Effects of weight, temperature and behaviour on the circadian rhythm of salivary cortisol in growing pigs

In farm animals, salivary cortisol has become a widely used parameter for measuring stress responses. However, only few studies have dealt with basal levels of concentration of cortisol in pigs and its circadian rhythm. The aim of this study was to examine the effects of ambient temperature and thermoregulatory behaviour on the circadian rhythm of salivary cortisol levels in fattening pigs. Subjects were 30 fattening pigs of different weight (60 to 100 kg), kept in six groups in an uninsulated building in pens with partly slatted floors. Saliva samples were taken every 2 h over periods of 24 h at different ambient temperatures at two times in winter and four times in summer. Thermoregulatory behaviour was recorded in the same 24-h time periods. The effect of time of day, body weight, ambient temperature and behaviour on the cortisol level was analysed using a mixed-effects model. Two peaks of cortisol levels per day were found. This circadian pattern became more pronounced with increasing weight and on days where thermoregulatory behaviour was shown. Mean cortisol levels per day were affected by weight but not by thermoregulatory behaviour. From our data, we conclude that long-term variations in cortisol concentration may be influenced by increasing age and weight more than by the respective experimental situation. In assessing animal welfare, it seems more reliable to consider the circadian pattern of cortisol concentration instead of only one value per day.     

Characterization of adrenal ACTH signaling pathway and steroidogenic enzymes in Erhualian and Pietrain pigs with different plasma cortisol levels

Our previous study demonstrated significant difference in the basal plasma cortisol levels between Erhualian (EHL) and Pietrain (PIE) pigs, implicating fundamental breed difference in adrenocortical function. The objectives of the present study were therefore to characterize the expression pattern of proteins involved in adrenal ACTH signaling and, including melanocortin type 2 receptor (MC2R), cAMP response element binding protein (CREB) and phosphorylated CREB (pCREB), steroidogenic acute regulatory protein (StAR), as well as that of the key enzymes involved in steroidogenesis in EHL and PIE pigs, in association with the plasma corticotrophin (ACTH) and cortisol levels. The plasma concentrations of the substrates for adrenal steroidogenesis, cholesterol and low-density lipoprotein (LDL) cholesterol, did not differ between breeds. Plasma concentration of ACTH and the adrenal contents of MC2R mRNA and protein were similar in two breeds of pigs, whereas the basal plasma concentrations of cortisol in EHL pigs were 1.5 folds higher than that in PIE pigs. The higher basal plasma cortisol levels in EHL pigs were found to be accompanied with the higher expression of ACTH post-receptor signaling components, cAMP, pCREB and StAR, as well as the higher expression of cholesterol side-chain cleavage cytochrome P450 (P450scc), 17alpha-hydroxylase cytochrome P450 (P450(17alpha)), 21-hydroxylase cytochrome P450 (P450c21) and 11beta-hydroxylase cytochrome P450 (P450(11beta)). These results indicated that the enhanced cAMP/PKA/pCREB-signaling system and augmented expression of StAR and steroidogenic enzymes are major attributes to the higher basal plasma cortisol concentrations in pigs.     

Lack of correlation between steroid sulfatase activities and lipid content in uterus and liver microsomes of guinea pigs

Lipid content and steroid sulfatase activities were determined in liver and uterus microsomes of non-pregnant guinea pigs. The results were compared with values obtained in pregnant and cortisol-treated animals. Steroid sulfatase activities were always higher in pregnant animals, and we supposed that the increase in circulating cortisol in pregnant guinea pigs before parturition has an influence on the membrane-bound sulfatase activities. Sulfatase activities were identical in cortisol-treated and untreated non-pregnant females, although cortisol induced changes in microsomal lipid composition. These results lead us to three conclusions: in intact female guinea pigs, cortisol induces variations in the lipid content of uterus and liver microsomes, especially in the cholesteryl sulfate to phospholipid ratios; the variations of the lipid composition in pregnant animals do not appear to be cortisol-dependent; membrane-bound steroid sulfatase activities are not directly influenced by the lipid composition of microsomes.     

A combination of behavioral and physiological indicators for assessing pig welfare on the farm

The purpose of this research was to identify pig welfare indicators that could help in recognizing stressful practices on farm. The study evaluated behavioral and physiological indicators (cortisol and negative acute phase proteins) in 2 groups of 20 female pigs 4 months old after a 48-hr transport. The first group (A) was transported at the end of May, the second (B) in June. Behavioral observations and blood collection occurred at arrival (D1) and 28 days later (D28). Compared with within-animal control samples obtained 28 days later, pigs of Group A had increased cortisol levels and decreased albumin concentrations after arrival. As demonstrated by lesion and behavior observations, the effect on cortisol and albumin was higher in Group B pigs after a tail-biting episode occurred. The study has reported no evidence of Retinol Binding Protein (RBP) in pigs. A method developed for swine RBP quantification found RBP strongly reduced in D28 samples of Group B, confirming it to be a negative protein in pigs. The suggested combination of physiological and behavioral indicators could provide useful information on the welfare state of an animal.     

The impact of chronic environmental stressors on growing pigs, Sus scrofa (Part 1): stress physiology, production and play behaviour

Commercially farmed animals are frequently housed in conditions that impose a number of concurrent environmental stressors. For pigs housed indoors, elevated levels of mechanical noise, atmospheric ammonia and low light intensities are commonplace. This experiment examined the effects on growing pigs of chronic exposure to combinations of commercially relevant levels of these potential stressors. Four-week-old hybrid female pigs (n = 224) were housed under experimentally manipulated conditions of nominally either <5 or 20 ppm atmospheric concentration of ammonia (24 h), a light intensity of 40 lux or 200 lux (12 h) and mechanical noise at either ⩽60 or 80 dB(A) (24 h) for 15 weeks in a fully factorial arrangement (2³) of treatments. The response of pigs to these environmental factors was assessed using a suite of physiological, production and behavioural measures. These included indicators of hypothalamic–pituitary–adrenal (HPA) axis activation such as salivary cortisol and adrenal morphometry, as well as body weight, food conversion efficiency and general health scores. Play behaviour was recorded as it is thought to be inversely related to stress. Chronic exposure to ammonia produced the strongest effect, shown by lower concentrations of salivary cortisol and larger adrenal cortices in the pigs reared under 20 ppm ammonia, which may have been indicative of a period of HPA activation leading to a downregulation of cortisol production. The pigs in the ammoniated rooms also performed less play behaviour than pigs in non-ammoniated rooms. There was evidence for an interaction between high noise and ammonia on the health scores of pigs and for brighter light to ameliorate the effect of ammonia on salivary cortisol. However, there was no measurable impact of these potential stressors on the productivity of the pigs or any of the other physiological parameters measured. We conclude that there should be little concern in terms of performance about the physical stressors tested here, within current European Union legal limits. However, 20 ppm ammonia may have had an adverse influence on the well-being of growing pigs. In this study, all other aspects of the pigs’ husbandry were optimal; therefore, it is possible that under less favourable conditions, more pronounced effects of ammonia, noise and dim light would be observed.     

Expression of steroidogenic enzyme messenger ribonucleic acid and cortisol production in adrenocortical cells isolated from halothane-sensitive and halothane-resistant pigs

Stress susceptibility in pigs is inherited by a single recessive gene (Hal(n)), and homozygous individuals can be identified by exposure to halothane anesthesia. Previous studies have shown that in stress-susceptible pigs, exposure to a high ambient temperature resulted in a twofold increase in corticotropin (ACTH) and lower plasma cortisol. To determine whether there is a fundamental difference in adrenocortical function between halothane-sensitive (HAL-S) and halothane-resistant (HAL-R) pigs, independent of other factors influencing the hypothalamic-pituitary-adrenal (HPA) axis, we compared cortisol responses to ACTH and 8-bromo-cyclic AMP (8-Br-cAMP) in HAL-S and HAL-R pig adrenocortical cells in vitro. We also determined directly the accumulation of four different mRNAs encoding cholesterol side-chain cleavage cytochrome P450 (P450(scc)), 17alpha-hydroxylase cytochrome P450 (P450(17alpha)), 21-hydroxylase cytochrome P450 (P450(c21)) and 11beta-hydroxylase cytochrome P450 (P450(11beta)) in HAL-S pig adrenal cells and compared them to HAL-R pigs. A time- and dose-dependent increase in medium content of cortisol and cAMP was observed after ACTH treatment. 8-Br-cAMP also caused a time- and dose-dependent increase in cortisol production in the medium. Addition of ACTH or 8-Br-cAMP to HAL-S and HAL-R male Lanyu small-ear miniature pig adrenocortical cells increased cortisol production in a dose- and time-related manner. However, cells isolated from HAL-S pigs had a lower cortisol production in response to ACTH or 8-Br-cAMP compared to those from HAL-R pigs. Treatment of cultured cells with 8-Br-cAMP (0.5 mM) for 18 h resulted in a significant increase in P450(scc), P450(17alpha), P450(c21), and P450(11beta) mRNA levels. In the absence of 8-Br-cAMP, the four genes were expressed constitutively in both HAL-S and HAL-R pig adrenal cells. Densitometric scanning of the autoradiograph indicated that the relative amounts of P450(scc) and P450(17(alpha)) mRNAs in HAL-S pig adrenal cells were between 48% and 53% of those detected in HAL-R pig adrenal cells (P < 0.05). No difference in the amounts of P450(c21) and P450(11beta) was seen in HAL-S and HAL-R pig adrenal cells. Addition of 8-Br-cAMP (0.5 mM) resulted in a uniform increase in the levels of all four P450 mRNAs in both HAL-S and HAL-R pig adrenal cells. However, the amounts of P450(scc) mRNA in HAL-S pig adrenal cells were 67% (P < 0.05) of those measured in HAL-R pig adrenal cells, whereas the amounts of P450(17alpha ), P450(c21), and P450(11beta) mRNAs were similar in these cells. Our data suggest an HPA axis defect in HAL-S pigs at the adrenal level. This defect appears to be at the level of P450scc gene expression, which could be partially related to reduced cortisol production by ACTH stimulation.     

Comparative assessment of native,crossbred and exotic pigs during different seasons (winter,spring and summer) based on rhythmic changes in the levels of serum cortisol,lactate dehydrogenase levels and PBMC HSP70 mRNA expression pattern

The present study was conducted to ascertain the adaptive capability of pigs to different seasons based on changes in serum cortisol and lactate dehydrogenase (LDH) levels, and peripheral blood mononuclear cell (PBMC) heat shock protein 70 (HSP70) mRNA expression. Based on average THI, the seasons were classified as winter (November–February), spring (March–June), and summer (July–October). Hormone cortisol was found to be influenced by season (p < 0.01), age (p < 0.05), and genetics of the animal (p < 0.05). However, level of LDH was not influenced by either of these factors. HSP70 mRNA expression was higher in almost all age groups in crossbred and exotic pigs during summer in comparison to other seasons. Lower HSP70 gene expression was observed in almost all age groups of native pigs in comparison to crossbred and exotic during summer. In conclusion, native pigs were acclimatized for thermal stress in comparison to crossbred and exotic breeds of pigs. Also, the expression pattern of HSP70 gene is breed-specific, most likely due to variations in thermal tolerance and adaptation to different environmental conditions. Both serum cortisol and HSP70 gene may act as reliable biological markers for assessing the adaptive capabilities of pigs to different seasons.     

The influence of male contact on plasma cortisol concentrations in the prepubertal gilt

Large White X (Large White X Landrace) prepubertal gilts, 165 days of age, were fitted with indwelling venous catheters and housed in modified metabolism crates. After a period of acclimatization, frequent blood samples were taken at regular intervals before, during and after the 7 gilts were exposed to various degrees of contact with male pigs. The plasma samples were assayed for cortisol concentration using a competitive protein-binding radioassay. Significantly elevated concentrations of plasma cortisol (P less than 0.001) occurred only when full physical contact between the boar and the gilts was allowed. Boar exposure without full physical contact induced only minor changes in plasma cortisol concentrations of gilts. Plasma cortisol concentrations have been shown to constitute a reliable indicator of a stress response in pigs, and so the results of this study suggest that tactile stimulation from a male pig induces a stress response in the recipient prepubertal gilt. This stress response in the gilt may be involved in the stimulation of puberty onset by contact with a mature boar (i.e. the 'boar effect').     

Cortisol responses and social buffering: a study throughout the life span

The ability of specific adult females to moderate plasma cortisol responses throughout the life span was examined in male guinea pigs maintained in large mixed age/sex groups. At four critical life stages of social development (preweaning, periadolescent, sexually but not socially mature, and sexually and socially mature), the same male guinea pigs were exposed to the stressor of exposure to a novel environment for 4 h while either alone, with an unfamiliar adult female, or with a favored adult female, as based on objective criteria from behavioral observation at that life stage. In preweaning males (9-19 days of age), the favored female (biological mother), but not an unfamiliar female, reduced the cortisol response in the novel environment. In periadolescents (49-61 days), an unfamiliar female, but not the favored female, buffered the cortisol response. At the sexually but not socially mature stage (114-126 days), the cortisol response to novelty was depressed in all conditions, and not affected by either female. At the sexually and socially mature stage (270-330 days), the favored female, but not the unfamiliar female, moderated cortisol levels. These results corroborate previous findings in infants and full adults, demonstrate marked age-specific changes in the ability of females to buffer hypothalamic-pituitary-adrenal responses, and identify a heretofore undescribed period of cortisol response suppression in maturing male guinea pigs. The changing pattern of social buffering during the life span described here for the guinea pig might represent a more general pattern for males of other group-living mammals.     

Physiological indicators of stress and meat and carcass characteristics in tail bitten slaughter pigs

Background

Tail biting is a common welfare problem in pig production and in addition to being a sign of underlying welfare problems, tail biting reduces welfare in itself. The aim of this study was to evaluate the effects of tail biting on different pre and post mortem indicators of stress in slaughter pigs and on carcass and meat characteristics. A total of 12 tail bitten (TB) and 13 control (C) pigs from a farm with a long-term tail biting problem were selected for salivary cortisol analyses before and after transport to the slaughterhouse. After stunning, samples were taken for the analysis of serum cortisol, blood lactate, intestinal heat shock protein 70 (HSP70), and meat quality characteristics. In addition, body temperature immediately after and muscle temperature 35 min after stunning were measured, as well as lean meat percentage and carcass weight.

Results

TB pigs showed a lower cortisol response to the transport-induced stress than C pigs and also had a lower serum cortisol concentration after stunning. HSP70 content in the small intestine was higher in the TB pigs than in C pigs. TB pigs had a considerably lower carcass weight therefore produced a lower total amount of lean meat per carcass than C pigs.

Conclusions

This study suggests that prolonged or repeated stress in the form of tail biting causes a blunted stress response, possibly a sign of hypocortisolism. In addition, it underlines the importance of reducing tail biting, both from an animal welfare and an economic point-of-view.

     

Plasma adrenocorticotropic hormone and cortisol in pigs: effects of time of day on basal and stressor-altered concentrations

An initial study was conducted to establish the presence in plasma of diurnal rhythms of immunoreactive porcine adrenocorticotropic hormone (pACTH) and cortisol in castrated male pigs (barrows). Fourteen barrows with jugular catheters were bled at 6-hr intervals for 24 hr. Significant changes in plasma pACTH were evident with peak levels (61 +/- 6 pg/ml) at 0100-0700 hr and a trough (38 +/- 4 pg/ml) at 1900 hr. Changes (P less than 0.05) in plasma cortisol were also present in barrows with a peak (44 +/- 6 ng/ml) at 0700 hr and a trough (21 +/- 5 ng/ml) at 1900 hr. Plasma norepinephrine and epinephrine were measured at the same time intervals and did not differ among hours. In these unstressed pigs the ratio cortisol/log10pACTH at 0700 hr (25.3 +/- 3.0) was greater than the ratio at 1900 hr (12.9 +/- 2.7). Sequential blood samples were subsequently taken on four of the barrows 12 and 26 days later. Plasma pACTH was variable among pigs and did not differ among hours. Plasma cortisol on both dates was greater (P less than 0.05) in the morning (0100 or 0700 hr) than at 1900 hr. The ratio cortisol/log10pACTH at 0700 hr was repeatedly greater than at 1900 hr. A second study was conducted to determine whether plasma pACTH and cortisol responses to mild (32 degrees C for 2 hr) or strong (20-min restraint) stressors were dependent on the time of day of stressor application (0800 hr, AM; 1600 hr, PM). Response-associated parameters (maximum concentration, maximum incremental concentration, and integrated response) for pACTH and cortisol did not differ between AM and PM. However, a qualitative difference existed between the AM and PM plasma pACTH responses to restraint +32 degrees C wherein the AM response consisted of a single prolonged surge, and the PM response of an initial major peak followed by a second significant minor peak. A suggested explanation is that the initial 20-min restraint stressor potentiated the hypothalamic-hypophyseal response to 32 degrees C. These studies are the first direct measurements which suggest the presence of diurnal changes in plasma ACTH and cortisol in barrows. The studies also indicate for barrows an absence of diurnal changes in plasma epinephrine and norepinephrine. The responsiveness of the pituitary-adrenocortical axis to stressors did not exhibit quantitative diurnal changes at the time periods measured. However, it is hypothesized that the repeatable AM-PM difference in the ratio cortisol/log10ACTH reflects a diurnal change in adrenal responsiveness to ACTH in unstressed pigs.     

Enhanced intestinal synthesis of polyamines from proline in cortisol-treated piglets

This study was conducted to determine a role for cortisol in regulating intestinal ornithine decarboxylase (ODC) activity and to identify the metabolic sources of ornithine for intestinal polyamine synthesis in suckling pigs. Thirty-two 21-day-old suckling pigs were randomly assigned to one of four groups with eight animals each and received daily intramuscular injections of vehicle solution (sesame oil; control), hydrocortisone 21-acetate (HYD; 25 mg/kg body wt), RU-486 (10 mg/kg body wt, a potent blocker of glucocorticoid receptors), or HYD plus RU-486 for two consecutive days. At 29 days of age, pigs were killed for preparation of jejunal enterocytes. The cytosolic fraction was prepared for determining ODC activity. For metabolic studies, enterocytes were incubated for 45 min at 37 degrees C in 2 ml of Krebs-bicarbonate buffer (pH 7.4) containing 1 mM [U-(14)C]arginine, 1 mM [U-(14)C]ornithine, 1 mM [U-(14)C]glutamine, or 1 mM [U-(14)C]proline plus 1 mM glutamine. Cortisol administration increased intestinal ODC activity by 230%, polyamine (putrescine, spermidine, and spermine) synthesis from ornithine and proline by 75-180%, and intracellular polyamine concentrations by 45-83%. Polyamine synthesis from arginine was not detected in enterocytes of control pigs but was induced in cells of cortisol-treated pigs. There was no detectable synthesis of polyamines from glutamine in enterocytes of all groups of pigs. The stimulating effects of cortisol on intestinal ODC activity and polyamine synthesis were abolished by coadministration of RU-486. Our data indicate that an increase in plasma cortisol concentrations stimulates intestinal polyamine synthesis via a glucocorticoid receptor-mediated mechanism and that proline (an abundant amino acid in milk) is a major source of ornithine for intestinal polyamine synthesis in suckling neonates.     

Endogenous monoamine oxidase inhibitory activity and HPA activation in the pig

Previously we have shown that an increase in endogenous monoamine oxidase A inhibitory activity (MAO-AI), measured in human saliva, both precedes and predicts psychological stress-induced activation of the hypothalamic pituitary adrenal (HPA) axis, as determined by the cortisol response. We now report the relationship between endogenous MAO-AI and the cortisol response in the plasma of prepubertal pigs (n=5 or 6) under two experimental paradigms of HPA activation. In the first condition, pigs were physically restrained (snaring) for 15 minutes. Blood samples were taken from indwelling catheters at intervals before and after snaring (a sampling period of about 1 hour), and at the same time intervals on a separate day to provide baseline measures. Both cortisol concentration and percentage MAO-AI were determined in each plasma sample. There was a pronounced cortisol response on the snaring day (cortisol peaked 30 minutes after the start of the snaring). There was also a significant MAO-AI response to snaring which peaked 15 minutes after the start of the stress challenge. In the second experimental paradigm, bacterial endotoxin (LPS: 20microg/pig) was used to induce HPA activation and plasma cortisol and MAO-AI were determined. This time, however, the cortisol response was not preceded by any change in MAO-AI. We conclude that generation of MAO-AI, which is associated with HPA activation induced by psychological stress, is not a component of the pathways involved in immunological stimulation of the HPA axis.     

Effect of environmental enrichment and herbal compound supplementation on physiological stress indicators (chromogranin A,cortisol and tumour necrosis factor-α) in growing pigs

Stress response induces physiological, behavioural, immunological and biochemical changes that directly affect health and well-being. Provision of environmental enrichment and herbal compounds may reduce stress in current commercial pig husbandry systems. The aim of this study was to evaluate the effect of providing different environmental enrichment materials (EE) and a herbal compound (HC) on physiological indicators of acute and chronic stress in growing pigs (salivary cortisol and chromogranin A (CgA), hair cortisol and tumour necrosis factor-α (TNF-α)). Salivary cortisol and CgA have been reported as biomarkers basically of acute stress, whereas hair cortisol and TNF-α have been more related to chronic stress. For this purpose, eight groups of seven pigs each (14 pigs/treatment, 56 pigs in total) were used: (a) two EE groups, (b) two groups supplemented with HC, (c) two groups provided both with EE and HC and (d) two control groups. Samples of hair, saliva and blood were taken to measure cortisol (in hair and saliva), CgA (in saliva) and TNF-α (in blood) at three different times: before starting the experiment (T0), and after 1 (T1) or 2 months (T2) of providing the materials and herbal compound. No differences were found at T0 in salivary or hair cortisol, CgA or TNF-α, whilst at T2, the control group showed significant increased concentrations of CgA and hair cortisol, when compared with the rest of the treatments (P<0.001). These differences were significant at T1 only for CgA (P<0.001). Furthermore, an overall correlation was reported between hair cortisol and salivary CgA (r=0.48, P<0.001). These results support that providing enrichment material or an herbal compound may reduce stress in growing pigs. Furthermore, the results support that hair cortisol and CgA may be proper non-invasive tools to detect stress, specially associated with factors of chronic exposure.     

A cortisol surge mediates the enhanced polyamine synthesis in porcine enterocytes during weaning

This study was conducted to determine whether a cortisol surge mediates the enhanced expression of intestinal ornithine decarboxylase (ODC) in weanling pigs. Piglets were nursed by sows until 21 days of age, when 40 pigs were randomly assigned into one of four groups (10 animals/group). Group 1 continued to be fed by sows, whereas groups 2-4 were weaned to a corn and soybean meal-based diet. Weanling pigs received intramuscular injections of vehicle solvent (sesame oil), RU-486 (a potent blocker of glucocorticoid receptors; 10 mg/kg body wt), and metyrapone (an inhibitor of adrenal cortisol synthesis; 5 mg/kg body wt), respectively, 5 min before weaning and 24 and 72 h later. At 29 days of age, pigs were used to prepare jejunal enterocytes for ODC assay and metabolic studies. To determine polyamine (putrescine, spermidine, and spermine) synthesis, enterocytes were incubated for 45 min at 37 degrees C in 2 ml Krebs-bicarbonate buffer containing 1 mM [U-(14)C]arginine, 1 mM [U-(14)C]ornithine, 1 mM [U-(14)C]glutamine, or 1 mM [U-(14)C]proline plus 1 mM glutamine. Weaning increased intestinal ODC activity by 230% and polyamine synthesis from ornithine, arginine, and proline by 72-157%. Arginine was a quantitatively more important substrate than proline for intestinal polyamine synthesis in weaned pigs. Administration of RU-486 or metyrapone to weanling pigs prevented the increases in intestinal ODC activity and polyamine synthesis, reduced intracellular polyamine concentrations, and decreased villus heights and intestinal growth. Our results demonstrate an essential role for a cortisol surge in enhancing intestinal polyamine synthesis during weaning, which may be of physiological importance for intestinal adaptation and remodeling.     

Health and immune traits of Basque and Large White pigs housed in a conventional or enriched environment

Since decades, production traits such as growth rate, feed efficiency or body composition have been drastically increased in pigs by genetic selection. Whether this selection impacted animal robustness is still unclear. In this study, we compared Large White (LW) pigs, a breed submitted to intense genetic selection for production traits, and Basque (B) pigs, a local rustic breed, reared in two different housing environments (conventional v. enriched). Adaptation to housing conditions among each breed was evaluated at the level of endocrine and immune traits. These are known to be impacted by housing conditions and breed; however, the interaction effects between genotype and environment are less described. Animals (20 per breed and housing environment) entered the experiment at 35 kg of live weight. Levels of cortisol, acute-phase inflammatory proteins, immunoglobulins and hydrogen peroxide, blood formula, lymphocyte proliferation and in-vitro cytokine expression were measured at ∼115 kg of live weight. Animals were checked for skin injuries during the growing period. At slaughter, at the average live weight of 145 kg, carcasses were examined for pathological conditions of the respiratory tract. The major result was that the two breeds exhibited differences in response to the housing environment. Among the 24 sanitary, endocrine or immune traits investigated, the housing conditions affected eight variables in both breeds (salivary cortisol at 0700 and 1900 h, severity of pneumonia at slaughter) or only in B pigs (severe skin lesions) or LW pigs (salivary cortisol at 1500 h, granulocyte numbers and lymphocyte/granulocyte ratio and lymphocyte proliferation). These observations strengthen the hypothesis that selection for high meat production level might be associated with an increased susceptibility of animals to environmental stressors.     

Stress neuroendocrine profiles in five pig breeding lines and the relationship with carcass composition

Stress neuroendocrine systems (hypothalamic–pituitary–adrenal axis and sympathetic nervous system) were studied in 100 female pigs from each of the five main genetic lines used in Europe for pork production: Piétrain, Large White, Landrace, Duroc and Meishan. Levels of cortisol and catecholamines were measured in urine collected at the farm, after transportation to the slaughterhouse and the next morning before slaughter. With the exception of the Piétrain line that showed intermediate levels of cortisol despite its extreme leanness, a significant positive relationship was found between basal cortisol levels and fatness, both across and within (except in Piétrain and Duroc) lines. Basal cortisol levels were 2.46-fold higher in Meishan (20.46 ng/mg creatinine) than in Large White pigs (8.30 ng/mg creatinine), the two extreme breeds. Post-transportation levels were highest but proportional to basal levels, suggesting that the adrenal reactivity to adrenocorticotropic hormone is a major source of variability between lines. Levels of catecholamines were less variable between lines but correlated also with fatness, partlyviapartial correlations with cortisol levels. In serum collected at exsanguination, creatine kinase activity was correlated with muscularity across the five breeds. However, this was due to a much larger activity than expected in Piétrain pigs, although all animals were negative for the allele of the ryanodine receptor gene responsible for stress sensitivity. Serum glucose levels were inversely related to fatness. These data show that the differences between breeds or lines can be utilised by cross-breeding and that this can lead to changes in stress hormones and in turn to some degree of changes in carcass traits.     

The influence of a magnesium-rich marine extract on behaviour,salivary cortisol levels and skin lesions in growing pigs

Growing pigs can display undesirable behaviours, reflecting or causing poor welfare. Addition of magnesium (Mg) to the diet could reduce these, as Mg supplementation has been associated with improved coping ability in response to stress. This study examined the effect of supplementation with a Mg-rich marine extract-based product (Supplement) on the behaviour, skin and tail lesion scores and salivary cortisol concentrations of growing pigs. At weaning (28 days), 448 piglets were assigned to either Control or Supplement (0.05%) diets in single-sex groups of 14. Four weeks later (c. 17 kg), pigs were blocked according to weight and back test scores. Seven piglets from each pen were mixed with seven from another pen of the same sex and dietary treatment to yield the following groups: control male, Supplement male, control female and Supplement female (n = 4 of each). This marked the start of the 9-week experimental period. Instances of the following behaviours were recorded in each pen for 8 × 2 min periods 1 day/week: aggression (fight, head-knock and bite); harmful (tail-in-mouth, ear-chewing and belly-nosing); and sexual/mounting behaviour. Four focal pigs were selected from each pen, and their behaviour was continuously recorded for 2 × 5 min periods on the same day. Saliva was collected once per week at 1000 h by allowing pigs to chew on a cotton bud for c. 1 min. Salivary cortisol was analysed in duplicate by an enzyme immunoassay. Skin and tail lesions were scored according to severity 1 day/week. There were fewer aggressive incidents in Supplement pens (P < 0.01), and mounting behaviour (performed only by males) was almost three times lower in Supplement than in control pens (P < 0.01). However, there was no effect of Supplement on the incidence of each of the harmful behaviours. Behaviour of the focal pigs showed no treatment effect on the duration or incidence of aggressive behaviour. However, Supplement pigs spent less time performing harmful behaviours compared with control pigs (P < 0.001). Supplement had no effect on the occurrence or severity of tail-biting outbreaks or on tail lesion scores. However, Supplement females had lower skin lesion scores, in particular in the ears and shoulders (P < 0.01). Finally, Supplement pigs had lower salivary cortisol concentrations (P < 0.01). Mounting is a major welfare concern in uncastrated pigs, and therefore this represents an important welfare benefit of Supplement. Reduced salivary cortisol, in conjunction with reduced skin lesion scores in supplemented females, suggests that addition of a Mg-rich marine extract improved pig welfare in this system.     

Studies on the growth of the fetal guinea pig. Changes in plasma hormone concentration during normal and abnormal growth

The endocrine changes associated with fetal growth retardation caused by unilateral uterine artery ligation of guinea pigs at day 30 of pregnancy were studied. Plasma hormone levels in fetuses that, about 20 or 30 days later, were 35-50% of normal size were measured by radioimmunoassay. The small fetuses were severely hypoglycaemic and hypoinsulinaemic; both showing close correlation and relationship to the degree of growth retardation. Plasma thyroid and cortisol and concentrations were much lower than normal and that glucagon and androstenedione were much higher. Plasma growth hormone level appeared to be unaffected by growth retardation. The developmental changes in glucagon and thyroid hormone concentrations were consistent with a delay in the timing of prenatal events in growth-retarded fetuses. However the late cortisol rise, although somewhat blunted, still occurred at 58-60 in the small fetal guinea pigs.     

Pigs' aggressive temperament affects pre-slaughter mixing aggression, stress and meat quality

Pre-slaughter stress has a negative impact on animal welfare and on meat quality. Aggressive behaviour when pigs are mixed together for transportation to, or on arrival at, the abattoir is an important factor in pre-slaughter stress. Aggressiveness of pigs varies between individuals in the population, and this study investigated its effects on stress and meat quality at slaughter. We mixed pigs at a young age to identify individuals of high (H) or low (L) aggressive temperament using the previously validated approach of lesion scoring. To contrast extremes of social stress single-sex groups of eight pigs were mixed according to their aggressiveness in HH, HL or LL combinations or left unmixed (U) prior to transport and slaughter (n = 271). Each treatment was replicated in at least two groups in each of four slaughter batches. Mixing per se had little effect, but mixed groups composed of aggressive pigs (HH) had more carcass skin lesions and higher levels of plasma cortisol at slaughter and had loin muscle samples with higher pH at 24 h, and lower redness (a*) and yellowness (b*) compared to the other treatments. Females had higher levels of plasma cortisol at slaughter, a more rapid decline in pH post-slaughter and greater lean content of meat. Lactate and creatine kinase (CK) levels and meat pH were affected by the interaction of sex and treatment. Genetic factors, dam and sire line composition, and halothane locus (ryanodine receptor 1, RYR1) genotype, also affected a number of production and meat quality parameters as expected. Additionally, 'commercially normal' levels of social stress were studied in four further slaughter batches with no manipulation of group composition (n = 313). In these pigs, the proportion of unfamiliar pigs and group size of lairage groups explained limited variation in lesion scores at slaughter, but earlier aggressiveness did not. High numbers of skin lesions on the carcass were associated with high levels of cortisol and lactate and low glucose at slaughter, but not with meat quality measures. When stress and meat quality measures were compared for all pigs, high lactate was associated with low early pH and high drip loss, while high cortisol and CK were associated with high pH at 24 h and changes in meat colour. In conclusion, mixing pigs of above average aggressiveness resulted in greater aggression and stress, and changes in meat quality parameters, consistent with the effects of pre-slaughter stress on muscle chemistry.