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.

Excessive heat exposure reduces intestinal integrity and post-absorptive energetics that can inhibit wellbeing and be fatal. Therefore, our objectives were to examine how acute heat stress (HS) alters intestinal integrity and metabolism in growing pigs. Animals were exposed to either thermal neutral (TN, 21°C; 35–50% humidity; n = 8) or HS conditions (35°C; 24–43% humidity; n = 8) for 24 h. Compared to TN, rectal temperatures in HS pigs increased by 1.6°C and respiration rates by 2-fold (P<0.05). As expected, HS decreased feed intake by 53% (P<0.05) and body weight (P<0.05) compared to TN pigs. Ileum heat shock protein 70 expression increased (P<0.05), while intestinal integrity was compromised in the HS pigs (ileum and colon TER decreased; P<0.05). Furthermore, HS increased serum endotoxin concentrations (P = 0.05). Intestinal permeability was accompanied by an increase in protein expression of myosin light chain kinase (P<0.05) and casein kinase II-α (P = 0.06). Protein expression of tight junction (TJ) proteins in the ileum revealed claudin 3 and occludin expression to be increased overall due to HS (P<0.05), while there were no differences in claudin 1 expression. Intestinal glucose transport and blood glucose were elevated due to HS (P<0.05). This was supported by increased ileum Na+/K+ ATPase activity in HS pigs. SGLT-1 protein expression was unaltered; however, HS increased ileal GLUT-2 protein expression (P = 0.06). Altogether, these data indicate that HS reduce intestinal integrity and increase intestinal stress and glucose transport.

The NIH miniature pig was developed specifically for xenotransplantation and has been extensively used as a large animal model in many other biomedical experiments. However the cloning efficiency of this pig is very low (less than 0.2%) and this has been an obstacle to the promising application of these inbred swine genetics for biomedical research. It has been demonstrated that increased histone acetylation in somatic cell nuclear transfer (SCNT) embryos, by applying histone deacetylase inhibitors (HDACi) such as trichostatin A (TSA), significantly enhances the developmental competence in several species. However some researchers also reported that TSA treatment had various detrimental effects on the in vitro and in vivo development of the SCNT embryos. Here we report that treatment with 500 nM Scriptaid, a novel HDACi, significantly enhanced the development SCNT embryos to the blastocyst stage when NIH inbred fetal fibroblast cells (FFCs) (21% vs. 9%, P < 0.05) were used as donors compared to the untreated group. Scriptaid treatment resulted in 8 pregnancies from 10 embryo transfers (ET) and 14 healthy NIH miniature pigs from 8 litters while no viable piglets (only 3 mummies) were obtained from 9 ETs in the untreated group. Thus Scriptaid dramatically increased the cloning efficiency when using inbred genetics from zero to 1.3%. In contrast, Scriptaid treatment decreased the blastocyst rate in IVF embryos (from 37% to 26%, P < 0.05). In conclusion, the extreme low cloning efficiency in the NIH miniature pig may be caused by its inbred genetic background and can be improved by alteration of genomic histone acetylation patterns.

Conceptus-uterine communication is established during trophoblastic elongation when the conceptus synthesizes and releases estrogen, the maternal recognition signal in the pig. Interleukin-1beta (IL-1beta) is a differentially expressed gene during rapid trophoblastic elongation in the pig. The current investigation determined conceptus and endometrial changes in gene expression for IL-1beta, IL-1 receptor antagonist (IL-1Rant), IL-1 receptor type 1 (IL-1RT1), and IL-1 receptor accessory protein (IL-1RAP) in developing peri- and postimplantation conceptuses as well as uterine endometrium collected from cyclic and pregnant gilts. Conceptus IL-1beta gene expression was enhanced during the period of rapid trophoblastic elongation compared with earlier spherical conceptuses, followed by a dramatic decrease in elongated Day 15 conceptuses. IL-1RT1 and IL-1RAP gene expression was greater in Day 12 and 15 filamentous conceptuses compared with earlier morphologies while IL-1Rant gene expression was unchanged by conceptus development. The uterine lumenal content of IL-1beta increased during the process of trophoblastic elongation on Day 12. Uterine IL-1beta content declined on Day 15, reaching a nadir by Day 18 of pregnancy. IL-1beta gene expression in porcine conceptuses was temporally associated with an increase in endometrial IL-1RT1 and IL-1RAP gene expression in pregnant gilts. Endometrial IL-1beta and IL-1Rant gene expression were lowest during Days 10-15 of the estrous cycle and pregnancy. The temporal expression of IL-1beta during conceptus development and the initiation of conceptus-uterine communication suggests conceptus IL-1beta synthesis plays an important role in porcine conceptus elongation and the establishment of pregnancy in the pig.

Faulty epigenetic reprogramming of somatic nuclei is likely to be a major cause of low success observed in all mammals produced through somatic cell nuclear transfer (SCNT). It has been demonstrated that the developmental competence of SCNT embryos in several species were significantly enhanced via treatment of histone deacetylase inhibitors (HDACi) such as trichostatin A (TSA) to increase histone acetylation. Here we report that 50 nM TSA for 10 hrs after activation increased the developmental competence of porcine SCNT embryos constructed from Landrace fetal fibroblast cells (FFCs) in vitro and in vivo, but not at higher concentrations. Therefore we optimized the application of another novel HDACi, Scriptaid, for development of porcine SCNT embryos. We found that treatment with 500 nM Scriptaid significantly enhanced the development SCNT embryos to the blastocyst stage when outbred Landrace FFCs and ear fibroblast cells (EFCs) were used as donors compared to the untreated group. Scriptaid increased the overall cloning efficiency from 0.4% (untreated group) to 1.6% for Landrace FFCs and 0% to 3.7% for Landrace EFCs. Moreover, treatment of SCNT embryos with Scriptaid improved the histone acetylation on Histone H4 at lysine 8 (AcH4K8) in a pattern similar to that of the in vitro fertilized (IVF) embryos.