Erupted front deciduous teeth are often resected in pig farms to limit lesions that intact teeth may inflict to other piglets or the sow's udder. Two techniques are commonly used: clipping with pliers and grinding with a rotating grindstone. Both techniques are potential sources of pain and stress. We analysed piglet behaviour just before and after tooth resection to identify changes that could indicate pain or distress. Behavioural observations focussed on oral behaviours, locomotion, ear position and movements, and vocalisations. In total, 120 piglets from 20 litters were allocated to clipping with sterilised pliers (CLIP), grinding with a hand-held rotative grindstone (GRIND) or SHAM-grinding at 1-4 days after birth (40 piglets/treatment, 2 piglets/treatment/litter). SHAM piglets were handled and treated as those in the GRIND group with a protective covering on the grinder head to prevent tissue damage. For resected piglets, the tip of the canines and third incisors was removed. Each litter was separated from the dam and placed in a heated holding trolley. Selected piglets were taken individually to a separate room and placed in an observation box for 1 min to be video recorded. Thereafter, tooth treatment was applied by a trained handler, and resected teeth were measured and checked for the presence of blood. The piglet was returned to the observation box and video recorded again for 1 min. Once all selected piglets had been treated, the litter was returned to the dam. Mean treatment duration was 53, 48 and 46 s in the SHAM, GRIND and CLIP groups, respectively. Presence of blood on teeth after resection was significantly more frequent (P < 0.001) in CLIP (97.5%) than GRIND (22.5%) treated piglets. Only one behaviour, 'champing' (opening and closing an empty mouth) differed (P = 0.005) between treatments: occurring in 45% of SHAM and 80% of CLIP pigs (P < 0.05) with GRIND pigs being intermediate (60%). This behaviour was never observed pre-treatment. A marked influence of handling on piglet behaviour regardless of the treatment was evident: walking, exploring walls and ears back decreased, while immobility, not exploring, ears in front position, and head flicks increased significantly (P < 0.05) between the pre- and post-treatment periods, but were not affected by treatment. In conclusion, although handling stress masked some of the behavioural effects of acute pain, tooth clipping appears to be more detrimental than grinding, as it led to more frequent presence of blood and champing behaviour.

ABSTRACT In sows, maternal behaviour is a commercially important trait which affects sow and piglet welfare and the quality and safety of human‐animal interactions, especially if free farrowing of sows without crates is in place. The aim of this study was to evaluate maternal behaviour and to estimate its quantitative genetic parameters in Swiss Landrace sows (SLR). The lactating sows, with an average lactation period of 29–30 days and different parities (one to eleven) at four nucleus farms of the Swiss pig breeding company Suisag underwent behaviour tests and observations during two 12‐week periods. The level of aggressiveness of the sows towards humans was assessed with a standardised Piglet Handling Test and with a Farmers' Aggressiveness Score, using five‐ and three‐point scoring systems, respectively. Additionally, the reaction to the playback of unknown squealing piglets was evaluated using a five‐point scoring system, and vocalising before lying down and time taken to lay down were recorded. Depending on the trait, data were collected on 451–705 sows, most of which had phenotypes available for more than one trait. Number of samples per measure varied between one and six. Given the non‐Gaussian distribution of the traits, variance components were estimated based on Bayesian generalised linear mixed models, including as random effects the sow genetic effects and the sow permanent environmental effects. The additive genetic relationships were either computed from the pedigree (1418 individuals across six generations), the genomic data (from 376 genotyped sows using SNP‐Chip 60 K), or their combination using the H matrix. The credibility intervals of the estimates indicate that all traits were repeatable independently of how the additive genetic relationships were modelled, with estimated repeatabilities varying between 0.18 ± 0.09 (mean ± SD; 95% CI = [0.01, 0.35]) and 0.66 ± 0.04 ([0.58, 0.74]). Both the level of aggressiveness towards humans (pedigree based: Piglet Handling Test: h 2 = 0.44 ± 0.12, [0.22, 0.69]; Farmers' Aggressiveness Score: h 2 = 0.24 ± 0.10, [0.04, 0.45]), and vocalising before lying down were found to be heritable (H matrix based: h 2 = 0.36 ± 0.15, [0.07, 0.63]). We found an unfavourable genetic correlation between the Farmers' Aggressiveness Score and piglet survival traits. Our results suggest that human‐directed aggression is heritable, indicating that improvement of stockpersons' safety and sow welfare through genetic selection is feasible, although piglet survival should be included in a balanced breeding index to ensure progress in both traits.

Pregnant (dry) sows are fed a restricted food ration to ensure good health, production and longevity, but this results in behavioural signs of hunger: oral behaviours increase and may be redirected 'unnaturally' towards non-food, prompting welfare concerns. 'Dietary fibre' encompasses a variety of chemical classes, with a variety of physiochemical properties. It reduces abnormal oral behaviours, and fibres that are soluble and fermentable in the hindgut appear to prolong satiety, reduce activity and improve welfare. EU rules require fibre in dry sow diets and access to foraging materials but implementation differs across member states. Diet, feeding system, number of meals and social structure combine to affect welfare of the sow and developing piglets, e.g., through pre-natal stress. Current breeding trends to increasing litter size and associated practices like the use of 'nurse sows' may require a rethink of sow nutrition to safeguard longevity and welfare.

Acceptable animal welfare is an integral part of sustainability. Selective breeding for improved animal welfare can benefit the economic and environmental aspects of pig farming, as well as being of direct benefit to the animal itself. Several traits have major welfare consequences but have proved difficult to improve through management change alone. Here we consider how past selection for productivity has affected welfare and give three examples of the state of the art in selective breeding aimed at improving welfare traits in their own right. Selection for complex welfare-relevant traits poses practical, economic, and ethical challenges. Current and emerging innovations will significantly reduce the economic and practical barriers to breeding and allow efficient selection for traits that previously have been too expensive to record. Examples will be given of the new phenotyping techniques and genetic methodologies that are expanding the range of welfare traits that selection pressure can be exerted upon.

The parents of broiler (meat) chickens (ie, broiler breeders) are food-restricted until sexual maturity, ensuring good health and reproduction, but resulting in hunger. We investigated whether diets with added insoluble fiber promote satiety and reduce behavioral, motivational, and physiological signs of hunger. Ninety-six broiler breeders were fed 1 of 4 feed treatments (n = 24 per diet) from 6 to 12 wk of age: 1) a commercial diet fed to the recommended ration (R) or 2) ad libitum (AL), the same diet as R but mixed with oat hulls at 3) 20% (OH20%) or 4) 40% (OH40%). The R, OH20% and OH40% diets were approximately iso-energetic and resulted in mean 12 wk of age weights within 2.5% of each other (1.21 kg), while AL birds weighed 221% as much (2.67kg). At 12 wk of age, agouti-related protein (AGRP) expression, was, on average, more than 12 times lower in AL birds (P P < 0.001) but did not differ between the fiber diet treatments and R. Pro-opiomelanocortin (POMC) expression, was, on average, over 1.5 times higher in AL birds, but was not statistically significantly affected by feed treatments (P = 0.33). In their home pens, AL birds stood/sat more, foraged less and fed more in total (P < 0.001) and OH40% birds spent longer feeding than R (P = 0.001). Motivation to forage tested by willingness to walk through water to access an area of wood shavings (without food) was not significantly affected by diet (P = 0.33). However, restricted birds were willing to cross in only 7.3% to 12.5% of tests. Mostly birds stayed on the start platform, where AL birds sat more than other treatments and OH40% birds reduced walking relative to R birds (P P = 0.016). Across the behavioral and physiological measurements there was a dichotomy of effects in response to approximately isoenergetic diets differing in fiber. There were some potentially beneficial behavioral effects related to reduced foraging and walking. However, there was no evidence that these diets significantly improved physiological measures of satiety of broiler breeders.

EDITORIAL article Front. Vet. Sci., 09 November 2023Sec. Animal Behavior and Welfare Volume 10 - 2023 | https://doi.org/10.3389/fvets.2023.1296461

The physiological, psychological and behavioural traits of tail biting/bitten pigs have been widely studied, with most research focusing on identifying traits to predict tail biting phenotypes (biters, victims, or uninvolved ‘neutrals’). However, it is not clear if these traits persist once pigs are no longer involved in performing or receiving tail bites. This study investigated whether there was a difference in behavioural responses to a novel object test (NOT) between pigs which were tail biting performers (BITER), recipients (VICTIM), or not involved in the biting events (NEUTRAL). We then investigated whether these differences in responses were still evident six weeks later, when tail biting was less prevalent. We hypothesised that biters would exhibit more behaviours indicative of boldness, but also stress, than victims or neutrals, and that these differences would still be present later. A total of 120 undocked pigs (BITER, n = 48; VICTIM, N = 48; NEUTRAL, n = 24; 60 male, 60 female) were selected for testing. At the time of the first test (one week after pigs were moved into the finisher house at 12 weeks of age; T1), the prevalence of tail biting peaked. The same test was repeated six weeks later (T2) when biting had eased. Each pig was tested separately in a novel arena. After a minute of habituation, a brush head was introduced by dropping it down from above, at which point the 5 min test began. A saliva sample was taken immediately before the habituation (baseline) and after each test to evaluate cortisol concentration. Direct continuous behaviour observation was conducted. Overall, salivary cortisol concentrations were higher after than before the NOT ( P < 0.001), although VICTIM pigs had a reduced elevation in cortisol after the test ( P = 0.02) compared to BITER and NEUTRAL pigs in T2. Between phenotypes, baseline saliva cortisol concentrations were similar. BITER pigs approached the object quicker than VICTIM pigs (P = 0.01), but also had more high-pitched vocalisations (P < 0.01), but these differences observed in T1 were no longer present in T2. The results suggested that the NOT was sensitive to detect different levels of behavioural response; however, differences in BITER pigs’ behavioural responses were transient and did not persist once biting behaviour ceased. The long-term consequence of chronic stress caused by being tail bitten was manifested in VICTIM pigs’ blunted cortisol elevation six weeks later, after severe tail biting events.

Broiler breeder chickens are commercially feed restricted to slow their growth and improve their health and production, however, there is research demonstrating that this leads to chronic hunger resulting in poor welfare. A challenge in these studies is to account for possible daily rhythms or the effects of time since last meal on measures relating hunger. To address this, we used 3 feed treatments: AL (ad libitum fed), Ram (restricted, fed in the morning), and Rpm (restricted, fed in the afternoon) to control for diurnal effects. We then conducted foraging motivation tests and collected home pen behavior and physiological samples at 4 times relative to feeding throughout a 24-h period. The feed treatment had the largest influence on the data, with AL birds weighing more, having lower concentrations of plasma NEFA, and mRNA expression of AGRP and NPY alongside higher expression of POMC in the basal hypothalamus than Ram or Rpm birds (P < 0.001). R birds were more successful at and had a shorter latency to complete the motivation test, and did more walking and less feeding than AL birds in the home pen (P < 0.01). There was little effect of time since last meal on many measures (P > 0.05) but AGRP expression was highest in the basal hypothalamus shortly after a meal (P < 0.05), blood plasma NEFA was higher in R birds just before feeding (P < 0.001) and glucose was higher in Ram birds just after feeding (P < 0.001), and the latency to complete the motivation test was shortest before the next meal (P < 0.05). Time of day effects were mainly found in the difference in activity levels in the home pen when during lights on and lights off periods. In conclusion, many behavioral and physiological hunger measures were not significantly influenced by time of day or time since the last meal. For the measures that do change, future studies should be designed so that sampling is balanced in such a way as to minimize bias due to these effects.

Visual observation of uncontrolled real-world behavior leads to noisy observations, complicated by occlusions, ambiguity, variable motion rates, detection and tracking errors, slow transitions between behaviors, etc. We show in this paper that reliable estimates of long-term trends can be extracted given enough data, even though estimates from individual frames may be noisy. We validate this concept using a new public dataset of approximately 20+ million daytime pig observations over 6 weeks of their main growth stage, and we provide annotations for various tasks including 5 individual behaviors. Our pipeline chains detection, tracking and behavior classification combining deep and shallow computer vision techniques. While individual detections may be noisy, we show that long-term behavior changes can still be extracted reliably, and we validate these results qualitatively on the full dataset. Eventually, starting from raw RGB video data we are able to both tell what pigs main daily activities are, and how these change through time.

To establish whether pig tail posture is affected by injuries and ill health, a machine vision system using 3D cameras to measure tail angle was used. Camera data from 1692 pigs in 41 production batches of 42.4 (±16.6) days in length over 17 months at seven diverse grower/finisher commercial pig farms, was validated by visiting farms every 14(±10) days to score injury and ill health. Linear modelling of tail posture found considerable farm and batch effects. The percentage of tails held low (0°) or mid (1–45°) decreased over time from 54.9% and 23.8% respectively by -0.16 and -0.05%/day, while tails high (45–90°) increased from 21.5% by 0.20%/day. Although 22% of scored pigs had scratched tails, severe tail biting was rare; only 6% had tail wounds and 5% partial tail loss. Adding tail injury to models showed associations with tail posture: overall tail injury, worsening tail injury, and tail loss were associated with more pigs detected with low tail posture and fewer with high tails. Minor tail injuries and tail swelling were also associated with altered tail posture. Unexpectedly, other health and injury scores had a larger effect on tail posture- more low tails were observed when a greater proportion of pigs in a pen were scored with lameness or lesions caused by social aggression. Ear injuries were linked with reduced high tails. These findings are consistent with the idea that low tail posture could be a general indicator of poor welfare. However, effects of flank biting and ocular discharge on tail posture were not consistent with this. Our results show for the first time that perturbations in the normal time trends of tail posture are associated with tail biting and other signs of adverse health/welfare at diverse commercial farms, forming the basis for a decision support system.

Environmental enrichment in pig housing is a legal requirement under current EU legislation, but some recommended loose materials may cause obstructions in fully-slatted systems. Wood is an organic material that could be compatible with slatted systems. This study investigated enrichment use in finishing pigs (three wood species and a rubber floor thy) and explored the relationship between use and damaging behaviours, and physiological and physical measures of stress and injury. Individual variation in enrichment use within pen was also investigated. Pigs (12 weeks old; week 0) were housed in 40 pens of seven pigs (n = 280). One of four different enrichment items (one spruce, larch, or beech wooden post, or rubber floor thy) was randomly assigned to each pen (10 pens/treatment). The behaviour of each individually marked pig was observed continuously from video recordings taken on six different occasions (twice during week 2, 4 and 7; 1 h per occasion). Individual tail/ear lesion and tear staining scores were recorded every 2 weeks. Saliva samples for cortisol analysis were obtained from three focal pigs per pen every 2 weeks. These focal pigs were selected based on the latency to approach the experimenter on the first sampling day and classified as 'Approach', 'Neutral' or 'Avoid'. Carcasses were inspected for tail lesions and potential oral damage. Time spent using enrichment was higher in pigs with spruce and rubber thy than with larch and beech (P < 0.001). Spruce was used up the most quickly and was the softest of the wood species (P < 0.001). High use of spruce was not due to consistent high use by certain pigs. No treatment effect on any other behaviour was recorded, but enrichment use was positively correlated with damaging behaviours at pen level (P < 0.001). Spruce pigs had slightly more severe tail lesion scores than Beech (P < 0.05). Salivary cortisol did not differ between treatments but was higher in 'Avoid' than 'Approach' pigs (P = 0.04). No clear oral damage that could be attributed to using wood was found. By investigating enrichment use at both pen and individual level, a more complete picture was obtained of how pigs used the enrichment. Wood appears to be a safe material to use as environmental enrichment for pigs and a softer wood species was preferred by pigs with equal preference for the rubber floor toy.

One of the difficulties in complying with the prohibition of routine tail docking is a lack of effective alternative solutions to prevent tail biting, especially in fully slatted systems. This study compared three slat-compatible enrichment replenishment strategies for pigs. Forty-eight mixed-sex pens (six males and six females/pen) of undocked pigs were followed from birth to slaughter. Pre-weaning, half the pigs were provided with enrichment materials (a cardboard cup, rubber toy, hessian cloth and bamboo), in addition to a rope for the sows, in all farrowing crates. Post-weaning, all pens were enriched with eight identical items, including an elevated rack supplied with fresh-cut grass, and objects of wooden, bamboo, rubber, and fabric materials presented in various ways. However, three different replenishment frequencies were applied: “Low” (replenished on Monday/Wednesday/Friday), “Medium” (replenished once daily), and “High” (replenished ad libitum). Individual pigs were weighed on days 0, 49, 91, and 113 post-weaning. Direct behavior observations were conducted twice weekly at pen level (10 min/day/pen), and tail and ear lesion scores of individual pigs were also recorded every other week. These measurements were taken during the post-weaning period. The cost of all enrichment materials used was calculated. Pre-weaning enrichment only contributed to a lower ear lesion score (P = 0.04). No difference in lesion scores was found between post-weaning treatments. “Low” replenishment rate pigs performed more damaging behaviors (tail/ear biting, belly-nosing, mounting, other biting, and aggressive behaviors combined) than “High” and “Medium” pigs (P < 0.01). The average daily gain in the finishing stage was higher in “High” than “Low” pigs (P < 0.05). Although sporadic tail biting occurred, only 0.69% of the pigs had their tails bitten severely enough that they became shorter than half of a normal undocked tail. The average enrichment cost for the post-weaning period was <€2 per pig. In conclusion, the high enrichment replenishment rate increased growth and reduced damaging behaviors compared to the low replenishment rate pigs. Overall, these findings show that the provision and regular replenishment of multiple, slat-compatible, enrichment sources can reduce tail damage to manageable levels without the need for tail docking.

This study evaluated the effectiveness of combined dietary and enrichment strategies to manage tail biting in pigs with intact tails in a conventional fully-slatted floor housing system. A 2 × 2 × 2 factorial design was used. Pigs had either a high fibre (weaner 5.3% and finisher 11.6% of crude fibre) or standard fibre diet (weaner 3.7% and finisher 5.9% of crude fibre). In the weaner stage, pigs had either a spruce wooden post (supplied in a wall-mounted dispenser) or a rubber floor toy as a enrichment device, and in the finisher stage, they had either the same or alternate enrichment item. Six hundred and seventy-two pigs were assigned to 48 pens of 14 pigs and followed from weaning until slaughter. Individual tail lesion scores and pen level behaviours were directly recorded every 2 weeks. Twenty-six pens had tail biting outbreaks and 161 injured pigs needed removal for treatment. Pigs fed with the high fibre diet performed more tail biting (p < 0.05) and tended to have a worse tail damage scores than those fed the standard fibre diet (p = 0.08). Pigs which had the floor toy as weaners and wood as finishers tended to have fewer tail lesions in the finisher stage than their counterparts (p = 0.06). Pigs receiving the floor toy as enrichment interacted with the enrichment more frequently overall (p < 0.001) and performed fewer harmful behaviours in the weaner stage (p < 0.05). Overall, higher fibre in the diet in a relatively barren environment did not help reduce tail biting or tail lesions. Altering the fibre level in the pigs' diet and providing a single enrichment device to undocked pigs on fully slatted floors resulted in a high level of tail biting and a large proportion of pigs with partial tail amputation.

Pregnant (dry) sows (S) are fed a rationed amount of feed to maintain healthy weight and production but this does not satisfy their hunger. This study measured the extent of feed restriction compared to sows' desired intake. Forty-seven Large White × Landrace sows were housed in small groups with straw bedding and individual feeding stalls. Following three days on a standard ration of 2.5 kg, they were offered 10 kg a day of commercial dry sow feed for three days, split into four 2.5-kg meals a day which enabled individual intakes to be measured. This quantity was effectively (maximum daily intake 9.4 kg). Mean(± SEM) intake per day over the three days was 5.67 (± 0.24) kg, compared to the 2.5-kg standard ration. The ration thus provides less than half (44.1%) of sows' desired intake. Behaviour on their third rationed day was compared with behaviour on the third day of . Eating rate and the display of hunger-related behaviours, particularly following the morning feed, was greater under ration feeding; sows spent more time in the food stall and less in the straw bed, and more time active rather than resting. During ration-feeding sows also chewed and nosed more at straw bedding and pen equipment and used the drinker more after their morning meal than when they were fed . Eating rate on the last rationed day was positively correlated with feed intake on each of the days. Despite an EU requirement for fibre to be added to diets to ameliorate this problem, and the provision of straw bedding, hunger resulting from food restriction remains a welfare concern for dry sows.

Personality is defined as individual behavioral differences that are consistent over time and across contexts and is constructed from a number of underlying traits. Over the last 27 years, studies on pig personality have investigated links between personality traits and behavioral and physiological responses. The objective of this paper was to review the literature on personality studies in pigs. Eighty-three peer-reviewed research articles were included. The most common objective of these studies was to identify personality types in pigs by comparing their response across multiple situations. The relationship with physiological responses was the next most common objective. Results were difficult to compare as there was little consistency in terminology or experimental design across studies. Only 24.1% of the studies reported reliability and even fewer explicitly assessed validity. The backtest was the most common test (used in 67.5% of the studies), though it is unclear what specific trait is being measured. Classifying pigs as proactive or reactive personality types using the backtest was common, but the relationship between backtest results and other variables are inconsistent. The human approach, novel object, and food competition tests were also popular methods. Exploration, aggressiveness, reactivity to humans, and fearfulness were the most common personality traits studied in pig populations. There was moderate support for relationships with physiological responses. Personality was related to other behaviors, such as vocalizations and social aggression. Studies on genetic control are promising, with the heritability of personality traits falling within the range seen for other traits already selected for in pigs, suggesting these traits can be considered in breeding programs to improve welfare. Pigs with reactive personality types were more influenced by their housing environment than proactive pigs. Housing influenced reactive pigs' immune response, manipulative oral behavior, response in cognitive tasks, play behavior, and gastric lesions, which has serious implications for the management of pigs. Few studies explored the predictive power of personality traits on future physiological or behavioral outcomes of pigs, however, there is support for the potential use of personality research in improving pig welfare and productivity. In order to move forward with this field, researchers need to agree on consistent terminology and methodologies, and investigate the reliability, validity, and practicality of common personality measures in pigs.

Tail biting in pigs is an injurious behaviour that spreads rapidly in a group. We investigated three different treatments to stop ongoing tail biting outbreaks in 65 pens of 6–30 kg undocked pigs (30 pigs per pen; SD = 2): (1) straw (7 g/pig/day on the floor), (2) rope, and (3) Bite-Rite (a hanging plastic device with chewable rods). Pigs were tail scored three times weekly, until an outbreak occurred (four pigs with a tail wound; day 0) and subsequently once weekly. After an outbreak had occurred, a subsequent escalation in tail damage was defined if four pigs with a fresh tail wound were identified or if a biter had to be removed. Straw prevented an escalation better (75%) than Bite-Rite (35%; p < 0.05), and rope was intermediate (65%). Upon introduction of treatments (day 0), pigs interacted less with tails than before (day −1; p < 0.05). Behavioural observations showed that pigs engaged more with rope than Bite-Rite (p < 0.05). Bite-Rite pigs (but not straw or rope) increased their interaction with tails between day 0 and day 7 (p < 0.05). Straw was the most effective treatment. However, further investigations may identify materials or allocation strategies which are more effective still.

Solutions are needed to keep pigs under commercial conditions without tail biting outbreaks (TBOs). However, as TBOs are inevitable, even in well managed farms, it is crucial to know how to manage TBOs when they occur. We evaluated the effectiveness of multi-step intervention protocols to control TBOs. Across 96 pens (1248 undocked pigs) managed on fully-slatted floors, 40 TBOs were recorded (≥3 out of 12–14 pigs with fresh tail wounds). When an outbreak was identified, either the biters or the victims were removed, or enrichment (three ropes) was added. If the intervention failed, another intervention was randomly used until all three interventions had been deployed once. Fifty percent of TBOs were controlled after one intervention, 30% after 2–3 interventions, and 20% remained uncontrolled. A high proportion of biters/victims per pen reduced intervention success more so than the type of intervention. When only one intervention was used, adding ropes was the fastest method to overcome TBOs. Removed biters and victims were successfully reintroduced within 14 days back to their home pens. In conclusion, 80% of TBOs were successfully controlled within 18.4 ± 1.7 days on average using one or multiple cost-effective intervention strategies.

In the mammalian brain, adult hippocampal neurogenesis (AHN) is suppressed by chronic stress, primarily at the ventral pole of the hippocampus. Based upon anatomy, we hypothesise that the caudal pole of the avian Hippocampal Formation (HF) presents a homologous subregion. We thus investigated whether AHN is preferentially suppressed in the caudal chicken HF by unpredictable chronic mild stress (UCMS). Adult hens were kept in control conditions or exposed to UCMS for 8 weeks. Hens experiencing UCMS had significantly fewer doublecortin-positive multipolar neurons (p < 0.001) and beaded axons (p= 0.021) at the caudal pole of the HF than controls. UCMS birds also had smaller spleens and lower baseline plasma corticosterone levels compared to controls. There were no differences in AHN at the rostral pole, nor were there differences in expression of genetic mediators of the HPA stress response in the pituitary or adrenal glands. Duration of tonic immobility and heterophil/lymphocyte (H/L) ratios were also not responsive to our UCMS treatment. These results support the hypothesised homology of the caudal pole of the avian HF to the ventral pole of the rodent hippocampus. Furthermore, quantifying neurogenesis in the caudal HF post-mortem may provide an objective, integrative measure of welfare in poultry, which may be more sensitive than current welfare measures.

Large-scale phenotyping of animal behaviour traits is time consuming and has led to increased demand for technologies that can automate these procedures. Automated tracking of animals has been successful in controlled laboratory settings, but recording from animals in large groups in highly variable farm settings presents challenges. The aim of this review is to provide a systematic overview of the advances that have occurred in automated, high throughput image detection of farm animal behavioural traits with welfare and production implications. Peer-reviewed publications written in English were reviewed systematically following Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines. After identification, screening, and assessment for eligibility, 108 publications met these specifications and were included for qualitative synthesis. Data collected from the papers included camera specifications, housing conditions, group size, algorithm details, procedures, and results. Most studies utilized standard digital colour video cameras for data collection, with increasing use of 3D cameras in papers published after 2013. Papers including pigs (across production stages) were the most common (n = 63). The most common behaviours recorded included activity level, area occupancy, aggression, gait scores, resource use, and posture. Our review revealed many overlaps in methods applied to analysing behaviour, and most studies started from scratch instead of building upon previous work. Training and validation sample sizes were generally small (mean±s.d. groups = 3.8±5.8) and in data collection and testing took place in relatively controlled environments. To advance our ability to automatically phenotype behaviour, future research should build upon existing knowledge and validate technology under commercial settings and publications should explicitly describe recording conditions in detail to allow studies to be reproduced.