Tonic Immobility Test Research Articles

Effect of different LED light colors on welfare, performance, some behavioral patterns, and blood parameters of Muscovy ducks

BackgroundThe current study was conducted to assess the impact of different LED light colors on welfare indicators in Muscovy ducks. These welfare parameters encompassed growth performance, specific behaviors, tonic immobility (TI), feather score, haematological, and serum biochemical parameters. Eighty-four healthy unsexed Muscovy ducklings aged two weeks were randomly assigned to four groups (3replicates/group; each replicate contains 7 birds) based on different LED light colors. The first group was raised under white light, the second under red light, the third under blue light, and the fourth under yellow light. To assess the impact of various LED light colors on welfare, growth performance indicators (body weight, body weight gain, feed intake, and feed conversion ratio) were measured. Behavioral patterns including feeding, drinking, standing, walking, sitting, feather pecking, and other activities were recorded. Tonic immobility test (TI) and feather condition scoring were conducted at 3, 6, and 10 weeks of age. At the end of the study blood samples were collected for hematological and serum biochemical analyses.ResultsThe results revealed that using blue, yellow, and red colors had no adverse effect on the final body weight of the ducks (P > 0.05). Unlike to red light, blue light significantly reduced feather pecking, TI time and cortisol concentrations and improved the feather condition score (P ≤ 0.05).ConclusionsThe current findings suggest that the application of blue light effectively improves welfare indices and has no detrimental impact on the growth performance of Muscovy ducks thereby positively contributing to their welfare.

Qualitative feed restriction affects frustration, fear, motivation to explore, and feather fault bars in Ross 308 broiler breeder cockerels

Broiler breeders show behaviours indicative of hunger and frustration stemming from unfulfilled behavioural needs for feeding. This is largely due to quantitative feed restriction which is common practice in the management of these birds, particularly in the rearing period. As an alternative, qualitative feed restriction allows a larger portion of feed to be provided without increasing the caloric intake. While several studies have assessed the effects of qualitative feeding on female broiler breeders, no such assessment has been done on broiler breeder cockerels. The aim of this study was to investigate the effects of feed dilution and roughage on the level of stress, fear and motivation to explore of broiler breeder cockerels. 200 Ross 308 broiler breeder cockerels (between 5 and 10 weeks of age) were housed in 12 pens (6 pens/treatment), 17 birds/pen. The treatments were standard feed (Control) and feed diluted with 20 % insoluble oat hulls and 150 g of alfalfa roughage daily/pen (D+R). The D+R birds received 20 % more feed per day. Novel object (NO) and frustration during thwarted feeding tests were performed in the home pen and the response recorded with video cameras. In addition, four birds from each pen were subjected to a tonic immobility test (TI). All behavioural tests were performed once a week at 6, 8 and 10 weeks of age. Finally, after euthanasia, two feathers from each bird were plucked and macroscopically examined for the presence of fault bars. The control birds showed a tendency to approach the NO faster than the D+R birds (P = 0.07) and were more likely to approach at 10 weeks of age (P = 0.006). In the frustration test, D+R birds spent less time pecking the feed container (P = 0.049), more time standing (P = 0.01) and tended to have fewer behavioural transitions (P = 0.09) than control birds, which indicates a reduction in frustration levels. In addition, Control birds stayed in TI longer than D+R birds (160.7 ± 15.5 s and 98.1 ± 15.4, respectively. P = 0.005). However, D+R had more fault bars compared to Control birds (P = 0.02), highlighting that care is needed to interpret these contradicting results. Nevertheless, the results show that the combination of feed dilution and daily roughage can have positive effects on the welfare of broiler breeder cockerels by reducing the sensation of hunger as indicated by fear, frustration, and motivation to explore.

207 Impacts of beak trimming and dietary fiber on welfare and productivity of laying hens

Abstract Beak trimming is a routine management practice in the egg industry to reduce damage caused by injurious pecking; however, it raises welfare concerns including pain and sensory loss. Dietary manipulation may be a feasible and welfare-friendly alternative to beak trimming in laying hens. Here, we hypothesized that dietary inclusion of insoluble fiber (chitin) throughout the starter and grower periods would result in improved welfare and productivity in both beak-trimmed and beak-intact chickens. One-day old female Hy-Line Browns (n = 192) were randomly assigned to one of four treatments in a 2 X 2 factorial design (n = 4 pens/treatment; 12 birds/pen): birds were infrared beak-trimmed or had their beaks left intact and were fed one of two diets (standard vs. 2% chitin) for 8 wk. Birds were housed in floor pens containing litter and perches with ad libitum access to feed and water. Body weight and feed intake were recorded weekly. Beak sensitivity was assessed using a pressure transducer to measure pecking force weekly from 3 to 8 wk of age. A tonic immobility test was performed at 7 wk of age to measure fearfulness. Plasma corticosterone was determined using enzyme-immunoassay procedures at 8 wk of age. Data were analyzed with linear mixed models with beak condition and dietary treatment modeled as fixed effects, and pen and bird ID as random effects. Beak-trimmed birds fed the standard diet weighed less (P < 0.001) than all other groups throughout all growth stages, including starter 1 (0-3 wk), starter 2 (4 to 6 wk), and grower (7 to 8 wk; Table 1). Beak-intact birds fed 2% chitin had a greater feed intake and feed conversion ratio (P < 0.05) compared with other groups during the starter 2 and overall experimental period. Beak-trimmed birds exhibited weaker pecking force than beak-intact birds for the first 7 wk (P < 0.001; Table 2). Beak-trimmed birds fed 2% chitin had significantly less corticosterone (Figure 1) than birds fed the standard diet (P < 0.05), and a shorter tonic immobility duration than all other groups (P < 0.05). Dietary chitin was also associated with a shorter latency until the first alert head movement and a greater number of inductions of tonic immobility than the standard diet (P < 0.05), which suggests that insoluble fiber supplementation reduces fearfulness regardless of beak-condition status. Our results suggest infrared beak trimming increases beak sensitivity for several weeks, potentially resulting in decreased feed intake and body weight in the first 8 wk of life (Table 3). Dietary supplementation with chitin appears to offset the effects of beak trimming on growth, but not beak sensitivity, and may improve welfare in beak-trimmed and beak-intact birds by reducing stress responses. Future studies are needed to elucidate the different mechanisms behind the observed effects.

The inflammatory immunity and gut microbiota are associated with fear response differences in laying hens

The fear response is a crucial adaptive mechanism for coping with environmental changes, and the individuals have different levels of fearfulness. The purpose of this study was to determine the status of the immune response and gut health in hens with different fear responses. A total of 80 healthy 75-week-old native Lindian chickens were individually housed in conventional cages and categorized into high (TH) and low (TL) levels of fearfulness using the tonic immobility (TI) test. The immunological status and intestinal health of the laying hens were assessed, and the intestinal microbial community was sequenced using 16S rRNA testing. The results showed that the immune-related genes of interleukin (IL)-1β, IL-4, IL-6, and IgG were significantly upregulated in the spleen of TH hens compared with hens in the TL group (P < 0.01). The inflammatory immune-related genes Toll-like receptor (TLR)2, TLR4, nuclear factor (NF)-κB, inducible nitric oxide synthase (iNOS), cyclooxygenase (COX)-2, IL-10, and IgG were significantly increased in the intestinal tract, whereas IL-4, IgA, and the intestinal barrier gene claudin-4 were significantly decreased in TH hens (P < 0.05). In addition, serum concentrations of IL-1β, IL-6, IL-10, interferon (IFN)-α and IgG were significantly higher in TH hens (P < 0.01). A high fear response also led to changes in gut microbial diversity, with a higher Simpson's index and lower β-diversity similarity than hens with a low-fear response (P < 0.05). The TH group showed an increase in eight genera, including Bacillaceae and Coprococcus, whereas the genus Anaerorhabdus decreased (P < 0.05). The gut microbiota has also been associated with gut barrier genes, and inflammatory cytokines. Bartonella stimulates IL-1β and IgG secretion, whereas Lactobacillus inhibits IL-6 secretion, and Coprococcus and Subdoligranulum are associated with the maintenance of intestinal barrier function. The results of this study suggest that laying hens with high fear response levels have a more sensitive immune response and a more enriched gut microbiota, which may have positive effects on adapting to a complex environment.

Effects of housing systems on behaviour and welfare of autochthonous laying hens and a commercial hybrid

The welfare of laying hens is crucial for a sustainable and ethical food industry. Free-range systems offer a more natural and stimulating environment, while dual-purpose autochthonous breeds and crossbreeding could address ethical concerns and improve productivity. In this study, behaviour, plumage status, and leg health of five genotypes (two local breeds, two crossbreeds with a medium growth hybrid, and one commercial hybrid) in two different housing systems (enriched cage/free-range) were evaluated. The animals were filmed with professional cameras for three consecutive days at 30 and 64 weeks of age. Each day the recording session lasted 20 minutes, resulting in a total of 120 minutes per pen (20 min X 6 days recorded). A total of 16 behaviours divided into six categories (feeding, movement, social, resting, comfort, stretching) were scored. In addition, the tonic immobility test was performed, and the plumage status and footpad dermatitis of the birds were assessed. The results revealed a significant influence of the housing system on the behaviour, plumage status, and foot health of laying hens. While the housing system affected all behaviours, mainly feeding and comfort behaviours were influenced by the genotype of the hens and the interaction between the housing system and genotype. All genotypes displayed a similar behavioural pattern within the two housing systems, except for the commercial hybrid, which differed in its behaviour from the others adapting better to the enriched cage environment. In particular, the free-range system provided hens with more opportunities to engage in movement and comfort behaviour, and social interactions. Furthermore, hens in the free-range system exhibited better plumage conditions and lower rates of footpad dermatitis, indicating a positive impact on their overall welfare.

The necessity of pen replication to account for and understand the impacts of social dynamics on individual laying hen behavior

Individual laying hens within the same group show variation in their temperament traits and cognitive learning abilities, which can be affected by both their early rearing experiences and housing environments. Hens also have distinct individual patterns of movement within housing systems that may correlate with temperament and cognition. Individual behavioral tests can measure treatment impacts, but social dynamics may impact on an individual’s behavior. The aims of this perspective piece are to provide further evidence of pen-level variation using original data on social ranging patterns and fear assessment of free-range hens exposed to different, enriched rearing environments; and to encourage more studies to consider pen replicate variation as a means to better understand causes and mechanisms. A literature review showed that, while most published studies over the past decade assessing individual laying hen behavior included group-level replication (i.e., 83% of 54 articles reviewed), almost none considered inter-pen variation. The original data analysis of individual hens’ range use recordings showed significant treatment pen replicate variation in pop-hole following movements and hen–pair associations in the time spent together inside or outside. Significant inter-pen variation was also seen in tonic immobility tests on a subset of hens from the same study. Pen-level replication is important for scientific validity and for improving our understanding of why commercial flocks in the same environment can be so variable in their behavior to inform management practices. Further research could help to understand the mechanisms behind why groups of hens reared and housed in the same environments will show significant inter-group variation.

Quantitative trait loci mapping of innate fear behavior in day-old F2 chickens of Japanese Oh-Shamo and White Leghorn breeds using restriction site-associated DNA sequencing

Understanding the genetic mechanisms that underlie innate fear behavior is essential for improving the management and performance of the poultry industry. This study aimed to map QTL associated with innate fear responses in open field (OF) and tonic immobility (TI) tests, using an F2 chicken intercross population between 2 behaviorally distinct breeds: the aggressive Japanese Oh-Shamo (OSM) and the docile White Leghorn T-line (WL-T). Genome-wide QTL analysis for the OF and TI traits was conducted using 2,109 single nucleotide polymorphism (SNP) markers obtained through restriction site-associated DNA sequencing (RAD-seq). While several suggestive QTL were identified for TI and OF traits at genome-wide 20% significance threshold levels, the analysis revealed 2 significant QTL for 2 OF traits (total distance and maximum speed) at genome-wide 5% significance threshold levels. These significant QTL were located between 12.34 and 30.49 megabase (Mb) on chromosome 1 and between 40.02 and 63.38 Mb on chromosome 2, explaining 6.75 to 7.40% of the total variances. These findings provide valuable insights for the poultry industry, particularly in refining chicken management strategies and informing targeted breeding efforts.

Weaned piglet’s reactivity to humans, tonic immobility and behaviour in a spatial maze test is affected by gestating sows’ relationship to humans and positive handling at weaning

Fear of human can impact negatively offspring’s behaviour and cognition whereas early positive handling has positive impacts. The aim of this study was to evaluate the crossed effects of trans-generational transfer and familiarisation with human on piglets’ behaviour. Sows were classified into two categories (Fearful, n = 11 and Docile, n = 13) based on whether they avoided human contact or not during a human approach test at 71 days of gestation. Fear of human was not related to salivary cortisol levels of the sows (F =2.72, P = 0.10). Fearful sows’ piglets stood immobilized longer (Chisq= 6.24, P = 0.01), as well females (8.70, P = 0.003) during a tonic immobility test (TIT) at 7 days but not at 15 days. The behaviour of two male and two female piglets per sow (n = 96) was studied after weaning (28 days). We found no effect of sow’s reaction to human on piglets’ emotionality expressed during an open-field test (OFT) at 32–33 days. However, during a Human voluntary approach test (VHAT) piglets born from fearful sows were more fearful than piglets born from docile sows (Chisq=8.23, P = 0.004,). Half of the piglets (n = 48, 1 male and 1 female per sow) were then familiarised with human while the others received minimum contact. We found no main or crossed effect of sow’s reaction to human and piglet’s treatment on piglets’ emotionality during an OFT, nor on their exploratory behaviour during VHAT at 46–47 days. Piglets’ born from fearful sows were less attracted to human during VHAT2 (Chisq=8.33, P = 0.004) and familiarised piglets were more attracted (Chisq=15.05, P < 0.001). Piglets born from docile sows found the reward faster in a spatial maze test than those born from fearful sows. Both sows HAR and piglet familiarisation with human seemed to specifically affect human related behaviours without affecting their general emotionality, but also behaviour in a spatial maze test.

Daylight exposure and circadian clocks in broilers: part I—photoperiod effect on broiler behavior, skeletal health, and fear response

The aim of this study was to examine effects of various daylight exposure during the 24-h light-dark (L-D) cycle on growth performance, skeletal health, and welfare state in broilers. Environmental photoperiod and related circadian clock, the 24-h L-D cycle, are important factors in maintaining productive performance, pathophysiological homeostasis, and psychological reaction in humans and animals. Currently, various lighting programs as management tools for providing a satisfactory environmental condition have been used in commercial broiler production. Four hundred thirty-two 1-day-old Rose 308 broiler chicks were assigned to 24 pens (18 birds/pen). The pens were randomly assigned to 1 of 4 thermal and lighting control rooms, then the birds were exposed to (n=6): 1) 12L, 2) 16L, 3) 18L, or 4) 20L at 15 d of age. Lighting program effects on bird body weight, behavioral patterns, bone health, and stress levels were evaluated from d 35 to d 45, respectively. The birds of 12L as well as 16L groups, reared under short photoperiods close to the natural 24-h L-D cycle, had improved production performance, leg bone health, and suppressed stress reaction compared to the birds of both 18L and 20L groups. Especially, 12L birds had heavier final body weight and averaged daily weight gain (P < 0.05), higher BMD and BMC with longer and wider femur (P < 0.05), lower H/L ratio (P < 0.05), and more birds reached the observer during the touch test (P < 0.05) but spent shorter latency during the tonic immobility test (P < 0.05). Taken together, the data suggest that supplying 12 h as well as 16L of daily light improves performance and health while decreasing stress levels in broilers, making it a potentially suitable approach for broiler production.

Influence of Perch-Provision Timing on Anxiety and Fearfulness in Laying Hens.

Perches can enhance laying hen welfare, but their effectiveness might be age-dependent. We investigated early and late perch access effects on anxiety and fear in pullets through attention bias (AB) and tonic immobility (TI) tests. Pullets (n = 728) were raised with or without multi-level perches: CP (continuous perch access: 0-37 weeks), EP (early perch access: 0-17 weeks), LP (late perch access: 17-37 weeks), and NP (no perch access). AB was conducted in weeks 21 and 37 (n = 84/week), and TI was performed in weeks 20, 25, and 37 (n = 112/week). CP hens fed quicker than EP, LP, and NP in AB at weeks 21 and 37 (p ≤ 0.05). CP and NP feeding latencies were stable, while EP and LP fed faster at week 37 (p ≤ 0.05). CP had the shortest TI at week 20 (p < 0.05). CP and LP had the shortest TI in weeks 25 and 37 (all p ≤ 0.05). Unlike NP, CP reduced anxiety and fear. Adding perches during laying (LP) raised anxiety at week 21, adapting by week 37, and removing pre-laying perches (EP) worsened fear at weeks 20 and 25 and anxiety at week 21, recovering by week 37. Adding or removing perches prior to the lay phase increased fear and anxiety, an effect that disappeared by week 37 of age. Our study indicates that continuous perch access benefits animal welfare compared to no perch access at all.

Increased dietary 5-hydroxytryptophan reduces fearfulness in red junglefowl hens (Gallus gallus).

Our production animals typically suffer poor welfare, which can be revealed by measuring the affective state these animals are in. Negative affective state is linked to poorer welfare, and can be measured as fearfulness. While continuing to research how to improve animal welfare, a compliment to reduce negative affective state could therefore be to reduce individuals' fearfulness, similar to how negative affective states are medicated in humans. A proposed mechanism for this is via the monoaminergic systems. This is based on previous studies across species that have linked the serotonergic system and fear-related behaviour. We here aimed to experimentally manipulate the serotonergic system in red junglefowl hens (Gallus gallus), the main ancestor of all domesticated chickens. We measured fearfulness as latency remaining immobile in a tonic immobility test, and did so both before and after our experimental manipulation. We set out to experimentally manipulate the serotonergic system via sub-chronic dietary treatment of 5-hydroxytryptophan (the precursor to serotonin). Our dietary manipulation of 5-hydroxytryptophan significantly reduced measured fearfulness in the manipulated hens, while latency in tonic immobility did not significantly change in our unmanipulated, control hens. This finding is promising since it indicates that increased tryptophan levels can be used to reduce fearfulness. Additionally, our result suggests that this can be done non-invasively via food (instead of injections), thus presenting a potentially feasible manipulation also for larger settings. Nevertheless, the serotonergic system is complex and its role in modulating behaviour in the fowl should be explored further to evaluate our findings, and more directly explored also in a production setting.

Effect of genotype on growth, fear-related behaviours, and walking ability of FUNAAB Alpha broiler chickens

The FUNAAB Alpha broiler, a tropical chicken breed developed in Nigeria, has three genotypes which are normal feather (NF), naked neck (NN), and frizzle feather (FF). This 56-day study investigated the effect of genotype on growth, fear-related behaviours, and walking ability of FUNAAB Alpha broiler chickens. Two hundred and four (204) chickens (68 NF, 68 NN, and 68 FF chickens; 34 males and 34 females per genotype) were used for the experiment. Body weight and growth rate were measured on days 27 and 56. The level of fear using the tonic immobility test (TI) on days 23 and 51, and emergence from a dark box on days 25 and 53 were measured. Walking ability was assessed using the latency to lie test on day 54. There was a genotype effect on body weight on days 27 and 56 (p = 0.02 and p = 0.01, respectively) and growth rate from days 1–27 and days 1–56 (p = 0.02 and p = 0.03, respectively). Of the three genotypes, the NN chickens were lighter in body weight, while the NF and FF had similar body weights on days 27 and 56 (p = 0.64 and p = 0.85, respectively), and growth rate from days 1–27 (p = 0.79). The male chickens were heavier on days 27 and 56 (p = 0.04 and p = 0.04, respectively) and had a better growth rate from days 1–27 (p = 0.03). The duration of tonic immobility on days 23 and 51 was similar in all three genotypes. The latency to emerge from a dark box on day 25 was not affected (p = 0.70) by genotype, but it took the NF chickens a longer time (138.20 ± 18.70 s) to emerge from the dark box on day 53. The walking ability of the birds was not affected (p = 0.83) by the genotype. However, male chickens had better (p = 0.01) walking ability by standing for a longer time than the females during the latency to lie test. In conclusion, the NF and FF chickens were heavier than the NN on days 27 and 56, and the NN and FF chickens were less fearful than the NF chickens on day 53. The FF genotype is recommended for meat production due to its better growth and less fearfulness.

Training for a cognitive judgement bias task does not affect fear or telomere shortening in laying hens

For behavioural tests such as the cognitive judgement bias task (JBT), animals usually undergo weeks of training involving various elements, such as handling, social isolation and learning the task. These may influence their affective state and other welfare indicators. Here, we investigated the effects of training for a JBT on fear-related behaviour in laying hens and a potential welfare indicator – telomere shortening. Hens were trained for a JBT (N = 16, across 2 batches), or kept as controls (N = 16, across 2 batches) that received no training or training-related handling. Hens that reached the learning criterion (N = 14) were tested in six JBT test sessions. Before and after the trained hens received JBT training, blood was collected from all hens, and they were assessed for fear-related behaviour by being subjected to open field, human approach, and tonic immobility tests. Relative telomere lengths (RTL; i.e., ratio of telomeric repeats versus a single copy control) were obtained from blood samples with a quantitative real-time polymerase chain reaction (PCR) method. As anticipation of the JBT sessions could affect the JBT outcome, we also recorded behavioural indicators of anticipation prior to each JBT test session. Except for an increased latency to first step in the open field test after training in the trained hens (t = 3.1, df=28, P = 0.012; conditional R2=0.59), no other fear-related behaviour significantly differed in either group (P > 0.05) and RTL was not affected. In addition, none of the anticipation indicators predicted the JBT test outcome. Contra to our hypotheses, welfare-related aspects may not be strongly affected by the JBT training. However, the enriched housing of the hens from both treatments might have minimised the effect of training on fear and telomere shortening, or training may have affected indicators other than the ones we investigated. We conclude that because JBT training and testing does not affect fear assessment and telomere shortening outcomes in hens housed in enriched housing conditions, the same individuals can be used in welfare assessments involving similar assessments. Our results also suggest that the JBT itself may be robust against the temporary affective states associated with anticipation.

Associations of range use with individual behaviour, clinical welfare indicators, fear response and gastrointestinal characteristics of two laying hen hybrids

Access to an outdoor range provides laying hens with increased space and improved opportunities for performing natural behaviours. However, not all hens utilise the range to the same extent, and this may be associated with the welfare of the individual hen. The aim of this study was to assess if extent of range use was associated with several clinical welfare indicators, time budgets, measures of tonic immobility and gastrointestinal characteristics. One hundred twenty focal individuals (Bovans Brown, n = 60; Dekalb White, n = 60) randomly chosen from 12 pens of 100 hens (10 hens from each pen) were housed in accordance with the EU organic standards. Clinical welfare indicators including plumage condition, foot health, keel bone damage and body weight were assessed upon arrival at 18 weeks of age and again at 23, 28, 33 and 38 weeks of age. Over five three-day periods at corresponding weeks, hens received individual back marks for identification and behaviour was recorded by instantaneous scan sampling from 8:30–15:30 in the house and on the range. Behaviour recorded included comfort behaviours, drinking, dust bathing, eating, foraging, locomotion, nest use, pecking, perching, resting and standing. Frequency of passes through the pophole and duration of time outdoors were also determined through video observations. At 18 weeks of age a tonic immobility test was performed and number of inductions, latency to first head movement after induction and the duration of tonic immobility were recorded. At the end of the study (38 weeks of age), gastrointestinal tract morphology and contents were assessed. Individual range use varied, with hens differing in time spent on range, number of exits and consistency in these measures over time. Extent of range use was not associated with clinical welfare indicators nor fear levels as assessed by a tonic immobility test. Hens’ time budgets differed depending on where they spent most of their day, with hens utilising the range to a greater extent generally being more active (duration on range: foraging: P < 0.001, standing: P = 0.005; number of exits: locomotion: P < 0.001). Hens that utilised the range to a greater extent likely consumed more forage, as evident by the greater weight of pasture found in their crop and gizzard (P < 0.001), contributing to more developed gastrointestinal organs including the crop (duration on range: P = 0.004), gizzard (P < 0.001), and proventriculus (duration on range: P = 0.014). To conclude, the fear level and clinical welfare condition of the hens were not associated with extent of range use, unlike the time budgets and gastrointestinal characteristics.

Differences among domestic chicken breeds in tonic immobility responses as a measure of fearfulness.

One priority for animal welfare is for animals to experience less fear, especially during human contact. For domestic animals, breeds that are less fearful may provide genetic resources to develop strains with improved welfare due to lower susceptibility to fear. Genetic predispositions inherited in these breeds might reflect the large diversity of chicken breeds. The goal of the present study was to systematically test a diverse group of chicken breeds to search for breeds that experience less fear. Nineteen chicken breeds from commercial hybrid lines, native layer-type, meat-type and dual-purpose breeds, ornamental breeds as well as bantam breeds were tested in a standardized tonic immobility (TI) test. Chickens were manually restrained on their back, and the time to first head movement and first leg movement, the duration of TI, as well as the number of attempts needed to induce TI were measured. The TI response differed among chicken breeds (p≤0.001) for naïve, mature hens. The median number of attempts required to induce TI ranged from 1 to 2 and did not differ significantly among breeds. Median durations were much more variable, with Lohmann Brown showing shortest durations (6 s, 12 s, 58 s for time to first head movement, first leg movement and total duration of TI, respectively). In contrast, medians reached the maximum of 600 s for all three measures in German Creepers. Repeated tests on the same individuals did not affect attempts needed to induce TI nor TI durations. Breeds clustered into two main groups, with layer-type native breeds and ornamental breeds having longer TI durations, and bantam, dual-purpose and meat-type native breeds having shorter TI durations. Our findings provide evidence for substantial variation of fearfulness among breeds. This variation could be linked to the intended use during the breed's specific history. Knowledge and quantitative measurement of these behavioural responses provide the opportunity to improve welfare through selection and future breeding.

Effect of silvopasture system on fearfulness and leg health in fast-growing broiler chickens.

A silvopasture system intentionally integrates trees, forages, and livestock, allowing dual land use. These systems can provide high-quality habitat for broiler chickens; however, such systems have not been widely adopted by the broiler industry in the United States. The objective of this study was to examine the effect of silvopasture versus open pasture access on fearfulness and leg health in fast-growing broiler chickens. A total of 886 mixed-sex Ross 708 chicks in Experiment 1 (Exp 1) and 648 chicks in Experiment 2 (Exp 2) were housed in coops and had access to 16 (Exp 1) or 12 (Exp 2) 125m2 silvopasture plots (x̄ = 32% canopy cover) or open pasture plots (no canopy cover) from day 24 of age. Fearfulness was measured using a tonic immobility test (tonic immobility duration), and leg health was assessed by quantifying footpad dermatitis, hock burns, gait, and performing a latency-to-lie test on days 37-39 of age. Birds in the silvopasture treatment were less fearful than birds in the open pasture treatment. Overall, birds in both silvopasture and open pasture systems had excellent leg health. Silvopasture birds had lower footpad dermatitis scores than open pasture birds. Silvopasture birds tended to have worse gait than open pasture birds in Exp 1, but not in Exp 2. Hock burn scores and latency-to-lie did not differ between treatments in Exp 1 or Exp 2. Raising birds in silvopasture reduced fear and improved footpad health compared to birds raised in open pastures, which indicates that silvopasture systems provide some benefits for affective state and leg health in fast-growing broilers.

Probiotic Effects on Behavior, Stress Indicators and Antioxidant Activity of Transported Broiler Chicken

Transportation before slaughtering causes bad effects on chicken welfare and health, but little is known about the effect of probiotic dietary fed in broiler chickens having transport stress. So, this study was designed to detect the effects of two doses of a probiotic (Bacillus subtilis) on some stress indicators, antioxidant activity and fear response of broiler chickens exposed to transportation stress. Two hundred and ten broiler chicks were distributed among 21 floor pens (10 chicks in each pen), each pen was exposed to one of three diet treatments containing a probiotic at 0 (control), 0.25 (0.25X), and 0.5 (0.5X) g/kg. At 35 days old, birds were exposed to transportation and then blood samples were collected for measuring stress and antioxidant markers. The serum corticosterone and cholesterol levels were decreased in probiotic fed birds in comparison with controls (P &lt; 0.05). Compared to control broiler chickens, 0.5X birds had higher levels of catalase and serum superoxide dismutase (P &lt; 0.05). In addition, the 0.5X birds spent less time in the tonic immobility test (P = 0.0427). The results suggest that the probiotic supplement may prove to be an important management tool for the broiler industry to diminish the negative effects of transport stress, potentially safeguarding the welfare and health of broiler chickens.

Neurotoxicity of xylazine in chicks

Despite the widespread use of xylazine in veterinary medicine, studies on its neurotoxicity are limited. So, our current study aims to reveal its neurotoxicity in chicks by determining the (LD50) of xylazine in Dixon's procedure. Moreover, it aims to study the effects of a small and repeated dose of xylazine on neurobehavioral test and the toxic doses of xylazine on the concentration of (glycine and glutamate) in the plasma of chicks and on the brain tissue after 60 and 90 minutes of injection. The LD50 of xylazine by injection into the chest muscle was 26.65 mg/kg. The injection of xylazine at a dose of 3 and 6 mg/kg in the chest muscle for three consecutive days caused an inhibition in motor activity within the open field as well as a significant elevation in the tonic immobility test response, injection of xylazine at doses 48.96 mg/kg ,60 and 90 minutes after the injection led to a significant increase in the glycine concentration as well as a significant decrease in glutamate after 90 minutes in the plasma of chicks, accompanied by histological variation in the brain tissue characterized by necrosis of neurons, vasogenic edema, neurophagia, cavities, infarction, necrosis of Purkinjean cell with decrees in the number of it. Our results revealed that xylazine had neurotoxic effects in chicks, represented by inhibition of neural behavior and motor activity within the open field, accompanied by a change in the concentration of glycine and glutamate in the plasma of chicks and histological variation in the brain tissue of chicks.

Acute toxicity events of ivermectin in chicks’ model

Ivermectin is a very safe drug; however, there are many studies on its toxic effects in different animals due to sensitivity, misuse, or accidental overdose. This study aimed to further characterize the neurotoxic effects of ivermectin in chicks and identify possible therapeutic strategies for use in cases of ivermectin toxicity. The LD₅₀ of ivermectin was determined by the Dixon method. The acute toxicity signs of ivermectin were induced at doses of 131.5,2629 and 394.5 mg/kg orally. The therapeutic effect of flumazenil on ivermectin poisoning was also studied. Administration of repeated doses of ivermectin for five consecutive days was recorded to measure the neurobehavioral within the open field and tonic immobility test. The oral LD₅₀ of ivermectin was 525.9mg/kg. The acute signs of poisoning on ivermectin-treated chicks were lethargy, ataxia, tremor, diarrhea, recumbency, and death. Flumazenil at a dose of 0.1mg/kg significantly reduced the toxicity signs induced by the ivermectin in chicks, especially tremor and ataxia, and prevented death. The administration of ivermectin at 26.3, 52.6, and 105.2 mg/kg doses led to a significant decrease in motor activity through a significant increase in the time of starting the movement and a decrease in the number of cross lines. We concluded that ivermectin has a neurotoxic effect in chicks when used in high doses; the results also indicate a potential clinical application of flumazenil for treatment side effects and toxicity of ivermectin, as well as ivermectin, has depressant effect in chicks represented by open-field activity.

An exploratory study on differences in maternal care between two ecotypes of Nigerian indigenous chicken hens

The Yoruba (YRE) and Fulani (FLE) are the two notable indigenous chicken ecotypes in Nigeria. They exhibit broodiness and post-hatch care of their chicks. Studies on welfare, productivity, and maternal behaviors of these two ecotypes are scarce, hence the need for this study. Separate flocks of these ecotypes were housed intensively and hens that showed broodiness (ten YRE and five FLE) were monitored. Brooding behaviors were monitored for 3 days in the 1st and 2nd weeks of brooding and daily in the 3rd week of brooding for 6 h/day (07:00–09:00 h, 11:00–13:00 h, and 15:00–17:00 h). During brooding, surface body temperatures (eye, brood patch and under the wings), egg temperature and body weight of the hens were measured. Chicks hatched (44 chicks from the YRE and 24 chicks from the FLE) by these hens were subjected to tonic immobility tests on the 7th, 14th, and 21st days post-hatch and to a simulated predator test on the 8th, 15th, and 22nd days post-hatch to determine their level of fear. In each ecotype, brooding behaviors did not change over the three weeks, but the YRE hens spent longer time sitting on their eggs at the 2nd (U = 5.000, z = −2.454, P = 0.014) and 3rd (U = 9.000, z = −1.961, P = 0.050) week of brooding. The surface body temperatures of both ecotypes, egg temperature, and relative weekly weight loss were similar over the brooding period, but relative weekly weight loss was greater (P < 0.05) at the 3rd than 1st and 2nd week of brooding. The surface body temperatures were positively correlated (P < 0.01) with egg temperature. In both ecotypes, attempts to induce and duration of tonic immobility were similar over the test periods but on the 7th day post-hatch, the duration of tonic immobility was longer (U = 323.000, z = −2.632, P = 0.008) and on the 14th day post-hatch, the number of attempts to induce tonic immobility was less (U = 332.000, z = −2.630, P = 0.009) in the YRE chicks. In conclusion, YRE hens sat more on the eggs and their chicks were more fearful.