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A case control study with a questionnaire was carried out to compare feeding practices, diet composition, housing and management in 78 herds with or without a history of tail-biting in undocked pigs (Sus scrofa) in Finland. Tail-biting was measured as the mean annual prevalence score of tail-biting damage (TBD) for a farm. Logistic regression parameters were calculated separately for risk factors present in piglet (lactation), weaner, and finishing units. Risk factors found in piglet units for TBD were slatted floors and area of slats. In the weaner units, slatted floors, area of slats, use of whey or wheat in the diet, and use of purchased compound feeds were associated with a risk of TBD. In the finishing units, slatted floors, area of slats, increasing number of finisher pigs at the farm, absence of bedding, liquid feeding, several meals per day, specialised production type and a group size greater than nine pigs were found as risk factors for TBD. Increased farm size was connected to risk for TBD in the overall dataset. The nutritional risk factors seem to operate together with other risk factors, but with relatively lower odds. The risk factors of undocked herds in this study seem to be similar to the risk factors from earlier studies of docked pigs. This study provides information which can be used to refine decision-support tools for management of the potentially higher risk for tail-biting among long-tailed pigs, thus aiding compliance with EU law and enhancing pig welfare.
The aim of this study was, firstly, to investigate the connection between on-farm assessed welfare scores and production parameters for sows, and secondly, to examine how farmers perceive the connection between their disposition, animal welfare and productivity. We assessed environmental and management preconditions on animal welfare and interviewed farmers on 30 Finnish farms. We studied the relationship between welfare and production using correlation and regression analyses. The theory of planned behaviour served as an articulation of farmer disposition when studying farmer perceptions. Concerning the production data, better welfare scores from the ‘health and stockmanship’ category during lactation were correlated with shorter reproduction cycle and fewer stillborn piglets and it also explained some of the variation in the number of piglets per year and the length of the farrowing interval. The farmers agreed that the productivity parameters and the principles of assessing welfare used in this study were relevant. A majority of farmers considered that animal welfare affects productivity and that there are associations between farmer attitudes, animal welfare and productivity. There were no statistical relationships between farmer perceptions and animal welfare; yet on the farms of farmers with positive perceptions of attitudes to animal welfare and productivity there were slightly lower piglet mortality rates and lower stillbirth rates than on the farms with farmers holding less positive views. We conclude that actions to improve animal welfare also have an economic impact as they enhance sow production. Good stockmanship and healthier animals result in more piglets born and a shorter reproduction cycle.
The Welfare Quality® (WQ) on-farm welfare assessment protocols for fattening pigs (n = 95 farms) and sows, as well as suckling piglets (n = 103 farms), were applied on Finnish farms. In order to identify distinct types of welfare problems (WPTs) Principal Component Analysis (PCA) was applied to the pooled animal-based items within both categories of animals. Measures describing suckling piglets did not contribute to the WPTs. The main WPTs (seemingly) reflected fighting in fattening pigs and lack of bedding in both fattening pigs and sows. The results imply that WQ includes biologically plausible shortlists of animal-based measures with decent to good internal consistency describing distinct types of welfare problems in growing pigs and in sows. The 20 descriptors of Qualitative Behavioural Assessment were analysed similarly to identify distinct mood types, which were named active positive, passive positive and passive positive behaviours. The different mood types had close to identical build-up in both fattening pigs and in sows and suckling piglets.
This study aimed to establish associations between the environment and animal-based measures of welfare collected on 158 Finnish farms according to the Welfare Quality® systems for pigs. The data consisted of 95 welfare assessments in fattening pigs and 103 in sows, including suckling piglets. Principal Component Analysis had previously been applied to animal-based welfare measures (ABWM) and to the 20 descriptors of QBA to identify distinct types of welfare problems (WPT) and mood (MT), respectively. Generalised linear modeling was used to investigate environmental (space allowance, group size, feeding arrangement, floor type and use of enrichment or bedding) effects on WPT and MT scores. Those ABWMs not contributing to the major WPTs, but occurring on more than 40% of the farms, were considered important and used as outcome variables as well. The most important environmental determinants of pig welfare were space allowance for fattening pigs, group size in gestation and in the use of bedding for both fattening pigs and gestating sows. Bedding decreased tail biting and signs of fighting when used as a fairly thick layer for fattening pigs. In sows, the benefits of bedding, including less frustration and bursitis, required a smaller amount of material than in fattening pigs. An increasing space allowance was advantageous for fattening pigs, although signs of fighting increased in very spacious bedded pens. The positive effects of space, including a decrease of tail lesions and a more positive mood continued at least up to 1.5 m2 per fattening pig. Signs of resource shortage in sows increased with a growing group size according to a steepening curve.
This study sought to investigate Chinese farmers’ attitude towards animal welfare by using the Theory of Planned Behaviour (TPB). According to the TPB, an individual's intention to behave in a certain way is determined by his/her attitude towards the behaviour (specific attitude — importance — and general attitudes), the perceived behavioural control (easiness), and the supposed opinion of the people who are important to him/her (subjective norms). A total of 253 questionnaires were used, which included the three main animal productions in China (swine, poultry and cattle). Chinese farmers have perceived the improvement of animal welfare as two abstracts: general attitudes (reward-seeking, and empathic farmer); and four specific categories of actions (favourable environment, animal health, humane treatment of animals and farmers’ well-being). Our analysis revealed that general and specific attitudes were the strongest predictors of farmers’ intentions to improve animal welfare in the questionnaire study. In fact, Chinese farmers considered it fairly important to improve the animal welfare measures considered in the survey. In contrast, the same animal welfare measures were considered difficult to improve by the farmers as indicated by the lack of association between the easiness of improving animal welfare and the intentions. In addition, veterinarians, agricultural advisers, and scientific experts were considered to be relatively influential subjective norms as regards the activities of the farmers. This is the first study to provide an insight into the underlying meanings and values of Chinese farmers’ views on improvements to animal welfare.
The welfare of production animals provokes wide social discussion among the public, yet, despite this, farmers’ voices and their representations of animal welfare are rarely heard, even though farmers are the ones actually able to improve animal welfare. Farmers’ perceptions of what constitutes animal welfare and how it may be improved can differ from those of consumers and other stakeholders, and therefore it is crucial to understand what farmers mean when they talk about improving animal welfare. To chart farmers’ perceptions, we conducted qualitative interviews and a questionnaire study using the theory of planned behaviour as a conceptual framework. We found that the farmers perceived the improvement of animal welfare as four specific, practical attitude objects (providing animals with a favourable environment; taking care of animal health; treating the animals humanely; and taking care of the farmer's own well-being) and two different but often overlapping general attitudinal dimensions (the instrumental and intrinsic evaluations of animal welfare). The farmers’ intentions to improve animal welfare were best explained by their attitudes towards the specific welfare-improving actions. The concept of the improvement of animal welfare examined in this study outlines measures to improve animal welfare from the farmers’ point of view and discusses their influence. Our study demonstrates that by adapting a valid conceptual framework and applying relevant qualitative and quantitative methods that support each other, we are able to elucidate the underlying meanings and values in farmers’ views on improving animal welfare.
This study aimed to identify differences in stress measures in pigs (Sus scrofa) with different roles during a tail-biting outbreak. Quartets (n = 16) of age- and gender-matched fattening pigs including a tail biter (TB; n = 16), a victim (V; n = 16), a control in the same pen (Ctb; n = 10), and one in a pen without tail biting (Cno; n = 14) were chosen by direct behavioural observation. Stress measures used were behaviour (dog-sitting, sniffing of pen-mates and aggression), thyroid hormone concentration, morphology of adrenal and thyroid glands and salivary cortisol concentration sampled at 0700, 1000, 1600 and 1900h. Category (TB, V, Ctb, Cno) effects were investigated using a mixed model with replicate as subject and category as repeated effect. Category had a significant effect on adrenal total (cortex + medulla) and cortical area, salivary cortisol at 1900h, serum triiodothyronine (T3) and the behaviours performing and receiving sniffing. Victims suffered from a triad of chronic stress, pathology and suppressed T3 secretion. Evidence for stress in tail biters, a possible cause of the behaviour, consisted of a slightly flattened day-time cortisol pattern and more performed sniffing than all other categories. Differences in evening cortisol concentration and T3 levels between the categories in the pen with ongoing tail biting emphasise the qualities of the control animal. It supports the view that neutral pigs represent a phenotype that adopts a coping strategy leading to lower stress levels than in tail biters and victims, despite being housed in the same pen.
Pain is an indicator of welfare status in livestock, and attitudes play a key role in the assessment and treatment of pain in animals. Veterinarians’ and dairy producers’ perceptions of cattle pain are affected by gender, age and work experience. The aim of this paper was to study beef producers’ attitudes regarding disbudding as well as the painfulness of certain cattle diseases. A questionnaire was sent out to 1,000 Finnish beef producers and the response rate was 44%, representing 19% of all Finnish beef producers. Producers graded their attitudes on a five-point Likert scale and perception about pain on an eleven-point numerical scale. Factor analysis was used and four factors were established. These factors described producers’ assessment of disbudding-related pain, their sensitivity to pain in cattle, their willingness to self-medicate disbudded calves and their perceived importance of horns. Factor scores were tested for differences between genders and the use of disbudding on farms with Mann Whitney U-tests. Kruskal-Wallis tests were used to assess differences among producers’ age, work experience and herd size. Female beef producers assessed animal pain higher than male beef producers. Older and more experienced beef producers showed more positive attitudes towards cattle with horns than younger or less-experienced ones. Older beef producers were more sensitive to cattle pain than younger producers and beef producers with a smaller herd size took disbudding pain more seriously and were more sensitive to cattle pain than the producers with larger herds. Producers who did not use disbudding valued horns more than producers using disbudding.
Tear staining (TS) in the pig has been related to different stressors and may be a useful tool for assessing animal welfare on farm. The aim of the current study was to investigate TS across the finisher period and its possible relation to age, growth, sex and experimentally induced stressors. The study included 80 finisher pens divided between three batches. Within each batch, the pens either included pigs with docked or undocked tails, had straw provided (150 g/pig/day) or not and had a low (1.21 m2/pig, 11 pigs) or high stocking density (0.73 m2/pig, 18 pigs). Tear staining (scores 1 to 4; from smaller to larger tear stain area, respectively) and tail damage were scored on each individual pig three times per week over the 9-week study period, and the individual maximum TS score within each week was chosen for further analysis. Data were analysed using logistic regression separately for each of the four possible TS score levels. The TS scores 1 and 2 decreased with weeks into the study period and were negatively related to the average daily gain (ADG) of the pigs, whereas the TS score 4 increased with weeks into the study period and was positively related to ADG. None of the TS scores differed between females and castrated males, and neither straw provision nor lowering the stocking density affected the TS scores. However, the TS score 1 decreased the last week before an event of tail damage (at least one pig in the pen with a bleeding tail wound), whereas the TS score 4 increased. The results of the current study advocates for a relation between TS and the factors such as age, growth and stress in the pig, while no relation was found between TS and the environmental factors straw provision and lowered stocking density. The relations to age and growth are important to take into consideration if using TS as a welfare assessment measure in the pig in the future.
Wooden breast myopathy, a condition where broiler breast muscles show a hardened consistency post-mortem, has been described recently. However, it is not known how wooden breast myopathy affects the bird activity or welfare. Altogether, over 340 birds of five commonly used commercial hybrids were housed in 25 pens, and sample birds killed at ages of 22, 32, 36, 39 and 43 days. Their breast muscle condition was assessed post-mortem by palpation. The birds were gait scored and their latency to lie was measured before killing. For further behavior observations, one affected and healthy bird in 12 pens were followed on 5 days for 20 minutes using video recordings. The connection of myopathy to gait score and activity was analyzed with mixed models. A higher gait score of wooden-breast-affected birds than that of unaffected birds (2.9 ± 0.1 v. 2.6 ± 0.1, P < 0.05) indicated a higher level of locomotor difficulties over all age groups. The wooden-breast-affected birds had fewer crawling or movement bouts while lying down compared with unaffected (P < 0.05). Wooden breast myopathy-affected birds were heavier (2774 ± 91 v. 2620 ± 91 g; P < 0.05) and had higher breast muscle yield (21 ± 1 v. 19 ± 1%; P < 0.05) than unaffected birds overall. Older birds had longer lying bouts, longer total lying time, fewer walking bouts, more difficulties to walk and to stand compared with younger birds (P < 0.05). Birds with poorer gait had longer total lying time and fewer walking bouts (P < 0.05). Birds with greatest breast muscle yield had the largest number of lying bouts (P < 0.05). It was concluded that wooden breast myopathy was associated with an impairment of gait scores, and may thus be partly linked to the common walking abnormalities in broilers.
The present study aimed to identify the factors that affect immediate (within 24 h after farrowing onset) postnatal piglet mortality in litters with hyperprolific sows, and investigate their associations with behaviour of postpartum sows in two different farrowing housing systems. A total of 30 sows were housed in: (1) CRATE (n=15): the farrowing crate closed (0.80×2.20 m) within a pen (2.50×1.70 m), and (2) OPEN (n=15): the farrowing crate open (0.80×2.20×1.80 m) within a pen (2.50×2.40 m) with a provision of 20 ls of hay in a rack. A total of 518 live born piglets, produced from the 30 sows, were used for data analyses during the first 24 h after the onset of parturition (T24). Behavioural observations of the sows were assessed via video analyses during T24. Total and crushed piglet mortality rates were higher in OPEN compared with CRATE (P<0.01, for both). During T24, the OPEN sows tended to show higher frequency of postural changes (P=0.07) and duration of standing (P=0.10), and showed higher frequencies of bar-biting (P<0.05) and piglet trapping (P<0.01), when compared with the CRATE sows. During T24, the mortality rates caused by crushing were correlated with the piglet trapping event (r=0.93, P<0.0001), postural changes (r=0.37, P<0.01), duration of standing (r=0.32, P<0.01) and frequency of bar-biting behaviour (r=0.51, P<0.01) of the sows (n=30). In conclusion, immediate postnatal piglet mortality, mainly due to crushing, may be associated with potential increases in frequency of postural changes, duration of standing and incidence of piglet trapping in postpartum sows in the open crate system with large litters.
Group housing of gestating sows benefits their welfare by allowing them freedom of movement and the opportunity for social interaction. However, social life could also bring disadvantages for individuals who receive direct aggression or are displaced from the feeder. The aim of this study was to investigate associations between social behaviour, body condition and live weight. Gestating sows (n=298) were investigated on a commercial farm. Sows were housed in mixed parity groups where two single space, ad libitum trough feeders served 12 animals. Sows were weighed, body condition scored and had their back fat layer measured at mixing, 4 weeks after insemination and again before farrowing. Social status was estimated based on the numbers of won and lost agonistic interactions at mixing and at the end of gestation. In addition, tear staining was scored before the farrowing and reproductive performance data were collected. With the aid of video recordings, 100 to 150 interactions per group were observed. Winning percentage at mixing and at the end of gestation were associated (P<0.05) and appeared relatively stable within individuals. Tear staining scores and litter sizes were not associated with winning percentage at the end of gestation. However, live weight, relative weight, body condition and back fat thickness were associated with winning percentage (P<0.05), giving heavier animals an advantage. Low winning percentage related to lower live weight gain, probably due to poorer success in competition for feed. Live weight within a mixed parity group could be used as a proxy measure for social status. Sows with low body condition score and submissive sows might need special attention with regard to group dynamics and housing to alleviate the effects of competition in group housing.
Modern fast-growing broilers spend excessive periods resting and their activity further decreases with age. Inactivity has been suggested to increase impaired gait and the incidence of leg disorders. Tibial dyschondroplasia (TD) is a common leg pathology in broilers. A more complex environment might facilitate more activity and improve leg health. Perches or elevated platforms bring variety to broilers’ environment and could motivate more locomotion. This study examined the impact of perches and elevated platforms on walking ability, the occurrence of TD and level of bone ash and mineral contents. The investigation was performed on four commercial broiler farms throughout six consecutive batches with platforms and four to five with perches. On each farm at least two separate houses were included, enabling the comparison of furnished flocks to control flocks during each batch. Plastic slats with ramp access elevated by 30 cm or wooden perches of 10 and 30 cm height were offered in the furnished house. Farmers recorded the platform and perch usage twice a week with a five-point scale. Gait was scored before slaughter on a six-point scale according to the Welfare Quality® assessment protocol for poultry. The severity of TD was determined using a four-point scale on farm from all birds gait scored as 3 and at slaughter from 200 birds/flock. Farmers estimated 50% to 100% of the platforms to be occupied in all flocks throughout the entire growing period. Only single birds were perching, thus perch structures were constantly evaluated to be empty. Due to the low use, the perch-equipped houses were excluded when analysing bone content, walking ability and TD. On average, 30% of the tested birds exhibited gait score ⩾3. Younger scoring age resulted in a lower mean gait score and a lower percentage of scores 3 and 4 to 5. Overall, 2.3% of the birds examined at slaughter and 3.5% of the birds with gait score 3 were affected by TD. Leg health was better in birds with access to platforms: mean gait score, the percentage of birds scoring 3, and TD percentage and severity were lower in birds in platform-equipped houses. Elevated structures such as platforms, offering additional possibilities for locomotion to broilers seem to improve their leg health.
Colostrum is an essential source of immunoglobulin G (IgG) for neonate piglets. However, colostrum IgG content and nutritional composition can vary considerably among sows due to age, parity, feeding regime and immunological background. Currently, there is no practical way to obtain information about colostrum IgG concentration at herd level. We evaluated sows’ colostrum IgG content on-farm using a Brix refractometer and its performance was compared with that of an IgG ELISA. In addition, nutritional compositions of the colostrum samples were analyzed using Fourier transform IR spectroscopy. Colostrum samples (5 to 6 ml) (n=153) were obtained within 0 to 3 h of farrowing. However, to obtain a 24 h IgG profile for 11 sows, colostrum samples were collected at 0, 2, 4, 6, 8, 10, 16 and 24 h after farrowing. A 0.3 ml of freshly drawn colostrum sample was used for the on-farm measurement of Brix percentages using a digital refractometer shortly after collection. The remaining fractions of the samples were frozen and submitted to laboratory analysis for total IgG, using a commercially available pig IgG ELISA kit. For nutritional composition analysis, a 35 ml colostrum sample (n=34) was obtained immediately after birth of first piglet from the first three pairs of frontal teats. Colostrum concentrations of IgG averaged 52.03±30.70 mg/ml (mean±SEM) at 0 to 3 h after farrowing. Concentration of IgG decreased on average by 50% during the 1st day of lactation (P<0.01). Sow parity did not influence colostrum concentrations of IgG. Differences in colostrum composition were recorded between two herds and among the parity groups (P<0.05). The Brix refractometer measurement of colostrum and the corresponding log transformed IgG measurements from the ELISA were moderately correlated (r=0.63, P<0.001, n=153). Based on the classification we suggest here, low levels of IgG (14.5±1.8 mg/ml) were recorded for colostrum samples with Brix readings below 20%. Borderline colostrum IgG content (43.8±2.3 mg/ml) had Brix readings of 20% to 24%, adequate colostrum IgG content (50.7±2.1 mg/ml) had Brix % readings of 25% to 29% and very good IgG colostrum content (78.6±8.4 mg/ml) had Brix readings >30%. Colostrum IgG concentration is highly variable among sows, Brix measurement of a sows’ fresh colostrum is an inexpensive, rapid and satisfactorily accurate method of estimating IgG concentration, providing indication of differentiation between good and poor IgG content of colostrum.
Tear staining or chromodacryorrhea refers to a dark stain below the inner corner of the eye, caused by porphyrin-pigmented secretion from the Harderian gland. It has been shown to be a consistent indicator of stress in rats and to correlate with social stress and a barren environment in pigs. The current study was, to our knowledge, the first to test it on commercial pig farms as a potential welfare indicator. The study was carried out on three commercial farms in Finland, in connection to a larger study on the effects of different types of manipulable objects on tail and ear biting and other behavioural parameters. Farm A was a fattening farm, on which 768 growing-finishing pigs were studied in 73 pens. Farm B had a fattening unit, in which 656 growing-finishing pigs were studied in 44 pens, and a farrowing unit, in which 29 sows and their litters totalling 303 piglets were studied in 29 pens. Farm C was a piglet-producing farm, on which 167 breeder gilts were studied in 24 pens. Data collection included individual-level scoring of tear staining; scoring of tail and ear damage in the growing-finishing pigs and breeder gilts; a novel object test for the piglets; and a novel person test for the growing-finishing pigs on Farm B and the breeder gilts on Farm C. On Farm A, tear staining was found to correlate with tail damage scores (n=768, rs=0.14, P<0.001) and ear damage scores (n=768, rs=0.16, P<0.001). In the growing-finishing pigs on Farm B, tear staining of the left eye correlated with tail damage (n=656, rs=0.12, P<0.01) and that of the right eye correlated with ear damage (n=656, rs=0.10, P<0.01). On Farm A, tear-staining sores were lower in the treatment with three different types of manipulable objects as compared with controls (mean scores 3.3 and 3.9, respectively, n=31, F29=4.2, P<0.05). In the suckling piglets on Farm B, tear staining correlated with the latency to approach a novel object (n=29, rp=0.41, P<0.05). Although correlations with tail and ear damage were low, it was concluded that tear staining has promising potential as a new, additional welfare indicator for commercial pig farming. Further research is needed on the mechanisms of tear staining.
Tail biting has several identified feeding-related risk factors. Tail biters are often said to be lighter and thinner than other pigs in the pen, possibly because of nutrition-related problems such as reduced feed intake or inability to use nutrients efficiently. This can lead to an increase in foraging behavior and tail biting. In this study, a total of 55 pigs of different ages were selected according to their tail-biting behavior (bouts/hour) and pen-feeding system to form eight experimental groups: tail-biting pigs (TB), victim pigs (V) and control pigs from a tail-biting pen (Ctb) and control pen (Cno) having either free access to feed with limited feeding space or meal feeding from a long trough. After euthanasia, a segment of jejunal cell wall was cut from 50 cm (S50) and 100 cm (S100) posterior to the bile duct. Villus height, crypt depth and villus : crypt ratio (V : C) were measured morphometrically. Blood serum concentration of minerals and plasma concentration of amino acids (AA) was determined. Villus height was greater in Cno than Ctb pigs in the proximal and mid-jejunum (P < 0.05), indicative of better ability to absorb nutrients, and increased with age in the proximal jejunum (P < 0.001). Serum mineral concentration of inorganic phosphate (Pi) and calcium (Ca) was lower in Ctb compared with Cno pigs, and that of Pi in V compared with all the other pigs. Many non-essential AA were lower in pigs from tail-biting pens, and particularly in victim pigs. Free access feeding with shared feeding space was associated with lower levels of essential AA in blood than meal feeding with simultaneous feeding space. Our data suggest that being a pig in a tail-biting pen is associated with decreased jejunal villus height and blood AA levels, possibly because of depressed absorption capacity, feeding behavior or environmental stress associated with tail biting. Victim pigs had lower concentrations of AA and Pi in plasma, possibly as a consequence of being bitten.
Health in relation to tail-biting behaviour was investigated on a problem farm. Quartets (n = 16) of age- and gender-matched fattening pigs including a tail biter (TB, n = 16), a victim (V, n = 16), a control in the same pen (Ctb, n = 10) and a control in a pen where no tail biting was observed (Cno, n = 14) were chosen by direct behavioural observation. Haematological and clinicochemical analyses, autopsy and histological examination of 16 different tissues were carried out. Tail lesion severity was evaluated both macroscopically, on the basis of inspection, and histologically, in the sagittally cut tail. Category effects were tested using Friedman's ANOVA by Ranks, Cochran's Q or a repeated-measure GLM and, if significant, pair-wise tests were conducted using Wilcoxon Signed Ranks or McNemar's Test. The number of received tail bites correlated better with histological than with macroscopic tail lesion scoring because of deep inflammation beneath healthy skin in some cases. Most individuals had mild inflammatory lesions in internal organs suggestive of generalized activation of the immune system, and 30% of the animals were anaemic, possibly because of systemic spread of infectious agents. V had more severe respiratory organ lesions and higher serum protein concentrations than all other categories of pigs. Liver- and muscle-specific enzymes (alanine aminotransferase, alkaline phosphatase and creatine kinase) differed between categories. In conclusion, most animals had signs of generalized activation of the immune system, possibly because of systemic spread of infectious agents. V pigs suffered from more severe inflammatory lesions than TB, Ctb or Cno. Deep infections may exist under healthy skin in the tail of bitten pigs.
Effects of environmental enrichment at different stages of life on stress physiology of pigs were investigated in a trial with 63 groups, each of four siblings. In each of the three growing phases (suckling 0 to 4 weeks of age, nursery 5 to 9 weeks, fattening 10 to 24 weeks) pens either were (=E) or were not (=0) enriched. Accordingly, the treatments were (i) 000, (ii) E00, (iii) EE0, (iv) 00E, (v) 0EE and (vi) EEE. The enrichment material, renewed twice daily to leave a thin layer, consisted of wood shavings and chopped straw. Salivary cortisol was sampled hourly from 0700 to 1900 h at the age of 9 and 21 weeks. The presence of a circadian secretion rhythm was evaluated by an intra-assay coefficient of variation-based method. An adrenocorticotropic hormone test was performed at 21 weeks. Treatment effects on the odds of a physiological cortisol rhythm were assessed by logistic regression, and effects on cortisol concentrations with a repeated measures GLM. Substrate-enrichment from 0 to 9 weeks of age increased the odds of a rhythm as compared to barren housing (odds ratio (OR) = 30.0, P < 0.01). A flat cortisol secretion pattern may indicate chronic stress and/or delayed maturation of the rhythm. Barren as compared to enriched rearing (0 to 4 weeks of age) seemed to cause a blunted secretion rhythm at 21 weeks of age. Although behavioural and tail lesion observations provided support to the assumption that a blunted rhythm indicates chronic stress, the biological significance of these cortisol results needs confirmation in future studies.
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