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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.

Beef cow reproductive traits are critical for system profitability and difficult to improve using selection. A custom array with 131 SNPs identified within genes related to cow puberty and fertility was evaluated in privately owned Angus (A), Charolais, Brangus, and Red Brangus cows in México (n = 828) and in A, Brahman (B), Hereford (H), Nellore (N), and crossbred (F₁ and F₂ B-H, F₂ B-A, first- and second-generation 3/8 B 5/8 A, and 3/8 N 5/8 A) cows in a Texas research herd (n = 449). Cow traits included age at first and second calving, calving interval, and reproductive success. Calf traits were birth weight and occurrences of calving difficulty, calves with inadequate vigor at birth, and mortality. Residuals from fixed effect models were used in association analyses. The detection of associated loci was mostly within combined groups. A marker in RHEBL1 was associated (p < 0.05) with age at calving in Angus. A locus in FAM19A4 was associated (p < 0.05) with reproductive success in Brangus and inadequate calf vigor in all data combined. Markers in SYCE1 and CPNE5 were associated (p < 0.05) with reproductive success and calf mortality in Bos indicus. Functional panels may be more effective when designed for individual breeds or sub-species.

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.

Fertility in Brangus cattle raised in semi-arid regions is crucial for herd profitability, so the selection of genetically superior cows is desirable. The objective was to study single nucleotide polymorphisms (SNPs) of the IGF1 gene as genetic markers of fertility in Brangus heifers. Blood samples were collected from 264 heifers for DNA extraction and genotyping of 4 SNPs. An associative study was conducted using a statistic mixed-effects model. Only the SNP rs5367940596 met quality criteria and resulted as predictor of age at first calving (AFC). The favorable genotype was found to be TT because it was associated with a reduction in AFC of 56.2 days for each T allele present in the genotype. This SNP showed an additive effect since fertility improved as the number of favorable T alleles increased. Additionally, the expression of the IGF1 gene was increased (P<0.05) in heifers with the favorable genotype. In conclusion, the SNP rs5367940596 within the gene IGF1 is proposed as genetic marker to improve AFC in Brangus heifers managed in semi-arid environments. These results provide biological evidence of the regulatory role of the IGF1 gene in Brangus cattle fertility.

Oxidative stress impairs the productivity and welfare of heat-stressed hair sheep; however, the key factors contributing to its occurrence remain unclear. Twenty-two Dorper × Katahdin ewe lambs weighing 23.5 ± 2.8 kg and experiencing outdoor heat stress in a desert region were used to establish the contribution of climatic variables, physiological responses, metabolism, and feedlot performance to the oxidant-antioxidant imbalance. Pearson’s correlation, principal component analysis, and multiple linear regression were applied to the datasets. Oxidative stress biomarkers showed positive relationships with average and minimum climatic variables, morning rectal temperature, serum triglycerides and insulin, and feed efficiency. Still, these biomarkers were negatively correlated with maximum ambient temperature (Te) and temperature-humidity index (THI), morning and afternoon respiratory rate (RR), total protein, and feed intake. While total oxidant capacity and fat oxidation were mainly associated with decreased maximum Te, protein oxidation was primarily associated with increased morning RR. Total antioxidant capacity was favored by a reduction in maximum THI and oxidative stress index (OSI) by an increase in maximum relative humidity. With minimal contribution (≤6%), protein and fat oxidation were also explained by increased serum insulin and feed intake, respectively, whereas OSI was explained by increased weight gain. Overall, the presence of oxidative stress in feedlot hair sheep experiencing outdoor heat stress was regulated by a combination of climatic conditions, morning RR, and, to a lesser extent, productive performance.

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.

Congenital hydrocephalus is a recessive genetic abnormal condition affecting Friesian horses, so the identification of healthy carrier animals is crucial to avoid its spread. Therefore, the objective of the present study was the detection of the mutation in the B3GALNT2 gene related to the presence of hydrocephalus through the rhAmp SNP technique to detect healthy carrier horses. The study was performed in 4 locations in southern Sonora, Mexico. Blood samples were collected from 51 Friesian horses using EDTA tubes, which were centrifuged until the leucoplatelet layer was obtained. Subsequently, the TACOTM DNA extraction kit was used to obtain DNA, which was processed by the rhAmp SNP assay to detect the mutation in the B3GALNT2 gene. A total of 7 (13.7%) Friesian horses were found to be heterozygous carriers (C/T). In conclusion, the presence of the mutant allele was confirmed by the rhAmp SNP assay, which was proposed as an effective molecular technique for the detection of horses as carriers of genetic abnormal conditions.

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.

Background: Bovine trichomoniasis, caused by Tritrichomonas foetus, is a venereal disease that affects the reproductive efficiency of cattle, especially in extensive breeding systems. Infected bulls could spread the protozoan by artificial insemination if the semen is contaminated. The loop-mediated isothermal amplification (LAMP) is an alternative assay to detect genetic material of pathogens without the need to purify inhibitors contained in a biological sample. Objective: Detection of T. foetus in cryopreserved semen and genital fluids from bulls raised in Sonora Mexico by a colorimetric LAMP assay. Methods: The conditions for a colorimetric LAMP assay were standardized using PCR as analytical reference in order to detect T. foetus (crLAMP-TF). A total of 110 preputial samples were tested by crLAMP-TF. From positive males to T. foetus (TF+), seminal samples were collected, cryopreserved and tested by crLAMP-TF. Results: The crLAMP-TF assay was sensitive, and allow the visual detection at 35 min. without inhibitors purification of biological samples previous to DNA extraction. The 29.1% of the bulls were bTF+ and 27.3% of the thaws were contaminated. Conclusion: This survey confirms the presence of T. foetus in Sonora, Mexico and the ability of the protozoan to contaminate semen, which represents a potential risk of transmission during assisted reproduction programs by artificial insemination. The crLAMP-TF assay represents a viable alternative against traditional molecular techniques and its potential in the epidemiological surveillance of pathogens under field conditions.

Anti-Müllerian hormone (AMH) is proposed as a biomarker for fertility in cattle, yet this associative relationship appears to be influenced by heat stress (HS). The objective was to test serum AMH and AMH-related single nucleotide polymorphisms (SNPs) as markers potentially predictive of reproductive traits in dairy cows experiencing HS. The study included 300 Holstein cows that were genotyped using BovineSNP50 (54,000 SNP). A genome-wide association study was then executed. Nine intragenic SNPs within the pathways that influence the AMH gene were found important with multiple comparisons adjustment tests (p < 1.09 × 10⁻⁶). A further validation study was performed in an independent Holstein cattle population, which was divided into moderate (MH; n = 152) and severe heat-stressed (SH; n = 128) groups and then subjected to a summer reproductive management program. Serum AMH was confirmed as a predictor of fertility measures (p < 0.05) in MH but not in the SH group. Cows were genotyped, which revealed four SNPs as predictive markers for serum AMH (p < 0.01), reproductive traits (p < 0.01), and additional physiological variables (p < 0.05). These SNPs were in the genes AMH, IGFBP1, LGR5, and TLR4. In conclusion, serum AMH concentrations and AMH polymorphisms are proposed as predictive markers that can be used in conjunction with genomic breeding value approaches to improve reproductive performance in Holstein cows exposed to summer HS conditions.