Heat Stress Pigs Research Articles

PSI-28 Effect of supplementing a Bacillus spp.-based probiotic on intestinal tight junction proteins expression and abundance of selected microorganisms in heat stressed pigs

Abstract The maintenance of small intestine epithelial barrier function, depending in part on tight junction proteins (TJP), prevents the system from invasion of undesired materials but may become altered in heat stressed pigs. Heat stress (HS) also appears to modify the composition of intestinal microbiota that, combined with a weak barrier, may cause health deterioration of pigs. Probiotics, in contrast, can help animals to maintain a healthy intestinal environment. A study, conducted with pigs [n = 80; body weight (BW) = 21.6 ± 3.4 kg], analyzed the effect of HS and the supplementation of a Bacillus spp-based probiotic on gene expression of the TJP occludin, claudins, and TJP1 in jejunum and ileum. Abundance of Lactobacillus sp., Bifidobacterium sp., Bacillus subtilis and E. coli in ileal content was also analyzed. Treatments were thermal neutral (TN) pigs fed a control diet without probiotic (TN-C) or with 0.05% probiotic (TN-P), and HS pigs fed a control without probiotic (HS-C) or with 0.05% probiotic (HS-P). The control diet was based on wheat and soybean meal, added with free Lys, Thr, Met, and Val. Feed and water were freely available during the 21-d study. At termination, six pigs per treatment were sacrificed and samples from jejunum and ileum tissue were collected to analyze TJP gene expression; ileal content was collected to analyze abundance of intestinal microorganisms. Ambient temperature inside TN and HS rooms ranged from 19 to 25°C and 30 to 38.5°C, respectively. In jejunum, claudin2 expression was greater in TN-P than in TN-C (P = 0.05) but there was no effect of HS. In ileum, HS increased claudin3 but decreased occludin gene expression (P < 0.05). HS did not affect TJP1gene expression (P > 0.10). Probiotic supplementation did not affect gene expression of TJP (P > 0.10). Relative to TN-C pigs, abundance of Lactobacillus sp. and Bifidobacterium sp. tended to decrease in HS-C pigs (P < 0.10), and that of Bifidobacterium sp. decreased in HS-P pigs (P < 0.05). Abundance of E. coli tended to be greater (P < 0.10) in both HS-C and HS-P pigs, than in the TN-C pigs. Abundance of Bacillus sp. was greater (P < 0.01) in HS pigs fed the diet supplemented with the probiotic, compared with the TN-C (P < 0.01) and HS-C (P < 0.05) pigs. In conclusion, these data indicate that HS affects TJP gene expression and composition of intestinal microbiota, but supplementing 0.05% of a probiotic based on Bacillus spp. did not affect the abundance of measured microbiota except for Bacillus sp. under HS conditions.

A Capsaicin-Based Phytogenic Solution Improves Performance and Thermal Tolerance of Heat-Stressed Growing Pigs.

Exposure to heat stress (HS) detrimentally affects pig performance. This study explored whether a dietary phytogenic solution based on Capsicum spp. (PHY) could enhance the thermal tolerance of heat-stressed growing pigs. Forty-two individually housed pigs were randomly assigned to three treatments: thermoneutral pigs on a control diet (TN-C) and pigs subjected to HS fed the control diet either without (HS-C) or with supplemental PHY (HS-PHY). The TN-C group exhibited increased average daily gain (ADG) and feed intake (FI) compared to both HS-C (p < 0.01) and HS-PHY pigs (p < 0.05) and better feed efficiency compared to HS-C pigs only (p < 0.01). However, the HS-PHY pigs showed significantly higher FI (p < 0.01) and ADG (p < 0.05) compared to HS-C pigs. HS pigs displayed higher body temperatures (BTs) than TN pigs (p < 0.01), yet HS-PHY pigs experienced a lesser increase in BT compared to HS-C pigs (p < 0.05). Supplementation with PHY mitigated some effects of HS, increasing serum superoxide dismutase and catalase activity, reducing HSP90 expression in longissimus dorsi muscle, and elevating jejunal villus height compared to HS-C pigs (p < 0.05), reaching levels akin to TN-C pigs. Additionally, PHY supplementation resulted in lower serum urea levels than HS-C pigs (p < 0.01) and similar myosin gene expression to TN-C pigs (p > 0.1), suggesting enhanced amino acid post-absorptive utilization for lean tissue growth. In conclusion, dietary PHY supplementation partially offset the adverse effects of HS on pig performance by improving thermal tolerance.

Zearalenone exposure differentially affects the ovarian proteome in pre-pubertal 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 (TN) and HS pigs. Pre-pubertal gilts (n = 38) were fed ad libitum and assigned to either (TN: 21.0 ± 0.1 °C) or HS (12h 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); 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.

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

Study objectives were to evaluate the effects of mitoquinol (MitoQ) on production parameters, gastrointestinal tract (GIT; stomach and small and large intestines) weight, and circulating leukocytes during a 24-h acute heat stress (HS) challenge. Crossbred gilts [n = 32; 49.1 ± 2.4kg 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 moved into individual pens and allowed to acclimate for 6 d. The study consisted of 2 experimental periods (P). During P1 (2 d), all pigs remained in TN conditions (20.6 ± 1.5 °C) and were fed ad libitum. During P2 (24h), pigs were fed ad libitum and exposed to either TN or constant HS (37.3 ± 1.3 °C). Mitoquinol (40mg/d) was orally administered twice daily (0700 and 1800 hours) during P1 and P2. As expected, pigs exposed to HS had increased rectal temperature, skin temperature, and respiration rate (+1.5 °C, +8.7 °C, and +86 bpm, respectively; P < 0.01) compared to their TN counterparts. Compared to TN, HS pigs had decreased feed intake (67%; P < 0.01) and significant BW loss (+1.5 vs. -1.9kg, respectively; P < 0.01). Total GIT weight was decreased in HS relative to TN pigs (P < 0.01), and this was influenced by decreased luminal contents (2.43 vs. 3.26kg, respectively; P < 0.01) and reduced empty GIT mass (3.21 vs. 3.48kg, respectively; P = 0.03). Stomach contents remained similar between TN and HS pigs (P > 0.54) but tended to increase in MitoQ relative to CON pigs (0.90 vs. 0.63kg, respectively; P = 0.08). Stomach content as a percentage of the previous 24h feed intake was increased in HS compared to the TN controls (93% vs. 31%; P < 0.01). In contrast, small and large intestinal contents were decreased in HS compared to TN pigs (23% and 49%, respectively; P < 0.01). Liver weight decreased in HS relative to TN pigs (1.15 vs. 1.22kg, respectively; P = 0.02), and was decreased in MitoQ compared to CON pigs (1.13 vs. 1.24kg; P < 0.01). Circulating lymphocytes tended to be decreased in HS relative to TN pigs (16%; P = 0.07). In summary, acute HS increased all body temperature indices, negatively influenced animal performance, and differentially altered GIT motility as evidenced by decreased gastric emptying and increased intestinal transit. However, MitoQ supplementation did not appear to ameliorate these effects.

Effect of supplementing a Bacillus subtilis-based probiotic on performance, intestinal integrity, and serum antioxidant capacity and metabolites concentrations of heat-stressed growing pigs.

Exposing pigs to heat stress (HS) seems to modify the intestinal microbiota which may compromise the integrity of the small intestine epithelia. Probiotics, live microorganisms, can help pigs to maintain a healthy intestinal environment. Eighty pigs (21.6 ± 3.4kg body weight) exposed to HS or thermal neutral (TN) conditions were used to evaluate the effect of a Bacillus subtilis-based probiotic on performance, body temperature, and intestinal integrity. Treatments were: TN pigs fed a control diet without (TN-C) or with 1 × 106 CFU probiotic/g of feed (TN-P), and HS pigs fed a control without (HS-C) or with probiotic (HS-P). The control diet was formulated with wheat, soybean meal, and free amino acids (AA). Feed and water were freely available during the 21-d study. At completion, samples from duodenum, jejunum, and ileum were collected to analyze epithelial histology and tight junction protein expression; antioxidant activity, and free AA and metabolites in serum. Relative abundance of Lactobacillus, Bifidobacterium, Escherichia coli, and Bacillus in ileal content was analyzed. Ambient temperature in the TN room ranged from 19 to 25 °C, and in HS room from 30 to 38.5 °C. Intestinal temperature in HS-P pigs was lower than in HS-C pigs. Weight gain and feed intake reduced, but feed:gain and respiration rate increased in HS compared to TN pigs, regardless of diet (P < 0.01). Probiotic increased weight gain and improved feed:gain (P < 0.05) in both TN and HS pigs, but feed intake did not differ. Heat stress decreased villi height in jejunum and villi height:crypt depth in duodenum and jejunum (P < 0.05). Probiotic increased villi height in duodenum and ileum, and villi height:crypt depth in all small intestine segments (P < 0.05). Relative abundance of Lactobacillus and Bifidobacterium tended to reduce, and E. coli tended to increase (P < 0.10) in ileal content of HS-C pigs. Ileal relative abundance of Bacillus was higher (P < 0.01) in HS-P pigs than in HS-C and TN-C pigs. Cystathionine, homocysteine, hydroxylysine, α-amino-adipic acid, citrulline, α-amino-n-butyric acid, P-Ser, and taurine were higher in HS than in TN pigs (P < 0.05). These data confirm the negative effect of HS on performance, body temperature, and intestinal integrity of pigs. These data suggest that supplementing 1 × 106 CFU probiotic/g of feed based on Bacillus subtilis DSM 32540 may help to counteract the negative effects of HS on the performance and intestinal integrity of pigs.

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 ± 1.9kg body weight [BW]) were randomly assigned to 1 of 7 environmental-therapeutic treatments: (1) thermoneutral (TN) control (TNCon; n = 6), (2) 2h HS control (2h HSCon; n = 6), (3) 2h HS + Ket (2h HSKet; n = 6); (4) 6h HSCon (n = 6), (5) 6h HSKet (n = 6), (6) 12h HSCon (n = 6), or (7) 12h HSKet (n = 6). Following 5d of acclimation to individual pens, pigs were enrolled in two experimental periods (P). During P1 (3d), pigs were housed in TN conditions (21.5 ± 0.8°C) for the collection of baseline measurements. During P2, TNCon pigs remained in TN conditions for 12h, while HS pigs were exposed to constant HS (38.1 ± 0.2°C) for either 2, 6, or 12h. 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 12h of HS relative to TNCon pigs (P < 0.01). Blood cortisol increased at 2h of HS (2-fold; P = 0.04) and returned to baseline by 6h. 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.

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 ± 2kg 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 (0.13g/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.

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

Abstract 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 hours) 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 per minute, respectively; P &amp;lt; 0.01) compared to their TN counterparts. Acute HS markedly decreased feed intake (FI; 67%; P &amp;lt; 0.01); however, FI tended to be increased in HSMitoQ relative to HSCon pigs (1.5 kg vs. 0.9 kg, respectively; P = 0.08). Heat-stressed pigs lost BW compared to their TN counterparts (−4.7 kg vs. +1.6 kg, respectively; P &amp;lt; 0.01); however, the reduction in BW was attenuated in HSMitoQ compared to HSCon pigs (−3.9 kg vs. −5.5 kg, respectively; P &amp;lt; 0.01). Total gastrointestinal tract weight (empty tissue and luminal contents) was decreased in HS pigs relative to their TN counterparts (6.2 kg vs. 8.6 kg, respectively; P &amp;lt; 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 &amp;lt; 0.01), although this difference was disproportionately influenced by elevated NEFA in HSCon relative to HSMitoQ pigs (251 μEq/L vs. 142 μEq/L; P &amp;lt; 0.01). Heat-stressed pigs had decreased circulating insulin relative to their TN counterparts (47%; P = 0.04); however, the insulin:FI ratio tended to increase in HS relative to TN pigs (P = 0.09). Overall, circulating leukocytes were similar across treatments (P &amp;gt; 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 dietary supplementation with L-arginine on the endogenous losses of amino acids in growing pigs exposed to heat stress

Exposing pigs to heat stress (HS) provokes higher death of intestinal cells, resulting in elevated endogenous intestinal losses (EIL) of amino acids (AA) and damage to intestinal epithelia. Arginine (Arg) is precursor for the synthesis of polyamines, which are involved in proliferation of intestinal cells and restoration of the intestinal epithelia. Thus the effect of adding L-Arg to diets for HS pigs on the EIL of AA was analyzed. Twelve pigs (23.1 ± 1.1 kg body weight) implanted with T-type cannulas at the end of ileum were individually housed and allowed 15-days for surgery recovery under thermoneutral (TN) conditions (22 ± 2 °C). Following, the pigs were randomly assigned to one of three treatments: TN pigs fed a semi-purified, corn starch-3% casein basal diet (TN-B); HS pigs with the basal diet (HS–B); HS pigs consuming the basal diet supplemented with 0.20% L-Arg (HS-Arg). The experiment consisted of two 9-day periods; each period included 7-days of adaptation to their respective diet, followed by a 2-day ileal digesta collection period. Digesta was collected during 12 consecutive hours each day. The pigs were fed twice a-day. Ambient temperature (AT) inside the TN and HS rooms ranged from 18.6 to 27.6 °C and from 29.5 to 40.7 °C, respectively. Body temperature followed a pattern similar to that of AT. The daily EIL of indispensable AA increased (P < 0.01) in the HS-B pigs compared to both the TN-B and the HS-Arg pigs, however, there was no EIL difference between the TN-B and the HS-Arg pigs (P > 0.05). Likewise, with the exception of serine, daily losses of endogenous dispensable AA in the HS-B pigs were higher (P < 0.01) in comparison with those of TN-B and HS-Arg pigs. In summary, HS exposure compared to TN conditions increases the loss of endogenous AA, but dietary supplementation with L-Arg helped to counteract the negative HS effect.

102 Growth Performance in Pigs fed a High Soybean Meal Diet During Heat Stress

Abstract In the U.S. swine industry, feeding programs are focused on using feed ingredients that are easily digestible and cost effective. With the predicted increases in soybean processing, pig producers may have increased availability of a cost-effective protein source in soybean meal (SBM). This expanded availability of SBM may result in feeding protein above the ostensible requirements, which would likely intensify the thermic effect of digestion, potentially increasing the susceptibility of the pig to heat stress (HS). Heat stress has damaging effects on feed intake and growth performance, costing the swine industry &amp;gt;$900 million annually. Therefore, the study objectives were to evaluate the effects of dietary crude protein diets (in the form of SBM) during HS on growth performance in growing pigs. Growing pigs (n = 40; initial BW = 55 ± 5.6 kg) were allocated into six treatments: 1) thermoneutral (TN) ad libitum control diet (TN-Ctl; n = 6), 2) TN pair-fed (PF) control diet (PF-Ctl; n = 6), 3) HS ad libitum control diet (HS-Ctl; n = 8), 4) TN ad libitum high SBM diet (TN-SBM; n = 6), 5) TN PF high SBM diet (PF-SBM; n = 6), and 6) HS ad libitum high SBM diet (HS-SBM; n = 8). The control diet included 15% crude protein (CP) while the high SBM diet included 23% CP with excess amino acids. The study consisted of two periods: Period 1 (P1; 7 d) in which all pigs were housed in TN environments (26.7 ± 1.4°C) with ad libitum access to respective diets. Period 2 (P2; 21 d), HS groups were exposed to cyclical HS with daytime temperatures reaching 35°C and evening temperatures decreased to 29.4°C. During P2, PF groups were fed to respective HS-Ctl or HS-SBM equivalents in TN conditions. Pigs exposed to HS had an overall increase in rectal temperature and respiration rate (0.91°C and 45 bpm, respectively; P ≤ 0.01) and HS-SBM pigs had increased evening rectal temperature (± 0.13°C; P ≤ 0.01), relative to HS-Ctrl. Overall, HS decreased ADFI (19%; P ≤ 0.01), ADG (26%; P ≤ 0.01) and increased F:G (10%; P ≤ 0.01) irrespective of dietary CP levels. Loin muscle area (P = 0.19) and backfat (P = 0.98) were not different between the TN and HS pigs regardless of diet. Circulating blood urea nitrogen levels did not differ between HS and TN pigs (P = 0.68), but an increase was observed in pigs fed the SBM diet relative to the control diet (P ≤ 0.01). In summary, these results demonstrate that HS decreases growth performance, but the negative effects are not augmented by feeding a high SBM diet.

PSIII-10 Effects of Mitoquinol During an Acute Heat Stress in Growing Gilts

Abstract Objectives were to evaluate the effects of mitoquinol (MitoQ) on production parameters, gastrointestinal (GIT) contents, GIT mass, and circulating leukocytes during acute heat stress (HS). Crossbred gilts [49.1±2.4 kg body weight (BW)] were blocked by BW and randomly assigned to 1 of 4 therapeutic-environmental treatments: 1) thermoneutral (TN) control (TNCON; n = 8), 2) TN and MitoQ (TNMitoQ; n = 8), 3) HS control (HSCON; n = 8), or 4) HS and MitoQ (HSMitoQ; n = 8). The study consisted of two experimental periods (P). During P1 (2 d) pigs were fed ad libitum and housed in TN conditions (20.6±1.5°C). During P2 (24 h) pigs were fed ad libitum and exposed to either TN or constant HS (37.3±1.3°C). In MitoQ fed pigs, MitoQ (20 mg) was administered twice daily (0700 and 1800 h; 40 mg/d) during both P1 and P2. Rectal temperature (TR), skin (TS), respiration rate (RR), and feed intake (FI) were recorded every 4 h during P2. Following P2, all pigs were euthanized, and organs were weighed. As expected, pigs exposed to HS had increased TR, TS, and RR (1.5°C, 8.7°C, and 86 bpm, respectively; P &amp;lt; 0.01) relative to TN. Compared with TN, HS pigs had decreased FI (67%; P &amp;lt; 0.01). Additionally, HS pigs lost BW compared with TN (-1.9 vs. +1.5 kg, respectively; P &amp;lt; 0.01). Despite consuming 67% less feed, stomach contents were similar in TN and HS pigs (P &amp;gt; 0.54), regardless of environment. Large and small intestine contents were decreased in HS pigs relative to TN (23 and 49%, respectively; P ≤ 0.01). Total GIT luminal contents (stomach, small and large intestines) were decreased in HS relative to TN pigs (2.43 vs. 3.26 kg; P = 0.01); however, MitoQ fed pigs tended to have increased GIT contents regardless of the environment (3.05 vs. 2.63 kg; P = 0.08). Total empty GIT and liver weights decreased in HS relative to TN pigs (3.21 vs. 3.48 and 1.16 vs. 1.22 kg, respectively; P ≤ 0.03). In addition, liver weight was decreased in MitoQ relative to CON pigs (1.13 vs. 1.24 kg; P = 0.01). Further, total GIT weight (tissue and contents) was decreased in HS relative to TN pigs (5.63 vs. 6.70 kg; P = 0.01). Environment nor therapeutic treatment affected circulating leukocytes (P &amp;gt; 0.16); however, HS pigs tended to have decreased lymphocytes relative to TN (16%; P = 0.07). Based upon the changes in GIT content, it appears HS decreases gastric emptying while increasing intestinal passage rate. Overall, acute HS increased body temperature indices, and decreased FI, GIT mass and BW; however, MitoQ administration did not appear to ameliorate these metrics.

230 Effect of Supplementing a Bacillus Spp-Based Probiotic on Performance, Body Temperature, and Intestinal Histology of Heat Stressed Pigs

Abstract The integrity of the small intestine epithelia may become compromised when pigs are exposed to heat stress (HS) increasing the risk of health deterioration. Dietary supplementation with probiotics can help animals to maintain a healthy intestinal environment. An experiment was conducted with 80 pigs [21.6 ± 3.4 kg body weight (BW); 2 pigs/pen] exposed to either HS or thermal neutral (TN) conditions to evaluate the effect of supplementing the diet with a Bacillus subtilis DSM 32540 based probiotic on performance, body temperature, and intestinal histology. Treatments were: TN pigs fed a control diet without (TN-C) or with 0.05% probiotic (TN-P), and HS pigs fed a control without (HS-C) or with 0.05% probiotic (HS-P). The control diet (1.05% SID Lys) adequate in all nutrients was formulated with wheat, soybean meal, and feed-grade Lys, Thr, and Met. Feed and water were freely available during the 21-days (d) experiment. At the end, pigs were sacrificed to collect intestinal samples from duodenum, jejunum, and ileum to analyze the epithelia histology. Additionally, 12 ileal cannulated pigs kept in the HS room fed the same diets (6/diet) were implanted with a thermometer that registered body temperature (BT) at 5-min intervals. Ambient temperature (AT) inside the HS and TN rooms ranged from 19 to 25 °C and from 30 to 38.5 °C, respectively. The BT of HS-P pigs was less than that of HS-C pigs from 1400 to 2400 h (P&amp;lt; 0.05). There was no diet x AT interaction effect for performance variables. Body weight gain, feed intake, and gain:feed was less but respiration rate was greater in HS than in TN pigs regardless of the diet (P &amp;lt; 0.01). Probiotic supplementation increased BW gain and gain:feed (P &amp;lt; 0.05) of both TN and HS pigs, but feed intake was not affected. Exposure to HS decreased villi height in jejunum and ileum, but increased crypt depth and villi height:crypt depth in duodenum, jejunum, and ileum (P &amp;lt; 0.05). Probiotic supplementation increased villi height in duodenum and ileum, whereas crypt depth decreased but villi height:crypt depth increased in the three segments of the small intestine (P &amp;lt; 0.05). These data confirm the negative effect of HS exposure on performance, body temperature, and intestinal histology of pigs. These results also suggest that supplementing with 0.05% Bacillus subtilis DSM 32540 probiotic may help to counteract the negative effects of HS on performance and intestinal histology of pigs.

Apparent and standardised ileal amino acid digestibilities in heat-stressed pigs fed wheat-soybean meal diets supplemented with l-arginine and dl-methionine.

Heat stress (HS) exposure may damage the small intestine epithelia of pigs affecting the digestibility and absorption of amino acids (AA). Arg and Met can enhance antioxidant and intestinal cell proliferation activity, thus supplementing them in diets might alleviate epithelial damage and correct the reduced AA digestibility. The effect of adding extra l-Arg and dl-Met to diets on the apparent (AID) and standardised ileal digestibility (SID) of AA was analysed in a 10-day experiment conducted with 10 ileal-cannulated HS pigs (25.3 ± 2.4 kg body weight). The pigs were divided into two treatments: Control, wheat-soybean meal diet supplemented with l-Lys, l-Thr, dl-Metand l-Trp; and control diet plus 0.20% l-Arg and 0.20% dl-Met (Arg + Met). Following an 8-day diet adaptation period, ileal digesta was continuously collected for 12 h, starting at 0700, on Days 9 and 10. All pigs were daily exposed to 29.6-36.1°C; ileal temperature was continuously monitored at 15-min intervals. Feed was provided twice a day. The ileal temperature ranged from 40.3 to 41.5°C. Daily ileal outflow of His, Ile, Leu, Phe, Thr, Serand Tyr decreased (p < 0.05), and that of Arg, Valand Pro tended to decrease (p < 0.10) in the Arg + Met pigs. The AID of Arg, His, Met, Thrand Tyr, and the SID of His, Met, and Thr increased in pigs fed the Arg + Met diet (p < 0.05). Thr and Val had the lowest AID values whereas Arg, Met, and Lys had the highest values. Arg (r = 0.64) and Met (r = 0.84) intake were highly correlated with their AID values; Met intake was highly correlated with its SID value (r = 0.72). Valine and Arg had the lowest whereas Arg had the highest SID values. In conclusion, supplementing l-Arg and dl-Met above the requirement decreases the ileal outflow of several AA, and increases the AID and SID of some essential AA in HS pigs.

Algunas alternativas para mitigar el estrés por calor en animales: arginina y metionina como antioxidantes

Exposure of animals to ambient temperature above the thermo neutral zone caused heat stress. Alterations in digestion and absorption of nutrients as well as damage to the small intestine epithelia associated with the production of reactive oxygen species (ROS) may occur in heat stress pigs, resulting in depressed performance. The cells possess an antioxidant system capable of protecting the animals against the effect of heat stress. However, when ambient temperature increases beyond the thermo neutral zone, ROS production also increases provoking an imbalance between ROS and antioxidant production. This review provides relevant information related to the alterations that occur at intestinal, cellular and molecular level in animals exposed to heat stress, and the effect that methionine and arginine as antioxidant amino acids, and their use in diets for heat stress pigs.

Efecto de un probiótico en dietas para cerdos en estrés por calor sobre el comportamiento, temperatura corporal y frecuencia respiratoria

The addition of a probiotic to the diet of heat-stressed pigs was evaluated on body temperature, respiratory rate, and productive performance. Eighty pigs of 22 kg BW were assigned to the following treatments: 1) housed in thermoneutral conditions (TN) fed with a conventional diet (TN-C); 2) TN, conventional diet added with probiotic (TN-P); 3) housed under heat stress (HS) conditions, conventional diet (HS-C); 4) HS, diet added with probiotic (HS-P). Twenty pigs were used per treatment. Respiration rate and body temperature were recorded, and productive performance was measured. The body temperature of HS pigs decreased by the addition of the probiotic (P<0.05). Although no differences were observed between treatments (P>0.05), the respiration rate was higher at 1700 h than at 0700 h (P<0.05). The addition of the probiotic increased daily weight gain and feed efficiency (P<0.01). It is concluded that the addition of probiotic to diets for HS pigs improves their weight gain and feed conversion.

Arginina afecta la pérdida endógena de aminoácidos en cerdos en estrés por calor

The effect of adding arginine to the diet on the endogenous amino acids (AA) loss in pigs under heat stress (HS) was evaluated. Twelve pigs (25 ± 2.6 Kg) cannulated in the distal ileum were used. There were three treatments: thermal neutral pigs fed a basal semi-purified diet (TN-B); HS pigs fed the basal diet (HS-B); HS pigs fed the basal diet added with 0.20% free Arg (HS-Arg). Pigs were adapted to the diets for 5 days followed by 2 days of ileal digesta collection (12 continuous hours, 0700 to 1900). The endogenous loss of all essential AA was lower (P < 0.001) in the HS-B pigs than in the TN-B or the HS-Arg diet. These data show that HS negatively affects the loss of endogenous AA, and indicate that Arg in the diet helps to counteract that effect.

Short- and Long-Term Exposure to Heat Stress Differently Affect Performance, Blood Parameters, and Integrity of Intestinal Epithelia of Growing Pigs.

Simple SummaryHigh ambient temperature provokes heat stress in animals. Observed signs of heat stress in pigs include altered physiological constants, changes in feeding behavior, reduced weight gain, or even body weight loss. Short-term exposition to heat stress has been associated with alterations in small intestine physiology, including digestion and absorption of nutrients. Those alterations reduce when pigs start the acclimation process to heat stress, which may occur at around one week of exposure to high ambient temperature. In this study, the short- (2 days) and long- (7 days) term exposure to natural heat stress on performance, blood components, and intestinal integrity of growing pigs were analyzed. Short-term heat stress reduced pig performance and altered blood components. Intestinal integrity was affected drastically at day 2 under heat stress conditions, but pigs started to recover most of their growth rate and intestinal integrity at day 7.The effect of short- and long-term exposure to heat stress (HS) was analyzed on blood components, performance, and intestinal epithelium integrity of pigs. Eighteen pigs (36.0 ± 3.5 kg BW) were assigned to three groups: thermo-neutral (TN); 2 d exposure to HS (2dHS); and 7 d exposure to HS (7dHS). Blood chemistry and hemogram analyses were performed; small intestine samples were analyzed for mRNA expression and histology. Compared to TN, 2dHS and 7dHS pigs reduced weight gain and feed intake; weight gain was higher in 7dHS than in 2dHS pigs (p < 0.05). White blood cells, platelet, and hematocrit were affected in 2dHS and 7dHS compared to TN pigs (p < 0.05). Short- and long-term exposure to HS affected blood concentration of triglycerides, urea, total protein, and albumin (p ≤ 0.05). Villi-height and crypt-depth decreased in HS pigs (p < 0.01). Mucin-producing and apoptotic cell number increased in 7dHS compared to TN pigs (p < 0.05). Expression of tight-junction-proteins decreased in 2dHS pigs compared to TN and 7dHS pigs (p < 0.05). Short-term exposure of pigs to HS dramatically affects performance, blood components, and integrity of the small intestine epithelia; nevertheless, pigs show signs of recovery at 7 d of HS exposure.

Effect of live yeast supplementation and feeding frequency in male finishing pigs subjected to heat stress.

In growing pigs, reduced growth during heat stress (HS) is mainly related to decreased feed intake. The study aimed to determine whether the reported positive effects of live yeast (LY) supplementation in HS pigs were due to a modified feeding behaviour or energy metabolism, and if these can be replicated by imposing an increased meal frequency. The effect of LY supplementation [0 (NS) vs. 100 (LY) g/ton of feed], and of feeding window (FW) [unlimited or Unli, 2FW of 1 h each, and 8FW of 15 min each] were measured in entire male finishing pigs (n=36). Ambient temperature was at 22°C during the thermoneutral period (TN; 5 d) and at 28°C during the HS period (5 d). Heat exposure decreased dry matter intake (DMI) and retained energy (RE) (-627 and -460 kJ∙kg BW-0.60∙d-1, respectively; P<0.01). During HS, LY-supplementation in Unli pigs decreased inter-meal intervals (P=0.02) attenuating HS effect on DMI which tended to improve RE (P=0.09). NS-8FW had higher DMI and RE than NS-2FW (P<0.05) but protein deposition (PD) were similar. Supplemented pigs had higher PD during HS regardless of FW (+18 g∙d-1; P=0.03). Comparing the 2FW groups, improved heat tolerance of LY-supplemented pigs were due to improved insulin sensitivity (P<0.05) and latent heat loss capacity after a meal (P<0.05) allowing them to increase their DMI (via an increased number of meals) and thus their energy efficiency. Imposing an increased meal frequency improved DMI in HS pigs but did not replicate positive effects of LY on protein deposition.

Supplementation with artificial sweetener and capsaicin alters metabolic flexibility and performance in heat-stressed and feed-restricted pigs.

Substantial economic losses in animal agriculture result from animals experiencing heat stress (HS). Pigs are especially susceptible to HS, resulting in reductions in growth, altered body composition, and compromised substrate metabolism. In this study, an artificial high-intensity sweetener and capsaicin (CAPS-SUC; Pancosma, Switzerland) were supplemented in combination to mitigate the adverse effects of HS on pig performance. Forty cross-bred barrows (16.2 ± 6 kg) were assigned to one of five treatments: thermal neutral controls (TN) (22 ± 1.2 °C; 38%-73% relative humidity) with ad libitum feed, HS conditions with ad libitum feed with (HS+) or without (HS-) supplementation, and pair-fed to HS with (PF+) or without supplementation (PF-). Pigs in heat-stressed treatments were exposed to a cyclical environmental temperature of 12 h at 35 ± 1.2 °C with 27%-45% relative humidity and 12 h at 30 ± 1.1 °C with 24%-35% relative humidity for 21 d. Supplementation (0.1 g/kg feed) began 7 d before and persisted through the duration of environmental or dietary treatments (HS/PF), which lasted for 21 d. Rectal temperatures and respiration rates (RR; breaths/minute) were recorded thrice daily, and feed intake (FI) was recorded daily. Before the start and at the termination of environmental treatments (HS/PF), a muscle biopsy of the longissimus dorsi was taken for metabolic analyses. Blood samples were collected weekly, and animals were weighed every 3 d during treatment. Core temperature (TN 39.2 ± 0.02 °C, HS- 39.6 ± 0.02 °C, and HS+ 39.6 ± 0.02 °C, P < 0.001) and RR (P < 0.001) were increased in both HS- and HS+ groups, but no difference was detected between HS- and HS+. PF- pigs exhibited reduced core temperature (39.1 ± 0.02 °C, P < 0.001), which was restored in PF+ pigs (39.3 ± 0.02 °C) to match TN. Weight gain and feed efficiency were reduced in PF- pigs (P < 0.05) but not in the PF+ or the HS- or HS+ groups. Metabolic flexibility was decreased in the HS- group (-48.4%, P < 0.05) but maintained in the HS+ group. CAPS-SUC did not influence core temperature or weight gain in HS pigs but did restore core temperature, weight gain, and feed efficiency in supplemented PF pigs. In addition, supplementation restored metabolic flexibility during HS and improved weight gain and feed efficiency during PF, highlighting CAPS-SUC's therapeutic metabolic effects.

Heat Stress More Negatively Impacts Cardiac Muscle Mitochondria in Female Versus Male Pigs

With continued trends toward more frequent and more severe heat events there is a greater risk of environment‐induced heat stress (HS). How persistently elevated core temperatures impacts body tissues remains largely unknown. Our preliminary evidence indicates HS may negatively impact cardiac tissue and that biological sex may play a role in HS‐mediated pathology. To further test the hypothesis that cardiac muscle mitochondria are more negatively impacted by HS in females than in males, samples were isolated from the left ventricle (LV) of the heart from 3‐month‐old castrated male and prepubertal female pigs that were exposed to thermoneutral (TN) conditions (n = 4 per sex) or HS conditions for 24 h at 37°C (HS; n = 6 per sex). Samples were analyzed for citrate synthase (CS) and cytochrome c oxidase (COX) activities, and for mitochondrial oxidative phosphorylation (P) and electron transfer (E) capacities via high resolution respirometry. Data were analyzed by mixed linear models in SAS v9.4 with treatment, sex, and treatment × sex as fixed effects. A traditional marker of mitochondrial volume density, CS activity, tended to be greater in TN males compared to HS males (P = 0.08) but was unaffected by HS in female pigs. Conversely, intrinsic (relative to CS activity) mitochondrial function, as measured by COX activity, was greater in TN females than HS females (P = 0.04) and within HS, males maintained greater intrinsic mitochondrial function than females (P = 0.02). Both integrative (relative to tissue wet weight) and intrinsic mitochondrial leak respiration were greater in HS than TN pigs (P = 0.03) but the contribution of leak to total E (flux control ratio; FCRLEAK) tended to be greater in males than females (P = 0.07). Conversely, both integrative and intrinsic maximal E (ECI+II) tended to be greater in female than male pigs (P = 0.08) indicating a greater degree of excess electron transfer capacity in females. The contribution of complex I‐supported P (PCI) to total E (FCRPCI) tended to be greater in TN compared to HS pigs regardless of sex (P = 0.09) and the contribution of maximal P to E (FCRPCI+II) was greater in TN females compared to HS females (P = 0.05). This resulted in the FCRPCI+IIbeing greater in males compared to females in the HS condition (P = 0.01), suggesting greater coupling of oxidative phosphorylation and electron transfer in cardiac mitochondria in males during 24 h of HS. These results suggest that HS may negatively impact cardiac muscle mitochondria in female pigs compared to males. Moreover, these data indicate that persistent HS has deleterious consequences for the myocardium and may represent an additional health concern caused by global climate trends. This project was supported by USDA NIFA Award #2020‐68014‐31954.