Analysis of nonsynonymous SNPs in candidate genes that influence bovine temperament and evaluation of their effect in Brahman cattle.

BACKGROUND: Temperament is an important production trait in cattle and multiple strategies had been developed to generate molecular markers to assist animal selection. As nonsynonymous single nucleotide polymorphisms are markers with the potential to affect gene functions, they could be useful to predict phenotypic effects. Genetic selection of less stress-responsive, temperamental animals is desirable from an economic and welfare point of view. METHODS AND RESULTS: Two nonsynonymous single nucleotide polymorphisms identified in HTR1B and SLC18A2 candidate genes for temperament were analyzed in silico to determine their effects on protein structure. Those nsSNPs allowing changes in proteins were selected for a temperament association analysis in a Brahman population. Transversion effects on protein structure were evaluated in silico for each amino acid change model, revealing structural changes in the proteins of the HTR1B and SLC18A2 genes. The selected nsSNPs were genotyped in a Brahman population (n = 138), and their genotypic effects on three temperament traits were analyzed: exit velocity, pen score, and temperament score. Only the SNP rs209984404-HTR1B (C/A) showed a significant association (P = 0.0144) with pen score. The heterozygous genotype showed a pen score value 1.17 points lower than that of the homozygous CC genotype. CONCLUSION: The results showed that in silico analysis could direct the selection of nsSNPs with the potential to change the protein. Non-synonymous single nucleotide polymorphisms causing structural changes and reduced protein stability were identified. Only rs209984404-HTR1B shows that the allele affecting protein stability was associated with the genotype linked to docility in cattle.

Evidence of differentiation and population structure in Charolais cattle of Mexico.

Charolais is one of the most important beef cattle breeds in the world. In Mexico, it was introduced almost a century ago, and it has been suggested that particular breeding management and genetic material origin have caused a process of divergence among the current population. By a high-density SNP array genome-wide analysis, this study aimed to assess the proposed differentiation and population structure of local populations by genetic distances and structure approaches, and a European Charolais sample was included as a reference population. The differentiation statistics indicated that local populations exhibit moderate divergence, confirming a significant differentiation process between northeastern and northwestern Charolais populations (Fst≥ 0.043, D≥ 0.031). These results were strongly supported by PCA and structure analysis. Genetic isolation and low genetic flow between populations and divergent origins of introduced genetic material (i.e., semen) are likely the main drivers of the outcomes. Some implications are discussed.

Genetic Variants and Their Putative Effects on microRNA-Seed Sites: Characterization of the 3' Untranslated Region of Genes Associated with Temperament.

The 3' untranslated region has an important role in gene regulation through microRNAs, and it has been estimated that microRNAs regulate up to 50% of coding genes in mammals. With the aim of allelic variant identification of 3' untranslated region microRNA seed sites, the 3' untranslated region was searched for seed sites of four temperament-associated genes (CACNG4, EXOC4, NRXN3, and SLC9A4). The microRNA seed sites were predicted in the four genes, and the CACNG4 gene had the greatest number with 12 predictions. To search for variants affecting the predicted microRNA seed sites, the four 3' untranslated regions were re-sequenced in a Brahman cattle population. Eleven single nucleotide polymorphisms were identified in the CACNG4, and eleven in the SLC9A4. Rs522648682:T>G of the CACNG4 gene was located at the predicted seed site for bta-miR-191. Rs522648682:T>G evidenced an association with both exit velocity (p = 0.0054) and temperament score (p = 0.0097). The genotype TT had a lower mean exit velocity (2.93 ± 0.4 m/s) compared with the TG and GG genotypes (3.91 ± 0.46 m/s and 3.67 ± 0.46 m/s, respectively). The allele associated with the temperamental phenotype antagonizes the seed site, disrupting the bta-miR-191 recognition. The G allele of CACNG4-rs522648682 has the potential to influence bovine temperament through a mechanism associated with unspecific recognition of bta-miR-191.

Características y factores de riesgo de mortalidad por COVID-19 en Tamaulipas, a un año de pandemia / Characteristics and risk factors of COVID-19 mortality in Tamaulipas, one year after the pandemic

Resumen Coronavirus 19 (COVID-19), es una enfermedad viral prevalente y diseminada a nivel mundial, considerada una pandemia con alta tasa de mortalidad. A la fecha no existen estudios que describan la influencia de las variables asociadas a la enfermedad en el estado fronterizo de Tamaulipas, México. El objetivo del presente estudio fue evaluar y analizar las características, complicaciones, tasas de letalidad y factores de riesgo asociados a mortalidad en paciente positivos a COVID-19 en el estado de Tamaulipas, a un año de la emergencia local. Se utilizó la frecuencia de casos observados en relación a características, complicaciones y comorbilidades para estimar prevalencias y tasas de letalidad. Se ajustó un modelo de regresión logística multivariada para estimar los factores de riesgo significativos y se utilizaron curvas de supervivencia de Kaplan-Meier para describir las comorbilidades más importantes. Los análisis indicaron una mayor infección en pacientes en edad productiva, con una probabilidad significativa de muerte a partir de los 40 años, más evidente en pacientes masculinos. Los riesgos asociados a la hospitalización, como intubación endotraqueal y neumonía, son factores muy importantes. Las comorbilidades con alta prevalencia (diabetes, hipertensión y obesidad) y enfermedad renal crónica (ERC) están asociados significativamente (P < 0.01) a mayor mortalidad por COVID-19 en pacientes positivos. El presente estudio demostró algunos patrones generales de prevalencia y tasas de letalidad por COVID-19, por lo que se sugieren particularidades en los factores asociados a mortalidad en la población de Tamaulipas que requieren atención en sus grupos vulnerables, sobre todo en posibles casos de rebrotes de la enfermedad.

Abstract Coronavirus 19 (COVID-19) is a prevalent and globally disseminated viral disease that has become a pandemic associated with a high case fatality rate. To date, there are no published studies that describe the influence of the variables associated with the disease, specifically in the border state of Tamaulipas, Mexico. The objective of the present study was to assess the characteristics, complications, fatality rates and risk factors associated to mortality in patients positive to COVID-19 in Tamaulipas, one year after the local emergency. Descriptive frequency of characteristics, complications for prevalence and case fatality rates were used. A multivariate logistic regression model was adjusted to estimate the meaningful risk factors, and Kaplan-Meier survival curves were used to describe the most important comorbidities. The analysis indicated higher infection rates in patients of productive age, with a significant death probability in male patients from the age of 40. The risks associated with hospitalization, such as endotracheal intubation and the presence of pneumonia are important risk factors. Comorbidities with high prevalence; diabetes, hypertension, obesity, and chronic kidney disease (CKD) were significantly associated (P < 0.01) with higher COVID-19 mortality risk in the assessed population. The present study demonstrated some COVID-19 general patterns on frequency and mortality rates. It also suggested particularities in factors associated to mortality in the Tamaulipas population, which require proper attention in vulnerable groups, especially in future outbreaks of the disease.

Tasas de letalidad y factores de riesgo por COVID-19 en México / Case fatality rates and risk factors by COVID-19 in Mexico

Introducción: La COVID-19 es una enfermedad viral diseminada a nivel mundial, que es considerada una pandemia con alta tasa de mortalidad, cuyo estudio epidemiológico es fundamental para entender el riesgo asociado a poblaciones específicas. Objetivos: Estimar las tasas de letalidad y factores de riesgo asociados a mortalidad por COVID-19 en cinco Estados con más contagios en México. Métodos: Se analizaron de 297 230 pacientes positivos a COVID-19 mediante prueba de RT-PCR procedentes de 475 unidades de monitoreo en cinco Estados de México. Se estimaron tasas de letalidad y razones de probabilidad mediante el ajuste de un modelo de regresión logística multivariada. Se consideraron los factores de riesgo en un modelo que incluyó los efectos del sexo, edad, hábitos de fumador, historial de hospitalización, diagnóstico de neumonía y comorbilidades como diabetes, hipertensión, enfermedad pulmonar obstructiva crónica, asma, inmunodepresión, enfermedad renal crónica y enfermedades cardiovasculares, entre otras. Resultados: Existe mayor contagio entre las personas de 41 a 60 años de edad. Más del 90 por ciento de los fallecimientos ocurrieron después de los 41 años, con aumento de la tasa de letalidad a mayor edad. Los hombres mostraron mayor proporción de casos, fallecimientos y tasa de letalidad. El análisis logístico multivariado mostró que la edad, sexo, hospitalización, neumonía, diabetes y enfermedad renal crónica son factores de riesgo significativos (p < 0,0001) para mortalidad por COVID-19. Conclusiones: En México la edad, el sexo, la hospitalización, neumonía, diabetes y enfermedad renal crónica son factores que aumentan el riesgo de mortalidad por COVID-19. Se sugiere tener en cuenta esta información para determinar los grupos vulnerables e incrementar la atención sobre ellos para disminuir, en la medida de lo posible, el riesgo de contagio y mortalidad(AU)

Introduction: COVID-19 is a viral disease disseminated worldwide, considered a pandemic with a high mortality rate, whose epidemiological study is fundamental to understand the risk associated with specific populations. Objectives: Estimate the case fatality rates and risk factors associated with mortality from COVID-19 in the five states with more infections in Mexico. Methods: 297,230 COVID-19 positive patients were analyzed using RT-PCR tests from 475 monitoring units in five states of Mexico. Case fatality rates and probability ratios were estimated by adjusting a multivariate logistic regression model. Risk factors were considered in a model that included the effects of sex, age, smoking habits, hospitalization history, pneumonia diagnosis, and comorbidities such as diabetes, hypertension, chronic obstructive pulmonary disease, asthma, immunosuppression, chronic kidney disease, and cardiovascular disease, among others. Results: There is greater contagion among people aged 41 to 60 years. More than 90percent of deaths occurred after the age of 41, with the case fatality rate increasing at an older age. Men showed a higher proportion of cases, deaths and case fatality rate. Multivariate logistic analysis showed that age, sex, hospitalization, pneumonia, diabetes, and chronic kidney disease are significant risk factors (p < 0.0001) for COVID-19 mortality. Conclusions: In Mexico, age, sex, hospitalization, pneumonia, diabetes and chronic kidney disease are factors that increase the risk of mortality from COVID-19. It is suggested to take this information into account to determine vulnerable groups and increase attention to them to reduce, as far as possible, the risk of contagion and mortality(AU)

Discovering of Genomic Variations Associated to Growth Traits by GWAS in Braunvieh Cattle.

A genome-wide association study (GWAS) was performed to elucidate genetic architecture of growth traits in Braunvieh cattle. Methods: The study included 300 genotyped animals by the GeneSeek® Genomic Profiler Bovine LDv.4 panel; after quality control, 22,734 SNP and 276 animals were maintained in the analysis. The examined phenotypic data considered birth (BW), weaning (WW), and yearling weights. The association analysis was performed using the principal components method via the egscore function of the GenABEL version 1.8-0 package in the R environment. The marker rs133262280 located in BTA 22 was associated with BW, and two SNPs were associated with WW, rs43668789 (BTA 11) and rs136155567 (BTA 27). New QTL associated with these liveweight traits and four positional and functional candidate genes potentially involved in variations of the analyzed traits were identified. The most important genes in these genomic regions were MCM2 (minichromosome maintenance complex component 2), TPRA1 (transmembrane protein adipocyte associated 1), GALM (galactose mutarotase), and NRG1 (neuregulin 1), related to embryonic cleavage, bone and tissue growth, cell adhesion, and organic development. This study is the first to present a GWAS conducted in Braunvieh cattle in Mexico providing evidence for genetic architecture of assessed growth traits. Further specific analysis of found associated genes and regions will clarify its contribution to the genetic basis of growth-related traits.

Chronic kidney disease is a very significant comorbidity for high risk of death in patients with COVID-19 in Mexico.

Chronic kidney disease (CKD) is a recognized public health problem and key determinant of poor health outcomes. In Mexico, this condition has been associated with high and significant risk of death in COVID-19 patients; however, not enough attention has been given to the vulnerable population as the increasing numbers and fatality rates suggest. This study evaluated the effect of interaction between CKD condition and other risk factors (sex, diabetes, hypertension and obesity) on the survival rate of positive patients for COVID-19 in Mexico. The results from this study support that CKD patients is a population at high risk for mortality for COVID-19 and that COVID-19 positive inpatients with CKD and diabetes are highly vulnerable to death.

Effect of Leptin, Pituitary Transcription Factor and Luteinizing Hormone Receptor Genes Polymorphisms on Reproductive Traits and Milk Yield in Holstein Cattle

Abstract The aim of this study was to estimate allelic and genotypic frequencies of markers in the leptin (LEP), pituitary transcription factor (PIT-1) and luteinizing hormone receptor (LHR) genes and evaluate their effects on reproductive traits and milk yield of Holstein cattle. Data from 147 cows from department of Francisco Morazán, Honduras, were collected and PCR-Restriction Fragment Length Polymorphism (RFLP) assays were performed to characterize the PIT-1-HinfI, LEP- A59V and LHR-rs41256848 polymorphisms. To estimate the effect of genotypes on reproductive traits and milk yield fixed and mixed linear models were fitted. The frequencies of the genotypes CC, CT and TT of A59V, AA, AB and BB of HinfI, and CC, CG and GG of rs41256848 were 0.46, 0.33 and, 0.21; 0.09, 0.32 and 0.58; and 0.37, 0.61 and 0.02, respectively. The genotypes of LEP and LHR showed deviations from Hardy-Weinberg equilibrium. The A59V polymorphism was significantly associated with the calving to conception interval (CCI) (p=0.01), being the C allele favorable. The HinfI and rs41256848 polymorphism were significantly associated (p=0.08 and p=0.04) with age to first calving (AFC), being the A and G the alleles favorable associated, respectively. The results suggest that LEP, PIT and LHR polymorphisms can probably act as candidate to be used in marker-assisted selection for AFC and CCI traits.

Clinical characteristics and risk factors for mortality of patients with COVID-19 in a large data set from Mexico.

PURPOSE: The purpose of this study was to assess clinical characteristics and risk factors for mortality of patients with coronavirus disease 2019 (COVID-19) from Mexico, given that it currently is in active community transmission. METHODS: Multivariate logistic regression model and Kaplan-Meier survival curves were fitted to study odds of death of characteristics and comorbidities in patients with COVID-19 in Mexico. RESULTS: Age, sex, and the most frequent comorbidities diabetes, obesity, and hypertension were significantly associated to the risk of death by COVID-19 (P < .0001). Smoking habit was not identified as a risk factor for death. Less-frequent comorbidities such as chronic obstructive pulmonary disease, chronic kidney disease, and patients with immunosuppressed conditions also showed a significant risk for death (P < .0001). Hospitalized patients and those with pneumonia had serious risks for mortality (P < .0001), and more attention to specific conditions might be considered during clinical admission. CONCLUSIONS: A more vulnerable positive patient is depicted by a male patient, older than 41 years, which increases their risk with more prevalent comorbidities such as diabetes, hypertension, and obesity. Some implications on outcomes are discussed.

Non-synonymous polymorphisms in candidate gene associated with growth traits in Channel catfish (Ictalurus punctatus, Rafinesque, 1818).

Resequencing of Myostatin, Growth Hormone, Follistatin-A-like, Insulin-like Growth Factor I (IGF-I) and Myogenin (MYOG) genes was completed to discover novel genetic variations and assess non synonymous (ns) polymorphisms (SNPs) effect on growth related traits of channel catfish. Wild and farmed animals were used as a discovering population. Resequencing lead to the identification of 59 new variants in the five analyzed genes; 66% found in introns and 34% in coding regions. From coding regions, 14 variants were synonyms and six were ns variations. A mutation rate of one in 129 bp was estimated. Four ns variations were selected for validation and association analysis. In IGF-I two ns polymorphisms, at IGF-I19 the G wild type allele was fixed in population and for IGF-I63 the C allele had a frequency of 0.972 and for mutate allele G of 0.027. In MYOG two ns SNPs were assessed. MYOG131 presented a frequency of alleles T and A, of 0.754 and 0.246, respectively and MYOG233, with a frequency of G and C of 0.775 and 0.225, respectively. Only MYOG131 (g.529T>A) was significantly associated (P < 0.04) to some growth traits. Results suggest MYOG131 g.529T>A as candidate locus for genetic enhancement of growth traits in channel catfish.

Signatures of selection in Charolais beef cattle identified by genome-wide analysis.

Charolais cattle are one of the most important breeds for meat production worldwide; in México, its selection is mainly made by live weight traits. One strategy for mapping important genomic regions that might influence productive traits is the identification of signatures of selection. This type of genomic features contains loci with extended linkage disequilibrium (LD) and homozygosity patterns that are commonly associated with sites of quantitative trait locus (QTL). Therefore, the objective of this study was to identify the signatures of selection in Charolais cattle genotyped with the GeneSeek Genomic Profiler Bovine HD panel consisting of 77 K single nucleotide polymorphisms (SNPs). A total 61,311 SNPs and 819 samples were used for the analysis. Identification of signatures of selection was carried out using the integrated haplotype score (iHS) methodology implemented in the rehh R package. The top ten SNPs with the highest piHS values were located on BTA 4, 5, 6 and 14. By identifying markers in LD with top ten SNPs, the candidate regions defined were mapped to 52.8-59.3 Mb on BTA 4; 67.5-69.3 on BTA 5; 39.5-41.0 Mb on BTA 6; and 26.4-29.6 Mb on BTA 14. The comparison of these candidate regions with the bovine QTLdb effectively confirmed the association (p < 0.05) with QTL related to growth traits and other important productive traits. The genomic regions identified in this study indicated selection for growth traits on the Charolais population via the conservation of haplotypes on various chromosomes. These genomic regions and their associated genes could serve as the basis for haplotype association studies and for the identification of causal genes related to growth traits.

Screening genetic diseases prevalence in Braunvieh cattle.

Heritable abnormalities can cause a reduction in productive performance, structural defects, or death of the animal. There are reports of hereditary abnormalities in Braunvieh cattle from several countries, but no evidence was found on their existence in Mexico. In this study, 28 genes associated with hereditary diseases were screened with the GGP-LD 30K array (GeneSeek®) in 300 Mexican registered Braunvieh animals. Allelic frequencies of the markers associated with illness were obtained for the following: citrullinaemia, spinal dysmyelination, spinal muscular atrophy, Brows Swiss fertility haplotype 2, congenital muscular dystonia, epidermolysis bullosa, Pompes, maple syrup urine, syndactyly, Weaver syndrome, crooked tail, deficiency of uridine monophosphate synthase, hypotrichosis, Marfan syndrome, and weak calf syndrome. The allelic frequency values were low for all the analysed loci (from 0.0015 to 0.0110), with exception of syndactyly (0.4145). Although homozygous animals for these genetic conditions were detected, no physical or physiological abnormalities associated with the clinical form of the diseases were observed in the sampled animals. Markers associated with a crooked tail, deficiency of uridine monophosphate synthase, hypotrichosis, Marfan syndrome, and weak calf syndrome were absent. The studied Mexican Braunvieh population does not present clinical or subclinical effects for ten diseases in homozygous animals. However, since the assessed animals are considered as breeding stock, the monitoring of carrier animals might be periodically necessary.

Signatures of Selection From Candidate Gene Polymorphisms Panel in Five Zebu Breeds

ABSTRACT The signals of selection using candidate genes polymorphism were studied in five zebu breeds of Mexico. Three loci from GHRH and complementarily Steroyl Co Desaturase F762, Dopamine Beta Hydroxilase 17299, and LEP3272 were identified under selection. Findings depict Zebu selection pressure mainly on Brahman breed resulting in a divergent structure pattern.

Meat tenderness genetic polymorphisms occurrence and distribution in five Zebu breeds in Mexico

Background The Zebu cattle are represented by a diverse group of breeds in México. Traditionally these breeds have been associated with the tough beef characteristic. Validated genetic markers have the potential to be included in marker-assisted selection and management programs in order to improve traits such as beef tenderness. The incidence and distribution of Calpain and Calpastatin polymorphisms strongly associated with beef tenderness were estimated in registered cattle of five Zebu breeds in Mexico. Results A low and in some cases null frequency of favorable C allele of CAPN316 was determined in all breeds. Conversely, a more equilibrated frequency in CAPN4751 and CAST loci was observed. Conclusions Although the relatively low occurrence of favorable alleles in assessed loci may limit their use in selection programs, genotyping availability might be a practical and comprehensive tool for introgression programs by marker assisted selection and management as to improve meat tenderness of Zebu breeds.

Associations of SNPs located at candidate genes to bovine growth traits, prioritized with an interaction networks construction approach.

BACKGROUND: For most domestic animal species, including bovines, it is difficult to identify causative genetic variants involved in economically relevant traits. The candidate gene approach is efficient because it investigates genes that are expected to be associated with the expression of a trait and defines whether the genetic variation present in a population is associated with phenotypic diversity. A potential limitation of this approach is the identification of candidates. This study used a bioinformatics approach to identify candidate genes via a search guided by a functional interaction network. RESULTS: A functional interaction network tool, BosNet, was constructed for Bos taurus. Predictions for candidate genes were performed using the guilt-by-association principle in BosNet. Association analyses identified five novel markers within BosNet-prioritized genes that had significant effects on different growth traits in Charolais and Brahman cattle. CONCLUSIONS: BosNet is an excellent tool for the identification of single nucleotide polymorphisms that are potentially associated with complex traits.

Single and composite influence of growth-related candidate gene polymorphisms on additive genetic variation of birth weight in Charolais beef cattle.

The objective of the present experiment work was to evaluate the effect of the inclusion of genomic information on the additive genetic variance of birth weight (BW) of Charolais cattle in Mexico. Variance components and heritability were estimated using four linear models. The first model was the base model (BM) from which single and composite effects of selected single-nucleotide polymorphism (SNP) markers were evaluated (BM1, BM2, and a composite BM3). Genetic markers were included in a regression model and analyzed by stepwise regression against adjusted BW from a panel of growth-related traits candidate gene markers. After two regression rounds, two SNPs (R (2) > 0.02) were chosen to include into the animal models as fixed effects. Growth hormone receptor gene GHR 4.2 and GHR 6.1 SNPs were selected from a panel of 39 SNPs. GHR 4.2 had a negligible effect on BW, whilst GHR6.1, interestingly, explained ∼9 % of genetic variance (p = 0.0877) with an αG>A = 0.509. The inclusion of markers in M2 and M3 reduced 19 and 15 % of the additive genetic variance, respectively. Both adjusted significantly better the linear model (LRT = p < 0.01). Results obtained suggest that the previous selection of markers in a candidate gene approach and subsequent inclusion of selected SNPs into animal model might provide a better fit, avoiding the overestimation of genetic variance components and breeding values for BW.

Genetic diversity of tyrosine hydroxylase (TH) and dopamine ß-hydroxylase (DBH) genes in cattle breeds.

DNA from four cattle breeds was used to re-sequence all of the exons and 56% of the introns of the bovine tyrosine hydroxylase (TH) gene and 97% and 13% of the bovine dopamine ß-hydroxylase (DBH) coding and non-coding sequences, respectively. Two novel single nucleotide polymorphisms (SNPs) and a microsatellite motif were found in the TH sequences. The DBH sequences contained 62 nucleotide changes, including eight non-synonymous SNPs (nsSNPs) that are of particular interest because they may alter protein function and therefore affect the phenotype. These DBH nsSNPs resulted in amino acid substitutions that were predicted to destabilize the protein structure. Six SNPs (one from TH and five from DBH non-synonymous SNPs) were genotyped in 140 animals; all of them were polymorphic and had a minor allele frequency of > 9%. There were significant differences in the intra- and inter-population haplotype distributions. The haplotype differences between Brahman cattle and the three B. t. taurus breeds (Charolais, Holstein and Lidia) were interesting from a behavioural point of view because of the differences in temperament between these breeds.

Importancia de la verificación-asignación de progenitores en sistemas extensivos de pie de cría / Importance of parentage verification-assignment in extensive multiple-sired breeding herds

Se aplicó un panel de nueve marcadores microsatélites para estructurar la genealogía de un hato de ganado Braford manejado bajo empadre múltiple y destinado a pié de cría, para evaluar las repercusiones de la adecuada asignación de progenitores, así como las implicaciones en su mejoramiento genético. Se logró la asignación de paternidad en el 100% de la progenie, mientras que en los ensayos de verificación de maternidad se estimó un porcentaje de error de asignación de aproximadamente 90%. Los resultados encontrados apoyan el uso de la asignación de paternidad para verificar la estructura genealógica (paternidad y maternidad) de hatos cuya certeza en el pedigrí es crítica para el mejoramiento genético de su raza, y en donde el sistema de manejo extensivo y empadre múltiple limitan el registro adecuado de la progenie al momento del parto.

To assess the implications of parentage assignation on herds-genetic improvement nine microsatellite markers were used in order to structure the genealogy of a multisired Braford herd. All progeny (100%) had satisfactory paternity assignment, conversely the maternity verification analysis showed assignation errors up to 90%. Our results support the use of molecular tools to verify the pedigree structure in those herds with management systems that limit the proper registration of progeny at calving.

Genetic parameters for growth traits in Mexican Nellore cattle.

The aim of this study was to estimate genetic parameters for growth traits in Mexican Nellore cattle. A univariate animal model was used to estimate (co)variance components and genetic parameters. The traits evaluated were birth weight (BW), weaning weight (WW), and yearling weight (YW). Models used included the fixed effects of contemporary groups (herd, sex, year, and season of birth) and age of dam (linear and quadratic) as a covariate. They also included the animal, dam, and residual as random effects. Phenotypic means (SD) for BW, WW, and YW were 31.4 (1.6), 175 (32), and 333 (70) kg, respectively. Direct heritability, maternal heritability, and the genetic correlation between additive direct and maternal effects were 0.59, 0.17, and -0.90 for BW; 0.29, 0.17, and -0.90 for WW; and 0.24, 0.15, and -0.86 for YW, respectively. The results showed moderate direct and maternal heritabilities for the studied traits. The genetic correlations between direct and maternal effects were negative and high for all the traits indicating important tradeoffs between direct and maternal effects. There are significant possibilities for genetic progress for the growth traits studied if they are included in a breeding program considering these associations.

Assessment of genetic structure in Mexican charolais herds using microsatellite markers

Knowledge of livestock genetic diversity is an essential step to respond to commercial demands and reach production objectives in different environments and production systems. The evaluation of animal genetic diversity is achieved by using molecular markers. Microsatellites are the most used markers for studies of this type. Eleven microsatellites were used to evaluate the genetic variation from three populations of Charolais cattle located in northeast Mexico. The studied populations exhibited a high allelic variability with a mean heterozygosity of 0.5. A moderate genetic differentiation between the Charolais populations (F ST = 0.079; P < 0.001) was observed. This suggests subdivisions in Charolais breed established in Mexico, due to genetic material origin, reproductive and selective management and local isolation.