Time course determination of the effects of rapid and gradual cooling after acute hyperthermia on body temperature and intestinal integrity in pigs

Interactions between corticotropin releasing factor signaling and prophylactic antibiotics on measures of intestinal function in weaned and transported pigs

The study objective was to evaluate the interaction between corticotrophin releasing factor (CRF) receptor signaling and prophylactic antibiotic administration on intestinal physiology in newly weaned and transported pigs. Pigs (n = 56; 5.70 ± 1.05 kg) were weaned (20.49 ± 0.64 d), a blood sample was taken, and then pigs were given an intraperitoneal injection of saline (SAL; n = 28 pigs) or a CRF receptor antagonist (CRFA; n = 28 pigs; 30 μg/kg body weight; Astressin B), and then were transported in a livestock trailer for 12 h and 49 min. A second and third intraperitoneal injection was given at 4 h 42 min and 11 h 36 min into the transport process, respectively. Following transport, 4 SAL and 4 CRFA pigs were blood sampled and euthanized. The remaining 48 pigs were individually housed and given dietary antibiotics [AB; n = 12 SAL and 12 CRFA pigs; chlortetracycline (441 ppm) + tiamulin (38.6 ppm)] or no dietary antibiotics (NAB; n = 12 SAL and 12 CRFA pigs) for 14 d post-transport. Blood was collected at 12 h and on d 3, 7, and 14, and then pigs were euthanized on d 7 (n = 24) and d 14 (n = 24) post-weaning and transport. Circulating cortisol was reduced (p = 0.05) in CRFA pigs when compared to SAL pigs post-weaning and transport. On d 7, jejunal villus height and crypt depth was greater overall (p < 0.05) in AB-fed pigs versus NAB-fed pigs. On d 14, ileal crypt depth was reduced (p = 0.02) in CRFA pigs when compared to SAL pigs. Jejunal CRF mRNA abundance tended to be reduced (p = 0.09) on d 7 in CRFA pigs versus SAL pigs. On d 14, jejunal tumor necrosis factor-alpha was reduced (p = 0.01) in AB-fed pigs versus NAB-fed pigs. On d 7, change in glucose short-circuit current tended to be increased (p = 0.07) in CRFA pigs fed the AB diet when compared to CRFA pigs fed the NAB diet. In conclusion, CRFA pigs and pigs fed AB had some similar biological intestinal function measures post-weaning and transport.

A behavior and physiology-based decision support tool to predict thermal comfort and stress in non-pregnant, mid-gestation, and late-gestation sows

BACKGROUND

Although thermal indices have been proposed for swine, none to our knowledge differentiate by reproductive stage or predict thermal comfort using behavioral and physiological data. The study objective was to develop a behavior and physiology-based decision support tool to predict thermal comfort and stress in multiparous (3.28 ± 0.81) non-pregnant (n = 11), mid-gestation (n = 13), and late-gestation (n = 12) sows.

RESULTS

Regression analyses were performed using PROC MIXED in SAS 9.4 to determine the optimal environmental indicator [dry bulb temperature (TDB) and dew point] of heat stress (HS) in non-pregnant, mid-gestation, and late-gestation sows with respiration rate (RR) and body temperature (TB) successively used as the dependent variable in a cubic function. A linear relationship was observed for skin temperature (TS) indicating that TDB rather than the sow HS response impacted TS and so TS was excluded from further analyses. Reproductive stage was significant for all analyses (P < 0.05). Heat stress thresholds for each reproductive stage were calculated using the inflections points of RR for mild HS and TB for moderate and severe HS. Mild HS inflection points differed for non-pregnant, mid-gestation, and late gestation sows and occurred at 25.5, 25.1, and 24.0 °C, respectively. Moderate HS inflection points differed for non-pregnant, mid-gestation, and late gestation sows and occurred at 28.1, 27.8, and 25.5 °C, respectively. Severe HS inflection points were similar for non-pregnant and mid-gestation sows (32.9 °C) but differed for late-gestation sows (30.8 °C). These data were integrated with previously collected behavioral thermal preference data to estimate the TDB that non-pregnant, mid-gestation, and late-gestation sows found to be cool (TDB < TDB preference range), comfortable (TDB = TDB preference range), and warm (TDB preference range < TDB < mild HS).

CONCLUSIONS

The results of this study provide valuable information about thermal comfort and thermal stress thresholds in sows at three reproductive stages. The development of a behavior and physiology-based decision support tool to predict thermal comfort and stress in non-pregnant, mid-gestation, and late-gestation sows is expected to provide swine producers with a more accurate means of managing sow environments.

Thermoregulation mechanisms and perspectives for validating thermal windows in pigs with hypothermia and hyperthermia: An overview

Specific anatomical characteristics make the porcine species especially sensitive to extreme temperature changes, predisposing them to pathologies and even death due to thermal stress. Interest in improving animal welfare and porcine productivity has led to the development of various lines of research that seek to understand the effect of certain environmental conditions on productivity and the impact of implementing strategies designed to mitigate adverse effects. The non-invasive infrared thermography technique is one of the tools most widely used to carry out these studies, based on detecting changes in microcirculation. However, evaluations using this tool require reliable thermal windows; this can be challenging because several factors can affect the sensitivity and specificity of the regions selected. This review discusses the thermal windows used with domestic pigs and the association of thermal changes in these regions with the thermoregulatory capacity of piglets and hogs.

Systematic review of animal-based indicators to measure thermal, social, and immune-related stress in pigs

The intense nature of pig production has increased the animals’ exposure to stressful conditions, which may be detrimental to their welfare and productivity. Some of the most common sources of stress in pigs are extreme thermal conditions (thermal stress), density and mixing during housing (social stress), or exposure to pathogens and other microorganisms that may challenge their immune system (immune-related stress). The stress response can be monitored based on the animals’ coping mechanisms, as a result of specific environmental, social, and health conditions. These animal-based indicators may support decision making to maintain animal welfare and productivity. The present study aimed to systematically review animal-based indicators of social, thermal, and immune-related stresses in farmed pigs, and the methods used to monitor them. Peer-reviewed scientific literature related to pig production was collected using three online search engines: ScienceDirect, Scopus, and PubMed. The manuscripts selected were grouped based on the indicators measured during the study. According to our results, body temperature measured with a rectal thermometer was the most commonly utilized method for the evaluation of thermal stress in pigs (87.62%), as described in 144 studies. Of the 197 studies that evaluated social stress, aggressive behavior was the most frequently-used indicator (81.81%). Of the 535 publications examined regarding immune-related stress, cytokine concentration in blood samples was the most widely used indicator (80.1%). Information about the methods used to measure animal-based indicators is discussed in terms of validity, reliability, and feasibility. Additionally, the introduction and wide spreading of alternative, less invasive methods with which to measure animal-based indicators, such as cortisol in saliva, skin temperature and respiratory rate via infrared thermography, and various animal welfare threats via vocalization analysis are highlighted. The information reviewed was used to discuss the feasible and most reliable methods with which to monitor the impact of relevant stressors commonly presented by intense production systems on the welfare of farmed pigs.

Physiological and Behavioral Mechanisms of Thermoregulation in Mammals

This review analyzes the main anatomical structures and neural pathways that allow the generation of autonomous and behavioral mechanisms that regulate body heat in mammals. The study of the hypothalamic neuromodulation of thermoregulation offers broad areas of opportunity with practical applications that are currently being strengthened by the availability of efficacious tools like infrared thermography (IRT). These areas could include the following: understanding the effect of climate change on behavior and productivity; analyzing the effects of exercise on animals involved in sporting activities; identifying the microvascular changes that occur in response to fear, pleasure, pain, and other situations that induce stress in animals; and examining thermoregulating behaviors. This research could contribute substantially to understanding the drastic modification of environments that have severe consequences for animals, such as loss of appetite, low productivity, neonatal hypothermia, and thermal shock, among others. Current knowledge of these physiological processes and complex anatomical structures, like the nervous systems and their close relation to mechanisms of thermoregulation, is still limited. The results of studies in fields like evolutionary neuroscience of thermoregulation show that we cannot yet objectively explain even processes that on the surface seem simple, including behavioral changes and the pathways and connections that trigger mechanisms like vasodilatation and panting. In addition, there is a need to clarify the connection between emotions and thermoregulation that increases the chances of survival of some organisms. An increasingly precise understanding of thermoregulation will allow us to design and apply practical methods in fields like animal science and clinical medicine without compromising levels of animal welfare. The results obtained should not only increase the chances of survival but also improve quality of life and animal production.

Heat stress on microbiota composition, barrier integrity, and nutrient transport in gut, production performance, and its amelioration in farm animals

Livestock species experience several stresses, particularly weaning, transportation, overproduction, crowding, temperature, and diseases in their life. Heat stress (HS) is one of the most stressors, which is encountered in livestock production systems throughout the world, especially in the tropical regions and is likely to be intensified due to global rise in environmental temperature. The gut has emerged as one of the major target organs affected by HS. The alpha- and beta-diversity of gut microbiota composition are altered due to heat exposure to animals with greater colonization of pathogenic microbiota groups. HS also induces several changes in the gut including damages of microstructures of the mucosal epithelia, increased oxidative insults, reduced immunity, and increased permeability of the gut to toxins and pathogens. Vulnerability of the intestinal barrier integrity leads to invasion of pathogenic microbes and translocation of antigens to the blood circulations, which ultimately may cause systematic inflammations and immune responses. Moreover, digestion of nutrients in the guts may be impaired due to reduced enzymatic activity in the digesta, reduced surface areas for absorption and injury to the mucosal structure and altered expressions of the nutrient transport proteins and genes. The systematic hormonal changes due to HS along with alterations in immune and inflammatory responses often cause reduced feed intake and production performance in livestock and poultry. The altered microbiome likely orchestrates to the hosts for various relevant biological phenomena occurring in the body, but the exact mechanisms how functional communications occur between the microbiota and HS responses are yet to be elucidated. This review aims to discuss the effects of HS on microbiota composition, mucosal structure, oxidant-antioxidant balance mechanism, immunity, and barrier integrity in the gut, and production performance of farm animals along with the dietary ameliorations of HS. Also, this review attempts to explain the mechanisms how these biological responses are affected by HS.

Effect of a Synbiotic Supplement on Fear Response and Memory Assessment of Broiler Chickens Subjected to Heat Stress

The aim of this study was to evaluate the effect of a synbiotic containing a probiotic (Enterococcus faecium, Pediococcus acidilactici, Bifidobacterium animalis, and Lactobacillus reuteri) and a prebiotic (fructooligosaccharides) on fear response, memory assessment, and selected stress indicators in broilers subjected to heat stress. A total of 360 1-day-old Ross 708 chicks were evenly divided among three treatments: a basal diet mixed with a synbiotic at 0 (G-C), 0.5 (G-0.5X), and 1.0 (G-1.0X) g/kg. After 15 d, the broilers were exposed to 32 °C for 9 h daily until 42 d. The object memory test was conducted at 15 day; touch, novel object, and isolation tests were conducted at 35 day; tonic immobility (TI) took place at 41 day. At 42 day, plasma corticosterone and tryptophan concentrations and heterophile/lymphocyte (H/L) ratios were measured. Compared to controls, synbiotic-fed broilers, regardless of concentration, had a shorter latency to make the first vocalization, with higher vocalization rates during the isolation test (p = 0.001). the G-1.0 group had the lowest H/L ratio (p = 0.001), but higher plasma tryptophan concentrations and a greater number of birds could reach the observer during the touch test (p = 0.001 and 0.043, respectively). The current results indicate that the synbiotic can be used as a growth promoter to reduce the fear response and stress state of heat-stressed broilers.

Effects of Feed Removal during Acute Heat Stress on the Cytokine Response and Short-Term Growth Performance in Finishing Pigs

The study objective was to evaluate the effects of feed removal during acute heat stress (HS) on the cytokine response and its short-term effect on growth performance in finishing pigs. Thirty-two pigs (93.29 ± 3.14 kg initial body weight; 50% barrows and 50% gilts) were subjected to thermoneutral (TN; 23.47 ± 0.10 °C; n = 16 pigs) or HS (cycling of 25 to 36 °C; n = 16 pigs) conditions for 24 h. Within each temperature treatment, 50% of the pigs were provided with feed (AF; n = 8 pigs/temperature treatment) and 50% of the pigs had no feed access (NF; n = 8 pigs/temperature treatment). Following the 24 h temperature and feeding treatment (TF) period, all pigs had ad libitum access to feed and water and were maintained under TN conditions for 6 d. During the first 12 h of the TF period, gastrointestinal (T_GI) and skin (T_sk) temperatures were recorded every 30 min. Serum cytokines were determined at 0, 4, 8, 12, and 24 h during the TF period and on Days 3 and 6 of the post-TF period. Average daily gain (ADG) and average daily feed intake were measured on Days 1, 3, and 6 of the post-TF period. Behavioral data were collected from Days 1 to 6 of the post-TF period. Heat stress increased (p < 0.02) the T_GI and T_sk. During the post-TF period, interleukin-1α was greater (p < 0.01) in HS + NF compared to HS + AF and TN + NF pigs. From Days 1 to 2 of the post-TF period, the ADG was reduced (p < 0.01) in TN + AF compared to HS + AF, HS + NF, and TN + NF pigs. In conclusion, feed removal during an acute HS challenge did not reduce the cytokine response or improve short-term growth performance in finishing pigs.

Impact of single or repeated short-term heat challenges mimicking summer heat waves on thermoregulatory responses and performances in finishing pigs

The objectives of this study were to determine the effects of single or repeated short heat stress (HS) challenges that mimicked summer heat waves on performance and thermoregulatory responses in finishing pigs. A total of 45 crossbred castrated males were tested in three consecutive replicates of 15 pigs. Within each replicate, pigs were assigned to one of five treatments. Pigs in treatment group TTT were maintained in thermoneutral conditions (22 °C) for the entire experiment (45 d). Pigs in treatment group HHH were subjected to an HS challenge (32 °C for 5 d) at 113, 127, and 141 d of age (in experimental periods P1, P2, and P3, respectively). Pigs in treatment groups HTT, THT, and TTH were subjected to the HS challenge at 113, 127, or 141 d of age, respectively. Each 5-d challenge was preceded by a 3-d prechallenge period and followed by a 7-d recovery period. Pigs were housed in individual pens and fed ad libitum. HS significantly reduced average daily feed intake (ADFI) and the average daily gain (ADG). Expressed as a percentage of the performance observed during the prechallenge period, ADFI decreased by 12%, 22%, and 26% and ADG decreased by 12%, 43%, and 72% in the HTT, THT, and TTH groups, respectively. Regardless of the experimental group, no compensatory performance was observed during the recovery period, suggesting that HS has a long-lasting effect on animal performance. Pigs subjected to HS had an immediate increase in core body temperature (T_core), skin temperature, and respiratory rate, all of which gradually decreased during the HS challenge. Based on T_core measurements, hypothermia was observed during the recovery period in each of the three experimental periods, especially for pigs in the HHH and the HTT groups but only during the first HS cycle. Repeated exposure to HS for the HHH group resulted in heat acclimation responses characterized by a lower increase in T_core and lower decrease in ADFI during P2 and P3 than during P1.

Effects of feed removal on thermoregulation and intestinal morphology in pigs recovering from acute hyperthermia

Feed consumption increases body temperature and may delay a return to euthermia and exacerbate intestinal injury following acute hyperthermia recovery in pigs. Therefore, the study objective was to evaluate the effects of feed removal on body temperature and intestinal morphology in pigs exposed to acute hyperthermia and then rapidly cooled. Twenty-four gilts (78.53 ± 5.46 kg) were exposed to thermoneutral (TN; n = 12 pigs; 21.21 ± 0.31 °C; 61.88 ± 6.93% RH) conditions for 6 h, or heat stress (HS; 38.51 ± 0.60 °C; 36.38 ± 3.40% RH) conditions for 3 h followed by a 3-h recovery period of rapid cooling (HSC;n = 12 pigs; TN conditions and cold water dousing). Within each recovery treatment, one-half of the pigs were provided feed ad libitum (AF; n = 6 pigs per recovery treatment) and one-half of the pigs were not provided feed (NF; n = 6 pigs per recovery treatment). Gastrointestinal (TGI), vaginal (TV), and skin (TSK) temperatures and respiration rate (RR) were recorded every 15 min. Pigs were video-recorded to assess feeding and drinking attempts. Immediately following the 6-h thermal stress period, pigs were euthanized, and intestinal samples were collected to assess morphology. During the HS period, Tv, TGI, TSK, and RR were increased (P < 0.01; 1.63, 2.05, 8.32 °C, and 88 breaths per min, respectively) in HSC vs. TN pigs, regardless of feeding treatment. Gastrointestinal temperature was greater (P = 0.03; 0.97 °C) in HSC + AF vs. HSC + NF pigs from 45 to 180 min of the recovery period. During the recovery period, feeding attempts were greater (P = 0.02; 195.38%) in AF vs. NF pigs. No drinking attempt differences were detected with any comparison (P > 0.05). A decrease (P < 0.01) in jejunum and ileum villus height (24.72% and 26.11%, respectively) and villus height-to-crypt depth ratio (24.03% and 25.29%, respectively) was observed in HSC vs. TN pigs, regardless of feeding treatment. Ileum goblet cells were reduced (P = 0.01; 37.87%) in HSC vs. TN pigs, regardless of feeding treatment. In summary, TGI decreased more rapidly following acute hyperthermia when the feed was removed, and this may have implications toward using feed removal as a strategy to promote acute hyperthermia recovery in pigs.