Therapeutic effects of mitoquinol during an acute heat stress challenge in growing barrows.

Study objectives were to determine the effects of mitoquinol (MitoQ, a mitochondrial-targeted antioxidant) on biomarkers of metabolism and inflammation during acute heat stress (HS). Crossbred barrows [n=32; 59.0±5.6 kg body weight (BW)] were blocked by BW and randomly assigned to 1 of 4 environmental-therapeutic treatments: 1) thermoneutral (TN) control (n=8; TNCon), 2) TN and MitoQ (n=8; TNMitoQ), 3) HS control (n=8; HSCon), or 4) HS and MitoQ (n=8; HSMitoQ). Pigs were acclimated for 6 d to individual pens before study initiation. The trial consisted of two experimental periods (P). During P1 (2 d), pigs were fed ad libitum and housed in TN conditions (20.6±0.8°C). During P2 (24 h), HSCon and HSMitoQ pigs were exposed to continuous HS (35.2±0.2°C), while TNCon and TNMitoQ remained in TN conditions. MitoQ (40 mg/d) was orally administered twice daily (0700 and 1800 h) during P1 and P2. Pigs exposed to HS had increased rectal temperature, skin temperature, and respiration rate (+1.5°C, +6.8°C, and +101 breaths/min, respectively; P<0.01) compared to their TN counterparts. Acute HS markedly decreased feed intake (FI; 67%; P<0.01); however, FI tended to be increased in HSMitoQ relative to HSCon pigs (1.5 vs. 0.9 kg, respectively; P=0.08). Heat-stressed pigs lost BW compared to their TN counterparts (-4.7 vs. +1.6 kg, respectively; P<0.01); however, the reduction in BW was attenuated in HSMitoQ compared to HSCon pigs (-3.9 vs. -5.5 kg, respectively; P<0.01). Total gastrointestinal tract weight (empty tissue and luminal contents) was decreased in HS pigs relative to their TN counterparts (6.2 vs. 8.6 kg, respectively; P<0.01). Blood glucose increased in HSMitoQ relative to HSCon pigs (15%; P=0.04). Circulating non-esterified fatty acids (NEFA) increased in HS compared to TN pigs (P<0.01), although this difference was disproportionately influenced by elevated NEFA in HSCon relative to HSMitoQ pigs (251 vs. 142 µEq/L; P<0.01). Heat-stressed pigs had decreased circulating insulin relative to their TN counterparts (47%; P=0.04); however, the insulin:feed intake ratio tended to increase in HS relative to TN pigs (P=0.09). Overall, circulating leukocytes were similar across treatments (P>0.10). Plasma C-reactive protein remained similar among treatments; however, haptoglobin increased in HS relative to TN pigs (48%; P=0.03). In conclusion, acute HS exposure negatively altered animal performance, inflammation, and metabolism, which were partially ameliorated by MitoQ.

Effects of supplemental citrulline on thermal and intestinal morphology parameters during heat stress and feed restriction in growing pigs.

Study objectives were to characterize the effects of citrulline (CIT) on physiological and intestinal morphology metrics during heat stress (HS) and feed restriction. Forty crossbred gilts (30 ±â€…2 kg body weight [BW]) were assigned to one of five treatments: (1) thermoneutral (TN) fed ad libitum (AL) with control (CON) supplement (TNAL; n = 8), (2) TN pair-fed (PF) with CON (PF-CON; n = 8), (3) TN PF with CIT (PF-CIT; n = 8), (4) HS AL with CON (HS-CON; n = 8), and (5) HS AL with CIT (HS-CIT; n = 8). During the period (P) 1 (7 d), pigs were in TN conditions (23.6 °C) and fed AL their respective supplemental treatments. During P2 (2.5 d), HS-CON and HS-CIT pigs were fed AL and exposed to cyclical HS (33.6 to 38.3 °C), while TNAL, PF-CON, and PF-CIT remained in TN and were fed either AL or PF to their HS counterparts. Citrulline (0.13 g/kg BW) was orally administered twice daily during P1 and P2. HS increased rectal temperature (Tr), skin temperature (Ts), and respiration rate (RR) relative to TN pigs (0.8 °C, 4.7 °C, and 47 breaths/min, respectively; P < 0.01). However, HS-CIT had decreased RR (7 breaths/min, P = 0.04) and a tendency for decreased Tr (0.1 °C, P = 0.07) relative to HS-CON pigs. During P2, HS pigs had decreased feed intake (22%; P < 0.01) and a tendency for decreased average daily gain (P = 0.08) relative to TNAL pigs, and by experimental design, PF pigs followed this same pattern. Circulating lipopolysaccharide-binding protein tended to be decreased (29%; P = 0.08) in PF relative to TNAL pigs and was increased (41%; P = 0.03) in HS compared to PF pigs. Jejunum villus height was decreased in PF relative to TNAL pigs (15%; P = 0.03); however, CIT supplementation improved this metric during feed restriction (16%; P = 0.10). Jejunum mucosal surface area decreased in PF (16%; P = 0.02) and tended to decrease in HS (11%; P = 0.10) compared to TNAL pigs. Ileum villus height and mucosal surface area decreased in HS compared to TNAL pigs (10 and 14%, respectively; P ≤ 0.04), but both parameters were rescued by CIT supplementation (P ≤ 0.08). Intestinal myeloperoxidase and goblet cell area remained similar among treatments and intestinal segments (P > 0.24). In summary, CIT supplementation slightly improved RR and Tr during HS. Feed restriction and HS differentially affected jejunum and ileum morphology and while CIT ameliorated some of these effects, the benefit appeared dependent on intestinal section and stressor type.

Heat stress (HS) negatively affects animal health and production efficiency and is a significant economic burden to global animal agriculture. Although the mechanisms responsible for reduced animal productivity during HS are complex and multifaceted, increasing evidence points to decreased intestinal barrier function as an important mediator of this response. Furthermore, HS causes a voluntary reduction in feed intake, and feed restriction independently induces gastrointestinal hyperpermeability. Loss of intestinal barrier integrity facilitates bacteria translocation across the epithelium into local and systemic circulation, thus initiating an immune response. Dietary citrulline has been shown to support gut health by improving intestinal barrier integrity and modulating intestinal inflammation. Therefore, the current study investigated the effects of citrulline supplementation on physiological and intestinal morphology parameters in heat-stressed and feed-restricted growing pigs. Herein, citrulline supplementation reduced respiration rate and rectal temperature in pigs exposed to the thermal load. Heat stress and feed restriction compromised small intestinal morphology, and while supplementing citrulline improved some of these parameters, the effects depended on the intestinal region and stressor type. Additional research is needed to evaluate the potential effects of citrulline supplementation on gut health during HS or nutrient restriction.

Zearalenone exposure differentially affects the ovarian proteome in prepubertal gilts during thermal neutral and heat stress conditions.

Zearalenone (ZEN), a nonsteroidal estrogenic mycotoxin, causes endocrine disruption and porcine reproductive dysfunction. Heat stress (HS) occurs when exogenous and metabolic heat accumulation exceeds heat dissipation. Independently, HS and ZEN both compromise swine reproduction; thus, the hypothesis investigated was two-pronged: that ZEN exposure would alter the ovarian proteome and that these effects would differ in thermal neutral and HS pigs. Pre-pubertal gilts (n = 38) were fed ad libitum and assigned to either thermal neutral (TN: 21.0 ± 0.1°C) or HS (12 h cyclic temperatures of 35.0 ± 0.2°C and 32.2 ± 0.1°C). Within the TN group, a subset of pigs were pair-fed (PF) to the amount of feed that the HS gilts consumed to eliminate the confounding effects of dissimilar nutrient intake. All gilts orally received a vehicle control (CT) or ZEN (40 µg/kg/BW) resulting in six treatment groups: thermoneutral (TN) vehicle control (TC; n = 6); TN ZEN (TZ; n = 6); pair-fed (PF) vehicle control (PC; n = 6); PF ZEN (PZ; n = 6); HS vehicle control (HC; n = 7); or HS ZEN (HZ; n = 7) for 7 d. When compared to the TC pigs, TZ pigs had 45 increased and 39 decreased proteins (P ≤ 0.05). In the HZ pigs, 47 proteins were increased and 61 were decreased (P ≤ 0.05). Exposure to ZEN during TN conditions altered sec61 translocon complex (40%), rough endoplasmic reticulum membrane (8.2%), and proteasome complex (5.4%), asparagine metabolic process (0.60%), aspartate family amino acid metabolic process (0.14%), and cellular amide metabolic process (0.02%) pathways. During HS, ZEN affected cellular pathways associated with proteasome core complex alpha subunit complex (0.23%), fibrillar collagen trimer (0.14%), proteasome complex (0.05%), and spliceosomal complex (0.03%). Thus, these data identify ovarian pathways altered by ZEN exposure and suggest that the molecular targets of ZEN differ in TN and HS pigs.

Heat stress alters the ovarian proteome in prepubertal gilts.

Heat stress (HS) occurs when exogenous and metabolic heat accumulation exceeds heat dissipation; a thermal imbalance that compromises female reproduction. This study investigated the hypothesis that HS alters the ovarian proteome and negatively impacts proteins engaged with insulin signaling, inflammation, and ovarian function. Prepubertal gilts (n = 19) were assigned to one of three environmental groups: thermal neutral with ad libitum feed intake (TN; n = 6), thermal neutral pair-fed (PF; n = 6), or HS (n = 7). For 7 d, HS gilts were exposed to 12-h cyclic temperatures of 35.0 ±â€…0.2 °C and 32.2 ±â€…0.1 °C, while TN and PF gilts were housed at 21.0 ±â€…0.1 °C. Liquid chromatography-tandem mass spectrometry (LC-MS/MS) was performed on ovarian protein homogenates. Relative to TN gilts, 178 proteins were altered (P ≤ 0.05, log2foldchange ≥ 1) by HS, with 76 increased and 102 decreased. STRING gene ontology classified and identified 45 biological processes including those associated with chaperone protein refolding, cytoplasmic translational initiation, and immune activation; with a protein-protein interaction web network of 158 nodes and 563 edges connected based on protein function (FDR ≤ 0.05). Relative to PF, HS altered 330 proteins (P ≤ 0.05, log2foldchange ≥ 1), with 151 increased and 179 decreased. Fifty-seven biological pathways associated with protein function and assembly, RNA processing, and metabolic processes were identified, with a protein-protein interaction network of 303 nodes and 1,606 edges. Comparing HS with both the TN and PF treatments, 72 ovarian proteins were consistently altered by HS with 68 nodes and 104 edges, with biological pathways associated with translation and gene expression. This indicates that HS alters the ovarian proteome and multiple biological pathways and systems in prepubertal gilts; changes that potentially contribute to female infertility.

Heat stress impairs female fertility, yet the mechanisms underlying reduced fecundity remain unclear. This study investigated the ovarian proteomic changes resultant from heat stress in prepubertal gilts and discovered changes related to several important biological processes that could be responsible for reduced female fertility.

Calcium trafficking and gastrointestinal physiology following an acute lipopolysaccharide challenge in pigs.

The influence of systemic immune activation on whole-body calcium (Ca) trafficking and gastrointestinal tract (GIT) physiology is not clear. Thus, the study objectives were to characterize the effects of lipopolysaccharide (LPS) on Ca pools and GIT dynamics to increase understanding of immune-induced hypocalcemia, ileus, and stomach hemorrhaging. Twelve crossbred pigs [44 ±â€…3 kg body weight (BW)] were randomly assigned to 1 of 2 intramuscular treatments: (1) control (CON; 2 mL saline; n = 6) or (2) LPS (40 µg LPS/kg BW; n = 6). Pigs were housed in metabolism stalls to collect total urine and feces for 6 h after treatment administration, at which point they were euthanized, and various tissues, organs, fluids, and digesta were weighed, and analyzed for Ca content. Data were analyzed with the MIXED procedure in SAS 9.4. Rectal temperature and respiration rate increased in LPS relative to CON pigs (1.4 °C and 32%, respectively; P ≤ 0.05). Inflammatory biomarkers such as circulating alkaline phosphatase, aspartate aminotransferase, and total bilirubin increased in LPS compared with CON pigs whereas albumin decreased (P ≤ 0.02). Plasma glucose and urea nitrogen decreased and increased, respectively, after LPS (43% and 80%, respectively; P < 0.01). Pigs administered LPS had reduced circulating ionized calcium (iCa) compared to CON (15%; P < 0.01). Considering estimations of total blood volume, LPS caused an iCa deficit of 23 mg relative to CON (P < 0.01). Adipose tissue and urine from LPS pigs had reduced Ca compared to CON (39% and 77%, respectively; P ≤ 0.05). There did not appear to be increased Ca efflux into GIT contents and no detectable increases in other organ or tissue Ca concentrations were identified. Thus, while LPS caused hypocalcemia, we were unable to determine where circulating Ca was trafficked. LPS administration markedly altered GIT dynamics including stomach hemorrhaging, diarrhea (increased fecal output and moisture), and reduced small intestine and fecal pH (P ≤ 0.06). Taken together, changes in GIT physiology suggested dyshomeostasis and alimentary pathology. Future research is required to fully elucidate the etiology of immune activation-induced hypocalcemia and GIT pathophysiology.

Lipopolysaccharide (LPS) activates the immune system and this is accompanied with hypocalcemia and altered gastrointestinal tract (GIT) physiology. The study objectives were to characterize whole-body calcium (Ca) trafficking and evaluate GIT dynamics during LPS-induced immune activation. Ca concentrations were analyzed after intramuscular LPS injection. Administering LPS caused marked alterations in metabolic and inflammatory biomarkers and GIT dynamics, characterized by increased lower GIT motility and stomach hemorrhaging. Circulating Ca and adipose tissue and urine Ca output were decreased after LPS. Ca concentrations in other tissues and GIT contents were not detectably different. Thus, we were unable to account for about 110 mg Ca following LPS. Where and how circulating Ca is partitioned during immune activation remains unclear.

Subepithelial Stromal Cells: Their Roles and Interactions with Intestinal Epithelial Cells during Gut Mucosal Homeostasis and Regeneration.

Intestinal epithelial cell activities during homeostasis and regeneration are well described, but their potential interactions with stromal cells remain unresolved. Exploring the functions of these heterogeneous intestinal mesenchymal stromal cells (iMSCs) remains challenging. This difficulty is due to the lack of specific markers for most functionally homogenous subpopulations. In recent years, however, novel clustering techniques such as single-cell RNA sequencing (scRNA-seq), fluorescence-activated cell sorting (FACS), confocal microscope, and computational remodeling of intestinal anatomy have helped identify and characterize some specific iMSC subsets. These methods help researchers learn more about the localization and functions of iMSC populations during intestinal morphogenic and homeostatic conditions. Consequently, it is imperative to understand the cellular pathways that regulate their activation and how they interact with surrounding cellular components, particularly during intestinal epithelial regeneration after mucosal injury. This review provides insights into the spatial distribution and functions of identified iMSC subtypes. It focuses on their involvement in intestinal morphogenesis, homeostasis, and regeneration. We reviewed related signaling mechanisms implicated during epithelial and subepithelial stromal cell crosstalk. Future research should focus on elucidating the molecular intermediates of these regulatory pathways to open a new frontier for potential therapeutic targets that can alleviate intestinal mucosa-related injuries.

Investigating intestinal mast cell dynamics during acute heat stress in growing pigs.

Objectives were to examine the temporal pattern of intestinal mast cell dynamics and the effects of a mast cell stabilizer (ketotifen [Ket]) during acute heat stress (HS) in growing pigs. Crossbred barrows (n = 42; 32.3 ±â€…1.9 kg body weight [BW]) were randomly assigned to 1 of 7 environmental-therapeutic treatments: (1) thermoneutral (TN) control (TNCon; n = 6), (2) 2 h HS control (2 h HSCon; n = 6), (3) 2 h HS + Ket (2 h HSKet; n = 6); (4) 6 h HSCon (n = 6), (5) 6 h HSKet (n = 6), (6) 12 h HSCon (n = 6), or (7) 12 h HSKet (n = 6). Following 5 d of acclimation to individual pens, pigs were enrolled in two experimental periods (P). During P1 (3 d), pigs were housed in TN conditions (21.5 ±â€…0.8 °C) for the collection of baseline measurements. During P2, TNCon pigs remained in TN conditions for 12 h, while HS pigs were exposed to constant HS (38.1 ±â€…0.2 °C) for either 2, 6, or 12 h. Pigs were euthanized at the end of P2, and blood and tissue samples were collected. Regardless of time or therapeutic treatment, pigs exposed to HS had increased rectal temperature, skin temperature, and respiration rate compared to their TNCon counterparts (1.9 °C, 6.9° C, and 119 breaths/min; P < 0.01). As expected, feed intake and BW gain markedly decreased in HS pigs relative to their TNCon counterparts (P < 0.01). Irrespective of therapeutic treatment, circulating corticotropin-releasing factor decreased from 2 to 12 h of HS relative to TNCon pigs (P < 0.01). Blood cortisol increased at 2 h of HS (2-fold; P = 0.04) and returned to baseline by 6 h. Plasma histamine (a proxy of mast cell activation) remained similar across thermal treatments and was not affected by Ket administration (P > 0.54). Independent of Ket or time, HS increased mast cell numbers in the jejunum (94%; P < 0.01); however, no effects of HS on mast cell numbers were detected in the ileum or colon. Jejunum and ileum myeloperoxidase area remained similar among treatments (P > 0.58) but it tended to increase (12%; P = 0.08) in the colon in HSCon relative to TNCon pigs. Circulating lymphocytes and basophils decreased in HSKet relative to TN and HSCon pigs (P ≤ 0.06). Blood monocytes and eosinophils were reduced in HS pigs relative to their TNCon counterparts (P < 0.01). In summary, HS increased jejunum mast cell numbers and altered leukocyte dynamics and proinflammatory biomarkers. However, Ket administration had no effects on mast cell dynamics measured herein.

Heat stress (HS) affects various physiological, metabolic, and endocrine parameters, ostensibly due to reduced intestinal barrier integrity and the ensuing immune response. Evidence indicates that generalized "stress" may be a critical component of HS-induced leaky gut, a mechanism likely mediated by mast cells. Mast cell activation has been extensively associated with various stress-related intestinal inflammatory conditions; however, its contribution to intestinal barrier dysfunction during HS remains unclear. Thus, this study was designed to evaluate mast cell dynamics during an acute HS challenge and to assess the effects a mast cell stabilizer on biomarkers of intestinal inflammation. Herein, HS induced a rapid increase in circulating cortisol, increased jejunum mast cell numbers, and altered metabolism, leukocyte dynamics, and proinflammatory biomarkers. Contrary to our hypothesis, HS did not alter circulating histamine (a biomarker of mast cell activation), and mast cell stabilization did not affect mast cell numbers nor altered histamine concentrations. Altogether, our observations support a connection between HS and intestinal mast cell infiltration that may contribute to the pathophysiology of intestinal dysfunction during a heat load.

Phenotypic, endocrinological, and metabolic effects of zearalenone exposure and additive effect of heat stress in prepubertal female pigs.

Independently, both heat stress (HS) and zearalenone (ZEN) compromise female reproduction, thus the hypothesis that ZEN would affect phenotypic, endocrine, and metabolic parameters in pigs with a synergistic and/or additive impact of HS was investigated. Prepubertal gilts (n = 6-7) were assigned to: thermoneutral (TN) vehicle control (TC; n = 6); TN ZEN (40 µg/kg; TZ; n = 6); pair-fed (PF; n = 6) vehicle control (PC; n = 6); PF ZEN (40 µg/kg; PZ; n = 6); HS vehicle control (HC; n = 7); and HS ZEN (40 µg/kg; HZ; n = 7) and experienced either constant 21.0 ± 0.10 °C (TN and PF) or 35.0 ± 0.2 °C (12 h) and 32.2 ± 0.1 °C (12 h) to induce HS for 7 d. Elevated rectal temperature (P < 0.01) and respiration rate (P < 0.01) confirmed induction of HS. Rectal temperature was decreased (P = 0.03) by ZEN. Heat stress decreased (P < 0.01) feed intake, body weight, and average daily gain, with absence of a ZEN effect (P > 0.22). White blood cells, hematocrit, and lymphocytes decreased (P < 0.04) with HS. Prolactin increased (P < 0.01) in PC and PZ and increased in HZ females (P < 0.01). 17ß-estradiol reduced (P < 0.01) in HC and increased in TZ females (P = 0.03). Serum metabolites were altered by both HS and ZEN. Neither HS nor ZEN impacted ovary weight, uterus weight, teat size or vulva area in TN and PF treatments, although ZEN increased vulva area (P = 0.02) in HS females. Thus, ZEN and HS, independently and additively, altered blood composition, impacted the serum endocrine and metabolic profile and increased vulva size in prepubertal females, potentially contributing to infertility.

Effects of dietary live yeast supplementation on growth performance and biomarkers of metabolism and inflammation in heat-stressed and nutrient-restricted pigs.

Study objectives were to determine the effects of dietary live yeast (Saccharomyces cerevisiae strain CNCM I-4407; ActisafHR+; 0.25g/kg of feed; Phileo by Lesaffre, Milwaukee, WI) on growth performance and biomarkers of metabolism and inflammation in heat-stressed and nutrient-restricted pigs. Crossbred barrows (n = 96; 79 ± 1 kg body weight [BW]) were blocked by initial BW and randomly assigned to one of six dietary-environmental treatments: 1) thermoneutral (TN) and fed ad libitum the control diet (TNCon), 2) TN and fed ad libitum a yeast containing diet (TNYeast), 3) TN and pair-fed (PF) the control diet (PFCon), 4) TN and PF the yeast containing diet (PFYeast), 5) heat stress (HS) and fed ad libitum the control diet (HSCon), or 6) HS and fed ad libitum the yeast diet (HSYeast). Following 5 d of acclimation to individual pens, pigs were enrolled in two experimental periods (P). During P1 (7 d), pigs were housed in TN conditions (20 °C) and fed their respective dietary treatments ad libitum. During P2 (28 d), HSCon and HSYeast pigs were fed ad libitum and exposed to progressive cyclical HS (28-33 °C) while TN and PF pigs remained in TN conditions and were fed ad libitum or PF to their HSCon and HSYeast counterparts. Pigs exposed to HS had an overall increase in rectal temperature, skin temperature, and respiration rate compared to TN pigs (0.3 °C, 5.5 °C, and 23 breaths per minute, respectively; P < 0.01). During P2, average daily feed intake (ADFI) decreased in HS compared to TN pigs (30%; P < 0.01). Average daily gain and final BW decreased in HS relative to TN pigs (P < 0.01); however, no differences in feed efficiency (G:F) were observed between HS and TN treatments (P > 0.16). A tendency for decreased ADFI and increased G:F was observed in TNYeast relative to TNCon pigs (P < 0.10). Circulating insulin was similar between HS and TN pigs (P > 0.42). Triiodothyronine and thyroxine levels decreased in HS compared to TN treatments (~19% and 20%, respectively; P < 0.05). Plasma tumor necrosis factor-alpha (TNF-α) did not differ across treatments (P > 0.57) but tended to decrease in HSYeast relative to HSCon pigs (P = 0.09). In summary, dietary live yeast did not affect body temperature indices or growth performance and had minimal effects on biomarkers of metabolism; however, it tended to improve G:F under TN conditions and tended to reduce the proinflammatory mediator TNF-α during HS. Further research on the potential role of dietary live yeast in pigs during HS or nutrient restriction scenarios is warranted.

Effects of continuously infusing glucose or casein into the terminal ileum on biomarkers of metabolism, inflammation, and intestinal morphology in growing pigs.

Study objectives were to determine the effects of continuously infusing glucose (GLC) or casein (CAS) into the terminal ileum on biomarkers of metabolism, inflammation, and intestinal morphology in growing pigs. Crossbred gilts (n = 19; 81 ± 3 kg body weight [BW]) previously fitted with T-cannulas at terminal ileum were used in the current experiment. Following 4 d of acclimation, pigs were enrolled in 2 experimental 4-d periods (P). During P1, pigs were housed in individual pens and fed ad libitum for collection of baseline parameters. At the beginning of P2, pigs were assigned to 1 of 3 infusion treatments: 1) control (CON; water; 3 liters/d; n = 7), 2) GLC (dextrose 50%; 500 g/d; n = 6;), or 3) CAS (casein sodium salt; 300 g/d; n = 6). Water, GLC, and CAS solutions were continuously infused at a rate of 125 mL/h for the entirety of P2. Animals were euthanized at the end of P2, and intestinal tissue was collected. During P2, average daily feed intake differed across treatments and was reduced in GLC compared with CON pigs (14%), while CAS pigs consumed an intermediate amount (P = 0.05). Average daily gain and final BW were similar across treatments. A treatment by time interaction was observed for blood urea nitrogen (BUN; P < 0.01), as it decreased in GLC (21%) while it gradually increased in CAS (76%) pigs relative to CON pigs. Mild hyperthermia occurred with both GLC and CAS infusions relative to CON (+0.3 and 0.2 °C, respectively; P < 0.01). Blood neutrophils increased in CAS relative to CON pigs (26%) but remained similar between CON and GLC treatments (P < 0.01). Blood monocytes decreased in GLC relative to CON pigs (24%) while CAS pigs had an intermediate value (P = 0.03). Circulating lipopolysaccharide binding protein tended to decrease in GLC (29%) relative to CON pigs but remained similar between CON and CAS pigs (P = 0.10). Plasma tumor necrosis factor-alpha was similar across treatments. Ileum villus height:crypt depth was increased in CAS compared with CON pigs (33%; P = 0.05) while GLC pigs had an intermediate value. Colon myeloperoxidase-stained area increased in CAS compared with CON pigs (45%; P = 0.03) but remained similar between GLC and CON pigs. In summary, continuously infusing GLC or CAS into the terminal ileum appeared to stimulate a mild immune response and differently altered BUN patterns but had little or no effects on blood inflammatory markers, intestinal morphology, or key production parameters.

Rapamycin administration during an acute heat stress challenge in growing pigs.

Study objectives were to determine the effects of rapamycin (Rapa) on biomarkers of metabolism and inflammation during acute heat stress (HS) in growing pigs. Crossbred barrows (n = 32; 63.5 ± 7.2 kg body weight [BW]) were blocked by initial BW and randomly assigned to 1 of 4 environmental-therapeutic treatments: 1) thermoneutral (TN) control (n = 8; TNCon), 2) TN and Rapa (n = 8; TNRapa), 3) HS control (n = 8; HSCon), or 4) HS and Rapa (n = 8; HSRapa). Following 6 d of acclimation to individual pens, pigs were enrolled in two experimental periods (P). During P1 (10 d), pigs were fed ad libitum and housed in TN conditions (21.3 ± 0.2°C). During P2 (24 h), HSCon and HSRapa pigs were exposed to constant HS (35.5 ± 0.4°C), while TNCon and TNRapa pigs remained in TN conditions. Rapamycin (0.15 mg/kg BW) was orally administered twice daily (0700 and 1800 hours) during both P1 and P2. HS increased rectal temperature and respiration rate compared to TN treatments (1.3°C and 87 breaths/min, respectively; P < 0.01). Feed intake (FI) markedly decreased in HS relative to TN treatments (64%; P < 0.01). Additionally, pigs exposed to HS lost BW (4 kg; P < 0.01), while TN pigs gained BW (0.7 kg; P < 0.01). Despite marked changes in phenotypic parameters caused by HS, circulating glucose and blood urea nitrogen did not differ among treatments (P > 0.10). However, the insulin:FI increased in HS relative to TN treatments (P = 0.04). Plasma nonesterified fatty acids (NEFA) increased in HS relative to TN treatments; although this difference was driven by increased NEFA in HSCon compared to TN and HSRapa pigs (P < 0.01). Overall, circulating white blood cells, lymphocytes, and monocytes decreased in HS compared to TN pigs (19%, 23%, and 33%, respectively; P ≤ 0.05). However, circulating neutrophils were similar across treatments (P > 0.31). The neutrophil-to-lymphocyte ratio (NLR) was increased in HS relative to TN pigs (P = 0.02); however, a tendency for reduced NLR was observed in HSRapa compared to HSCon pigs (21%; P = 0.06). Plasma C-reactive protein tended to differ across treatments (P = 0.06) and was increased in HSRapa relative to HSCon pigs (46%; P = 0.03). Circulating haptoglobin was similar between groups. In summary, pigs exposed to HS had altered phenotypic, metabolic, and leukocyte responses; however, Rapa administration had limited impact on outcomes measured herein.

The effect of Mitoquinol (MitoQ) on heat stressed skeletal muscle from pigs, and a potential confounding effect of biological sex.

Heat stress (HS) poses a major threat to human health and agricultural production. Oxidative stress and mitochondrial dysfunction appear to play key roles in muscle injury caused by HS. We hypothesized that mitoquinol (MitoQ), would alleviate oxidative stress and cellular dysfunction in skeletal muscle during HS. To address this, crossbred barrows (male pigs) were treated with placebo or MitoQ (40 mg/d) and were then exposed to thermoneutral (TN; 20 °C) or HS (35 °C) conditions for 24 h. Pigs were euthanized following the environmental challenge and the red portion of the semitendinosus (STR) was collected for analysis. Unexpectedly, malondialdehyde concentration, an oxidative stress marker, was similar between environmental and supplement treatments. Heat stress decreased LC3A/B-I (p < 0.05) and increased the ratio of LC3A/B-II/I (p < 0.05), while p62 was similar among groups suggesting increased degradation of autophagosomes during HS. These outcomes were in disagreement with our previous results in muscle from gilts (female pigs). To probe the impact of biological sex on HS-mediated injury in skeletal muscle, we compared STR from these barrows to archived STR from gilts subjected to a similar environmental intervention. We confirmed our previous findings of HS-mediated dysfunction in muscle from gilts but not barrows. These data also raise the possibility that muscle from gilts is more susceptible to environment-induced hyperthermia than muscle from barrows.

Effects of dietary electrolytes, osmolytes, and energetic compounds on body temperature indices in heat-stressed lactating cows.

Objectives were to determine the effects of a product containing electrolytes, osmolytes, and energetic compounds (EOEC) on body temperature indices in heat-stressed (HS) Holstein cows. Lactating cows were assigned to 1 of 2 treatments: 1) a control diet (n = 10) or 2) a control diet supplemented with 113 g/d of EOEC (n = 10; Bovine BlueLite® Pellets; TechMix LLC, Stewart, MN). The trial consisted of 2 experimental periods (P). During P1 (4 d), cows were fed their respective treatments and housed in thermoneutral conditions. During P2 (4 d), HS was artificially induced using an electric heat blanket (EHB). Overall, HS markedly increased vaginal temperature (Tv), rectal temperature (Tr), skin temperature (Ts), and respiration rate (RR) (P < .01). There were no dietary treatment differences in Tv, Tr, or RR; however, during P2 EOEC-supplemented cows had increased Ts (0.8 °C; P = .04). Compared to P1, HS decreased DMI and milk yield (45 and 27%, respectively, P < .01) similarly amongst treatments. Relative to P1, circulating insulin decreased (41%; P = .04) in CON cows, whereas it remained unaffected in EOEC-supplemented cows, resulting in a 2-fold increase in EOEC compared with CON-fed cows (P < .01) during P2. Relative to P1, HS increased circulating non-esterified fatty acids (NEFA; 63%; P < .01). During P2, there tended to be a treatment by day interaction on circulating NEFA, as concentrations decreased from d 2 to 4 of P2 in EOEC-fed cows but continued to increase in CON cows. In summary, feeding EOEC altered some key aspects of energetic metabolism and increased Ts.

Effects of an oral supplement containing calcium and live yeast on post-absorptive metabolism, inflammation and production following intravenous lipopolysaccharide infusion in dairy cows.

Objectives were to evaluate the effects of an oral supplement containing soluble Ca, and live yeast in LPS-challenged dairy cows. The trial consisted of 2 experimental periods (P). During P1 (3 d), cows (n = 12) were fed ad libitum and baseline data was collected. At the beginning of P2 (which lasted 96 h), all cows were i.v. challenged with 0.375 µg/kg BW LPS. Cows were assigned randomly to 1 of 2 treatments: 1) control (CON; no bolus; n = 6) or 2) an oral bolus containing Ca and live yeast (CLY; YMCP Vitall® 44.718 g of elemental Ca; TechMix, LLC., Stewart, MN; n = 6), administered -0.5 and 6.5 h relative to LPS infusion. Following LPS administration, circulating Ca decreased in both treatments but supplemental CLY ameliorated the hypocalcemia (48 h area under the curve: -10.8 vs. -1.9 mmol/L × h; P < .01). Lipopolysaccharide decreased dry matter intake (DMI; 60%) similarly for both treatments on d 1, but overall (d 1-4) DMI tended to be reduced less (14 vs. 30%; P = .06) in CLY supplemented vs CON cows. Lipopolysaccharide reduced milk yield (70%; P < .01) from 12 to 24 h, but throughout P2, milk yield from CLY supplemented cows was increased (38%; P = .03) relative to CON cows. Overall during P2, circulating LPS-binding protein and serum amyloid A increased post LPS (3- and 4-fold, respectively, P < .01), but were unaffected by treatment (P ≥ .68). In conclusion, providing an oral supplement containing Ca and live yeast prior to and following LPS administration markedly ameliorated LPS-induced hypocalcemia and improved DMI and milk yield.

Effects of dietary chromium propionate on growth performance, metabolism, and immune biomarkers in heat-stressed finishing pigs1.

Study objectives were to determine the effects of chromium (Cr) propionate (Cr propionate 0.04%; 0.5 g/kg of feed to deliver 200 parts per billion Cr/d; KemTRACE Cr, Kemin Industries, Inc., Des Moines, IA) on growth performance, metabolism, and health biomarkers in heat-stressed and nutrient-restricted pigs. Crossbred barrows (n = 96; 105 ± 1 kg BW) were enlisted in an experiment conducted in two replicates, blocked by initial BW, and randomly assigned to one of six dietary-environmental treatments: (i) thermoneutral (TN) and fed ad libitum a control diet (TNCtl), (ii) TN and fed ad libitum a Cr supplemented diet (TNCr), (iii) TN and pair-fed a control diet (PFCtl), (iv) TN and pair-fed a Cr supplemented diet (PFCr), (v) heat stress (HS) and ad libitum fed a control diet (HSCtl), or (vi) HS and ad libitum fed a Cr supplemented diet (HSCr). The study consisted of three experimental periods (P). During P0 (5 d), all pigs were housed in TN conditions (21.3 ± 0.1 °C, 56.8 ± 0.3% relative humidity [RH]) and fed the control diet ad libitum. During P1 (5 d), pigs were fed their respective dietary treatments ad libitum and kept in TN conditions. During P2 (35 d), HSCtl and HSCr-treated pigs were fed ad libitum and exposed to progressive cyclical HS conditions (27 to 31 °C, 50 ± 0.3% RH), while TNCtl, TNCr, PFCtl, and PFCr pigs remained in TN conditions and were fed ad libitum or pair-fed to their respective HSCtl and HSCr counterparts to eliminate the confounding effects of dissimilar feed intake. Overall, HS pigs had increased (P < 0.01) rectal temperature, skin temperature, and respiration rate (0.3 °C, 3.8 °C, and 32 breaths per minute, respectively) relative to TN pigs. Overall, HS decreased ADFI and ADG (20 and 21%, respectively; P < 0.01) compared with TN controls. Final BW tended to be increased in HSCr (2.7 kg, P = 0.06) compared with HSCtl pigs. Similarly, ADG tended to be increased during P2 in HSCr relative to HSCtl-treatment (0.77 vs. 0.72 kg/d; P = 0.10). There were no effects of Cr on most production parameters, but ADFI tended to be increased in Cr relative to Ctl-fed pigs (3.19 vs. 3.09 kg/d; P = 0.08). No effects of Cr supplementation were detected on circulating glucose, insulin, NEFA, cholesterol, triglycerides, or lipopolysaccharide binding protein. However, blood neutrophils were increased in HSCr (37%; P < 0.01) relative to HSCtl pigs. In summary, these results suggest Cr supplementation may benefit growth performance during HS.

The effect of recovery from heat stress on circulating bioenergetics and inflammatory biomarkers.

Heat stress (HS) jeopardizes animal productivity and health. The intestinal barrier is sensitive to HS and heat-induced hyperpermeability plays a key role in its pathophysiology. However, the biology of recovery following HS is less understood. Thus, study objectives were to determine the temporal pattern of metabolic, inflammatory, and intestinal histological parameters during HS recovery. Female pigs (n = 32; 19.5 ± 0.5 kg BW) were sacrificed following exposure to 1 of 4 environmental treatments: 1) constant thermoneutral (TN) conditions (TNC; 24.2 ± 0.5°C), 2) no TN recovery post HS (0D), 3) 3 d of TN recovery post HS (3D), and 4) 7 d of TN recovery post HS (7D). The HS protocol was cyclical (33.6 ± 1.8 to 37.4 ± 2.1°C) and lasted for 3 d for all HS treatments. During the 3 d of HS, rectal temperature, skin temperature, and respiration rates were increased (1.3°C, 4.8°C, and 77 breaths/min, respectively; P < 0.01) and ADFI was decreased (27%; P < 0.01) compared to TNC pigs. Skin temperature tended to be decreased 0.6°C in 3D pigs during days 1-3 of recovery (P = 0.06) and was decreased 1.6 and 0.7°C during days 1-3 and 4-7 of recovery, respectively, in 7D pigs (P ≤ 0.03) compared to TNC. Relative to TNC pigs, ADFI remained 14% decreased during days 1-3 of recovery in both 3D and 7D pigs, and 17% decreased during days 4-7 in 7D pigs (P ≤ 0.01). Plasma glucose was decreased (10%; P = 0.03) for 0D and 3D relative to TNC pigs. Circulating lipopolysaccharide-binding protein was increased in 3D and 7D vs. TNC pigs (110 and 147%, respectively; P = 0.01) and tended to increase linearly with increasing recovery time (P = 0.08). Circulating tumor necrosis factor alpha was decreased (15%) in 0D pigs and increased linearly with advancing recovery time (P < 0.01). Jejunum and ileum villus height were reduced 17 and 11% in 0D vs. TNC pigs and increased linearly with progressive recovery time (P < 0.01). Jejunum and ileum mucosal surface areas were reduced 17 and 9% in 0D pigs and remained decreased in the jejunum while the ileum recovered to TNC levels by day 3 of recovery. Relative to TNC pigs, goblet cell area was similar in jejunum and colon of 0D pigs but was reduced in the ileum of 0D pigs and in jejunum, ileum, and colon of 3D and 7D relative to TNC pigs (P < 0.01). In summary, HS has deleterious effects on intestinal morphology that seem to improve with recovery time. In contrast, feed consumption remained suppressed and inflammatory biomarkers indicative of leaky gut increased following the heat load.

Effects of zinc amino acid complex on biomarkers of gut integrity and metabolism during and following heat stress or feed restriction in pigs.

Study objectives were to determine the effects of zinc (Zn) amino acid complex (Availa Zn, Zinpro Corporation, Eden Prairie, MN) on metabolism, biomarkers of leaky gut, and inflammation during and following heat stress (HS) and nutrient restriction. Crossbred gilts (n = 50; 50 ± 2 kg BW) were blocked by initial BW and randomly assigned to one of five treatments: 1) thermoneutral (TN) and ad libitum fed a control diet (TNCtl), 2) TN and pair-fed a control diet (PFCtl), 3) TN and pair-fed a Zn-supplemented diet (PFZn), 4) HS and ad libitum fed a control diet (HSCtl), and 5) HS and ad libitum fed a Zn-supplemented diet (HSZn). The study consisted of 3 experimental periods (P): during P1 (7 d), all pigs were fed their respective diets ad libitum and housed in TN conditions (20.84 ± 0.03 °C, 47.11 ± 0.42% relative humidity). During P2 (7 d), HSCtl and HSZn pigs were exposed to progressive cyclical HS conditions (27 to 30 °C, 41.9 ± 0.5% relative humidity), while TNCtl, PFCtl, and PFZn pigs remained in TN conditions and were fed ad libitum or pair-fed to their respective HSCtl and HSZn counterparts. During P3 (5 d; "recovery phase"), all pigs were housed in TN conditions and fed ad libitum. Pigs exposed to HS had overall increased rectal temperature, skin temperature, and respiration rate (0.33 °C, 3.76 °C, and 27 bpm, respectively; P < 0.01). Relative to TN controls, HS decreased ADFI and ADG (28 and 35%, respectively; P < 0.05), but these variables were unaffected by dietary treatment. Additionally, circulating insulin did not differ between HS and TN pigs (P = 0.41), but was decreased in PF relative to TN pigs (P < 0.01). During recovery, no differences were observed in rectal temperature or respiration rate across treatments, but HSZn pigs had decreased skin temperature relative to TN, PF, and HSCtl pigs (P < 0.01). During P3, no Zn effects were observed in production parameters; however, PF pigs had increased ADFI and ADG relative to TN and HS treatments (P < 0.01). During P3, circulating insulin was increased in pigs that were HS relative to TN and PF pigs (75%, P < 0.05). Interestingly, tumor necrosis factor alpha (TNFα) levels were decreased during P3 (P = 0.04) in Zn relative to Ctl-fed pigs. Circulating lipopolysaccharide-binding protein was not different among periods (P > 0.10). In summary, Zn reduced TNFα (regardless of HS), and the stimulatory effect of HS on insulin secretion is amplified during HS recovery.