Conceptus interferon gamma is essential for establishment of pregnancy in the pig†.

Establishment and maintenance of pregnancy in the pig is a complex process that relies on conceptus regulation of the maternal proinflammatory response to endometrial attachment. Following elongation, pig conceptuses secrete interferon gamma (IFNG) during attachment to the endometrial luminal epithelium. The objective here was to determine if conceptus production of IFNG is important for early development and establishment of pregnancy. CRISPR/Cas9 gene editing and somatic cell nuclear transfer technologies were used to create an IFNG loss-of-function study in pigs. Wild-type (IFNG+/+) and null (IFNG-/-) fibroblast cells were used to create embryos through somatic cell nuclear transfer. IFNG expression was not detected in IFNG-/- conceptuses on either day 15 or day 17 of pregnancy. Ablation of conceptus IFNG production resulted in the reduction of stromal CD3+ and mast cells, which localized to the site of conceptus attachment on day 15. The uteri of recipients with IFNG-/- conceptuses were inflamed, hyperemic and there was an abundance of erythrocytes in the uterine lumen associated with the degenerating conceptuses. The endometrial stromal extracellular matrix was altered in the IFNG-/- embryo pregnancies and there was an increased endometrial mRNA levels for collagen XVII (COL17A1), matrilin 1 (MATN1), secreted phosphoprotein 1 (SPP1), and cysteine-rich secretory protein 3 (CRISP3), which are involved with repair and remodeling of the extracellular matrix. These results indicate conceptus IFNG production is essential in modulating the endometrial proinflammatory response for conceptus attachment and survival in pigs.

Characterizing the postnatal hypothalamic-pituitary-adrenal axis response of in utero heat stressed pigs at 10 and 15 weeks of age.

In utero heat stress alters postnatal physiological and behavioral stress responses in pigs. However, the mechanisms underlying these alterations have not been determined. The study objective was to characterize the postnatal hypothalamic-pituitary-adrenal axis response of in utero heat-stressed pigs. Pigs were subjected to a dexamethasone suppression test followed by a corticotrophin releasing hormone challenge at 10 and 15 weeks of age. Following the challenge, hypothalamic, pituitary, and adrenal tissues were collected from all pigs for mRNA abundance analyses. At 10 weeks of age, in utero heat-stressed pigs had a reduced (P < 0.05) cortisol response to the corticotrophin releasing hormone challenge versus controls. Additionally, the cortisol response tended to be greater overall (P < 0.10) in 15 versus 10-week-old pigs in response to the dexamethasone suppression test. The cortisol response tended to be reduced overall (P < 0.10) in 15 versus 10-week-old pigs in response to the corticotrophin releasing hormone challenge. Hypothalamic corticotropin releasing hormone mRNA abundance tended to be greater (P < 0.10) in in utero heat-stressed versus control pigs at 15-weeks of age. In summary, in utero heat stress altered some aspects of the hypothalamic-pituitary-adrenal axis related to corticotropin releasing hormone signaling, and age influenced this response.

In utero heat stress alters the postnatal innate immune response of pigs.

The effects of in utero heat stress (IUHS) range from decreased growth performance to altered behavior, but the long-term impact of IUHS on postnatal innate immune function in pigs is unknown. Therefore, the study objective was to determine the effects of early gestation IUHS on the immune, metabolic, and stress response of pigs subjected to an 8 hr lipopolysaccharide (LPS) challenge during postnatal life. Twenty-four pregnant gilts were exposed to thermoneutral (TN; n = 12; 17.5 ± 2.1 °C) or heat stress (HS; n = 12; cyclic 26 to 36 °C) conditions from days 6 to 59 of gestation, and then TN conditions (20.9 ± 2.3 °C) from day 60 of gestation to farrowing. At 12 wk of age, 16 IUHS and 16 in utero thermoneutral (IUTN) pigs were selected, balanced by sex and given an intravenous injection of LPS (2 µg/kg BW mixed with sterile saline [SAL] and injected at 2 µL/kg BW) or SAL (2 µL/kg BW). Body temperature was monitored every 30 min, and blood was obtained at 0, 1, 2, 3, 4, 6, and 8 hr following the LPS challenge. Blood samples were analyzed for glucose, insulin, non-esterified fatty acids (NEFA), cortisol, and cytokine concentrations. In addition, white blood cell counts were determined at 0 and 4 hr. Hour 0 data were used as covariates. Body temperature was increased (P < 0.01) in LPS (40.88 ± 0.08 °C) vs. SAL (39.83 ± 0.08 °C) pigs. Eosinophils tended to be decreased overall (P = 0.09; 43.9%) in IUHS vs. IUTN pigs. Glucose concentrations were reduced overall (P = 0.05; 5.9%) in IUHS vs. IUTN pigs. The NEFA concentrations tended to be greater (P = 0.07; 143.4%) in IUHS-LPS pigs compared with all other treatments, and IUTN-LPS pigs tended to have greater (127.4%) circulating NEFA concentrations compared with IUTN-SAL and IUHS-SAL pigs. Cortisol was increased (P = 0.04) in IUHS-LPS compared with IUTN-LPS pigs at 3 hr (21.5%) and 4 hr (64.3%). At 1 hr, tumor necrosis factor α was increased (P = 0.01; 115.1%) in IUHS-LPS compared with IUTN-LPS pigs. Overall, interleukin-1ß (IL-1ß) and interleukin-6 (IL-6) were greater (P < 0.04; 281.3% and 297.8%, respectively) in IUHS-LPS pigs compared with all other treatments, and IUTN-LPS pigs had increased IL-1ß and IL-6 concentrations compared with IUTN-SAL and IUHS-SAL pigs. In summary, IUHS altered the postnatal cytokine, metabolic, and physiological stress response of pigs during postnatal life, which may have negative implications toward the innate immune response of IUHS pigs to pathogens.

Evaluation and mitigation of the effects of in utero heat stress on piglet growth performance, postabsorptive metabolism, and stress response following weaning and transport.

In utero heat stress (IUHS) increases the energy requirements of pigs during postnatal life, and this may compound weaning and transport stress. The study objective was to evaluate and mitigate the negative effects of IUHS following weaning and transport through the provision of a nutrient-dense (ND) nursery diet formulated to meet the greater energy requirements of IUHS pigs during the first 14 d postweaning and transport. Twenty-four pregnant gilts were exposed to thermoneutral (TN; n = 12; 17.5 ± 2.1 °C) or heat stress (HS; n = 12; cycling 26 to 36 °C) conditions for the first half of gestation (day 6 to 59) and then TN conditions (20.9 ± 2.3 °C) until farrowing. Nine TN gilts and 12 HS gilts produced litters. At weaning (16.2 ± 0.4 d), mixed-sex piglets (N = 160; 4.78 ± 0.15 kg body weight [BW]) were transported (loading + transport + unloading) for 11 h 40 min. Following transport, piglets were blocked into pens (n = 4 pigs/pen) by in utero and dietary treatments: in utero thermoneutral (IUTN) + control (C) diet (n = 10 pens), IUTN + ND (n = 10 pens), IUHS + C (n = 10 pens), and IUHS + ND (n = 10 pens). Treatment diets were fed from day 1 to 14 postweaning and transport (period 1), and the C diet was fed to all pigs from day 14 to 35 postweaning and transport (period 2). Production measures were taken in 7 d intervals to calculate average daily gain (ADG), average daily feed intake (ADFI), average daily net energy intake (ADEI), gain:feed, and gain:net energy intake. Blood samples were collected prior to transport, following transport, and on days 2, 7, 14, 28, and 35 postweaning and transport to analyze cortisol, glucose, insulin, and nonesterified fatty acids. Behavior was assessed through video-recording on days 3, 5, 8, 11, and 13 postweaning and transport. In period 1, ADG was reduced (P = 0.04; 20.0 g/d) in IUHS vs. IUTN pigs. Pigs fed ND diets had reduced ADFI (P = 0.02; 9.3%) compared with C diet-fed pigs during period 1, which resulted in similar ADEI (P = 0.23; 1,115 ± 35 kcal/d). During transport, cortisol was decreased (P = 0.03; 25.8%) in IUHS vs. IUTN pigs. On day 2, glucose was decreased (P = 0.01; 13.8%) in IUHS vs. IUTN pigs. No in utero treatment-related behavior differences were observed but lying was reduced (P = 0.03; 6.5%) and standing was increased (P = 0.04; 14.1%) in ND vs. C pigs overall. In summary, IUHS reduced growth performance in pigs following weaning and transport, and providing an ND diet did not rescue the lost performance.