Breeding for robustness: the role of cortisol

Events with Different Emotional Valence Affect the Eye's Lacrimal Caruncle Temperature Changes in Sheep

Infrared thermography (IRT) has been recently applied to measure lacrimal caruncle temperature non-invasively since this region is related to the sympathetic response, and it seems a promising technique that is able to infer negative emotions in sheep (e.g., fear). However, the scientific literature so far is limited in understanding whether a caruncle's temperature changes also in response to positive emotional states in sheep. Through classical conditioning, we aimed to assess how a positive or a negative event affects the physiological (lacrimal caruncle temperature measured with IRT and cortisol levels) and behavioral responses of sheep (ear position). Fourteen ewes from the same flock were randomly assigned to two treatment groups: positive (n = 7) and negative (n = 7). Each group was then trained through classical conditioning to associate a neutral auditory (ring bell) stimulus to an oncoming event: for the positive group, the presence of a food reward (maize grains), while for the negative one, the opening of an umbrella. After three weeks of training, before (at rest) and after (post-treatment), lacrimal caruncle temperature was non-invasively measured via IRT, and saliva samples were gently collected to measure cortisol levels. During treatment, sheep behavior was videorecorded and then analyzed using a focal animal sampling technique. At rest, the eye's lacrimal caruncle temperature was similar in both groups, while post-treatment, a significant increase was shown only in the negative group (t-test; p = 0.017). In the anticipation phase, sheep in the positive group kept their ears forward longer compared to those in the negative one (Mann-Whitney; p < 0.014), 8.3 ± 2.1 s and 5.2 ± 4.2 s, respectively. The behavioral response observed reflects a learnt association between a neutral stimulus and events with different emotional valence. Cortisol concentration slightly increased in both groups post-treatment. Our results confirm that IRT is a non-invasive technique that can be useful when applied to assess how positive and negative events may affect the physiological response in sheep.

Effect of dietary oregano essential oil and milk replacer on physiological status and immunological responses of pre- and post-weaned Ghoongroo piglets

Ghoongroo pigs have good adaptability in a low input production system with high prolificacy. The present study was conducted on pre-and post-weaned Ghoongroo piglets from 2-3 days to 12 weeks of age to evaluate the effect of a milk replacer and oregano essential oil (EO) on growth, physiological and immunological responses. Thirty six piglets were randomly divided into three groups. The control group (n = 12) was allowed to suck mother's milk. Second group piglets were provided milk replacer (MR) and piglets of the third group were provided milk replacer along with oregano EO at 500 mg/kg diet. After weaning, piglets were provided standard concentrate diets. The results showed that the body weight in MR and MR + EO groups were significantly higher compared with the control. The MR + EO group had better intestinal microbiota, greater nonspecific innate immunity with the phagocytosis efficacy of neutrophils, lower cortisol concentration and more stable thyroid hormones than the other groups. The better haematological status supported the rapid organ development and improved intestinal health status in both the experimental groups. In conclusion, milk replacer, especially with the inclusion of oregano EO, can lower weaning stress, enhance nonspecific immunity and improve growth and health status of piglets.

Temperature and humidity index (THI) affects salivary cortisol (HC) and dehydroepiandrosterone (DHEA) concentrations in growing bulls following stress generated by performance test procedures

The hypothalamus-pituitary-adrenal axis response to a challenge was proposed for genetic selection of robust and resilient animals. As ACTH (adrenocorticotropic hormone) test and hormone measurements in blood may result impractical, it may be useful to measure salivary hormones in response to natural stressors, after an accurate biological validation, to control factors that could contribute to the response. We evaluated whether animal handling during performance test affects salivary HC and DHEA secretion and could be used for selection. We tested the effects of habituation to repeated handling and THI as putative bias. Bull calves (N = 273) undergoing performance test were sampled at 8-9 and 11-13 months (N = 101), 8-9 months (N = 131), or 11-13 months (N = 41). On each test day (D0), calves were isolated, conducted to a squeeze chute and immobilized for 6 min. Saliva samples were collected in the morning after feed administration (T0), and after 6 min immobilization in the squeeze chute (T1) for HC and DHEA measurement. Environmental temperature and relative humidity were recorded every hour from 1:00 h to 24:00 h during the 6 days before the performance test and on D0. Salivary HC and DHEA concentrations were higher in T1 (p < 0.01), although a clear individual positive response to handling could be observed in less than 10% of subjects. The mixed model revealed: (i) HC and HC/DHEA were higher in Young bulls (p < 0.05). (ii) The time of T0 sample collection significantly affected DHEA (p < 0.01) and HC/DHEA (p < 0.05). (iii) THI affected both steroids (p < 0.001) but not HC/DHEA. Spearman correlations suggested that THI weakly affected salivary HC at T0 only (ρ = 0.150, p < 0.01), while moderate statistically significant correlations were found between DHEA and THI at T0 (ρ = 0.316, p < 0.001), and T1 (ρ = 0.353, p < 0.001). Salivary HC and DHEA in response to handling procedures might identify subpopulations of subjects with sensitive HPA axis. Habituation to repeated handling played a role, as the hormone response was lower in older animals. Chronic exposure to high THI had a minor effect on salivary HC visible at T0. A more intense THI effect was observed on salivary DHEA concentrations at both T0 and T1, which should be worth of further investigations.

Comparative analysis of whole blood transcriptomics between European and local Caribbean pigs in response to feed restriction in a tropical climate

BACKGROUND

Feed restriction occurs frequently during pig growth, either due to economic reasons or stressful environmental conditions. Local breeds are suggested to have better tolerance to periods of feed restriction. However, the mechanisms underlying the response to feed restriction in different breeds is largely unknown. The aims of the present study were (1) to compare the blood transcriptome profile in response to feed restriction and refeeding of two contrasted breeds, Large White (LW), which has been selected for high performance, and Creole (CR), which is adapted to tropical conditions, and (2) to investigate the effect of a moderate feed restriction and refeeding on whole blood transcriptome. Analysis of blood transcriptome allows to study the response to feed restriction and refeeding in a dynamic way. RNAseq was performed on blood samples of growing LW and CR pigs at two time points: after 3 weeks of feed restriction and after 3 weeks of refeeding. The data was compared with samples from control animals offered the same diet on an ad libitum basis throughout the whole experiment.

RESULTS

In terms of performance (body weight and feed efficiency), CR pigs were less impacted by feed restriction than LW. The transcriptional response to feed restriction and refeeding between CR and LW was contrasted both in terms of number of DEGs and enriched pathways. CR demonstrated a stronger transcriptional response to feed restriction whereas LW had a stronger response to refeeding. Differences in the transcriptional response to feed restriction between CR and LW were related to cell stress response (Aldosterone Signalling, Protein ubiquitination, Unfolded Protein Signalling) whereas after refeeding, differences were linked to thermogenesis, metabolic pathways and cell proliferation (p38 MAPK, ERK/MAPK pathway). In both breeds, transcriptional changes related to the immune response were found after restriction and refeeding.

CONCLUSIONS

Altogether, the present study indicates that blood transcriptomics can be a useful tool to study differential genetic response to feed restriction in a dynamic way. The results indicate a differential response of blood gene expression to feed restriction and refeeding between breeds, affecting biological pathways that are in accordance with performance and thermoregulatory results.

Genetic parameters of feather corticosterone and fault bars and correlations with production traits in turkeys (Meleagris gallopavo)

Robustness can refer to an animal's ability to overcome perturbations. Intense selection for production traits in livestock has resulted in reduced robustness which has negative implications for livability as well as production. There is increasing emphasis on improving robustness through poultry breeding, which may involve identifying novel phenotypes that could be used in selection strategies. The hypothalamic-pituitary-adrenal (HPA) axis and associated hormones (e.g., corticosterone) participate in many metabolic processes that are related to robustness. Corticosterone can be measured non-invasively in feathers (FCORT) and reflects the average HPA axis activity over the feather growing period, however measurement is expensive and time consuming. Fault bars are visible feather deformities that may be related to HPA axis activity and may be a more feasible indicator trait. In this study, we estimated variance components for FCORT and fault bars in a population of purebred turkeys as well as their genetic and partial phenotypic correlations with other economically relevant traits including growth and efficiency, carcass yield, and meat quality. The estimated heritability for FCORT was 0.21 ± 0.07 and for the fault bar traits (presence, incidence, severity, and index) estimates ranged from 0.09 to 0.24. The genetic correlation of FCORT with breast weight, breast meat yield, fillet weight, and ultimate pH were estimated at -0.34 ± 0.21, -0.45 ± 0.23, -0.33 ± 0.24, and 0.32 ± 0.24, respectively. The phenotypic correlations of FCORT with breast weight, breast meat yield, fillet weight, drum weight, and walking ability were -0.16, -0.23, -0.18, 0.17, and 0.21, respectively. Some fault bar traits showed similar genetic correlations with breast weight, breast meat yield, and walking ability but the magnitude was lower than those with FCORT. While the dataset is limited and results should be interpreted with caution, this study indicates that selection for traits related to HPA axis activity is possible in domestic turkeys. Further research should focus on investigating the association of these traits with other robustness-related traits and how to potentially implement these traits in turkey breeding.

Intra- and Inter-sample Variation in Wool Cortisol Concentrations of Australian Merino Lambs Between Twice or Single Shorn Ewes

Stress in Merino sheep can cause a reduction in the quantity and quality of fine wool production. Furthermore, it has been found that environmental stress during pregnancy can negatively affect the wool follicles of the developing fetus. This study was part of a larger field investigation on the effects maternal shearing frequency on sheep reproductive and productivity outcomes. For this study, we investigated the intra- and inter- sample variation in wool cortisol levels of weaner lambs. We conducted two experiments, the first was to determine the intra- and inter- sample variation in wool samples taken from the topknot of weaned lambs, and the other aim was to determine any difference between maternal shearing treatment (single or twice shearing) on absolute wool cortisol levels of weaned lambs. In the first experiment, topknot wool was collected from 10 lambs, and each sample was further divided into four subsamples, leading to a total of 40 wool subsamples. For the second experiment, we collected the topknot from the 23 lambs produced by the shearing frequency treatment ewes (once or twice shorn). The samples were then extracted and analyzed using a commercially available cortisol enzyme-immunoassay in order to determine the concentration of cortisol in each of the samples. Statistical analysis for the first experiment showed that there was no significant difference between the subsamples of each topknot wool sample taken from each lamb (p = 0.39), but there was a statistical difference between samples (p &lt; 0.001), which was to be expected. In the second experiment, there was a significant difference between the lambs born to the one shearing and two shearing treatments (p = 0.033), with the lambs of the twice sheared ewes having higher average wool cortisol levels [2.304 ± 0.497 ng/g (SE); n = 14] than the ones born to once shorn ewes [1.188 ± 0.114 ng/g (SE), n = 8]. This study confirms that the topknot wool sampling can be a reliable method adapted by researchers for wool hormonal studies in lambs. Second, ewes shorn mid-pregnancy gave birth to lambs with higher cortisol concentrations than ewes that remained unshorn during pregnancy. This result warrants further investigation in a controlled study to determine if maternal access to nutrition (feed and water) may impact on the HPA-axis of lambs.

Serum Cortisol and Its Correlation with Leucocyte Profile and Circulating Lipids in Donkeys (Equus asinus)

The values for basal serum cortisol concentrations of horses are available in many studies. However, there are limited data about serum cortisol in donkeys. The present study aimed to determine the baseline values for serum cortisol, to evaluate the influence of age and pregnancy on its levels, and to correlate its values with leucocyte profile, serum cholesterol, and triglycerides. Serum samples were collected from 97 healthy donkeys. Cortisol was analyzed by chemo-luminescent assay. The median and the 2.5th and 97.5th percentiles of serum cortisol measured and calculated in all donkeys were 5.64, 3.40, and 10.54 µg/dL, respectively. Females (n.91) were divided into three groups: Group A (young), Group B (adult), and Group C (pregnant at the 9th−11th months). The effect of age and physiological status was investigated by the Mann−Whitney test. Group C showed significantly higher levels than Group B (p < 0.05). Significant correlations were found in Group B with monocytes (r = 0.37, p < 0.01) and triglycerides (r = 0.30, p < 0.05), and in Group C with monocytes (r = 0.79, p < 0.01), basophils (r = 0.6, p < 0.05), and neutrophil/lymphocyte ratio (r = −0.63, p < 0.05). Higher cortisol values related to late pregnancy are also found in this species. These preliminary results provide evidence for a relationship between cortisol and the immune system as well as cortisol and lipid metabolism modulated by age and pregnancy when parameters are within normal values.

Plasticity of feeding behaviour traits in response to production environment (temperate vs. tropical) in group-housed growing pigs

Heat stress affects pig metabolism, health and welfare, resulting in reduced growth and important economic losses. The present experiment aimed to evaluate the effects of two climatic environments [temperate (TEMP) vs. tropical humid (TROP)] on feeding behaviour in growing pigs. The feeding behaviour traits were measured with automated feeders and included: daily feed intake, daily eating time, feeding rate, daily number of meals, feed intake per meal, and feeding time per meal. Pigs came from a backcross population between Large White (LW, heat sensitive) and Creole (CR, heat tolerant) pigs. The same 10 F1 LW × CR boars (sire families [SF]) were mated with related LW sows in each environment. Feeding behaviour was recorded for a total of 1,296 pigs (n = 634 pigs for TEMP and n = 662 pigs for TROP) between 11 and 23 weeks of age. Growth performance and thermoregulatory responses (rectal and skin temperatures) were also measured. Results show that TROP conditions affect feeding behaviour traits: animals had more meals per day but these meals were smaller both in duration and in size, resulting in lower daily feed intake and less time eating per day. Significant SF by environment (GxE) interactions were found for all feeding behaviour traits. When SF were distributed into robust and sensitive groups (previously defined according to performance and thermoregulatory traits), results showed group by environment interactions for all feeding traits, except meal frequency. Moreover, a significant difference in feeding rate between robust and sensitive group was detected in TEMP, suggesting that feeding rate may be a good candidate to evaluate heat tolerance.

The Genetics of Thermoregulation in Pigs: A Review

Heat stress (HS) affects pig performance, health and welfare, resulting in a financial burden to the pig industry. Pigs have a limited number of functional sweat glands and their thermoregulatory mechanisms used to maintain body temperature, are challenged by HS to maintain body temperature. The genetic selection of genotypes tolerant to HS is a promising long-term (adaptation) option that could be combined with other measures at the production system level. This review summarizes the current knowledge on the genetics of thermoregulation in pigs. It also discusses the different phenotypes that can be used in genetic studies, as well as the variability in thermoregulation between pig breeds and the inheritance of traits related to thermoregulation. This review also considers on-going challenges to face for improving heat tolerance in pigs.

Long term genetic selection for reproductive success affects neonatal lamb vitality across cold stress conditions

Adverse weather conditions are important contributors to mortality in new-born lambs. Previous studies have shown variation between lambs in their ability to cope with circumstances of cold stress, and genetic selection could be a viable option for improving animal robustness. The Elsenburg Merino flock was divergently selected on number of lambs weaned (NLW). This resulted in divergent responses in reproduction and lamb survival. This study evaluated lamb vitality and mortality of positively selected H-Line relative to the negatively selected L-Line in response to cold stress. Traits included lamb rectal temperature (RT), surface temperature (ST), shiver score (SS), lamb vigor score (LVS), breaths per minute (BPM), mortality to three days of age (M3) and to weaning (TM). Cold stress was described by a chill index derived from daily rainfall, wind speed and ambient temperature, and represented as the mean of the one (CI), two (CI-2) or three (CI-3) days since parturition. Overall, H-Line lambs had a higher neonatal RT and were less likely to succumb than L-Line contemporaries. In a significant (P < 0.05) interaction, the predicted RT of L-Line showed a non-linear decline with increased levels of CI-2, while H-Line lambs better maintained their core temperature. M3 was also affected by a significant interaction between CI-3 and selection line, further suggesting that observed lower mortality rates in the H-Line depends on H-Line lambs' improved ability to cope with stressful environments. Long term selection for NLW in the H-Line led to improvements in both adaptations associated with lower lamb losses. The continued recording of viability traits to produce larger datasets amenable to genetic analysis is recommended, specifically for rectal temperature.

Differential haptoglobin responsiveness to a Mannheimia haemolytica challenge altered immunologic, physiologic, and behavior responses in beef steers

Indicator traits associated with disease resiliency would be useful to improve the health and welfare of feedlot cattle. A post hoc analysis of data collected previously (Kayser et al., 2019a) was conducted to investigate differences in immunologic, physiologic, and behavioral responses of steers (N = 36, initial BW = 386 ± 24 kg) that had differential haptoglobin (HPT) responses to an experimentally induced challenge with Mannheimia haemolytica (MH). Rumen temperature, DMI, and feeding behavior data were collected continuously, and serial blood samples were collected following the MH challenge. Retrospectively, it was determined that 9 of the 18 MH-challenged steers mounted a minimal HPT response, despite having similar leukocyte and temperature responses to other MH-challenged steers with a greater HPT response. Our objective was to examine differences in behavioral and physiological responses between MH-challenged HPT responsive (RES; n = 9), MH-challenged HPT nonresponsive (NON; n = 9), and phosphate-buffered saline-inoculated controls (CON; n = 18). Additionally, 1H NMR analysis was conducted to determine whether the HPT-responsive phenotype affected serum metabolite profiles. The RES steers had lesser (P < 0.05) cortisol concentrations than NON and CON steers. The magnitude of the increases in neutrophil concentrations and rumen temperature, and the reduction in DMI following the MH challenge were greatest (P < 0.05) in RES steers. Univariate analysis of serum metabolites indicated differences between RES, NON, and CON steers following the MH challenge; however, multivariate analysis revealed no difference between HPT-responsive phenotypes. Prior to the MH challenge, RES steers had longer (P < 0.05) head down and bunk visit durations, slower eating rates (P < 0.01) and greater (P < 0.05) daily variances in bunk visit frequency and head down duration compared with NON steers, suggesting that feeding behavior patterns were associated with the HPT-responsive phenotype. During the 28-d postchallenge period, RES steers had decreased (P < 0.05) final BW, tended (P = 0.06) to have lesser DMI, and had greater (P < 0.05) daily variances in head down and bunk visit durations compared with NON steers, which may have been attributed to their greater acute-phase protein response to the MH challenge. These results indicate that the HPT-responsive phenotype affected feeding behavior patterns and may be associated with disease resiliency in beef cattle.

Large-Scale Phenotyping of Livestock Welfare in Commercial Production Systems: A New Frontier in Animal Breeding

Genomic breeding programs have been paramount in improving the rates of genetic progress of productive efficiency traits in livestock. Such improvement has been accompanied by the intensification of production systems, use of a wider range of precision technologies in routine management practices, and high-throughput phenotyping. Simultaneously, a greater public awareness of animal welfare has influenced livestock producers to place more emphasis on welfare relative to production traits. Therefore, management practices and breeding technologies in livestock have been developed in recent years to enhance animal welfare. In particular, genomic selection can be used to improve livestock social behavior, resilience to disease and other stress factors, and ease habituation to production system changes. The main requirements for including novel behavioral and welfare traits in genomic breeding schemes are: (1) to identify traits that represent the biological mechanisms of the industry breeding goals; (2) the availability of individual phenotypic records measured on a large number of animals (ideally with genomic information); (3) the derived traits are heritable, biologically meaningful, repeatable, and (ideally) not highly correlated with other traits already included in the selection indexes; and (4) genomic information is available for a large number of individuals (or genetically close individuals) with phenotypic records. In this review, we (1) describe a potential route for development of novel welfare indicator traits (using ideal phenotypes) for both genetic and genomic selection schemes; (2) summarize key indicator variables of livestock behavior and welfare, including a detailed assessment of thermal stress in livestock; (3) describe the primary statistical and bioinformatic methods available for large-scale data analyses of animal welfare; and (4) identify major advancements, challenges, and opportunities to generate high-throughput and large-scale datasets to enable genetic and genomic selection for improved welfare in livestock. A wide variety of novel welfare indicator traits can be derived from information captured by modern technology such as sensors, automatic feeding systems, milking robots, activity monitors, video cameras, and indirect biomarkers at the cellular and physiological levels. The development of novel traits coupled with genomic selection schemes for improved welfare in livestock can be feasible and optimized based on recently developed (or developing) technologies. Efficient implementation of genetic and genomic selection for improved animal welfare also requires the integration of a multitude of scientific fields such as cell and molecular biology, neuroscience, immunology, stress physiology, computer science, engineering, quantitative genomics, and bioinformatics.

The ACTH challenge and its repeatability in fattening bulls-influences of physiological state, challenge time standardization, and horn status

Adrenocorticotropic hormone (ACTH) challenges are frequently performed in repetition when evaluating stress or welfare in animals. To our knowledge, the repeatability of ACTH challenges in cattle, although fundamental to further studies of this type, has not yet been the subject of research. Therefore, the objective of this study was to evaluate the repeatability of ACTH challenges in fattening bulls of different horn status. Eight-one bulls were subjected to 3 consecutive ACTH challenges. The first challenge (C1) was performed in calves aged 1.5 mo. Subsequently, animals were characterized as high or low cortisol responders and either disbudded or left with horns. They were then assigned to 1 of 3 rearing groups: a horned group (H+), a disbudded group (H-), and a mixed group (M; 50% horned and 50% disbudded), with each group containing an equal number of high and low responders. The second ACTH challenge (C2) was performed at the age of 11 mo. Time of day (TOD) of challenge was either fixed (ST = same TOD) or alternated (AT = alternate TOD) between C1 and C2. The third ACTH challenge (C3) was performed 7 d after and at the same TOD as C2. Saliva samples were taken 60 and 30 min before and 30, 60, 90, 120, and 150 min after each intravenous ACTH injection. The area under the curve (AUC) was calculated with respect to both ground (AUC_G) and to increase (AUC_I). The AUC_I increased markedly between C1 and C2 (P < 0.05) in ST bulls, and no effects were observed for AUC_G between C1 and C2 in ST or AT bulls, nor for any AUC between C2 and C3 (P > 0.1). The overall repeatability of AUC_G and AUC_I between C1 and C2, reflecting the repeatability between 2 different physiological states, was poor and moderate, respectively, for ST bulls (AUC_G: r = 0.24, P > 0.1, intraclass correlation coefficient (ICC) = 0.21; AUC_I: r = 0.48, P < 0.01, ICC = 0.41) and lacked in AT bulls (AUC_G: r = 0.07, P > 0.1; ICC = 0.03; AUC_I: r = 0.08, P > 0.1, ICC = 0.06). The repeatability of AUC_G and AUC_I between C2 and C3, reflecting the repeatability within the same physiological state, was moderate (AUC_G: r = 0.59, P < 0.001; ICC = 0.53; AUC_I: r = 0.58, P < 0.001, ICC = 0.52). Assignment to high and low responder groups based on peak cortisol concentration in C1 did not persist over time. H+ bulls showed higher AUC_I in C2 and C3 (P < 0.1 and P < 0.05, respectively) than H- bulls. The M group differed from the H- group only in C3 (P < 0.05). Thus, the effect of horn status on ACTH challenges needs further investigation. In conclusion, our results report poor repeatability of the cortisol response to ACTH challenges for challenges performed in different physiological states and moderate repeatability for challenges performed within the same physiological state. Moreover, they point out the importance of standardization of TOD when performing repeated ACTH challenge.

Prospects for sustainability of pig production in relation to climate change and novel feed resources

Pig production systems provide multiple benefits to humans. However, the global increase in meat consumption has profound consequences for our earth. This perspective describes two alternative scenarios for improving the sustainability of future pig production systems. The first scenario is a high input-high output system based on sustainable intensification, maximizing animal protein production efficiency on a limited land surface at the same time as minimizing environmental impacts. The second scenario is a reduced input-reduced output system based on selecting animals that are more robust to climate change and are better adapted to transform low quality feed (local feeds, feedstuff co-products, food waste) into meat. However, in contrast to the first scenario, the latter scenario results in reduced predicted yields, reduced production efficiency and possibly increased costs to the consumer. National evaluation of the availability of local feed and feedstuff co-product alternatives, determination of limits to feed sourced from international markets, available land for crop and livestock production, desired production levels, and a willingness to politically enforce policies through subsidies and/or penalties are some of the considerations to combine these two scenarios. Given future novel sustainable alternatives to livestock animal protein, it may become reasonable to move towards an added general premium price on 'protein from livestock animals' to the benefit of promoting higher incomes to farmers at the same time as covering the extra costs of, politically enforced, welfare of livestock animals in sustainable production systems. © 2020 The Authors. Journal of The Science of Food and Agriculture published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.

Effects of divergent selection upon adrenocortical activity on immune traits in pig

Background

The sustainability of farming and animal welfare requires the reconsideration of current selection schemes. In particular, implementation of new selection criteria related to animal health and welfare should help to produce more robust animals and to reduce anti-microbial use. The hypothalamo-pituitary-adrenocortical (HPA) axis plays a major role in metabolic regulation and adaptation processes and its activity is strongly influenced by genetic factors. A positive association between HPA axis activity and robustness was recently described. To explore whether selecting pigs upon HPA axis activity could increase their robustness, a divergent selection experiment was carried out in the Large White pig breed. This allowed the generation of low (HPA^lo) and high (HPA^hi) responders to adrenocorticotropic hormone administration.

Results

In this study, we compared 23 hematologic and immune parameters of 6-week-old, HPA^lo and HPA^hi piglets and analysed their response to a low dose of lipopolysaccharide (LPS) two weeks later. At six weeks of age, HPA^hi piglets displayed greater red blood cell and leucocyte number including CD8α⁺ γδ cells, cytotoxic T lymphocytes, naive T helper (Th) cells and B lymphocytes as compared to HPA^lo individuals. The ability of blood cells to secrete TNFα in response to LPS ex vivo was higher for HPA^hi pigs. At week eight, the inflammatory response to the LPS in vivo challenge was poorly affected by the HPA axis activity.

Conclusions

Divergent selection upon HPA axis activity modulated hematologic and immune parameters in 6-week-old pigs, which may confer an advantage to HPA^hi pigs at weaning. However, HPA^lo and HPA^hi piglets did not exhibit major differences in the parameters analysed two weeks later, i. e. in 8-week-old pigs. In conclusion, chronic exposure to high cortisol levels in HPA^hi pigs does not negatively impact immunity.

Electronic supplementary material

The online version of this article (10.1186/s12917-019-1809-9) contains supplementary material, which is available to authorized users.

Methodologies for Assessing Disease Tolerance in Pigs

Features of intensive farming can seriously threaten pig homeostasis, well-being and productivity. Disease tolerance of an organism is the adaptive ability in preserving homeostasis and at the same time limiting the detrimental impact that infection can inflict on its health and performance without affecting pathogen burden per se. While disease resistance (DRs) can be assessed measuring appropriately the pathogen burden within the host, the tolerance cannot be quantified easily. Indeed, it requires the assessment of the changes in performance as well as the changes in pathogen burden. In this paper, special attention is given to criteria required to standardize methodologies for assessing disease tolerance (DT) in respect of infectious diseases in pigs. The concept is applied to different areas of expertise and specific examples are given. The basic physiological mechanisms of DT are reviewed. Disease tolerance pathways, genetics of the tolerance-related traits, stress and disease tolerance, and role of metabolic stress in DT are described. In addition, methodologies based on monitoring of growth and reproductive performance, welfare, emotional affective states, sickness behavior for assessment of disease tolerance, and methodologies based on the relationship between environmental challenges and disease tolerance are considered. Automated Precision Livestock Farming technologies available for monitoring performance, health and welfare-related measures in pig farms, and their limitations regarding DT in pigs are also presented. Since defining standardized methodologies for assessing DT is a serious challenge for biologists, animal scientists and veterinarians, this work should contribute to improvement of health, welfare and production in pigs.

Invited review: Phenotyping strategies and quantitative-genetic background of resistance, tolerance and resilience associated traits in dairy cattle

In dairy cattle, resistance, tolerance and resilience refer to the adaptation ability to a broad range of environmental conditions, implying stable performances (e.g. production level, fertility status) independent from disease or infection pressure. All three mechanisms resistance, tolerance and resilience contribute to overall robustness, implying the evaluation of phenotyping and breeding strategies for improved robustness in dairy cattle populations. Classically, breeding approaches on improved robustness rely on simple production traits, in combination with detailed environmental descriptors and enhanced statistical modelling to infer possible genotype by environment interactions. In this regard, innovative environmental descriptors were heat stress indicators, and statistical modelling focussed on random regression or reaction norm methodology. A robust animal has high breeding values over a broad spectra of environmental levels. During the last years, direct health traits were included into selection indices, implying advances in genetic evaluations for traits being linked to resistance or tolerance against infectious and non-infectious diseases. Up to now, genetic evaluation for health traits is primarily based on subjectively measured producer-recorded data, with disease trait heritabilities in a low-to-moderate range. Thus, it is imperative to identify objectively measurable phenotypes as suitable biomarkers. New technologies (e.g. mid-infrared spectrometry) offer possibilities to determine potential biomarkers via laboratory analyses. Novel biomarkers include measurable physiological traits (e.g. serum metabolites, hormone levels) as indicators for a current infection, or the host's reaction to environmental stressors. The rumen microbiome composition is proposed as a biomarker to detect interactions between host genotype and environmental effects. The understanding of host genetic variation in disease resistance and individual expression of robustness encourages analyses on the underlying immune response (IR) system. Recent advances have been made in order to infer the genetic background of IR traits and cows immunological competence in relation to functional and production traits. Thus, a last aspect of this review addresses the genetic background and current state of genetic control for resistance to economically relevant infectious and non-infectious dairy cattle diseases by considering immune-related factors.

Cortisol advantage of neighbouring the opposite sex in utero

Population sex ratios naturally fluctuate around equality. It is argued that the production of an equal number of male and female offspring by individual parents should be favoured by selection, if all costs and benefits are equal. Theoretically, an even sex ratio should yield the highest probability for a fetus to be adjacent to a fetus of the opposite sex in utero. This may cause developmental costs or benefits that have been overlooked. We examined the physiological and developmental parameters associated with in utero sex ratios in the nutria (Myocastor coypus), an invasive wildlife species with a strong reproductive output. Using hair testing, we found that litters with even sex ratios had the highest average cortisol levels. Fetuses neighbouring the opposite sex exhibited longer trunks than those neighbouring the same sex, which might imply better lung development. Our results are the first, to our knowledge, to link intra-utero sex ratios and fetal cortisol and suggest that fetal cortisol might be a mechanism by which even sex ratios are maintained via developmental advantages.

Effects of Diet and Genetics on Growth Performance of Pigs in Response to Repeated Exposure to Heat Stress

Heat stress (HS) is one of the costliest issues in the U.S. pork industry. Aims of the present study were to determine the consequences of repeated exposure to HS on growth performance, and the effects of a high fiber diet, the genetic potential for high lean tissue accretion, and the genetic potential for residual feed intake (RFI) on resilience to HS. Barrows (n = 97) from three genetic lines (commercial, high RFI, low RFI) where subjected three times to a 4-day HS treatment (HS1, HS2, and HS3) which was preceded by a 9-day neutral (TN) adaptation period (TN1) and alternated by 7-day periods of neutral temperatures (TN2, TN3, and TN4). Body weight gain (BWG), feed intake (FI), feed conversion efficiency (FCE), RFI, and the drop in BWG and FI between TN and HS were estimated for each period, and slaughter traits were measured at the end of TN4. Commercial pigs had lower FI when fed a high fiber diet compared to a regular diet (2.70 ± 0.08 vs. 2.96 ± 0.08 kg/d; P < 0.05), while no differences were found for BWG, RFI or FCE. HS reduced FI, BWG, and FCE, increased RFI, and resulted in leaner pigs that generate smaller carcasses at slaughter. In TN, commercial pigs grew faster than the low and high RFI pigs (1.22 ± 0.06 vs. 0.720 ± 0.05 and 0.657 ± 0.07; P < 0.001) but growth rates were not significantly different between the lines during HS. Growth rates for the low RFI and high RFI pigs were similar both during TN and during HS. Pigs of interest for genetic improvement are those that are able to maintain growth rates during HS. Our results show that response in growth to HS was repeatable over subsequent 4-d HS cycles, which suggests the potential for including this response in the breeding index. The best performing animals during HS are likely those that are not highly superior for growth in TN.

Glucocorticoid receptor number and affinity differ between peripheral blood mononuclear cells and granulocytes in domestic pigs

The aim of the present study was to characterize the number and affinity of glucocorticoid receptors (GR) in peripheral blood mononuclear cells (PBMC) and granulocytes of domestic pigs because glucocorticoid signaling is considered important for animal health and welfare. To investigate GR binding characteristics in intact porcine immune cells, blood samples of 6 castrated male pigs were collected via indwelling vein catheters. Porcine PBMC and granulocytes were isolated using two-layer density gradients, followed by radioligand binding assays to determine the number of GR sites per cell and the dissociation constant K_d as a measure for GR binding affinity. The present study revealed a greater number of GR sites per cell (P = 0.039) in PBMC (mean ± SEM: 1,953 ± 207 sites/cell) compared to granulocytes (1,561 ± 159 sites/cell) in domestic pigs. Furthermore, porcine PBMC had a higher GR binding affinity than porcine granulocytes (P = 0.003) as the dissociation constant K_d of PBMC (1.8 ± 0.2 nM) was lower than that of granulocytes (3.5 ± 0.4 nM). Our results point to differences in underlying mechanisms of glucocorticoid signaling in different porcine leukocyte populations.

A Hypothesis and Review of the Relationship between Selection for Improved Production Efficiency, Coping Behavior, and Domestication

Coping styles in response to stressors have been described both in humans and in other animal species. Because coping styles are directly related to individual fitness they are part of the life history strategy. Behavioral styles trade off with other life-history traits through the acquisition and allocation of resources. Domestication and subsequent artificial selection for production traits specifically focused on selection of individuals with energy sparing mechanisms for non-production traits. Domestication resulted in animals with low levels of aggression and activity, and a low hypothalamic-pituitary-adrenal (HPA) axis reactivity. In the present work, we propose that, vice versa, selection for improved production efficiency may to some extent continue to favor docile domesticated phenotypes. It is hypothesized that both domestication and selection for improved production efficiency may result in the selection of reactive style animals. Both domesticated and reactive style animals are characterized by low levels of aggression and activity, and increased serotonin neurotransmitter levels. However, whereas domestication quite consistently results in a decrease in the functional state of the HPA axis, the reactive coping style is often found to be dominated by a high HPA response. This may suggest that fearfulness and coping behavior are two independent underlying dimensions to the coping response. Although it is generally proposed that animal welfare improves with selection for calmer animals that are less fearful and reactive to novelty, animals bred to be less sensitive with fewer desires may be undesirable from an ethical point of view.

Acute social stress-induced immunomodulation in pigs high and low responders to ACTH

Pig husbandry is known as an intensive breeding system, piglets being submitted to multiple stressful events such as early weaning, successive mixing, crowding and shipping. These stressors are thought to impair immune defences and might contribute, at least partly, to the prophylactic use of antibiotics. Robustness was recently defined as the ability of an individual to express a high-production potential in a wide variety of environmental conditions. Increasing robustness thus appears as a valuable option to improve resilience to stressors and could be obtained by selecting piglets upon their adrenocortical activity. In this study, we aimed at depicting the consequences of an acute social stress on the immune capacity of piglets genetically selected upon divergent hypothalamic-pituitary-adrenocortical (HPA) axis activity. For this purpose, we monitored neuroendocrine and immune parameters, in high- (HPA^hi) and low- (HPA^lo) responders to ACTH, just before and immediately after a one-hour mixing with unfamiliar conspecifics. As expected, stressed piglets displayed higher levels of circulating cortisol and norepinephrine. Blood cell count analysis combined to flow cytometry revealed a stress-induced leukocyte mobilization in the bloodstream with a specific recruitment of CD8α⁺ lymphocytes. Besides, one-hour mixing decreased LPS-induced IL-8 and TNFα secretions in whole-blood assays (WBA) and reduced mononuclear cell phagocytosis. Altogether, our data demonstrate that acute social stress alters immune competence of piglets from both groups, and bring new insights in favour of good farming practices. While for most parameters high- and low-responders to ACTH behaved similarly, HPA^hi piglets displayed higher number of CD4⁺ CD8α^- T cells, as well as increased cytokine production in WBA (LPS-induced TNFα and PIL-induced IL-8), which could confer them increased resistance to pathogens. Finally, a principal component analysis including all parameters highlighted that overall stress effects were less pronounced on piglets with a strong HPA axis. Thus, selection upon adrenocortical axis activity seems to reduce the magnitude of response to stress and appears as a good tool to increase piglet robustness.

The relationship between physiological stress and wildlife disease: consequences for health and conservation

Wildlife populations are under increasing pressure from a variety of threatening processes, ranging from climate change to habitat loss, that can incite a physiological stress response. The stress response influences immune function, with potential consequences for patterns of infection and transmission of disease among and within wildlife, domesticated animals and humans. This is concerning because stress may exacerbate the impact of disease on species vulnerable to extinction, with consequences for biodiversity conservation globally. Furthermore, stress may shape the role of wildlife in the spread of emerging infectious diseases (EID) such as Hendra virus (HeV) and Ebola virus. However, we still have a limited understanding of the influence of physiological stress on infectious disease in wildlife. We highlight key reasons why an improved understanding of the relationship between stress and wildlife disease could benefit conservation, and animal and public health, and discuss approaches for future investigation. In particular, we recommend that increased attention be given to the influence of anthropogenic stressors including climate change, habitat loss and management interventions on disease dynamics in wildlife populations.

Time course of the response to ACTH in pig: biological and transcriptomic study

Background

HPA axis plays a major role in physiological homeostasis. It is also involved in stress and adaptive response to the environment. In farm animals in general and specifically in pigs, breeding strategies have highly favored production traits such as lean growth rate, feed efficiency and prolificacy at the cost of robustness. On the hypothesis that the HPA axis could contribute to the trade-off between robustness and production traits, we have designed this experiment to explore individual variation in the biological response to the main stress hormone, cortisol, in pigs. We used ACTH injections to trigger production of cortisol in 120 juvenile Large White (LW) pigs from 28 litters and the kinetics of the response was measured with biological variables and whole blood gene expression at 4 time points. A multilevel statistical analysis was used to take into account the longitudinal aspect of the data.

Results

Cortisol level reached its peak 1 h after ACTH injection. White blood cell composition was modified with a decrease of lymphocytes and monocytes and an increase of granulocytes (FDR<0.05). Basal level of cortisol was correlated with birth and weaning weights. Microarray analysis identified 65 unique genes of which expression responded to the injection of ACTH (adjusted P<0.05). These genes were classified into 4 clusters with distinctive kinetics in response to ACTH injection. The first cluster identified genes strongly correlated to cortisol and previously reported as being regulated by glucocorticoids. In particular, DDIT4, DUSP1, FKBP5, IL7R, NFKBIA, PER1, RGS2 and RHOB were shown to be connected to each other by the glucocorticoid receptor NR3C1. Most of the differentially expressed genes that encode transcription factors have not been described yet as being important in transcription networks involved in stress response. Their co-expression may mean co-regulation and they could thus provide new patterns of biomarkers of the individual sensitivity to cortisol.

Conclusions

We identified 65 genes as biological markers of HPA axis activation at the gene expression level. These genes might be candidates for a better understanding of the molecular mechanisms of the stress response.

Electronic supplementary material

The online version of this article (doi:10.1186/s12864-015-2118-8) contains supplementary material, which is available to authorized users.

Genotype by environment interaction and breeding for robustness in livestock

The increasing size of the human population is projected to result in an increase in meat consumption. However, at the same time, the dominant position of meat as the center of meals is on the decline. Modern objections to the consumption of meat include public concerns with animal welfare in livestock production systems. Animal breeding practices have become part of the debate since it became recognized that animals in a population that have been selected for high production efficiency are more at risk for behavioral, physiological and immunological problems. As a solution, animal breeding practices need to include selection for robustness traits, which can be implemented through the use of reaction norms analysis, or though the direct inclusion of robustness traits in the breeding objective and in the selection index. This review gives an overview of genotype × environment interactions (the influence of the environment, reaction norms, phenotypic plasticity, canalization, and genetic homeostasis), reaction norms analysis in livestock production, options for selection for increased levels of production and against environmental sensitivity, and direct inclusion of robustness traits in the selection index. Ethical considerations of breeding for improved animal welfare are discussed. The discussion on animal breeding practices has been initiated and is very alive today. This positive trend is part of the sustainable food production movement that aims at feeding 9.15 billion people not just in the near future but also beyond.

Domestication Effects on Stress Induced Steroid Secretion and Adrenal Gene Expression in Chickens

Understanding the genetic basis of phenotypic diversity is a challenge in contemporary biology. Domestication provides a model for unravelling aspects of the genetic basis of stress sensitivity. The ancestral Red Junglefowl (RJF) exhibits greater fear-related behaviour and a more pronounced HPA-axis reactivity than its domesticated counterpart, the White Leghorn (WL). By comparing hormones (plasmatic) and adrenal global gene transcription profiles between WL and RJF in response to an acute stress event, we investigated the molecular basis for the altered physiological stress responsiveness in domesticated chickens. Basal levels of pregnenolone and dehydroepiandrosterone as well as corticosterone response were lower in WL. Microarray analysis of gene expression in adrenal glands showed a significant breed effect in a large number of transcripts with over-representation of genes in the channel activity pathway. The expression of the best-known steroidogenesis genes were similar across the breeds used. Transcription levels of acute stress response genes such as StAR, CH25 and POMC were upregulated in response to acute stress. Dampened HPA reactivity in domesticated chickens was associated with changes in the expression of several genes that presents potentially minor regulatory effects rather than by means of change in expression of critical steroidogenic genes in the adrenal.

Genetic variants in glucocorticoid and mineralocorticoid receptors are associated with concentrations of plasma cortisol, muscle glycogen content, and meat quality traits in male Nellore cattle

The glucocorticoid receptor (GR) and mineralocorticoid receptor (MR) are key components in the regulation of the hypothalamic-pituitary-adrenal neuroendocrine axis and coordinate the physiological response to stress agents to reestablish homeostasis. Genetic variations of GR (NR3C1) and MR (NR3C2) genes could explain the alterations in animals to adapt to challenges, and therefore, their influence on production traits. The present study aimed to identify single-nucleotide polymorphisms (SNPs) in the bovine NR3C1 and NR3C2 genes and explore their associations to relevant traits of beef cattle production. Genotypes and phenotypes were collected from 241 male Nellore cattle (119 noncastrated and 122 castrated surgically) with an average of 24 ± 1.2 mo of age and live weight of 508 ± 39 kg. The traits evaluated were concentrations of plasma adrenocorticotropic hormone (ACTH) and cortisol, muscle glycogen and lactate content, and pH, color, cooking loss, and shear force of longissimus thoracis measured on the 1st, 7th, and 14th days postmortem. Five SNPs were identified, 2 in the NR3C1 gene and 3 in the NR3C2 gene. There was an associative relationship between the SNP NR3C1_1 g.3293A>G and postmortem plasma concentration of cortisol (P = 0.0008). The SNPs NR3C2_1 g.115T>C and NR3C2_2 g.570T>C were associated with muscle glycogen content (P = 0.0306 and P = 0.0158), postmortem plasma concentration of ACTH (P = 0.0118 and P = 0.0095), and cooking loss of the steak aged 1 d (P = 0.0398 and P = 0.0423). Haplotype analysis showed associations of GR haplotypes with postmortem plasma concentrations of cortisol and MR haplotypes with meat color, cooking losses, muscle glycogen content, and plasma concentrations of ACTH. The associations observed in the present study show that SNPs in GR and MR genes are related with changes of hypothalamic-pituitary-adrenal axis activity and metabolic profile in cattle, leading to individual variation in meat quality traits.

Analysis of non-synonymous SNPs of the porcine SERPINA6 gene as potential causal variants for a QTL affecting plasma cortisol levels on SSC7

Recently, the SERPINA6 gene encoding corticosteroid-binding globulin (CBG) has been proposed as a candidate gene for a quantitative trait locus (QTL) affecting cortisol level on pig chromosome 7. The QTL was repeatedly detected in different lines, including a Piétrain × (German Landrace × German Large White) cross (PiF1) and purebred German Landrace (LR). In this study, we investigated whether the known non-synonymous polymorphisms c.44G>T, c.622C>T, c.770C>T, c.793G>A, c.832G>A and c.919G>A of SERPINA6 are sufficient to explain the QTL in these two populations. Our investigations revealed that SNPs c.44G>T, c.622C>T, c.793G>A and c.919G>A are associated with cortisol level in PiF1 (P < 0.01). Haplotype analysis showed that these associations are largely attributable to differences between a major haplotype carrying SNPs c.793G>A and c.919G>A and a haplotype carrying SNPs c.44G>T and c.622C>T. Furthermore, some SNPs, particularly c.44G>T and c.622C>T and the carrier haplotype, showed association with meat quality traits including pH and conductivity (P < 0.05). In LR, the non-synonymous SNPs segregate at very low frequency (<5%) and/or show only weak association with cortisol level (SNPs c.832G>A and c.919G>A; P < 0.05). These findings suggest that the non-synonymous SNPs are not sufficient to explain the QTL across different breeds. Therefore, we examined whether the expression of SERPINA6 is affected by cis-regulatory polymorphisms in liver, the major organ for CBG production. We found allelic expression imbalance of SERPINA6, which suggests that its expression is indeed affected by genetic variation in cis-acting elements. This represents candidate causal variation for future studies of the molecular background of the QTL.

Genetic trends in maternal and neonatal behaviors and their association with perinatal survival in French Large White swine

Genetic trends in maternal abilities were studied in French Large White sows. Two lines representing old-type and modern-type pigs were obtained by inseminating modern sows with semen from boars born in 1977 or 1998. Successive generations were produced by inter-se mating. The maternal performance of sows from the second generation was compared in farrowing crates. Video analysis was performed for the 1st h after the onset of 43 and 36 farrowing events, and for the 6 first hours for 23 and 21 events, in old-type and modern-type sows, respectively. Genetic trends were estimated as twice the difference in estimates between the 2 lines. The contribution of behavior to the probability of stillbirth and piglet death in the first 2 days was estimated as the percentage of deviance reduction (DR) due to the addition of behavior traits as factors in the mortality model. Sow activity decreased strongly from the 1st to the 2nd h in both lines (P < 0.001). In the first 6 h, old-type sows sat (1st parity), stood (2nd parity) and rooted (both parities) for longer than modern-type sows, which were less active, especially in 2nd parity. In modern-type sows, stillbirth was associated positively with lying laterally in the first 6 h (4.6% DR) and negatively in the 1st h (9.1% DR). First-parity old-type sows were more attentive to piglets (P = 0.003) than modern-type sows which responded more to nose contacts at 2nd parity (P = 0.01). Maternal reactivity of modern-type sows was associated with a higher risk of piglet death (4.6% DR). Respiratory distress at birth tended to be higher in modern-type piglets than in old-type piglets (P < 0.10) and was associated with a higher risk of piglet death in both lines (2.7–3.1% DR). Mobility at birth was lower in modern-type than old-type piglets (P < 0.0001). Genetic trends show that sow and piglet behaviors at farrowing have changed. Our results indicate reduced welfare in parturient modern-type sows and their newborn piglets.

Exploration of the Hypothalamic-Pituitary-Adrenal Axis to Improve Animal Welfare by Means of Genetic Selection: Lessons from the South African Merino

It is a difficult task to improve animal production by means of genetic selection, if the environment does not allow full expression of the animal's genetic potential. This concept may well be the future for animal welfare, because it highlights the need to incorporate traits related to production and robustness, simultaneously, to reach sustainable breeding goals. This review explores the identification of potential genetic markers for robustness within the hypothalamic-pituitary-adrenal axis (HPAA), since this axis plays a vital role in the stress response. If genetic selection for superior HPAA responses to stress is possible, then it ought to be possible to breed robust and easily managed genotypes that might be able to adapt to a wide range of environmental conditions whilst expressing a high production potential. This approach is explored in this review by means of lessons learnt from research on Merino sheep, which were divergently selected for their multiple rearing ability. These two selection lines have shown marked differences in reproduction, production and welfare, which makes this breeding programme ideal to investigate potential genetic markers of robustness. The HPAA function is explored in detail to elucidate where such genetic markers are likely to be found.

Association study of molecular polymorphisms in candidate genes related to stress responses with production and meat quality traits in pigs

The hypothalamic-pituitary-adrenal (HPA) axis exerts a large range of effects on metabolism, the immune system, inflammatory processes, and brain functions. Together with the sympathetic nervous system, it is also the most important stress-responsive neuroendocrine system. Both systems influence production traits, carcass composition, and meat quality. The HPA axis may be a critical target for genetic selection of more robust animals. Indeed, numerous studies in various species have demonstrated the importance of genetic factors in shaping the individual HPA axis phenotype, and genetic polymorphism can be found at each level of the axis, including hormone production by the adrenal cortices under stimulation by adrenocorticotropic hormone (ACTH), hormone bioavailability, or receptor and postreceptor mechanisms. The aim of the present experiment was to extend these findings to the brain neurochemical systems involved in stress responses. To this end, a number of candidate genes were sequenced for molecular polymorphisms and their association was studied with stress neuroendocrine and production traits in a genetically diverse population consisting of 100 female pigs from an advanced intercross (F10-F12) between 2 highly divergent breeds, Large White (LW) and Meishan (MS). The LW breed has a high production potential for lean meat and a low HPA axis activity, and the MS breed has low growth rate, fat carcasses-but large litters of highly viable piglets-and a high HPA axis activity. Candidate genes were chosen in the catecholaminergic and serotonergic pathways, in the pituitary control of cortisol production, among genes previously demonstrated to be differentially expressed in ACTH-stimulated adrenal glands from LW and MS pigs, and in cortisol receptors. Sixty new polymorphisms were found. The association study with carcass and meat quality traits and with endocrine traits showed a number of significant results, such as monoamine oxidase (MAOA) polymorphisms with growth rate (P = 0.01); lean content and intramuscular fat (P < 0.01), which are the most important traits for carcass value; dopamine receptor D3 (DRD3) with carcass composition (P < 0.05); and vasopressin receptor 1B (AVPR1B) with meat quality traits (P ≤ 0.05). The effect of these polymorphisms on neuroendocrine parameters (eg DRD3 and HPA axis or AVPR1B and catecholamines) indicates information regarding their biological mechanism of action.

Minimising pain in farm animals: the 3S approach - 'Suppress, Substitute, Soothe'

Recently, the French National Institute for Agricultural Research appointed an expert committee to review the issue of pain in food-producing farm animals. To minimise pain, the authors developed a '3S' approach accounting for 'Suppress, Substitute and Soothe' by analogy with the '3Rs' approach of 'Reduction, Refinement and Replacement' applied in the context of animal experimentation. Thus, when addressing the matter of pain, the following steps and solutions could be assessed, in the light of their feasibility (technical constraints, logistics and regulations), acceptability (societal and financial aspects) and availability. The first solution is to suppress any source of pain that brings no obvious advantage to the animals or the producers, as well as sources of pain for which potential benefits are largely exceeded by the negative effects. For instance, tail docking of cattle has recently been eliminated. Genetic selection on the basis of resistance criteria (as e.g. for lameness in cattle and poultry) or reduction of undesirable traits (e.g. boar taint in pigs) may also reduce painful conditions or procedures. The second solution is to substitute a technique causing pain by another less-painful method. For example, if dehorning cattle is unavoidable, it is preferable to perform it at a very young age, cauterising the horn bud. Animal management and constraint systems should be designed to reduce the risk for injury and bruising. Lastly, in situations where pain is known to be present, because of animal management procedures such as dehorning or castration, or because of pathology, for example lameness, systemic or local pharmacological treatments should be used to soothe pain. These treatments should take into account the duration of pain, which, in the case of some management procedures or diseases, may persist for longer periods. The administration of pain medication may require the intervention of veterinarians, but exemptions exist where breeders are allowed to use local anaesthesia (e.g. castration and dehorning in Switzerland). Extension of such exemptions, national or European legislation on pain management, or the introduction of animal welfare codes by retailers into their meat products may help further developments. In addition, veterinarians and farmers should be given the necessary tools and information to take into account animal pain in their management decisions.

Immune response from a resource allocation perspective

The immune system is a life history trait that can be expected to trade off against other life history traits. Whether or not a trait is considered to be a life history trait has consequences for the expectation on how it responds to natural selection and evolution; in addition, it may have consequences for the outcome of artificial selection when it is included in the breeding objective. The immune system involved in pathogen resistance comprises multiple mechanisms that define a host's defensive capacity. Immune resistance involves employing mechanisms that either prevent pathogens from invading or eliminate the pathogens when they do invade. On the other hand, tolerance involves limiting the damage that is caused by the infection. Both tolerance and resistance traits require (re)allocation of resources and carry physiological costs. Examples of trade-offs between immune function and growth, reproduction and stress response are provided in this review, in addition to consequences of selection for increased production on immune function and vice versa. Reaction norms are used to deal with questions of immune resistance vs. tolerance to pathogens that relate host health to infection intensity. In essence, selection for immune tolerance in livestock is a particular case of selection for animal robustness. Since breeding goals that include robustness traits are required in the implementation of more sustainable agricultural production systems, it is of interest to investigate whether immune tolerance is a robustness trait that is positively correlated with overall animal robustness. Considerably more research is needed to estimate the shapes of the cost functions of different immune strategies, and investigate trade-offs and cross-over benefits of selection for disease resistance and/or disease tolerance in livestock production.

Cortisol production in sheep is influenced by the functional expression of two cytochrome P450 17α-hydroxylase/17,20-lyase (CYP17) isoforms

In commercial production systems, the full expression of the genetic potential of an animal is limited by its intrinsic and extrinsic environment. It is therefore necessary to include robustness as a breeding goal because robustness is defined as the ability of an animal to express a high production potential in a wide variety of environmental conditions. The ability of mammals to produce sufficient cortisol on stimulation of the hypothalamic-pituitary-adrenal (HPA) axis is vital in its adaptation to stress. The biosynthesis of cortisol is dependent on the enzymatic activity of the microsomal enzyme, cytochrome P450 17α-hydroxylase/17,20-lyase (CYP17). Two isoforms for sheep (Ovis aries) CYP17, previously identified in 2 independent studies, differ by 2 nucleotides, resulting in 2 AA differences (Ser210Gly and Tyr464Asn). The present study investigates the effect of these differences on cortisol production as a function of the HPA axis activity by comparing the catalytic activities of these isoforms. The activities of the CYP17 isoforms were compared by expressing the enzymes in vitro. The kinetic constants, Vmax and Km, which were determined for pregnenolone and progesterone (in the absence of cytochrome b(5)), showed no significant difference (P > 0.05) between the CYP17 isoforms. In contrast, a time course of the metabolism of pregnenolone, 17-hydroxypregnenolone, and progesterone, assayed in the presence and absence of ovine cytochrome b(5) overexpression, showed significant differences (P < 0.05) between the isoforms. Wild-type 1 CYP17 (WT1, GenBank accession number L40335) yielded more cortisol precursors than wild-type 2 (WT2, GenBank accession number AF251388). Site-directed mutagenesis indicated that a tyrosine residue at position 464 of WT1 increased the 17α-hydroxylation of progesterone compared with an asparagine residue at that position of WT2. In a subsequent insulin-induced hypoglycemic stress test, the presence of WT1 resulted in a greater cortisol output from the sheep adrenal than the presence of WT2, as homozygous WT1/WT1 sheep produced more cortisol than heterozygous WT1/WT2 sheep. The SNP located within the WT1 allele may therefore have a potential application in marker-assisted selection of sheep exhibiting a greater release of cortisol from the adrenal gland in response to stressors.

Genetics of behavioural adaptation of livestock to farming conditions

Behavioural adaptation of farm animals to environmental changes contributes to high levels of production under a wide range of farming conditions, from highly controlled indoor systems to harsh outdoor systems. The genetic variation in livestock behaviour is considerable. Animals and genotypes with a larger behavioural capacity for adaptation may cope more readily with varying farming conditions than those with a lower capacity for adaptation. This capacity should be exploited when the aim is to use a limited number of species extensively across the world. The genetics of behavioural traits is understood to some extent, but it is seldom accounted for in breeding programmes. This review summarizes the estimates of genetic parameters for behavioural traits in cattle, pigs, poultry and fish. On the basis of the major studies performed in the last two decades, we focus the review on traits of common interest in the four species. These concern the behavioural responses to both acute and chronic stressors in the physical environment (feed, temperature, etc.) and those in the social environment (other group members, progeny, humans). The genetic strategies used to improve the behavioural capacity for adaptation of animals differ between species. There is a greater emphasis on responses to acute environmental stress in fish and birds, and on responses to chronic social stress in mammals.

Molecular genetics of the adrenocortical axis and breeding for robustness

The concept of robustness refers to the combination of a high production potential and a low sensitivity to environmental perturbations. The importance of robustness-related traits in breeding objectives is progressively increasing toward the production of animals with a high production level in a wide range of climatic conditions and production systems, together with a high level of animal welfare. Current strategies to increase robustness include selection for "functional traits," such as skeletal and cardiovascular integrity, disease resistance, and mortality at various stages. It is also possible to use global evaluation of sensitivity to the environment (eg reaction norm analysis or canalization), but these techniques are difficult to implement in practice. The glucocorticoid hormones released by the adrenal cortex exert a wide range of effects on metabolism, the cardiovascular system, inflammatory processes, and brain function, for example. Protein catabolism toward energy production and storage (lipids and glycogen) supports their pivotal role in stress responses aiming at the adaptation and survival of individuals under strong environmental pressure. Large individual variations have been described in adrenocortical axis activity, with important physiopathological consequences. In terms of animal production, higher cortisol levels have negative effects on growth rate and feed efficiency and increase the fat:lean ratio of carcasses. On the contrary, cortisol has positive effects on functional traits and adaptation. Intense selection for lean tissue growth and more generally high protein output during the past decades has concomitantly reduced cortisol production, which may be responsible for the negative effects of selection on functional traits. In this paper, we review experimental evidence suggesting that the balance between production and functional traits was modified in favor of improved robustness by selecting animals with higher adrenocortical axis activity, as well as the molecular genetic tools that can be used to fine-tune this objective.