Biology of heat stress; the nexus between intestinal hyperpermeability and swine reproduction.

Unfavorable weather conditions are one of the largest constraints to maximizing farm animal productivity. Heat stress (HS), in particular, compromises almost every metric of profitability and this is especially apparent in the grow-finish and reproductive aspects of the swine industry. Suboptimal production during HS was traditionally thought to result from hypophagia. However, independent of inadequate nutrient consumption, HS affects a plethora of endocrine, physiological, metabolic, circulatory, and immunological variables. Whether these changes are homeorhetic strategies to survive the heat load or are pathological remains unclear, nor is it understood if they temporally occur by coincidence or if they are chronologically causal. However, mounting evidence suggest that the origin of the aforementioned changes lie at the gastrointestinal tract. Heat stress compromises intestinal barrier integrity, and increased appearance of luminal contents in circulation causes local and systemic inflammatory responses. The resulting immune activation is seemingly the epicenter to many, if not most of the negative consequences HS has on reproduction, growth, and lactation. Interestingly, thermoregulatory and production responses to HS are only marginally related. In other words, increased body temperature indices poorly predict decreases in productivity. Further, HS induced malnutrition is also a surprisingly inaccurate predictor of productivity. Thus, selecting animals with a "heat tolerant" phenotype based solely or separately on thermoregulatory capacity or production may not ultimately increase resilience. Describing the physiology and mechanisms that underpin how HS jeopardizes animal performance is critical for developing approaches to ameliorate current production issues and requisite for generating future strategies (genetic, managerial, nutritional, and pharmaceutical) aimed at optimizing animal well-being, and improving the sustainable production of high-quality protein for human consumption.

Characterizing the acute heat stress response in gilts: I. Thermoregulatory and production variables.

Identifying traits associated with susceptibility or tolerance to heat stress (HS) is a prerequisite for developing strategies to improve efficient pork production during the summer months. Study objectives were to determine the relationship between the thermoregulatory and production responses to acute HS in pigs. Prepubertal gilts (n = 235; 77.9 ± 1.2 kg BW) were exposed to a thermoneutral (TN) period (P1, 24 h; 21.9 ± 0.5 °C, 62 ± 13% RH; fed ad libitum) followed immediately by a subsequent acute HS period (P2, 24 h; 29.7 ± 1.3 °C, 49 ± 8% RH; fed ad libitum). Rectal temperature (TR), skin temperature (TS), and respiration rate (RR) were monitored and BW and feed intake (FI) were determined. All pigs had increased TR, TS, and RR (0.80 °C, 5.65 °C, and 61.2 bpm, respectively; P < 0.01) and decreased FI and BW (29% and 1.10 kg, respectively; P < 0.01) during P2 compared to P1. Interestingly, body temperature indices did not explain variation in FI during P2 (R2 ≤ 0.02). Further, the percent change in BW during P2 was only marginally explained by each body temperature index (R2 ≤ 0.06) or percent change in FI (R2 = 0.14). During HS, TR was strongly correlated with P1 TR (r = 0.72, P < 0.01), indicating a pig's body temperature during TN conditions predicts the severity of hyperthermia during HS. Additionally, the change in TR (ΔTR, HS TR - TN TR) was larger in pigs retrospectively classified as susceptible (SUS) as compared to tolerant (TOL) pigs (1.05 vs. 0.51 °C, respectively; P < 0.01). In summary, thermoregulatory responses and production variables during acute HS are only marginally related. Further, changes in BW and FI were unexpectedly poorly correlated during acute HS (r = 0.34; P < 0.01). Collectively, suboptimal growth is largely independent on the thermoregulatory response and hypophagia during acute HS. Consequently, incorporating solely body temperature indices into a genetic index is likely insufficient for substantial progress in selecting HS tolerant pigs.

Effects of heat stress and insulin sensitizers on pig adipose tissue.

Heat stress (HS) negatively impacts several swine production variables, including carcass fat quality and quantity. Pigs reared in HS have more adipose tissue than energetically predicted, explainable, in part, by HS-induced hyperinsulinemia. Study objectives were to evaluate insulin's role in altering fat characteristics during HS via feeding insulin-sensitizing compounds. Forty crossbred barrows (113 ± 9 kg BW) were randomly assigned to one of five environment by diet treatments: 1) thermoneutral (TN) fed ad libitum (TNAL), 2) TN and pair-fed (TNPF), 3) HS fed ad libitum (HSAL), 4) HS fed ad libitum with sterculic oil (SO) supplementation (HSSO; 13 g/d), and 5) HS fed ad libitum with dietary chromium (Cr) supplementation (HSCr; 0.5 mg/d; Kemin Industries, Des Moines, IA). The study consisted of three experimental periods (P). During P0 (2 d), all pigs were exposed to TN conditions (23 ± 3 °C, 68 ± 10% RH) and fed ad libitum. During P1 (7 d), all pigs received their respective dietary supplements, were maintained in TN conditions, and fed ad libitum. During P2 (21 d), HSAL, HSSO, and HSCr pigs were fed ad libitum and exposed to cyclical HS conditions (28 to 33 °C, 58 ± 10% RH). The TNAL and TNPF pigs remained in TN conditions and were fed ad libitum or pair-fed to their HSAL counterparts. Rectal temperature (TR), respiration rate (RR), and skin temperature (TS) were obtained daily at 0600 and 1800 h. At 1800 h, HS exposed pigs had increased TR, RR, and TS relative to TNAL controls (1.13 °C, 48 bpm, and 3.51 °C, respectively; P < 0.01). During wk 2 and 3 of P2, HSSO pigs had increased 1800 h TR relative to HSAL and HSCr (~0.40 and ~0.42 °C, respectively; P ≤ 0.05). Heat stress decreased ADFI and ADG compared to TNAL pigs (2.24 vs. 3.28 and 0.63 vs. 1.09 kg/d, respectively; P < 0.01) and neither variable was affected by SO or Cr supplementation. Heat stress increased or tended to increase moisture content of abdominal (7.7 vs. 5.9%; P = 0.07) and inner s.c. (11.4 vs. 9.8%; P < 0.05) adipose depots compared to TNAL controls. Interestingly, TNPF pigs also had increased adipose tissue moisture content and this was most pronounced in the outer s.c. depot (15.0 vs. 12.2%; P < 0.01) compared to TNAL pigs. Heat stress had little or no effect on fatty acid composition of abdominal, inner, and outer s.c. adipose tissue depots. In summary, the negative effects of HS on fat quality do not appear to be fatty acid composition related, but may be explained by increased adipose tissue moisture content.

Disruption of female reproductive function by endotoxins.

Endotoxemia can be caused by obesity, environmental chemical exposure, abiotic stressors and bacterial infection. Circumstances that deleteriously impact intestinal barrier integrity can induce endotoxemia, and controlled experiments have identified negative impacts of lipopolysaccharide (LPS; an endotoxin mimetic) on folliculogenesis, puberty onset, estrus behavior, ovulation, meiotic competence, luteal function and ovarian steroidogenesis. In addition, neonatal LPS exposures have transgenerational female reproductive impacts, raising concern about early life contacts to this endogenous reproductive toxicant. Aims of this review are to identify physiological stressors causing endotoxemia, to highlight potential mechanism(s) by which LPS compromises female reproduction and identify knowledge gaps regarding how acute and/or metabolic endotoxemia influence(s) female reproduction.

Determining the effects of early gestation in utero heat stress on postnatal fasting heat production and circulating biomarkers associated with metabolism in growing pigs.

The study objective was to characterize effects of early gestation in utero heat stress (IUHS) on postnatal fasting heat production (FHP) and blood biomarkers associated with metabolism in growing pigs. Based on previous observation of increased postnatal core body temperature set point in IUHS pigs, we hypothesized that FHP would be altered during postnatal life because of IUHS. Pregnant first-parity gilts were exposed to thermoneutral (TN; = 4; 17.8 ± 0.1°C) or heat stress (HS; = 4; cyclical 28 to 38°C) conditions from d 30 to 60 of gestation. At weaning (21 d of age), 2 median-weight male pigs (1 barrow and 1 boar) were selected from each litter ( = 8 in utero TN [IUTN] and 8 IUHS pigs) and then housed in TN conditions based on age. Blood samples were collected at 8, 9, and 10 wk of age when pigs were in a fed state to analyze thyroxine (T4) and triiodothyronine (T3) concentrations. Pigs were trained to enter an indirect calorimeter from wk 8 through 10 of life and then acclimated over a 24-h period 1 wk prior to testing. At 12 wk of age, pigs were fasted for 24 h, and then indirect calorimetry was performed on individual pigs over a 23-h testing period to determine FHP and the respiratory quotient in 3 intervals (0900 to 1700 h, 1700 to 0000 h, and 0000 to 0800 h). Body weight was determined before and after testing and was similar for all pigs ( = 0.77; 37.0 ± 0.5 kg BW). Data were analyzed using PROC MIXED in SAS 9.4. No boar vs. barrow differences were observed with any analysis. Overall, FHP per kilogram BW was greater ( = 0.03; 12.1%) in IUHS pigs compared with IUTN pigs. Fasting heat production per kilogram BW was greater ( < 0.01; 19.8%) from 0900 to 1700 h compared with 1700 to 0000 h and 0000 to 0800 h and was greater (10.9%) from 1700 to 0000 h compared with 0000 to 0800 h. The RQ did not differ by in utero treatment ( = 0.51; 0.72 ± 0.01); however, the RQ was increased ( < 0.01; 13.0%) from 1700 to 0000 h compared with 0900 to 1700 h and 0000 to 0800 h. No other FHP and RQ differences were detected. Although no in utero treatment differences were observed for T4 ( = 0.11; 52.2 ± 6.2 ng/mL), T3 was greater overall ( = 0.04; 19.5%) in IUHS pigs than in IUTN pigs. In summary, FHP and circulating T3 were increased in IUHS pigs, and this may have implications for postnatal production efficiency in pigs gestated during hot summer months.

Genome-wide methylation profile following prenatal and postnatal dietary omega-3 fatty acid supplementation in pigs.

The objective of this study was to determine how prenatal and postnatal dietary omega-3 fatty acids alter white blood cell (leukocyte) DNA methylation of offspring. Fifteen gilts (n = 5 per treatment) were selected from one of three treatments: (i) control diet throughout gestation, lactation and nursery phase (CON); (ii) algal omega-3 fatty acid supplementation enriched in EPA and DHA (Gromega™ ) fed throughout gestation, lactation and nursery phase (Cn3); or (iii) Gromega™ supplementation maternally, during gestation and lactation only, and control diet during the nursery phase (Mn3). At 11 weeks of age and after 8 weeks of post-weaning nursery feeding, buffy coat genomic DNA was subjected to methyl CpG binding protein sequencing. The methylation enriched profile mapped to 26% of the porcine genome. On chromosome 4, a 27.7-kb differentially methylated region downstream of RUNX1T1 was hypomethylated in the Mn3 and Cn3 groups by 91.6% and 85.0% respectively compared to CON pigs. Conversely, hypermethylation was detected in intergenic regions of chromosomes 4 and 12. Regulatory impact factor and differential hubbing methods were used to identify pathways that were coordinately regulated by methylation due to feeding EPA and DHA during pregnancy. Despite limited ability to detect differential methylation, we describe methods that allow the identification of coordinated epigenetic regulation that could not otherwise be detected from subtle single locus changes in methylation. These data provide evidence of novel epigenetic regulation by maternal and early life supplementation of omega-3 fatty acids that may have implications to growth and inflammatory processes.

In utero heat stress increases postnatal core body temperature in pigs.

In utero heat stress (IUHS) negatively impacts postnatal development, but how it alters future body temperature parameters and energetic metabolism is not well understood. Future body temperature indices and bioenergetic markers were characterized in pigs from differing in utero thermal environments during postnatal thermoneutral (TN) and cyclical heat stress (HS) exposure. First-parity pregnant gilts ( = 13) were exposed to 1 of 4 ambient temperature (T) treatments (HS [cyclic 28°C to 34°C] or TN [cyclic 18°C to 22°C]) applied for the entire gestation (HSHS, TNTN), HS for the first half of gestation (HSTN), or HS for the second half of gestation (TNHS). Twenty-four offspring (23.1 ± 1.2 kg BW; = 6 HSHS, = 6 TNTN, = 6 HSTN, = 6 TNHS) were housed in TN (21.7°C ± 0.7°C) conditions and then exposed to 2 separate but similar HS periods (HS1 = 6 d; HS2 = 6 d; cycling 28°C to 36°C). Core body temperature (T) was assessed every 15 min with implanted temperature recorders. Regardless of in utero treatment, T increased during both HS periods ( = 0.01; 0.58°C). During TN, HS1, and HS2, all IUHS pigs combined had increased T ( = 0.01; 0.36°C, 0.20°C, and 0.16°C, respectively) compared to TNTN controls. Although unaffected by in utero environment, the total plasma thyroxine to triiodothyronine ratio was reduced ( = 0.01) during HS1 and HS2 (39% and 29%, respectively) compared with TN. In summary, pigs from IUHS maintained an increased T compared with TNTN controls regardless of external T, and this thermal differential may have practical implications to developmental biology and animal bioenergetics.

Carcass composition of market weight pigs subjected to heat stress in utero and during finishing.

Objectives were to investigate the effects of prolonged gestational and/or postnatal heat stress on performance and carcass composition of market weight pigs. Pregnant gilts were exposed to gestational heat stress (GHS, 28°C to 34°C, diurnal) or thermal neutral (18°C to 22°C, diurnal) conditions during the entire gestation or during the first or second half of gestation. At 14 wk of age (58 ± 5 kg), barrows were housed in heat stress (32°C, HS) or thermal neutral (21°C, TN) conditions. Feed intake and BW were recorded weekly, and body temperature parameters were monitored twice weekly until slaughter (109 ± 5 kg). Organs were removed and weighed, and loin eye area (LEA) and back fat thickness (BF) were measured after carcass chilling. Carcass sides were separated into lean, separable fat, bone, and skin components and were weighed. Moisture, lipid, and protein content were determined in the LM at the 10th rib. Data were analyzed using a split plot with random effect of dam nested within gestational treatment. Carcass measurements included HCW as a covariate to control for weight. Planned orthogonal contrast statements were used to evaluate the overall effect of GHS in the first half, second half, or any part of gestation. Gestational heat stress did not alter postnatal performance or most body temperature parameters (P > 0.10). However, ADFI in the finishing period was increased (P < 0.05) in response to GHS, particularly in pigs receiving GHS in the first half of gestation. Gestational heat stress during the first half of gestation decreased head weight as a percent of BW (P = 0.02), whereas GHS in the second half of gestation decreased bone weight as a percent of BW (P = 0.02). Heat stress reduced ADG, BW, and HCW (P < 0.0001). Lean tissue was increased in HS pigs on both a weight and percentage basis (P < 0.0001), but LEA was similar to TN carcasses (P = 0.38). Carcasses from HS barrows also had less carcass separable fat (P < 0.01) and tended to have less BF (P = 0.06) compared with those from TN barrows, even after controlling for HCW. However, percent intramuscular fat did not differ between treatments (P = 0.48). The LM from HS carcasses had a greater moisture to protein ratio (P = 0.04). HS barrows also had decreased heart (P < 0.001) and kidney (P < 0.0001) as a percent of BW compared with TN pigs. In summary, GHS may affect head and bone development, subsequently affecting carcass composition. Chronic HS during finishing results in longer times to reach market weight and a leaner carcass once market weight is achieved.

Effects of in utero heat stress on postnatal body composition in pigs: I. Growing phase.

Environmentally induced heat stress (HS) negatively influences production variables in agriculturally important species. However, the extent to which HS experienced in utero affects nutrient partitioning during the rapid lean tissue accretion phase of postnatal growth is unknown. Study objectives were to compare future whole-body tissue accretion rates in pigs exposed to differing in utero and postnatal thermal environments when lean tissue deposition is likely maximized. Pregnant sows were exposed to thermoneutral (TN; cyclical 15°C nighttime and 22°C daytime; n = 9) or HS (cyclical 27°C nighttime and 37°C daytime; n = 12) conditions during their entire gestation. Twenty-four offspring from in utero TN (IUTN; n = 6 gilts and 6 barrows; 30.8 ± 0.2 kg BW) and in utero HS (IUHS; n = 6 gilts and 6 barrows; 30.3 ± 0.2 kg BW) were euthanized as an initial slaughter group (ISG). Following the ISG, 48 pigs from IUTN (n = 12 gilts and 12 barrows; 34.1 ± 0.5 kg BW) and IUHS (n = 12 gilts and 12 barrows; 33.3 ± 0.3 kg BW) were exposed to constant HS (34.1 ± 2.4°C) or TN (21.5 ± 2.0°C) conditions until they reached 61.5 ± 0.8 kg BW, at which point they were sacrificed and their whole-body composition was determined. Homogenized carcasses were analyzed for N, crude fat, ash, water, and GE content. Data were analyzed using PROC MIXED in SAS 9.3. Rectal temperature and respiration rate increased (P < 0.01) during postnatal HS compared to TN (39.4 vs. 39.0°C and 94 vs. 49 breaths per minute, respectively). Regardless of in utero environment, postnatal HS reduced (P < 0.01) feed intake (2.06 vs. 2.37 kg/d) and ADG (0.86 vs. 0.98 kg/d) compared to TN conditions. Postnatal HS did not alter water, protein, and ash accretion rates but reduced lipid accretion rates (198 vs. 232 g/d; P < 0.04) compared to TN-reared pigs. In utero environment had no effect on future tissue deposition rates; however, IUHS pigs from the ISG had reduced liver weight (P < 0.04; 17.9%) compared to IUTN controls. In summary, postnatal HS reduced adipose tissue accretion rates, but IUHS did not appear to impact either lean or adipose tissue accretion during this specific growth phase.

Effects of in utero heat stress on postnatal body composition in pigs: II. Finishing phase.

The detrimental effects of heat stress (HS) on animal productivity have been well documented. However, whether in utero HS interacts with a future thermal insult to alter tissue deposition during the finishing phase of pig growth is unknown. Study objectives were to compare the subsequent rate and quantity of whole-body tissue accretion in pigs exposed to differing in utero and postnatal thermal environments. Pregnant sows were exposed to thermoneutral (TN; cyclical 15°C nighttime and 22°C daytime; n = 9) or HS (cyclical 27°C nighttime and 37°C daytime; n = 11) conditions during their entire gestation. Twenty-four offspring from in utero TN (IUTN; n = 6 gilts and 6 barrows; 62.4 ± 0.7 kg BW) and in utero HS (IUHS; n = 6 gilts and 6 barrows; 61.9 ± 0.8 kg BW) were euthanized as part of an initial slaughter group (ISG). After the ISG, 48 pigs from IUTN (n = 12 gilts and 12 barrows; 66.1 ± 1.0 kg BW) and IUHS (n = 12 gilts and 12 barrows; 63.4 ± 0.7 kg BW) were exposed to constant HS (34.4 ± 1.8°C) or TN (22.7 ± 2.5°C) conditions until they reached 80.5 ± 1.5 kg BW, at which point they were sacrificed and their whole-body composition was determined. Homogenized carcasses were analyzed for N, crude fat, ash, water, and GE content. Data were analyzed using PROC MIXED in SAS 9.3. Rectal temperature and respiration rate increased during postnatal HS compared to TN (39.6 vs. 39.3°C and 92 vs. 58 breaths per minute, respectively; P < 0.01). Postnatal HS decreased (P < 0.01) feed intake (2.13 vs. 2.65 kg/d) and ADG (0.70 vs. 0.94 kg/d) compared to TN conditions, but neither variable was influenced by in utero environment. Whole-body protein and lipid accretion rates were reduced in HS pigs compared to TN controls (126 vs. 164 g/d and 218 vs. 294 g/d, respectively; P < 0.04). Independent of postnatal environments, IUHS reduced future protein accretion rates (16%; P < 0.01) and tended to increase lipid accretion rates (292 vs. 220 g/d; P < 0.07) compared to IUTN controls. The ratio of lipid to protein accretion rates increased (95%; P < 0.01) in IUHS pigs compared to IUTN controls. In summary, the future hierarchy of tissue accretion is altered by IUHS, and this modified nutrient partitioning favors adipose deposition at the expense of skeletal muscle during this specific phase of growth.

Identification of species-specific novel transcripts in pig reproductive tissues using RNA-seq.

Although structural properties of the porcine reproductive system are shared by many placental mammals, some combination of these properties is unique to pigs. To explore whether genomic elements specific to pigs could potentially underlie this uniqueness, we made the first step to identify novel transcripts in two representative pig reproductive tissues by the technique of massively parallel sequencing. To automate the whole process, we built a computational pipeline, which can also be easily extended for similar studies in other species. In total, 5516 and 9061 novel transcripts were found, and 159 and 252 novel transcripts appear to be specific to pigs for the placenta and testis respectively. Furthermore, these novel transcripts were found to be enriched in quantitative trait loci (QTL) regions for reproduction traits in pigs. We validated eight of these novel transcripts by quantitative real-time PCR. With respect to their genomic organization and their functional relationship to reproduction, these transcripts need to be further validated and explored in various pig breeds to better comprehend the relevant aspects of pig physiology that contribute to reproductive performance.

High fat diet induced obesity alters ovarian phosphatidylinositol-3 kinase signaling gene expression.

Insulin regulates ovarian phosphatidylinositol-3-kinase (PI3 K) signaling, important for primordial follicle viability and growth activation. This study investigated diet-induced obesity impacts on: (1) insulin receptor (Insr) and insulin receptor substrate 1 (Irs1); (2) PI3K components (Kit ligand (Kitlg), kit (c-Kit), protein kinase B alpha (Akt1) and forkhead transcription factor subfamily 3 (Foxo3a)); (3) xenobiotic biotransformation (microsomal epoxide hydrolase (Ephx1), Cytochrome P450 isoform 2E1 (Cyp2e1), Glutathione S-transferase (Gst) isoforms mu (Gstm) and pi (Gstp)) and (4) microRNA's 184, 205, 103 and 21 gene expression. INSR, GSTM and GSTP protein levels were also measured. Obese mouse ovaries had decreased Irs1, Foxo3a, Cyp2e1, MiR-103, and MiR-21 but increased Kitlg, Akt1, and miR-184 levels relative to lean littermates. These results support that diet-induced obesity potentially impairs ovarian function through aberrant gene expression.

The effects of heat stress and plane of nutrition on metabolism in growing pigs.

Heat stress (HS) jeopardizes pig health, reduces performance variables, and results in a fatter carcass. Whether HS directly or indirectly (via reduced feed intake) is responsible for the suboptimal production is not known. Crossbred gilts (n = 48; 35 ± 4 kg BW) were housed in constantly climate-controlled rooms in individual pens and exposed to 1) thermal-neutral (TN) conditions (20°C; 35% to 50% humidity) with ad libitum intake (n = 18), 2) HS conditions (35°C; 20% to 35% humidity) with ad libitum intake (n = 24), or 3) pair-fed [PF in TN conditions (PFTN), n = 6, to eliminate confounding effects of dissimilar feed intake (FI)]. Pigs in the TN and HS conditions were sacrificed at 1, 3, or 7 d of environmental exposure, whereas the PFTN pigs were sacrificed after 7 d of experimental conditions. Individual rectal temperature (Tr), skin temperature (Ts), respiration rates (RR), and FI were determined daily. Pigs exposed to HS had an increase (P < 0.01) in Tr (39.3°C vs. 40.8°C) and a doubling in RR (54 vs. 107 breaths per minute). Heat-stressed pigs had an immediate (d 1) decrease (47%; P < 0.05) in FI, and this magnitude of reduction continued through d 7; by design the nutrient intake pattern for the PFTN controls mirrored the HS group. By d 7, the TN and HS pigs gained 7.76 and 1.65 kg BW, respectively, whereas the PFTN pigs lost 2.47 kg BW. Plasma insulin was increased (49%; P < 0.05) in d 7 HS pigs compared with PFTN controls. Compared with TN and HS pigs, on d 7 PFTN pigs had increased plasma NEFA concentrations (110%; P < 0.05). Compared with TN and PFTN controls, on d 7 circulating N(τ)-methylhistidine concentrations were increased (31%; P < 0.05) in HS pigs. In summary, despite similar nutrient intake, HS pigs gained more BW and had distinctly different postabsorptive bioenergetic variables compared with PFTN controls. Consequently, these heat-induced metabolic changes may in part explain the altered carcass phenotype observed in heat-stressed pigs.

Heat stress reduces barrier function and alters intestinal metabolism in growing pigs.

High ambient temperature exposure can cause major reductions in intestinal function, pig performance, and, if severe enough, mortality. Therefore, our objective was to examine how acute heat stress (HS) alters growing pig intestinal integrity and metabolism. Individually penned crossbred gilts and barrows (46 ± 6 kg BW) were exposed to either thermal neutral (TN; 21°C; 35 to 50% humidity; n = 8) or HS conditions (35°C; 24 to 43% humidity; n = 8) for 24 h. All pigs had ad libitum access to feed and water. Rectal temperature (Tr), respiration rates (RR), BW, and feed intake (FI) were measured. Pigs were killed after 24 h of environmental exposure and freshly isolated ileum and colon samples were mounted into modified Ussing chambers. Segments were analyzed for glucose and glutamine nutrient transport and barrier integrity [transepithelial electrical resistance (TER) and fluorescein isothiocyanate-labeled dextran transport]. As expected, pigs exposed to HS had an increase in Tr (39.3 vs. 40.9°C; P < 0.01) and RR (52 vs. 119 breaths per minute; P < 0.05). Heat stress decreased FI (53%; P < 0.05) and BW (-2.2 kg; P < 0.05) compared to TN pigs. Compared to TN pigs, mucosal heat shock protein 70 increased (101%; P < 0.05) whereas intestinal integrity was compromised in the HS pigs (ileum and colon TER decreased 52 and 24%, respectively; P < 0.05). Furthermore, serum endotoxin concentrations increased 200% due to HS (P = 0.05). Intestinal glucose transport and blood glucose were elevated due to HS (P < 0.05). However, ileal sucrase and maltase activities decreased in HS pigs (30 and 24%, respectively; P < 0.05). Altogether, these data indicate that high ambient heat loads reduce intestinal integrity and increase circulating endotoxin and stress in pigs. Furthermore, glucose transport and digestive capacity are altered during acute HS.

The role of gene discovery, QTL analyses and gene expression in reproductive traits in the pig.

The reproductive performance of the sow is one of the key factors affecting production profitability of the pig industry. Reproductive traits are in general, lowly heritable, and with reliable markers, they can be used to enhance current selection procedures for improvement of these traits. To find potential markers, large scale quantitative trait loci (QTL) and candidate gene studies have been conducted for reproductive traits. The present review discusses QTL and candidate gene discovery, large scale SNP association studies, gene expression profiling and discovery of miRNA regulation of pig reproductive tissues. Many QTL have been found for reproduction traits and a limited number of useful genes (e.g.: ESR1, PRLR, FSHB, EPOR and RBP4) have been found to have significant associations with reproductive traits. Expression studies with reproductive tissues have revealed differential expression within a few gene networks which need further mapping and association analyses to select prospective gene markers. The near completion of the pig genome sequence and the development of high density SNP chips will allow for large scale SNP association studies for pig reproductive traits in the future. Collection of appropriate phenotypes in large numbers and in broad populations representative of the swine industry are required if such genomic studies will ultimately be successful.

Transcriptional, post-transcriptional and epigenetic control of porcine oocyte maturation and embryogenesis.

Embryogenesis is a complex process that is controlled at various levels. As new discoveries are made about molecular mechanisms that control development in other species, it is apparent that these same mechanisms regulate pig embryogenesis as well. Methylation of DNA and modification of histones regulate transcription, and mechanisms such as ubiquitinization, autophagy and microRNAs regulate development post-transcriptionally. Each of these systems of regulation is highly dynamic in the early embryo. A better understanding of each of these levels of regulation can provide tools to potentially improve the reproductive process in pigs, to improve methods of creating pig embryos and cloned embryos in vitro, and to provide markers for predicting developmental competence of the embryo.

Update on laparoscopic, robotic, and minimally invasive vaginal surgery for pelvic floor repair.

Advanced laparoscopic surgery marked the beginning of minimally invasive pelvic surgery. This technique lead to the development of laparoscopic hysterectomy, colposuspension, paravaginal repair, uterosacral suspension, and sacrocolpopexy without an abdominal incision. With laparoscopy there is a significant decrease in postoperative pain, shorter length of hospital stay, and a faster return to normal activities. These advantages made laparoscopy very appealing to patients. Advanced laparoscopy requires a special set of surgical skills and in the early phase of development training was not readily available. Advanced laparoscopy was developed by practicing physicians, instead of coming down through the more usual academic channels. The need for special training did hinder widespread acceptance. Nonetheless by physician to physician training and society training courses it has continued to grow and now has been incorporated in most medical school curriculums. In the last few years there has been new interest in laparoscopy because of the development of robotic assistance. The 3D vision and 720 degree articulating arms with robotics have made suture intensive procedures much easier. Laparosco-pic robotic-assisted sacrocolpopexy is in the reach of most surgeons. This field is so new that there is very little data to evaluate at this time. There are short comings with laparoscopy and even with robotic-assisted procedures it is not the cure all for pelvic floor surgery. Laparoscopic procedures are long and many patients requiring pelvic floor surgery have medical conditions preventing long anesthesia. Minimally invasive vaginal surgery has developed from the concept of tissue replacement by synthetic mesh. Initially sheets of synthetic mesh were tailored by physicians to repair the anterior and posterior vaginal compartment. The use of mesh by general surgeons for hernia repair has served as a model for urogynecology. There have been rapid improvements in biomaterials and specialized kits have been developed by industry. The purpose of this article is to present an update in urogynecologic laparoscopy, robotic surgery, and minimally invasive vaginal surgery.

Porcine conceptus Oct-4 mRNA expression during peri-implantation development.

OCT-4 is a transcriptional regulator of pluripotent cells throughout embryonic and germ cell lineage development prior to cellular differentiation during murine, bovine and porcine peri-implantation development. In contrast to murine OCT-4 expression, bovine and porcine expression is detected in both the inner cell mass and trophoblast. Delayed down regulation of OCT-4 gene expression in farm species may be a consequence of the lengthened period of peri-implantation. Expression of OCT-4 mRNA has not been characterized during conceptus attachment to the uterine surface in the pig. The objective of the present study was to determine conceptus OCT-4 mRNA expression during porcine peri-implantation development from days 10-17 of gestation. Total RNA was extracted from multiple pools of conceptuses collected on days 10, 12, 13, 15 and 17 of pregnancy. Quantitative RT-PCR was utilized to assay conceptus OCT-4 mRNA synthesis. Day of conceptus development significantly affected (p < 0.001) OCT-4 mRNA expression. Conceptus expression of OCT-4 was greatest on days 10 and 12 of pregnancy being approximately 7.7- and 11.6-fold greater compared to expression on days 15 and 17, respectively. Results from the present study suggest that down regulation of OCT-4 may be critical in trophoblastic expansion and uterine epithelial attachment during establishment of pregnancy in the pig.

Porcine endometrial and conceptus tissue kallikrein 1, 4, 11, and 14 gene expression.

Previous studies have suggested that the porcine endometrium may express several tissue kallikreins during the estrous cycle and early pregnancy. The present study investigated porcine endometrial and conceptus tissue kallikrein 1, 4, 11, and 14 mRNA expression during the estrous cycle and early pregnancy. Tissue kallikrein (KLK) gene expression was evaluated using quantitative RT-PCR and in situ hybridization. KLK1 expression was similar across the estrous cycle and early pregnancy, and localized to the endometrial luminal (L) and glandular (G) epithelium. KLK4 endometrial mRNA expression was greatest on days 0, 5, and 10 when compared with days 12, 15, and 17 of the estrous cycle and greater in cyclic compared with pregnant gilts. Expression of KLK4 was more intense in the stroma and uterine epithelium from days 0 to 10 of the estrous cycle. Endometrial KLK11 mRNA was not different between cyclic and pregnant gilts but the expression was greatest on days 10 and 12 compared with all other days evaluated. There was an increased intensity of KLK11 gene expression in the stratum compactum on day 10 of the estrous cycle and early pregnancy. Endometrial KLK14 mRNA expression was not detectable on days 5 and 10 but was expressed on days 0, 12, 15, and 17 of the estrous cycle and pregnancy. KLK14 expression was localized in the uterine L and G epithelium, and stroma throughout the endometrium after day 10. Conceptus KLK1 mRNA did not change from days 10 to 17 of gestation. However, conceptus KLK4, and 14 mRNA expression was greatest on day 10 with expression declining after day 14 of gestation. Expression of the various tissue kallikreins in the endometrium and conceptus during the estrous cycle and early pregnancy in the pig can serve in the activation of growth factors and tissue remodeling during the establishment of pregnancy.