Genetic Basis of Blood-Based Traits and Their Relationship With Performance and Environment in Beef Cattle at Weaning

Exploring the biological responses involved in the genetic resistance to Rhipicephalus microplus in Argentine Creole cattle

The common cattle tick Rhipicephalus microplus causes severe limitations to livestock production. Bovine genetics could be a decisive component for the success or failure of control programs for ticks and diseases transmitted. The objective of this work was to detect chromosomal regions associated with host resistance to R. microplus through an associative mapping study using medium and high density microarrays in a population of Argentine Creole cattle. The phenotypic record of the number of ticks that completed their development on the host, after artificial infestations, was obtained during 2015 to 2020. Genomic DNA was extracted for genotyping from 192 animals using Affymetrix high (Axiom™ Bos 1) and medium density (ArBos1) microarrays. In an exploratory study, chromosomal regions containing putative quantitative trait loci (QTLs) were recognized on chromosomes 27, 11, 10, 9, 16, 13, 3, 19, 8 and 18, associated with the variation of R. microplus load. Gene ontology based on genes located on these regions revealed an enrichment of terms and pathways for the immune system, blood coagulation, tissue regeneration, endopeptidase activity and protein phosphorylation. The information obtained in this work constitutes a first report of QTLs for tick count in the Argentine Creole cattle, and contributes with the knowledge about the underlying process involved in tick resistance.

Genetic background of hematological parameters in Holstein cattle based on genome-wide association and RNA sequencing analyses

Hematological parameters refer to the assessment of changes in the number and distribution of blood cells, including leukocytes (LES), erythrocytes (ERS), and platelets (PLS), which are essential for the early diagnosis of hematological system disorders and other systemic diseases in livestock. In this context, the primary objectives of this study were to investigate the genomic background of 19 hematological parameters in Holstein cattle, focusing on LES, ERS, and PLS blood components. Genetic and phenotypic (co)variances of hematological parameters were calculated based on the average information restricted maximum likelihood method and 1,610 genotyped individuals and 5,499 hematological parameter records from 4,543 cows. Furthermore, we assessed the genetic relationship between these hematological parameters and other economically important traits in dairy cattle breeding programs. We also carried out genome-wide association studies and candidate gene analyses. Blood samples from 21 primiparous cows were used to identify candidate genes further through RNA sequencing (RNA-seq) analyses. Hematological parameters generally exhibited low-to-moderate heritabilities ranging from 0.01 to 0.29, with genetic correlations between them ranging from -0.88 ± 0.09 (between mononuclear cell ratio and lymphocyte cell ratio) to 0.99 ± 0.01 (between white blood cell count and granulocyte cell count). Furthermore, low-to-moderate approximate genetic correlations between hematological parameters with one longevity, 4 fertility, and 5 health traits were observed. One hundred ninety-nine significant SNP located primarily on the Bos taurus autosomes (BTA) BTA4, BTA6, and BTA8 were associated with 16 hematological parameters. Based on the RNA-seq analyses, 6,687 genes were significantly downregulated and 4,119 genes were upregulated when comparing 2 groups of cows with high and low phenotypic values. By integrating genome-wide association studies (GWAS), RNA-seq, and previously published results, the main candidate genes associated with hematological parameters in Holstein cattle were ACRBP, ADAMTS3, CANT1, CCM2L, CNN3, CPLANE1, GPAT3, GRIP2, PLAGL2, RTL6, SOX4, WDFY3, and ZNF614. Hematological parameters are heritable and moderately to highly genetically correlated among themselves. The large number of candidate genes identified based on GWAS and RNA-seq indicate the polygenic nature and complex genetic determinism of hematological parameters in Holstein cattle.

The genetic architecture of complete blood counts in lactating Holstein dairy cows

Complete blood counts (CBCs) measure the abundance of individual immune cells, red blood cells, and related measures such as platelets in circulating blood. These measures can indicate the health status of an animal; thus, baseline circulating levels in a healthy animal may be related to the productive life, resilience, and production efficiency of cattle. The objective of this study is to determine the heritability of CBC traits and identify genomic regions that are associated with CBC measurements in lactating Holstein dairy cattle. The heritability of CBCs was estimated using a Bayes C0 model. The study population consisted of 388 cows with genotypes at roughly 75,000 markers and 16 different CBC phenotypes taken at one to three time points (n = 33, 131, and 224 for 1, 2, and 3 time points, respectively). Heritabilities ranged from 0.00 ± 0.00 (red cell distribution width) to 0.68 ± 0.06 (lymphocytes). A total of 96 different 1-Mb windows were identified that explained more than 1% of the genetic variance for at least one CBC trait, with 10 windows explaining more than 1% of the genetic variance for two or more traits. Multiple genes in the identified regions have functions related to immune response, cell differentiation, anemia, and disease. Positional candidate genes include RAD52 motif-containing protein 1 (RDM1), which is correlated with the degree of immune infiltration of immune cells, and C-X-C motif chemokine ligand 12 (CXCL12), which is critically involved in neutrophil bone marrow storage and release regulation and enhances neutrophil migration. Since animal health directly impacts feed intake, understanding the genetics of CBCs may be useful in identifying more disease-resilient and feed-efficient dairy cattle. Identification of genes responsible for variation in CBCs will also help identify the variability in how dairy cattle defend against illness and injury.

Genetic profile of adaptive immune traits and relationships with parasite resistance and productivity in Scottish Blackface sheep

Gastrointestinal (GI) parasites cause significant production losses in grazing ruminants which can be mitigated by breeding animals resistant to disease. Lymphocyte cytokine production and parasite-specific Immunoglobulin A (IgA) are adaptive immune traits associated with immunity to GI parasites. To explore the utility of these traits for selective breeding purposes, this study estimated the genetic parameters of the immune traits in sheep and assessed their relationship with disease and productivity traits. Whole blood stimulation assays were performed on 1 040 Scottish Blackface lambs at two months of age in 2016-2017. Blood was stimulated with either pokeweed mitogen (PWM), a non-specific activator of lymphocytes, and Teladorsagia circumcincta (T-ci) larval antigen to activate parasite-specific T lymphocytes. The type of adaptive immune response was determined by quantifying production of cytokines interferon-gamma (IFN-γ), interleukin (IL)-4, and IL-10, which relate to T-helper type (Th) 1, Th2 and regulatory T cell responses, respectively. Serum T-ci specific IgA was also quantified. Heritabilities were estimated for each immune trait by univariate analyses. Genetic and phenotypic correlations were estimated between different immune traits, and between immune traits vs. disease and productivity traits that were recorded at three months of age. Disease phenotypes were expressed as faecal egg counts (FEC) of nematode parasites (Strongyles and Nematodirus), faecal oocyst counts (FOC) of coccidian parasites, and faecal soiling score; production was measured as lamb live weight. Significant genetic variation was observed in all immune response traits. Heritabilities of cytokine production varied from low (0.14 ± 0.06) to very high (0.77 ± 0.09) and were always significantly greater than zero (P < 0.05). IgA heritability was found to be moderate (0.41 ± 0.09). Negative associations previously identified between IFN-γ production and FOC, and IL-4 production and strongyle FEC, were not evident in this study, potentially due to the time-lag between immune and parasitology measures. Instead, a positive genetic correlation was found between FOC and PWM-induced IFN-γ production, while a negative genetic correlation was found between FOC and T-ci induced IL-10. Live weight was negatively genetically correlated with IFN-γ responses. Overall, IFN-γ and IL-4 responses were positively correlated, providing little evidence of cross-regulation of Th1 and Th2 immunity within individual sheep. Furthermore, T-ci specific IgA was highly positively correlated with PWM-induced IL-10, indicating a possible role for this cytokine in IgA production. Our results suggest that while genetic selection for adaptive immune response traits is possible and may be beneficial for parasite control, selection of high IFN-γ responsiveness may negatively affect productivity.

Univariate and multivariate genome-wide association studies for hematological traits in Murciano-Granadina goats

Hematological traits are important indicators of health status, and they are frequently used as criteria for clinical diagnosis. In humans, the genomic architecture of blood traits has been investigated in depth and thousands of associations with genetic variants have been found. In contrast, the association between marker genotypes and the variation of hematological traits has not been investigated in goats yet. Herewith, we have recorded 12 hematological parameters in 882 Murciano-Granadina goats that were also genotyped with the Goat SNP50 BeadChip (Illumina). Performance of a univariate genome-wide association study (GWAS) made it possible to detect one genomic region on goat chromosome (CHI) 21 (19.2-19.5 Mb) associated, at the genome-wide level of significance, with 4 red blood cell traits. The three markers displaying the highest significances were rs268272996 (CHI21: 19225290 bp), rs268273004 (CHI21: 19565629 bp) and rs268239059 (CHI13: 9615190 bp). Consistently, a multivariate GWAS indicated that the rs268273004 marker on chromosome 21 is associated with seven blood cell traits. Interestingly, this marker maps close to the FA Complementation Group I (FANCI) gene (CHI21: 20021947-20077025 bp), which is functionally related to Fanconi anemia, a syndrome characterized by bone marrow failure, aplastic anemia, and congenital disorders. We have also uncovered additional chromosome-wide significant associations between genetic markers and erythrocyte and leukocyte traits in the univariate GWAS. These findings evidence that the phenotypic variation of hematological traits in goats is regulated, at least to some extent, by polygenic determinants distributed in multiple chromosomes.

Expression profiles of the CD274 and PLEKHH2 gene and association of its polymorphism with hematologic parameters in sheep

CD274 and PLEKHH2 genes have been identified as immune- and multiple diseases-related genes, and have recently garnered significant interest. However, their role in regulating immune functions in sheep remains largely unexplored. In this study, we aimed to investigate the effects of polymorphisms in CD274 and PLEKHH2 on hematologic parameters in 915 sheep. Our results showed that the CD274 and PLEKHH2 genes were most highly expressed in the spleen and tail fat, respectively, as determined by qRT-PCR. We also identified a G to A mutation (g 0.11858 G > A) in the exon 4 region of CD274, and a C to G mutation (g 0.38384 C > G) in the intron 8 region of PLEKH2. Association analysis revealed that CD274 g 0.11858 G > A was significantly associated with RBC, HCT, MCHC, and MCV (P < 0.05), while PLEKHH2 g 0.38384 C > G was significantly associated with HCT, MPV, MCHC, and MCV (P < 0.05). These results suggest that CD274 and PLEKHH2 genes may play a role in regulating blood physiological indicators and could be potential functional candidates for influencing immune traits in sheep breeding programs.

Genome-Wide Association and Mendelian Randomization Analysis Reveal the Causal Relationship Between White Blood Cell Subtypes and Asthma in Africans

Background: White blood cell (WBC) traits and their subtypes such as basophil count (Bas), eosinophil count (Eos), lymphocyte count (Lym), monocyte count (Mon), and neutrophil counts (Neu) are known to be associated with diseases such as stroke, peripheral arterial disease, and coronary heart disease. Methods: We meta-analyze summary statistics from genome-wide association studies in 17,802 participants from the African Partnership for Chronic Disease Research (APCDR) and African ancestry individuals from the Blood Cell Consortium (BCX2) using GWAMA. We further carried out a Bayesian fine mapping to identify causal variants driving the association with WBC subtypes. To access the causal relationship between WBC subtypes and asthma, we conducted a two-sample Mendelian randomization (MR) analysis using summary statistics of the Consortium on Asthma among African Ancestry Populations (CAAPA: n cases = 7,009, n control = 7,645) as our outcome phenotype. Results: Our metanalysis identified 269 loci at a genome-wide significant value of (p = 5 × 10-9) in a composite of the WBC subtypes while the Bayesian fine-mapping analysis identified genetic variants that are more causal than the sentinel single-nucleotide polymorphism (SNP). We found for the first time five novel genes (LOC126987/MTCO3P14, LINC01525, GAPDHP32/HSD3BP3, FLG-AS1/HMGN3P1, and TRK-CTT13-1/MGST3) not previously reported to be associated with any WBC subtype. Our MR analysis showed that Mon (IVW estimate = 0.38, CI: 0.221, 0.539, p < 0.001), Neu (IVW estimate = 0.189, CI: 0.133, 0.245, p < 0.001), and WBCc (IVW estimate = 0.185, CI: 0.108, 0.262, p < 0.001) are associated with increased risk of asthma. However, there was no evidence of causal relationship between Lym and asthma risk. Conclusion: This study provides insight into the relationship between some WBC subtypes and asthma and potential route in the treatment of asthma and may further inform a new therapeutic approach.

Complete Blood Count Analysis on Beef Cattle Exposed to Fescue Toxicity and Rumen-Protected Niacin Supplementation

Simple Summary

Fescue toxicity results from cattle consuming fungal (Ergot spp.) endophyte-infected tall fescue. Ergot alkaloids like ergovaline produce vasoconstriction in cattle. Our objectives were to analyze changes in complete blood count and performance due to ergot alkaloid detoxification in growing beef cattle and the effect of selecting dams tolerant or susceptible to fescue toxicity based on their tolerance index, measured through a genetic test currently available for beef producers. Furthermore, rumen-protected niacin supplementation is proposed as a potential alleviator for vasoconstriction produced by fescue toxicity. Therefore, we assessed the effects of consuming endophyte-infected tall fescue seeds in addition to rumen-protected niacin supplementation in offspring performance and hematological parameters. Signs for anemia were noticed in susceptible heifer offspring that did not receive rumen-protected niacin, whereas inflammation or infection was detected in tolerant steers that received niacin in their diet. Typical symptoms of heat stress and intoxication with ergot alkaloids were noticed in offspring. Our results suggest that susceptible heifer offspring might have a more active detox metabolism when under fescue toxicity. Findings from this study could be utilized as a new tool to help beef cattle producers to dampen the adverse effects of fescue toxicity.

Abstract

Offspring born to dams genetically tested for resistance to fescue toxicity were separated in groups based on their dams’ resistance level (tolerant vs. susceptible). Rumen-protected niacin (RPN) is proposed as a potential alleviator for vasoconstriction produced by fescue toxicity. Complete blood count (CBC) analysis was utilized for detection of significant responses to treatments applied. Our objectives were as follows: (a) to analyze changes in CBC due to fescue toxicity, maternal resistance level, and RPN in growing offspring; and (b) to assess the effects of maternal resistance level when consuming endophyte-infected tall fescue seeds in addition to RPN in offspring performance. Body weight, average daily gain, or health status were not improved by RPN or the genetic test to detect fescue toxicity resistance. Typical signs of alkaloids intoxication and heat stress were noticed in offspring. Particularly, rectal temperature was greater for susceptible control heifers. Results showed that susceptible control offspring presented signs of anemia denoted by low mean corpuscular hemoglobin (MCH) and mean corpuscular volume (MCV). High levels of white blood cells (WBC) and basophils in combination to low neutrophils to lymphocytes ratio were the signs of infection or inflammation detected in the CBC analysis, especially in tolerant niacin steers. Furthermore, offspring of control heifers had a greater percentage of reticulocytes and RDW, denoting signs of anemia.