Javier Rolando Reyna-Granados

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.

Heat stress (HS) is a major issue affecting productivity and physiological responses in dairy cattle. Advances in gene function research have made it possible to identify favorable genotypes for HS tolerance. This study evaluates the combined effects of temperature–humidity index (THI) and genomic load of favorable SNPs in the genes GRM8, SMAD3, and TLR4 on daily milk yield (DMY), rectal temperature (RT), and gene expression in Holstein cows (n = 160). Environmental conditions ranged from thermoneutral to severe HS, allowing the assessment of genotype by environment interactions. A subset of cows (n = 40) was selected based on genomic load to evaluate gene expression under opposite thermal conditions. Results showed that increasing THI was associated with reduced DMY and increased RT, with more pronounced effects in cows carrying fewer favorable genotypes. Slope analyses revealed that cows with higher genomic load exhibited a moderate decline in DMY and lower increase in RT, indicating enhanced resilience to HS. Significant THI × genomic load interactions were detected above a threshold of 79 units (p < 0.05). Gene expression analyses supported these findings, showing differential expressions of GRM8, SMAD3, and TLR4 under HS conditions. The functional and predictive value of these genes as markers of thermotolerance could help producers by supporting their application in genetic selection programs, thus providing another tool to combat HS and improve resilience and productivity in dairy systems.

Introduction: Rickettsia is an intracellular, Gram-negative, zoonotic bacterium that is transmitted by arthropods, such as ticks, fleas and lice. Rickettsioses have been reported in Mexico since the 1930s, with a higher prevalence in the northern states. Infections affect both dogs and humans in marginalized areas, with Rickettsia rickettsii being the most pathogenic species and associated with high mortality rates. Methodology: This study aimed to detect R. rickettsii in dogs from Ciudad Obregón, Sonora, using the ompA gene PCR. Between July and August 2024, 110 EDTA whole blood samples were collected: 95 from dogs with a presumptive clinical diagnosis of rickettsiosis, and 15 from stray dogs with active tick infestations. DNA extraction, PCR amplification and product purification were performed at the Veterinary Molecular Biology Laboratory of the Instituto Tecnológico de Sonora. Sanger sequencing, Snap Gene Viewer, and BLASTn against GenBank were used to confirm the identity of the sequences. Results: Sequencing of the ompA fragment confirmed 99–100% homology with R. rickettsii. One positive case (6.7%) was detected, corresponding to a stray dog from a disadvantaged area of the municipality of Cajeme, indicating the presence of the pathogen in a localized area. Conclusions: The detection of R. rickettsii in a stray dog in Ciudad Obregón confirms the presence of the pathogen in the area, highlighting the importance of free-roaming canines and environmental conditions in sustaining vectors. Early diagnosis and control of ectoparasites are critical to reducing zoonotic transmission, underlining the importance of continuous molecular surveillance in public health.

Porcine respiratory and reproductive syndrome is a viral disease that impacts the health and profitability of swine farms, largely due to significant variation in the vaccination response. The objective was to identify and validate molecular markers associated with the antibody response in gilts following vaccination against the PRRSV. The study included one hundred (n = 100) 6-month-old Yorkshire gilts that were negative for the PRRSV. Gilts were randomly assigned to one of two treatments, PRRS-vaccinated (n = 75) and control (n = 25) groups. Blood samples collected on day 21 were analyzed to evaluate the antibody response, as indicated by the sample-to-positive (S/P) ratio, to the PRRSV following vaccination. DNA was extracted and genotyped using a low-density chip containing 10,000 single nucleotide polymorphisms (SNPs). A genome-wide association study (GWAS) was conducted to identify candidate SNPs associated with the S/P ratio, which were validated in two independent gilt populations (n = 226). The SNPs rs707264998, rs708860811, and rs81358818 in the genes RNF144B, XKR9, and BMAL1, respectively, were significantly associated (p < 0.01) with the S/P ratio and demonstrated an additive effect. In conclusion, three SNPs are proposed as candidate markers for an enhanced immune response to vaccination against the PRRSV and may be beneficial in genetic selection programs.

Porcine respiratory and reproductive syndrome (PRRS) is a viral disease that affects health and profitability in swine farms, largely due to a high variation in vaccination response. The objective was to discover and validate molecular markers associated with the antibody response in gilts after vaccination against PRRS virus. The study included one hundred (n=100) 6-month-old gilts from the breed Yorkshire that were PRRS virus-negative. After 7 days of acclimation period, all gilts were vaccinated with a modified live PRRS virus (day 0). Blood samples collected on day 21 were used to evaluate the antibody response, as the sample-to-positive (S/P) ratio, to PRRS virus after vaccination. DNA was extracted and genotyped using a low-density chip including 10,000 single nucleotide polymorphisms (SNPs). A genome-wide association study (GWAS) was performed to discover candidate SNPs associated with the S/P ratio, which were validated in two independent gilt populations (n=226). The SNPs rs80904326, rs80896559 and rs81358818 in the genes RNF144B, XKR9 and BMAL1, respectively, were associated (p < 0.01) with the S/P ratio and exhibited an additive effect. In conclusion, three SNPs are proposed as candidate markers for an improved immune response to vaccination against PRRS virus and may be useful in genetic selection programs.

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.

Archivos Latinoamericanos de Producción Animal, es la publicación oficial de la Asociación Latinoamericana de Producción Animal The ability to tolerate extreme heat has been proposed as an important selection criterion to promote the breeding of thermo-tolerant animals, especially in climates characterized by environmental heat stress during most of the year. Novel genomic technologies are available to study genetic bases supporting the thermo-tolerance in cattle, among which are: Genome-wide association studies, validation of markers and candidate genes, RNA sequencing and transcriptome analysis. These technologies currently allow faster progress in the identification of thermotolerant cattle, which is highly relevant from the perspective of the current problems as global warming and food security. So, the objective of this review is to analyze the current status of the use of omics technologies in animal production studies under heat stress. La habilidad para tolerar el calor extremo ha sido propuesta como un importante criterio de selección para promover la cría de animales termo-tolerantes, sobre todo en climas caracterizados por estrés térmico ambiental gran parte del año. Novedosas tecnologías genómicas están disponibles para estudiar las bases genéticas que sustentan la termo-tolerancia del ganado, entre las que se encuentran: estudios asociativos del genoma completo, validación de marcadores y genes candidatos, la secuenciación de ARN y análisis de transcriptomas. Estas tecnologías actualmente permiten avanzar más rápido en la identificación de ganado termotolerante, lo cual tiene gran relevancia desde la perspectiva del problema del calentamiento global y la seguridad alimentaria. El objetivo de esta revisión es analizar el estado actual del uso de las tecnologías ómicas en estudios de producción animal bajo estrés por calor. A capacidade de tolerar calor extremo tem sido proposta como um importante critério de seleção para promover a reprodução de animais termotolerantes, principalmente em climas caracterizados por estresse térmico ambiental durante grande parte do ano. Novas tecnologias genômicas estão disponíveis para estudar as bases genéticas que suportam a termotolerância do gado, entre as quais: estudos associativos de todo o genoma, validação de marcadores e genes candidatos, sequenciamento de RNA e análise do transcriptoma. Atualmente, essas tecnologias permitem avanços mais rápidos na identificação de bovinos termotolerantes, o que é altamente relevante do ponto de vista do problema do aquecimento global e da segurança alimentar. O objetivo desta revisão é analisar o estado atual do uso de tecnologias ômicas em estudos de produção animal sob estresse térmico.

Components of the GH/IGF1 endocrine axis regulate growth and reproductive traits in cattle. The pro-melanin-concentrating hormone (PMCH) gene located within chromosome 5 belongs to this axis. Objective herein was to evaluate PMCH single-nucleotide polymorphisms (SNPs) as molecular markers associated with age at first calving, calving interval, and age at second calving in Angus and Brangus beef heifers raised in desert conditions. Five SNPs within the PMCH gene were included in the study. Three of these SNPs had minor allele frequency > 10% and only one SNP did not deviate from Hardy–Weinberg equilibrium. A genotype to phenotype association analyses was performed using a mixed-effects model which included phenotype as the response variable, SNP genotype, breed, year of birth and age of dam as fixed terms, and sire as a random effect. Genotypes from the SNP rs135033882 were found to be associated (P < 0.05) with all evaluated fertility traits, and the term breed resulted as a significant source of variation only for age at second calving. The allele A was the favorable allele because it decreased the age at first calving 98.6 days, the calving interval 85.3 days, and the age at second calving 183.1 days, in Angus and Brangus heifers. In conclusion, we proposed a SNP within the PMCH gene as a potential candidate marker associated with reproductive performance in Angus and Brangus beef heifers raised in a desert climate.

Paratuberculosis is caused by Mycobacterium avium subspecies paratuberculosis (MAP), a chronic disease of a negative economic impact on sheep production. In the state of Sonora, Mexico, there are no reports on the prevalence of MAP in sheep and risk factors associated with it. The objective of this study was to estimate the seroprevalence of MAP and risk factors associated by testing antibody-positive in sheep flocks located in the arid and hot region of Sonora, Mexico. A cross-sectional study was conducted from February 2012 to December 2014, in 43 flocks. Serum samples from 1178 individual sheep were obtained to detect antibodies against MAP by immunodiffusion in agar-gel. During blood sampling, information about animal and flock management risk factors were obtained by applying a questionnaire to the owners. Risk factors associated with seroprevalence of MAP were estimated using binary logistic regression. The true prevalence of MAP was 7.48% (95% CI 5.98, 8.98) and 53.5% of flocks had at least one seropositive animal. An animal was more likely to be seropositive if it was from a large flock (> 300 animals; OR 3.52, 95% CI 1.24, 9.99) and was born outside the farm (OR 6.24; 95% CI 2.9-1, 3.52). This is the first report of Mycobacterium avium subspecies paratuberculosis seroprevalence in sheep, in Sonora, Mexico. Large flocks and the entry of new animals to the flock were critical risk factors associated with MAP seropositivity.

Porcine reproductive and respiratory syndrome (PRRS) is a viral disease that severely affects the Mexican swine industry. Vaccination of replacement gilts is mostly used to prevent PRRS; however, individual response to this protocol is highly-variable. The objective herein was to predict vaccination response against PRRS virus in gilts using molecular markers associated to rectal temperature (RT) and average daily weight gain (ADG). The study included 6-month old replacement gilts (n = 100) with a breed composition of ¾ Landrace x ¼ Yorkshire. Gilts were vaccinated with a modified live PRRS-virus (day 0) and kept inside the quarantine area on a farm where the gilts were lately exposed to PRRS. Data from RT and ADG were recorded weekly from day -7 through 35. Individual blood samples were collected at day 40, spotted onto FTA cards, and processed for genomic analyses using a 10k low-density SNP chip. Resulting genotypes were analyzed using a multi-locus mixed model, which identified 59 SNP associated with RT and ADG. These SNP were validated using a mixed-effects model which included SNP genotype and age of dam as fixed effects, and sire as random effect; then, their allele substitution effects were calculated. The additive effects for each SNP that showed a significant association (P < 0.05) with either RT or ADG were summed to calculate their corresponding molecular breeding value (MBV). The mean MBV were 0.28±0.04°C and 0.21± .05kg for RT and ADG, respectively. A reduced regression model which only included MBV was used to predict both RT and ADG. Coefficients of determination were 4.26 and 3.87% for RT and ADG, respectively (P < 0.01). These results suggest that only a small proportion of the phenotypic variance for RT and ADG was explained by SNP genotypes. We suggest additional studies to determine if the highly-variable vaccination response to PRRS is influenced by genetics.