic approach and one with a tree-based classifier. We found the unprocessed data accurately determined birds’ presence/absence in each zone with an accuracy of 99% but overestimated the number of transitions taken by birds per zone, explaining only 23% of the actual variation. However, the two processed datasets were found to be suitable to monitor the number of transitions per individual, accounting for 91% and 99% of the actual variation, respectively. To further evaluate the tracking system, we estimated the error rate of registrations (by applying the classifier) in relation to three factors, which suggested a higher number of false registrations towards specific areas, periods with reduced humidity, and periods with reduced temperature. We concluded that the presented tracking system is well suited for commercial aviaries to measure individuals’ transitions and individuals’ presence/absence in predefined zones. Nonetheless, under these settings, data processing remains a necessary step in obtaining reliable data. For future work, we recommend the use of automatic calibration to improve the system’s performance and to envision finer movements

Similarity in Temporal Movement Patterns in Laying Hens Increases with Time and Social Association.

We explored the relationship between social associations and individual activity patterns in domestic hens. Out of 1420 laying hens, 421 hens were equipped with RFID tags attached to RFID-specific leg bands (leg bands from Company Roxan, Selkirk, Scotland) to continuously track their change in location across four different areas (one indoor and three outdoor areas). Using a combination of social network analysis for quantifying social relationships and dynamic time warping for characterizing the movement patterns of hens, we found that hens were consistent in their individual variation in temporal activity and maintained stable social relationships in terms of preferred association partners. In addition to being consistent, social associations correlated with movement patterns and this correlation strengthened over the period of observation, suggesting that the animals aligned their activity patterns with those of their social affiliates. These results demonstrate the importance of social relationships when considering the expression of individual behaviour. Notably, differences in temporal patterns emerge despite rather homogeneous rearing conditions, same environment, and low genetic diversity. Thus, while variation in behavioural phenotypes can be observed across isolated individuals, this study shows that the social environment within a group can shape and enhance variation in general movement patterns of individual animals

Similarity in Temporal Movement Patterns in Laying Hens Increases with Time and Social Association

We explored the relationship between social associations and individual activity patterns in domestic hens. Out of 1420 laying hens, 421 hens were equipped with RFID tags attached to RFID-specific leg bands (leg bands from Company Roxan, Selkirk, Scotland) to continuously track their change in location across four different areas (one indoor and three outdoor areas). Using a combination of social network analysis for quantifying social relationships and dynamic time warping for characterizing the movement patterns of hens, we found that hens were consistent in their individual variation in temporal activity and maintained stable social relationships in terms of preferred association partners. In addition to being consistent, social associations correlated with movement patterns and this correlation strengthened over the period of observation, suggesting that the animals aligned their activity patterns with those of their social affiliates. These results demonstrate the importance of social relationships when considering the expression of individual behaviour. Notably, differences in temporal patterns emerge despite rather homogeneous rearing conditions, same environment, and low genetic diversity. Thus, while variation in behavioural phenotypes can be observed across isolated individuals, this study shows that the social environment within a group can shape and enhance variation in general movement patterns of individual animals

Research Note: A validation of an image-based method to estimate chicken comb size

ABSTRACT: Chicken combs carry important information about the individual, especially the size has been related to sexual reproduction, health, and social signaling. Comb size is usually estimated by weighing removed combs or by calculating the product of the comb's longest and highest dimensions (LHA) to approximate comb area based on measures of a ruler or caliper. These methods have several shortcomings including invasiveness or imprecision. As a result, more recent efforts have employed pixel-based approximations of comb area (PBA) from images. However, the validity of PBA to estimate comb area and how the approximation compares to previous approximation methods, such as LHA, is unknown. Therefore, we developed an apparatus for taking standardized images of the head position of the hens and then applied PBA using the software ImageJ. The hens were each photographed 3 times by 2 different handlers. We first tested the accuracy of the pixel-based area approximation on 3 geometric shapes of known area. Second, we tested the precision of PBA of 15 hens (Dekalb White), evaluated as within-image and within-individual hen precision. Furthermore, we compared the PBA with the LHA based on measures of a caliper. The PBA was both accurate and precise, whereas the LHA overestimated comb area with increasing overestimation for larger combs. Due to the greater accuracy of the PBA, as well as future possibilities of automation and inclusion of further measures, we suggest PBA as a more reliable approach to estimate comb area than LHA. Additionally, our results demonstrate that the outcomes of LHA should be evaluated on an ordinal scale level only

DNA methylation variation in the brain of laying hens in relation to differential behavioral patterns

Domesticated animals are unique to investigate the contribution of genetic and non-genetic factors to specific phenotypes. Among non-genetic factors involved in phenotype formation are epigenetic mechanisms. Here we aimed to identify whether relative DNA methylation differences in the nidopallium between groups of individuals are among the non-genetic factors involved in the emergence of differential behavioral patterns in hens. The nidopallium was selected due to its important role in complex cognitive function (i.e., decision making) in birds. Behavioral patterns that spontaneously emerge in hens living in a highly controlled environment were identified with a unique tracking system that recorded their transitions between pen zones. Behavioral activity patterns were characterized through three classification schemes: (i) daily specific features of behavioral routines (Entropy), (ii) daily spatio-temporal activity patterns (Dynamic Time Warping), and (iii) social leading behavior (Leading Index). Unique differentially methylated regions (DMRs) were identified between behavioral patterns emerging within classification schemes, with entropy having the higher number. Functionally, DTW had double the proportion of affected promoters and half of the distal intergenic regions. Pathway enrichment analysis of DMR-associated genes revealed that Entropy relates mainly to cell cycle checkpoints, Leading Index to mitochondrial function, and DTW to gene expression regulation. Our study suggests that different biological functions within neurons (particularly in the nidopallium) could be responsible for the emergence of distinct behavior patterns and that epigenetic variation within brain tissues would be an important factor to explain behavioral variation