Environmental heat stress triggers a series of compensatory mechanisms in sheep that are dependent on their genetic regulation of thermotolerance. Our objective was to identify genes and regulatory pathways associated with thermotolerance in ewes exposed to heat stress. We performed next-generation RNA sequencing on blood collected from 16 pregnant ewes, which were grouped as tolerant and non-tolerant to heat stress according to a physiological indicator. Additional samples were collected to measure complete blood count. A total of 358 differentially expressed genes were identified after applying selection criteria. Gene expression analysis detected 46 GO terms and 52 KEGG functional pathways. The top-three signaling pathways were p53, RIG-I-like receptor and FoxO, which suggested gene participation in biological processes such as apoptosis, cell signaling and immune response to external stressors. Network analysis revealed ATM, ISG15, IRF7, MDM4, DHX58 and TGFβR1 as over-expressed genes with high regulatory potential. A co-expression network involving the immune-related genes ISG15, IRF7 and DXH58 was detected in lymphocytes and monocytes, which was consistent with hematological findings. In conclusion, transcriptomic analysis revealed a non-viral immune mechanism involving apoptosis, which is induced by external stressors and appears to play an important role in the molecular regulation of heat stress tolerance in ewes.

Frecuencia de parásitos gastrointestinales en bovinos del sur de Sonora, México

This study aimed to identify and validate functional genetic markers associated with fertility and thermotolerance traits in dairy cows exposed to HS. Spring-calving Holstein cows (n=400) from three dairy farms located in the Yaqui Valley, Mexico, were genotyped using the BovineSNP50 panel. Reproductive traits such as days open (DO) and services per conception (SPC) were recorded following a fixed-time artificial insemination protocol. After quality controls 45,832 SNPs were included in a genome-wide association study, which identified 21 and 20 SNPs associated with DO and SPC (P < 0.05), respectively. Five SNPs common to both traits were selected for a marker-assisted association study using a mixed effects statistical model. This validation analysis was performed in an independent Holstein cow population (n=184) confirming associations of the SNPs rs136074864, rs109479159, rs43520457, and rs133770320 in the genes EXOC4, GLI3, GPR151, and TRHDE1, with reproductive and thermotolerance traits. Cows carrying favorable genotypes showed increased gene expression, higher serum AMH, progesterone and HSP70, and lower cortisol levels. Correlation analyses confirmed the physiological relevance of these genes. In conclusion, these results highlighted the key role of four candidate genes as molecular markers for improving reproductive efficiency and thermotolerance in Holstein cows managed under HS.

Porcine respiratory and reproductive syndrome virus (PRRSV) in replacement gilts is an infection that decreases reproductive performance in breeding females and affects the economy of the Mexican swine industry. The objective of this study was to validate the associative relationship among average number of piglets alive (NPA) at first and second farrowing with genotypes in PRRSV early-infected gilts. The experiment included seventy-five 8-mo-old females with breed composition of three-fourths Landrace × one-fourth Yorkshire. All gilts were exposed to a wild strain of PRRSV once they arrived into the breeding area, and blood samples were collected 2 wk later to confirm virus infection by real-time PCR (Tetracore Nextgen Real-Time PCR). Gilts observed in estrus received 2 natural services with fertility-tested boars. Females confirmed as pregnant were maintained in a gestation area and then moved to the farrowing area the day before parturition. Blood samples were collected on each individual and spotted onto FTA cards for genotyping using a 8,826 low-density SNP chip (Infinium BeadChip; Illumina, San Diego, CA). Previous analysis of these genomic data identified 12 SNP associated with average NPA (P < 0.001), using multilocus mixed models, which were performed in SNP Variation Suite 7 of Golden Helix, Inc. A mixed effects model was used to validate the associative relationship between these SNP and reproductive phenotypes; this model included SNP genotype and age of dam as fixed effects and sire as a random effect. An allele substitution effect was also calculated using a regression model that included genotype term as a covariate. Mean values for average NPA were 10.61 ± 0.38. From the SNP previously identified, only ALGA0056378 (rs81422969) and MARC0036292 (rs81229798) were associated with average NPA (P < 0.01). Least squares means among ALGA0056378 genotypes CC, CT, and TT were 11.93 ± 0.62, 9.45 ± 0.59, and 8.59 ± 2.51, respectively, and among MARC0036292 genotypes AA, AG, and GG were 6.22 ± 2.40, 8.69 ± 0.71, and 11.47 ± 0.51, respectively. The most favorable alleles increased NPA by 1.71 ± 0.88 and 2.73 ± 0.67 for ALGA0056378 and MARC0036292, respectively. In conclusion, a phenotype to genotype association analyses validated 2 specific genetic markers that explain genetic variation in the average number of piglets alive from gilts early infected with PRRSV. Therefore, we propose such SNP as candidates to focus our study on the genetic basis that underlies reproductive performance in gilts infected with a wild PRRSV strain in southern Sonora. Copyright © 2017. American Society of Animal Science .