Heat stress (HS) negatively affects both human and farm-animal health and undermines efficiency in a variety of economically important agricultural variables, including reproduction. HS impairs the intestinal barrier, allowing for translocation of the resident microflora and endotoxins, such as lipopolysaccharide (LPS), from the gastrointestinal lumen into systemic circulation. While much is known about the cellular function of heat shock proteins (HSPs) in most tissues, the in vivo ovarian HSP response to stressful stimuli remains ill-defined. The purpose of this study was to compare the effects of HS or LPS on ovarian HSP expression in pigs. We hypothesized that ovarian HSPs are responsive to both HS and LPS. Altrenogest (15 mg/d) was administered per os for estrus synchronization (14 d) prior to treatment and three animal paradigms were used: (i) gilts were exposed to cyclical HS (31 ± 1.4 °C) or thermoneutral (TN; 20 ± 0.5 °C) conditions immediately following altrenogest withdrawal for 5 d during follicular development; (ii) gilts were subjected to repeated (4×/d) saline (CON) or LPS (0.1 μg/kg BW) i.v. infusion immediately following altrenogest withdrawal for 5 d; and (iii) gilts were subjected to TN (20 ± 1 °C) or cyclical HS (31 to 35 °C) conditions 2 d post estrus (dpe) until 12 dpe during the luteal phase. While no differences were detected for transcript abundances of the assessed ovarian HSP, the protein abundance of specific HSP was influenced by stressors during the follicular and luteal phases. HS during the follicular phase tended (P < 0.1) to increase ovarian protein abundance of HSP90AA1 and HSPA1A, and increased (P ≤ 0.05) HSF1, HSPD1, and HSPB1 compared with TN controls, while HS decreased HSP90AB1 (P = 0.01). Exposure to LPS increased (P < 0.05) HSP90AA1 and HSPA1A and tended (P < 0.1) to increase HSF1 and HSPB1 compared with CON gilts, while HSP90AB1 and HSPD1 were not affected by LPS. HS during the luteal phase increased (P < 0.05) abundance of HSPB1 in corpora lutea (CL), decreased (P < 0.05) CL HSP90AB1, but did not impact HSF1, HSPD1, HSP90AA1, or HSPA1A abundance. Thus, these data support that HS and LPS similarly regulate expression of specific ovarian HSP, which suggest that HS effects on the ovary are in part mediated by LPS.

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Seasonal infertility (SI) caused by heat stress (HS) impacts the US swine industry by reducing litter size, farrowing rates, and production efficiency. Identifying the biological underpinnings of SI is a foundational step towards developing mitigation strategies to reduce the nearly $1 billion annual revenue losses to the swine industry. The study objective was to investigate the direct and indirect effects of HS via HS conditioned serum infusion in swine. We hypothesized gilts housed in thermoneutral (TN) conditions receiving gradual infusions of serum obtained from HS gilts would experience altered endocrine and metabolic function compared to gilts receiving serum from TN gilts. Prepubertal gilts (n = 18) were assigned to donor or recipient groups and donors were allocated to TN or HS environments. Blood was collected from HS donors and TN donors exposed to 24-hours of HS or TN conditions, respectively. Serum was infused into recipients housed in TN conditions via indwelling jugular catheters. Over a 24-hour period approximately 20% of the estimated recipient gilt serum volume from donors (pooled by treatment) was infused into recipients. After infusions were completed, gilts were euthanized and tissues collected. Increased rectal temperatures were observed in HS recipients compared to TN recipients (P ≤ 0.05). Protein extracts from liver and ovary underwent proteomic analysis via liquid-chromatography with tandem mass-spectrometry (LC-MS/MS) to assess protein abundance. In the liver and ovary, we identified 135 and 264 proteins, respectively, that were differentially abundant between TN and HS recipients (P < 0.10). Gene Ontology enrichment analysis identified alterations to pathways involved in hormone regulation, immune response, and apoptosis. Collectively, these data demonstrate gilts receiving HS serum experienced altered endocrine and metabolic function compared to gilts receiving TN serum. This project was supported in part by the Iowa Pork Producers Association. USDA is an equal opportunity provider and employer.

Targeted genetic alteration provides opportunities for rapid genetic improvement in resilience, welfare and production traits. Somatostatin (SST) acts via negative feedback to regulate growth hormone (GH) activity by antagonizing GH releasing hormone via SST receptors (SSTR) located in the anterior pituitary. Our objective was to reduce the negative effect of SST in the anterior pituitary on protein accretion by reducing the number of functional copies of SSTR2 using the CRISPR/Cas9 system. We hypothesized that a reduction or elimination of SSTR2 would lead to improved growth performance. To test this hypothesis, three commercial gilts were bred with semen from a founder boar in a compound heterozygous state at the SSTR2 locus with a 1bp deletion in one allele resulting in a premature stop codon and a 3bp deletion in the other allele resulting in the loss of a single amino acid predicted to remain functional after translation. Three litters of F1 offspring were produced (n = 46) and all piglets were confirmed to be heterozygous at the SSTR2 locus with one wild type allele and the other possessing either the 1bp deletion (n = 22) or the 3bp (n = 2 4) deletion. No differences (P > 0.43; n=46) in body weight (1.27±0.03 kg) across comparisons were observed at birth. At weaning (n = 36), males (6.19±0.20 kg) were heavier (P = 0.007) than females (5.41±0.19 kg), and piglets possessing a 1bp deletion (6.00±0.20 kg) were numerically heavier (P = 0.14) than 3bp deletion pigs (5.59±0.18 kg). This observation was more pronounced in males at weaning, where the males with the 1bp deletion were 13% heavier (P = 0.058) than those with the 3bp deletion. These data suggest that altering SSTR2 may be a viable genetic advancement strategy to improve growth performance in pigs. This project was supported by the Lloyd L. Anderson Professorship in Physiology at Iowa State University.