Stress Response In Pigs Research Articles

A Review of Visual Estimation Research on Live Pig Weight.

The weight of live pigs is directly related to their health, nutrition management, disease prevention and control, and the overall economic benefits to livestock enterprises. Direct weighing can induce stress responses in pigs, leading to decreased productivity. Therefore, modern livestock industries are increasingly turning to non-contact techniques for estimating pig weight, such as automated monitoring systems based on computer vision. These technologies provide continuous, real-time weight-monitoring data without disrupting the pigs' normal activities or causing stress, thereby enhancing breeding efficiency and management levels. Two methods of pig weight estimation based on image and point cloud data are comprehensively analyzed in this paper. We first analyze the advantages and disadvantages of the two methods and then discuss the main problems and challenges in the field of pig weight estimation technology. Finally, we predict the key research areas and development directions in the future.

Estimation of Weight and Body Measurement Model for Pigs Based on Back Point Cloud Data.

Pig farming is a crucial sector in global animal husbandry. The weight and body dimension data of pigs reflect their growth and development status, serving as vital metrics for assessing their progress. Presently, pig weight and body dimensions are predominantly measured manually, which poses challenges such as difficulties in herding, stress responses in pigs, and the control of zoonotic diseases. To address these issues, this study proposes a non-contact weight estimation and body measurement model based on point cloud data from pig backs. A depth camera was installed above a weighbridge to acquire 3D point cloud data from 258 Yorkshire-Landrace crossbred sows. We selected 200 Yorkshire-Landrace sows as the research subjects and applied point cloud filtering and denoising techniques to their three-dimensional point cloud data. Subsequently, a K-means clustering segmentation algorithm was employed to extract the point cloud corresponding to the pigs' backs. A convolutional neural network with a multi-head attention was established for pig weight prediction and added RGB information as an additional feature. During the data processing process, we also measured the back body size information of the pigs. During the model evaluation, 58 Yorkshire-Landrace sows were specifically selected for experimental assessment. Compared to manual measurements, the weight estimation exhibited an average absolute error of 11.552 kg, average relative error of 4.812%, and root mean square error of 11.181 kg. Specifically, for the MACNN, incorporating RGB information as an additional feature resulted in a decrease of 2.469 kg in the RMSE, a decrease of 0.8% in the MAPE, and a decrease of 1.032 kg in the MAE. Measurements of shoulder width, abdominal width, and hip width yielded corresponding average relative errors of 3.144%, 3.798%, and 3.820%. In conclusion, a convolutional neural network with a multi-head attention was established for pig weight prediction, and incorporating RGB information as an additional feature method demonstrated accuracy and reliability for weight estimation and body dimension measurement.

Toward an integrated ethical review process: an animal-centered research framework for the refinement of research procedures.

The involvement of animals in research procedures that can harm them and to which they are deemed unable to consent raises fundamental ethical dilemmas. While current ethical review processes emphasize the application of the 3Rs (Replacement, Reduction, and Refinement), grounded in a human-centered utilitarian ethical approach, a comprehensive ethical review also involves a harm-benefit analysis and the consideration of wider ethical issues. Nevertheless, to our knowledge, approaches are still needed to facilitate the integrative assessment and iterative revision of research designs to improve their ethical value or to identify cases in which using animals is irremediably unethical. Additionally, frameworks are lacking that explicitly include an animal-centered perspective into the ethical review process beyond welfare concerns, failing to cover broader ethical considerations (such as consent). In previous work we proposed an Animal-Centered Research framework (ACRf) comprising four animal-centered research principles (relevance, impartiality, welfare and consent) which could help researchers and ethical review bodies apprise research designs from an animal-centered perspective. This paper builds on and further develops our previous work by contextualizing the ACRf within the bigger picture of animal research ethical review and by illustrating how the ACRf could be operationalized within current ethical review processes. We contribute an extended framework that integrates the application of the ACRf principles within the ethical review process. To this end, we present findings from a theoretical case study focusing on the ethical review of a research protocol on the study of stress response in pigs. We discuss how our extended framework could be easily applied to facilitate a holistic approach to the ethical review process, and inform an iterative process of refinement, to support the development of research designs that are both more ethical and scientifically valid.

Effect of lairage time prior to slaughter on stress in pigs: a path analysis

BackgroundPre-slaughter process during transportation, handling, and lairage causes stress in pigs, affecting animal welfare and meat quality. Therefore, lairage factors are important for relieving stress. A total of 24 LYD (Landrace × Yorkshire × Duroc) barrows were used to investigate the effect of 6 and 20 h lairage time (LT) on cortisol, serotonin, and catecholamine in blood and physiological factors in muscle, and to verify the causal relationship between these factors.ResultsThe results revealed that cortisol was increased (0.064 ± 0.007 µg/ml), and epinephrine (0.020 ± 0.002 µg/ml) and norepinephrine (1.518 ± 0.071 µg/ml) were lower at a LT of 20 h than those at 6 h, and there was no significant effect on the muscle and carcass characteristic factors. In addition, cortisol and norepinephrine showed a negative correlation (r = -50,346, p = 0.0121), epinephrine and glycogen had a positive correlation (r = 0.4417, p = 0.0307), and serotonin and heat shock protein 70 (HSP70) were positively correlated (r = 0.4715, p = 0.0200). Path analysis indicated that the increase in LT had a direct effect on cortisol, epinephrine, and norepinephrine, and an indirect effect on muscle glycogen.ConclusionThis study confirmed the effect of the increase in LT from 6 to 20 h in the lairage room on the stress response of pigs. These findings support the legal requirements that advocate for shorter lairage times, in alignment with enhanced animal welfare standards.

Stress responses in pigs postweaning: Effect of heavier hybrid and weaning intact litters

Early and abrupt weaning of pigs is a stressful event. In addition, the use of hyperprolific sows with increasing numbers of live born piglets has decreased the average pig’s birth weight, colostrum intake and weaning weight. The aim of this study was to investigate whether behavioural (tail posture, agonistic and abnormal behaviour), clinical (ear and tail lesions) and physiological (saliva cortisol) indicators of stress postweaning can be minimised by 1) using a pig hybrid that is heavier at birth and weaning, and 2) trough specific-stress-free housing where intact litters of pigs stay in the pen of birth after removing the sow at weaning. The study was a 2 × 2 factorial design, with pigs from Topigs Norsvin TN70 (TN) sows as a heavier alternative to the lighter pigs from DanBred LY sows (DB), and the specific-stress-free (SSF) weaning strategy as an alternative to the conventional weaning strategy (CON) where pigs are regrouped and moved to weaner pens. Fiftyseven litters, on average 26 days of age, were included. Behaviour recordings on the day (d) of weaning (d0), showed that the rate of fights and attacks were 23 and 42 times higher in CON compared to SSF, respectively. Furthermore, on d+1 pig in CON had a 9 (in DB) to 13 (in TN) times higher odds of having clinical ear lesions compared to SSF. Only on d+2, saliva cortisol was lower in TN-SSF than TN-CON, but not lower that DB-SSF. A higher rate of high tail posture was seen in CON d+1, which may reflect higher arousal due to mixing and moving. The rate of belly nosing was 5 times higher in the lighter hybrid (DB compared to TN), but increased from d+7 to d+14 in both hybrids. On d+7 the rate of ear directed behaviour tended to be higher in DB than TN, but the rate increased from d+7 to d+14 in TN to a similar rate as in DB. The rate of tail directed behaviour increased from d+7 to d+14 and tended to be higher in CON than SSF. In conclusion, specific-stress-free weaning reduced agonistic behaviour and ear lesions and tended to reduce tail directed behaviour postweaning. Using the heaver hybrid TN reduced belly nosing postweaning. However, since belly nosing and tail directed behaviour increased over time for both hybrids and weaning strategies additional measures are needed to reduce stress associated with early and abrupt weaning.

Early weaning and biological sex shape long-term immune and metabolic responses in pigs

During the early pre and postnatal life, host and environmental factors can impart a major influence on immune development, thus shaping lifelong disease resistance. Two major factors known to influence immune function and mortality in animals and people are early life stress and biological sex. How these two factors interact to shape long-term immune development and later life disease risk is poorly understood. Here we investigated how early weaning, a common early life stressor in pigs, and biological sex impacts long-term systemic inflammatory responses and hypothalamic–pituitary–adrenal axis (HPA axis) activation later in life. Ten-week-old female (F), intact-male (IM) and castrated-male (CM) pigs that were randomly assigned to early weaning (EW) and later weaning (LW) (at 15 or 28 days of age, respectively) were intramuscularly injected with either saline vehicle or lipopolysaccharide (LPS) to induce a systemic inflammatory response. Complete blood counts (CBC), proinflammatory cytokines, cortisol, testosterone, estradiol, and rectal temp were measured at 0 h, 2 h, and 4 h post-LPS challenge. At 4 h post-LPS, peritoneal fluid (PF) and white blood cells (WBC) were collected for differential analysis. LPS challenge significantly increased rectal temp and plasma cortisol level in all treatment groups. Together, the CBC results and immune cell counts in peritoneal cavity indicated that EW-F exhibited greater systemic immune response characterized by increased neutrophils to lymphocytes ratio (NLR) and enhanced neutrophil trafficking to the peritoneal cavity. Early weaning had an opposite effect on IM and CM pigs, which exhibited a suppressed LPS-induced neutrophil migration. Early weaning induced significantly greater cortisol responses only in IM pigs indicating a heightened HPA axis responses in EW-IM. how early weaning and biological sex affect immune and stress responses in pigs. Together, these results demonstrate that early weaning and biological sex and castration shape later life immune responses in pigs and provides insight into potential mechanisms driving sex differences in later life inflammatory disease risk and mortality.

Label-free quantitative proteomics and stress responses in pigs-The case of short or long road transportation.

Ethical livestock production is currently a major concern for consumers. In parallel, research has shown that transport duration is an important factor affecting animal welfare and has a negative impact on the final product quality and on the production cost. This study applied proteomics methods to the animal stress/welfare problem in pigs muscle-exudate with the aim to identify proteins indicative of molecular processes underpinning transport stress and to better characterise this species as a biomedical model. A broader perspective of the problem was obtained by applying label-free LC-MS to characterise the proteome response to transport stress (short or long road transportation) in pigs within the same genetic line. A total of 1,464 proteins were identified, following statistical analysis 66 proteins clearly separating pigs subject to short road transportation and pigs subject long road transportation. These proteins were mainly involved in cellular and metabolic processes. Catalase and stress-induced phosphoprotein-1 were further confirmed by Western blot as being involved in the process of self-protection of the cells in response to stress. This study provide an insight into the molecular processes that are involved in pig adaptability to transport stress and are a step-forward for the development of an objective evaluation method of stress in order to improve animal care and management in farm animals.

Min pig skeletal muscle response to cold stress.

The increased sensitivity of pigs to ambient temperature is due to today’s intensive farming. Frequent climate disasters increase the pressure on healthy pig farming. Min pigs are an indigenous pig breed in China with desirable cold resistance characteristics, and hence are ideal for obtaining cold-resistant pig breeds. Therefore, it is important to discover the molecular mechanisms that are activated in response to cold stress in the Min pig. Here, we conducted a transcriptomic analysis of the skeletal muscle of Min pigs under chronic low-temperature acclimation (group A) and acute short cold stress (group B). Cold exposure caused more genes to be upregulated. Totals of 125 and 96 differentially expressed genes (DEGs) were generated from groups A and B. Sixteen common upregulated DEGs were screened; these were concentrated in oxidative stress (SRXN1, MAFF), immune and inflammatory responses (ITPKC, AREG, MMP25, FOSL1), the nervous system (RETREG1, GADD45A, RCAN1), lipid metabolism (LRP11, LIPG, ITGA5, AMPD2), solute transport (SLC19A2, SLC28A1, SLCO4A1), and fertility (HBEGF). There were 102 and 73 genes that were specifically differentially expressed in groups A and B, respectively. The altered mRNAs were enriched in immune, endocrine, and cancer pathways. There were 186 and 91 differentially expressed lncRNAs generated from groups A and B. Analysis of the target genes suggested that they may be involved in regulating the MAPK signaling pathway for resistance to cold. The results of this study provide a comprehensive overview of cold exposure–induced transcriptional patterns in skeletal muscle of the Min pig. These results can guide future molecular studies of cold stress response in pigs for improving cold tolerance as a goal in breeding programs.

Characterizing the postnatal hypothalamic–pituitary–adrenal axis response of in utero heat stressed pigs at 10 and 15 weeks of age

In utero heat stress alters postnatal physiological and behavioral stress responses in pigs. However, the mechanisms underlying these alterations have not been determined. The study objective was to characterize the postnatal hypothalamic–pituitary–adrenal axis response of in utero heat-stressed pigs. Pigs were subjected to a dexamethasone suppression test followed by a corticotrophin releasing hormone challenge at 10 and 15 weeks of age. Following the challenge, hypothalamic, pituitary, and adrenal tissues were collected from all pigs for mRNA abundance analyses. At 10 weeks of age, in utero heat-stressed pigs had a reduced (P < 0.05) cortisol response to the corticotrophin releasing hormone challenge versus controls. Additionally, the cortisol response tended to be greater overall (P < 0.10) in 15 versus 10-week-old pigs in response to the dexamethasone suppression test. The cortisol response tended to be reduced overall (P < 0.10) in 15 versus 10-week-old pigs in response to the corticotrophin releasing hormone challenge. Hypothalamic corticotropin releasing hormone mRNA abundance tended to be greater (P < 0.10) in in utero heat-stressed versus control pigs at 15-weeks of age. In summary, in utero heat stress altered some aspects of the hypothalamic–pituitary–adrenal axis related to corticotropin releasing hormone signaling, and age influenced this response.

The effects of road transportation with or without homeopathic remedy supplementation on growth performance, apparent nutrient digestibility, fecal microbiota, and serum cortisol and superoxide dismutase levels in growing pigs

The specialization of swine production and the market demand for pigs at different growth stages makes road transportation inevitable. However, road transportation usually causes a stress response in pigs. It is reported that homeopathic remedies supplementation could alleviate the stress response in pigs. This study investigated the effects of road transportation with or without homeopathic remedy (Convermax) supplementation on growth performance, nutrient digestibility, fecal microbiota, and serum cortisol and superoxide dismutase (SOD) concentrations in growing pigs. A total of 180 crossbred 49-d-old growing pigs [(Yorkshire × Landrace) × Duroc] with an initial body weight of 13.17 ± 0.02 kg were randomly allotted to 2 groups based on the initial body weight, containing 18 replicates with 5 pigs (mixed sex) in each. The pigs were fed dietary supplementation of a homeopathic remedy (Convermax) (0 or 200 mg/kg of feed, as-fed) for 35 d. On day 21, 45 pigs (70-d old; 25.25 ± 0.37 kg) were randomly selected from each group and assigned to either 2 hr of road transportation or no road transportation, resulting in a 2 × 2 factorial design. We found that road transportation led to an increase in the fecal coliform bacteria counts (P = 0.023) and serum cortisol concentration (P = 0.039) and a decrease in the serum SOD concentration (P < 0.001). However, supplementing homeopathic remedy (Convermax) to the diet of growing pigs increased gain to feed ratio (P = 0.042), apparent nitrogen digestibility (P = 0.019), and serum SOD concentration (P = 0.007), whereas decreased serum cortisol concentration (P = 0.022). In brief, road transportation induced stress response for growing pigs and increased harmful bacteria counts in their intestines. Dietary supplementation of homeopathic remedy (Convermax) alleviated stress response, improved apparent nitrogen digestibility, and increased gain to feed ratio. However, no significant interactive effects between road transportation with or without dietary homeopathic remedy (Convermax) levels were observed on the detected parameters in growing pigs.

Pilot Study of the Relationship between Deck Level and Journey Duration on Plasma Cortisol, Epinephrine and Norepinephrine Levels in Italian Heavy Pigs.

Simple SummaryJourney duration, position of the animal in the vehicle and time spent in the lairage facilities before slaughtering can negatively affect pig welfare. The effects of journey duration and deck level on hormonal parameters were examined in this pilot study during three commercial truckloads. Plasma cortisol, epinephrine and norepinephrine increased with longer transportation time. The levels of the tested hormones were higher in pigs transported for 11 h than for 6.5 h or only 3 h. The loading position (deck level) of the animals on the truck strongly affected only norepinephrine. While the effects of journey duration on plasma cortisol levels were expected and in line with the literature, our findings on plasma catecholamines are novel and may be useful to monitor transportation stress responses in pigs. These preliminary findings need to be confirmed by future studies.The aim of this pilot study was to evaluate the relationship between journey duration, deck level and activation patterns of the hypothalamic-pituitary-adrenocortical axis (HPA) and sympathetic adrenal medullary system (SAM) in pigs. A total of 90 pigs were examined. The animals came from three different Italian farms associated with the same slaughterhouse located in Bari (Apulia region-Italy). A group of thirty animals was transported from Pordenone (11 h journey); a second group was transported from Terni (6.5 h journey); a third group was transported from Benevento (3 h journey). The animals were transported in the same vehicle, which complied with the structural characteristics indicated in the Council Regulation (EC) No. 1/2005. The truck was composed of a lorry and a trailer, each one divided into three decks. Only the animals transported in the trailer were tested for the study. Before transportation, blood samples were collected on each farm, at 6:00 a.m., from 30 pigs randomly selected out of 135 pigs ready to be transported. Blood samples were also collected during slaughter to evaluate plasma cortisol, epinephrine and norepinephrine, around 6:00 a.m. A journey duration of 11 h was associated with significantly higher plasma concentrations of stress hormones compared with shorter journeys. This increase was proportional to the journey duration, with the pigs travelling for 6.5 h displaying intermediate concentrations between those noticed after 3 h and 11 h journeys. The interaction between deck and journey distance was not significant on epinephrine, norepinephrine or cortisol levels collected at arrival. There was a significant effect of deck level on norepinephrine levels (p < 0.0001), a tendency to influence epinephrine levels (p = 0.073) but no effect on cortisol levels (p = 0.945). Overall, we observed that an 11 h-long journey seemed to impact negatively on pigs’ HPA-SAM activity, likely requiring the animals to spend more time in the lairage facilities to recover.

Transcriptome analysis identifies genes and co-expression networks underlying heat tolerance in pigs

BackgroundHeat stress adversely affects pig growth and reproduction performance by reducing feed intake, weight gain, farrowing rate, and litter size. Heat tolerance is an important characteristic in pigs, allowing them to mitigate the negative effects of heat stress on their physiological activities. Yet, genetic variation and signaling pathways associated with the biological processes of heat-tolerant pigs are currently not fully understood. This study examined differentially expressed genes and constructed gene co-expression networks on mRNAs of pigs under different heat-stress conditions using whole transcriptomic RNA-seq analyses. Semen parameters, including total sperm number per ejaculate, motility, normal morphology rate, droplets, and rejected ejaculate rate, were measured weekly on 12 boars for two time periods: thermoneutral (January to May), and heat stress (July to October). Boars were classified into heat-tolerant (n = 6) and heat-susceptible (n = 6) groups based on the variation of their ejaculate parameters across the two periods. RNA was isolated from the blood samples collected from the thermoneutral and heat stress periods for gene expression analysis.ResultsUnder heat stress, a total of 66 differentially expressed genes (25 down-regulated, 41 up-regulated) were identified in heat-tolerant pigs compared to themselves during the thermoneutral period. A total of 1041 differentially expressed genes (282 down-regulated, 759 up-regulated) were identified in the comparison between heat-tolerant pigs and heat-susceptible pigs under heat stress. Weighted gene co-expression network analysis detected 4 and 7 modules with genes highly associated (r > 0.50, p < 0.05) with semen quality parameters in heat-tolerant and heat-susceptible pigs under the effects of heat stress, respectively.ConclusionThis study utilized the sensitivity of semen to heat stress to discriminate the heat-tolerance ability of pigs. The gene expression profiles under the thermoneutral and heat stress conditions were documented in heat-tolerant and heat-susceptible boars. Findings contribute to the understanding of genes and biological mechanisms related to heat stress response in pigs and provide potential biomarkers for future investigations on the reproductive performance of pigs.

Effects of general anesthesia with ketamine in combination with the neuroleptic sedatives xylazine or azaperone on plasma metabolites and hormones in pigs12

Physiological research with swine often includes sedation or general anesthesia (GA), which may influence the basal physiological responses of experimental animals and may have the potential to confound or interfere with the effects of experimental factors of interest. Using 6 adult female pigs, we investigated whether selected plasma metabolites and hormones are influenced by GA induced with ketamine (K) and 2 neuroleptic sedatives, namely azaperone (A) and xylazine (X). Fasted pigs rotationally received either no drug, a single intravenous administration of A or X, or A or X combined with ketamine (AK or XK, respectively), and plasma concentrations of glucose, lactate, non-esterified fatty acids (NEFA), triglycerides (TG), glucagon, insulin, and cortisol were determined for a 5-h period following administration. Azaperone and X induced deep sedation, whereas AK and XK induced GA. Overall, the average plasma glucose concentrations were increased by A and X, with the latter exerting a stronger effect that was also associated with hypoinsulinemia ( < 0.05). Time-dependent effects indicated a more rapid increase in glucose concentration due to X or XK than AK. Plasma NEFA concentrations were elevated by A and AK and to a lesser extent by X and XK ( < 0.05). Plasma lactate and TG levels were elevated by A and AK and remained unaffected by X or XK. Plasma cortisol concentrations were elevated ( < 0.05) by X and XK and even more so with a single administration of A ( < 0.05), while the combined effect of A with ketamine resulted in the highest cortisol concentrations ( < 0.05). Our data suggest that the effects of azaperone are mediated by cortisol but less so for xylazine, which also indicates that azaperone elicits a stronger stress response in pigs. Xylazine probably induces long-lasting, fasting-state hyperglycemia through the stimulation of hepatic glucose production associated with hypoinsulinemia. A discriminant analysis based on the variation in all of the measured metabolites and hormones, collectively, indicated that ketamine induced no additional effect on the overall physiological response patterns than that of the individual sedatives. In conclusion, the neuroleptic sedatives azaperone, and to a lesser extent, xylazine, acutely affect the metabolism of pigs, so primary metabolic readouts obtained under these drugs may be confounded.

Effects of short term supplementation of l-tryptophan and reducing large neutral amino acid along with l-tryptophan supplementation on growth and stress response in pigs

Abstract Two experiments were conducted to evaluate the effects of short term dietary supplementation of l -Trp and reducing large neutral amino acid (LNAA; valine, leucine, isoleucine, tyrosine, and phenylalanine) on growth and stress response in nursery and growing pigs. In Exp. 1, 674 crossbred pigs in 40 pens at 9-week of age were randomly allotted to 2 dietary treatments with supplementation of 0.0% and 0.8% l -Trp to a corn and soybean meal basal diet. Experimental period was composed of 5 days in a nursery and 7 days in a finisher. After 12 days feeding of experimental diets, pigs were provided a common diet for an additional 7 days. In Exp. 2, 108 crossbred barrows at 6-week of age were randomly allotted to 3 dietary treatments: (1) a corn soybean meal basal diet (4.5% LNAA) supplemented with 0.0% l -Trp; (2) a corn soybean meal basal diet (4.5% LNAA) supplemented with 0.8% l -Trp; (3) a reduced LNAA (3.8%) diet supplemented with 0.7% l -Trp, which had the same Trp:LNAA ratio as treatment 2. The experimental period lasted 16 days. In Exp. 1, during the entire period, pigs fed the diet supplemented with 0.8% l -Trp had increased ADG and gain:feed (P l -Trp supplementation. On day 6, one day after mixing, pigs fed the diet supplemented with 0.8% l -Trp had a lower (P l -Trp supplementation. In Exp. 2, during the entire period, pigs fed the diet supplemented with 0.8% l -Trp or a reduced LNAA diet supplemented with 0.7% l -Trp had increased gain:feed (P l -Trp supplementation. Weight gain and gain:feed were similar (P > 0.05) between pigs fed the diet supplemented with 0.8% l -Trp and pigs fed a reduced LNAA diet supplemented with 0.7% l -Trp. In conclusion, short term supplementation of 0.8% l -Trp improved growth performance of pigs during period of social-mixing and was associated with reduced stress hormone concentrations. Dietary supplementation of 0.8% l -Trp had similar effects on feed efficiency as a reduced LNAA diet supplemented with 0.7% l -Trp, suggesting lowering LNAA is a valid method of reducing levels of l -Trp supplementation required for mitigating stress response.

Saliva chromogranin A in growing pigs: A study of circadian patterns during daytime and stability under different storage conditions

Salivary chromogranin A (CgA) is considered to be a biomarker of activation of the sympatho-adrenomedullary system, and has recently been proposed as a useful indicator of the acute stress response in pigs. The aim of the present study was to determinate whether salivary CgA concentrations in healthy growing pigs exhibits any circadian pattern during the daytime, and to evaluate its stability under different storage conditions. A total of 80 pigs (40 in spring and another 40 in autumn) of two different ages and genders were used. To establish the circadian pattern, saliva samples were collected at 07.00, 11.00, 15.00 and 19.00h on two consecutive days. Pooled samples were used for the stability study and were measured on the day of sampling and periodically for up to 360days later. Samples were stored at 4°C, −20°C or −80°C and the effect of repeated freezing and thawing was also evaluated.No circadian pattern was detected for salivary CgA in either season and there were no significant effects of gender or age. However, mean salivary CgA concentrations were significantly higher (P<0.0001) in the pigs sampled in autumn, compared to those sampled in the spring. Short term storage at 4°C is recommended for up to 2days, whereas frozen samples can be stored for 1year at −20°C or −80°C, without substantial reduction in CgA values. In addition, samples can be frozen and thawed up to seven times without significant loss of the biomarker.

Dietary ʟ-Tryptophan Supplementation with Reduced Large Neutral Amino Acids Enhances Feed Efficiency and Decreases Stress Hormone Secretion in Nursery Pigs under Social-Mixing Stress1–3

Tryptophan (Trp), the rate-limiting substrate of serotonin [5-hydroxytryptoamine (5-HT)] synthesis in the brain, competes with large neutral amino acids (LNAA) to cross the blood-brain barrier. This study was designed to evaluate the effect of ʟ-Trp supplementation on nursery pigs experiencing social-mixing stress and fed diets varying in LNAA concentrations. Forty-eight individually housed barrows at 6 wk of age were randomly allotted to 4 dietary treatments based on a 2 × 2 factorial arrangement, with ʟ-Trp supplementation (0 or 0.6%) and LNAA concentrations (4.5 or 3.8%) as the 2 main factors. Pigs were fed the diets for 7 d. On d 4, pigs within a treatment were paired in a new pen to create social-mixing stress and behavior was recorded for 24 h. Body weight was measured on d 0, 4, 5, and 7. Saliva and blood were collected on d 4 and 7. On d 7, pigs were killed to obtain hypothalami. During the entire period excluding the mixing day (d 5), ʟ-Trp supplementation improved (P < 0.01) feed efficiency of pigs and lowering the LNAA further enhanced (P < 0.05) the effects of ʟ-Trp. Supplementation of 0.6% ʟ-Trp increased (P < 0.001) hypothalamic 5-HT and 5-hydroxyindoleacetic acid. The salivary cortisol concentration was reduced (P < 0.05) by lowering the LNAA. Collectively, lowering the LNAA further enhanced the improvement of feed efficiency by ʟ-Trp supplementation of nursery pigs under social-mixing stress in association with reduced stress hormones, indicating that reducing LNAA in the diet can facilitate the effect of ʟ-Trp on the stress response of pigs.

Curcumin attenuates the effects of transport stress on serum cortisol concentration, hippocampal NO production, and BDNF expression in the pig

Curcumin, the active component of curcuma longa, has been reported to be effective in alleviating chronic stress-induced disorders in rodents by modulating neuroprotection and neuroendocrine functions of the central nervous system, especially hippocampus. However, it is unclear whether curcumin can attenuate the subacute stress response induced by 2 h of road transport in the pig. Therefore, the present study was designed to identify the changes of serum cortisol concentration, hippocampal nitric oxide (NO) production, and related gene expression in response to 2 h of transport and to explore whether curcumin treatment (8 mg/kg, p.o.) for 21 d before transport may alleviate the stress-induced responses in the hippocampus of pigs. We found that 2 h of transport elevated serum cortisol concentration ( P < 0.01), increased hippocampal NO content, and reduced brain-derived neurotrophic factor (BDNF) mRNA expression in pigs not treated with curcumin, whereas these stress responses were all reversed or attenuated in curcumin-treated pigs. In addition, the stress-induced increase in the expression of constitutive nitric oxide synthase (cNOS) and enzyme activities of total NOS, cNOS, and inducible NOS (iNOS) was also reversed or attenuated in curcumin-treated pigs. However, neither transport nor curcumin caused significant alterations in hippocampal expression of 11β-hydroxysteroid dehydrogenase type 1 and type 2 (11β-HSD1 and 2), glucocorticoid and mineralocorticoid receptors (GR and MR), or pro-/anti-apoptotic molecules (Bax-α and Bcl-xL). These results suggest that curcumin can alleviate subacute stress response in pigs through its neuroprotective effects on modulating hippocampal NO production and BDNF expression.

Transcriptome analysis of skeletal muscle tissue to identify genes involved in pre-slaughter stress response in pigs

The knowledge of genes and molecular processes controlling stress reactions and involved in the genetic system determining resistance to stress in pigs could be important for the improvement of meat quality. This research aimed to compare the expression profiles of skeletal muscle between physically stressed and not stressed pigs of different breeds immediately before slaughter. DNA microarray analysis showed that different functional categories of genes are up-regulated in stressed compared to not stressed pigs and relevant differences among breeds were found.

Exercise training alters effect of high-fat feeding on the ACTH stress response in pigs

Eating and physical activity behaviors influence neuroendocrine output. The purpose of this study was to test, in an animal model of diet-induced cardiovascular disease, the effects of high-fat feeding and exercise training on hypothalamo-pituitary-adrenocortical (HPA) axis activity. We hypothesized that a high-fat diet would increase circulating free fatty acids (FFAs) and decrease the adrenocorticotropic hormone (ACTH) and cortisol response to an acute stressor. We also hypothesized that exercise training would reverse the high-fat diet-induced changes in FFAs and thereby restore the ACTH and cortisol response. Pigs were placed in 1 of 4 groups (normal diet, sedentary; normal diet, exercise training; high-fat diet, sedentary; high-fat diet, exercise training; n = 8/group). Animals were placed on their respective dietary and activity treatments for 16-20 weeks. After completion of the treatments animals were anesthetized and underwent surgical intubation. Blood samples were collected after surgery and the ACTH and cortisol response to surgery was determined and the circulating concentrations of FFAs, glucose, cholesterol, insulin, and IGF-1 were measured. Consistent with our hypothesis, high-fat feeding increased FFAs by 200% and decreased the ACTH stress response by 40%. In exercise-trained animals, the high-fat diet also increased FFA; however, the increase in FFA in exercise-trained pigs was accompanied by a 60% increase in the ACTH response. The divergent effect of high-fat feeding on ACTH response was not expected, as exercise training alone had no effect on the ACTH response. Results demonstrate a significant interaction between diet and exercise and their effect on the ACTH response. The divergent effects of high-fat diet could not be explained by changes in weight gain, blood glucose, insulin, or IGF-1, as these were altered by high-fat feeding, but unaffected by exercise training. Thus, the increase in FFA with high-fat feeding may explain the blunted ACTH response to an acute stressor in sedentary animals, but cannot explain the exaggerated response in exercise trained animals.

Effects of pre-weaning exposure to a maze on stress responses in pigs at weaning and on subsequent performance in spatial and fear-related tests

Learning, memory and regulation of the stress response are mediated by the hippocampus. Biologically relevant hippocampal-dependent tasks that develop and integrate cognitive processing of this region may not be available to piglets in some current production systems. Additionally, weaning piglets at less than two weeks of age may make them particularly vulnerable to disruptions during cognitive development. We measured the effects of a spatial maze task (MT) on the stress response of piglets at weaning (12 days of age) and subsequent fear response (at 7 weeks of age). Twenty-seven pigs from four litters were assigned to one of three treatments: maze task (MT), isolation control (IC), or control with sow (SC), then combined into same sex groups with each treatment represented. Each group was tested four times per day from 5–11 days of age. MT piglets navigated the MT in order to return to the home farrowing crate containing the sow and litter. IC piglets were isolated for the same length of time taken for the MT piglet in their group to navigate the MT. SC piglets controlled for handling and were returned to sow as MT entered the MT. Saliva was collected immediately pre- and post-MT on day 11 to measure cortisol concentrations, which were lower pre-MT ( F(1, 8) = 5.65, P = 0.04). Weaning at 12 days of age increased cortisol concentrations 2 h post-weaning ( F(4, 75) = 5.67, P < 0.001). When exposed to a modified Morris water maze (MWM), a significant interaction of sex and treatment was found with MT males and IC females faster at solving the MWM than male IC pigs ( χ 2(2) = 9.14, P = 0.01). Lower cortisol concentrations were seen pre-water maze versus post-water maze ( F(1, 19) = 27.62, P < 0.001). At 50 days of age, fear response of pigs was examined using three fear-related tests (open field test (OFT), novel object test (NOT), and human approach test (HAT), each consisting of 1 m acclimation and 4 m testing. In the HAT, MT animals had a tendency to touch the unfamiliar person more quickly ( F(2, 19) = 2.51, P = 0.10), and more times than animals in other groups ( F(2, 49) = 6.31, P = 0.008). MT may result in less fear of novel persons and ameliorate cognitive deficits in male pigs, suggesting benefits of exposing young pigs to environments requiring spatial learning.