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Objective: In tropical, subtropical and arid zones, heat stress is the main cause of productivity reduction in cattle. When climate stressors occur, animals become thermal adapted through differential expression of some genes, including heat shock proteins (HSP) family. The aim of this study was to determine levels of expression of HSP60, HSP70, and HSP90 genes in Simmental cattle raised in tropical environments of Mexico.Methods: In this study, expression of HSP60, HSP70, and HSP90 genes was analyzed in 116 Simmental cattle from three farms with tropical climate located in western Mexico. Animals were sampled twice a day, in the morning and noon. Gene expression was evaluated by quantitative polymerase chain reaction using probes marked with fluorescence. The MIXED procedure of SAS with repeated measures was used for all statistical analysis.Results: HSP60 gene expression differences were found for sex (p = 0.0349). HSP70 gene differences were detected for sampling hour (p = 0.0042), farm (pHSP90 were observed for farm (pHSP70 gene showed to be a better marker of heat stress than HSP60 and HSP90 genes.Conclusion: Expression of HSP70 gene in Simmental herds of the tropical region of western México was different during early morning and noon, but the expression of the HSP60 and HSP90 genes was similar. Identification of resilient animals to heat stress will be useful in the genetic improvement of the Simmental breed.

Existe una gran posibilidad de mejorar la producción de embriones in vitro al enriquecer los medios de cultivo adicionando moléculas que regulen las condiciones óptimas de los gametos. El objetivo de este estudio fue adicionar la proteína de choque térmico recombinante HSC70, para evaluar su efecto en la producción de embriones in vitro. Se adicionaron 25 ng/mL de la proteína HSC70 al cultivo de embriones sometidos a estrés térmico, formando cuatro tratamientos T1= medio adicionado con HSC70 a 41 °C, T2= medio sin HSC70 a 41 °C, T3= medio adicionado con HSPC70 a 38.5 °C y T4= medio sin HSC70 a 38.5 °C. Bajo el protocolo de producción in vitro de embriones bovino en los medios de cultivo temprano (CDM1) y tardío (CDM2), con la finalidad de evaluar el desarrollo embrionario a través de las variables, porcentaje de división embrionaria, embriones de seis células o más y blastocistos al día 7 u 8 y número de células en blastocisto al día 7. El conteo de las células en los blastocitos al día 7 del cultivo, se llevó a cabo a través del protocolo de tinción diferencial de Hoescht 33342. Los datos se sometieron a un análisis de varianza con un arreglo factorial con el procedimiento GLM de SAS (2013), que incluyó los factores de proteína, temperatura y su interacción. El número de células se analizó asumiendo una distribución Poisson por tratarse de un conteo. Los resultados mostraron que el factor proteína fue significativa (p= 0.01) para todas las variables de respuesta y existe un efecto positivo de la proteína HSC70, agregada al medio de cultivo, sin importar la temperatura a la que fueron cultivados; este efecto se expresó tanto en un mayor porcentaje de embriones, como en una mayor tasa (p

Background: No dairy breed or crossbreed has superior overall performance in all environments; therefore, it is necessary to determine which crossbreed is the most suitable for the Mexican tropic and what proportion of European breed is optimum for reproduction. Objective: To assess the effect of the proportion of Bos taurus (Bt) genes on reproductive performance of Holstein×Zebu (HZ) and Brown Swiss×Zebu (BZ) cows, and compare reproductive performance of these genotypes in a dual-purpose production system. Methods: Cows were maintained in a rotational grazing system on African star grass (Cynodon plectostachyus) in Veracruz, Mexico. Cows were milked twice daily. Calves were kept tied to the side of their dams while the cows were milked. Results: The percentage of Bt genes did not affect (p>0.05) fertility traits (age at first calving, days to first service after calving, services per conception, conception rate at first service, days open until conception, gestation length, and calving interval) of BZ cows. In contrast, HZ cows with less than 75% Holstein (H) genes were 0.3 years younger (p

El objetivo fue presentar resultados de investigación sobre mejoramiento genético de bovinos productores de carne realizados por el Instituto Nacional de Investigaciones Forestales, Agrícolas y Pecuarias, así como los retos y perspectivas de investigación a corto, mediano y largo plazo en dicha área del conocimiento. Se utilizaron tesis de maestría, trabajos de congresos y artículos científicos publicados de 1987 a 2020. En los últimos 34 años, se logró caracterizar productiva y reproductivamente animales Bos indicus y Bos taurus x Bos indicus en condiciones tropicales, implementar evaluaciones genéticas multirraciales para las poblaciones Simmental-Simbrah y Charolais-Charbray, determinar la importancia de los efectos maternos en características de crecimiento y estimar la heredabilidad y correlaciones genéticas para características de crecimiento y reproductivas de machos y hembras en animales Bos taurus y Bos indicus, comprobar que la interacción genotipo-ambiente es un factor importante en la expresión de peso al destete en Simmental, desarrollar factores de ajuste de edad de la madre para pesos al nacimiento y destete, desarrollar un prototipo de evaluación genética nacional para permanencia productiva y otro para fertilidad de vaquillas, estimar la diversidad genética de las poblaciones Simmental, Charolais y Simbrah, e identificar SNP asociados a características de crecimiento en Simmental y Simbrah. En el corto plazo, se espera desarrollar índices de selección y predecir el mérito genético de características de canal; en el mediano, realizar evaluaciones genómicas para tolerancia al estrés calórico, consumo de alimento residual y características de salud; y a largo plazo, realizar predicciones genómicas a través de razas.

Objective: The aim was to characterize the genetic diversity evolution of the registered Mexican Charolais cattle population by pedigree analysis. Methods: Data consisted of 331,390 pedigree records of animals born from 1934 to 2018. Average complete generation equivalent, generation interval, effective population size (Ne), and effective numbers of founders (fe), ancestors (fa), and founder genomes (Ng) were calculated for seven five-year periods. The inbreeding coefficient was calculated per year of birth, from 1984 to 2018, whereas the gene contribution of the most influential ancestors was calculated for the latter period. Results: Average complete generation equivalent consistently increased across periods, from 4.76, for the first period (1984 through 1988), to 7.86, for the last period (2014 through 2018). The inbreeding coefficient showed a relative steadiness across the last seventeen years, oscillating from 0.0110 to 0.0145. During the last period, the average generation interval for the father-offspring pathways was nearly 1 yr. longer than that of the mother-offspring pathways. The effective population size increased steadily since 1984 (105.0) and until 2013 (237.1), but showed a minor decline from 2013 to 2018 (233.2). The population displayed an increase in the fa since 1984 and until 2008; however, showed a small decrease during the last decade. The effective number of founder genomes increased from 1984 to 2003, but revealed loss of genetic variability during the last fifteen years (from 136.4 to 127.7). The fa:fe ratio suggests that the genetic diversity loss was partially caused by formation of genetic bottlenecks in the pedigree; in addition, the Ng:fa ratio indicates loss of founder alleles due to genetic drift. The most influential ancestor explained 1.8% of the total genetic variability in the progeny born from 2014 to 2018. Conclusion: Inbreeding, Ne, fa, and Ng are rather beyond critical levels; therefore, the current genetic status of the population is not at risk.

El objetivo de este trabajo fue estimar la respuesta a la selección a través de diferentes índices de selección entre producción de metano y producción y componentes de la leche en los sistemas de lechería tropical especializada, doble propósito y lechería familiar. El muestreo de las emisiones de metano se realizó durante la ordeña mediante el equipo Guardian-NG. Se tomaron muestras de leche de manera individual durante el muestreo de metano. La extracción de ADN se realizó de folículos pilosos de todos los animales incluidos en el estudio. La estimación de los componentes de varianza y covarianza se realizó mediante la metodología de modelos mixtos. Se utilizaron los marcadores moleculares para construir la matriz de relaciones genómicas (Matriz G), debido a que no se contaba con información genealógica completa. La heredabilidad estimada para las emisiones de metano durante la ordeña fue de 0.18 y 0.32 para los análisis univariados y bivariados, respectivamente. Los resultados de las correlaciones genéticas entre porcentaje de grasa y proteína en leche con las emisiones de metano durante la ordeña fueron negativas, -0.09 y -0.18 respectivamente. La respuesta a la selección estimada mediante los índices de selección demostró que es factible obtener reducciones de hasta 0.021 mg/l de emisiones de metano durante la ordeña en cinco generaciones; lo anterior sin detrimento en los componentes de la leche.

Objective: The objective of this study was to perform genome (genome wide association studies [GWAS]) and chromosome (CWAS) wide association analyses to identify single nucleotide polymorphisms (SNPs) associated with growth traits in registered Simmental and Simbrah cattle.Methods: The phenotypes were deregressed BLUP EBVs for birth weight, weaning weight direct, weaning weight maternal, and yearling weight. The genotyping was performed with the GGP Bovine 150k chip. After the quality control analysis, 105,129 autosomal SNP from 967 animals (473 Simmental and 494 Simbrah) were used to carry out genotype association tests. The two association analyses were performed per breed and using combined information of the two breeds. The SNP associated with growth traits were mapped to their corresponding genes at 100 kb on either side.Results: A difference in magnitude of posterior probabilities was found across breeds between genome and chromosome wide association analyses. A total of 110, 143, and 302 SNP were associated with GWAS and CWAS for growth traits in the Simmental-, Simbrah-and joint -data analyses, respectively. It stands out from the enrichment analysis of the pathways for RNA polymerase (POLR2G, POLR3E) and GABAergic synapse (GABRR1, GABRR3) for Simmental cattle and p53 signaling pathway (BID, SERPINB5) for Simbrah cattle.Conclusion: Only 6,265% of the markers associated with growth traits were found using CWAS and GWAS. The associated markers using the CWAS analysis, which were not associated using the GWAS, represents information that due to the model and priors was not associated with the traits.

Objective. Compare the fertility of Brown Swiss x Zebu and Simmental x Zebu crossbred cows reared in a tropical environment. Materials and methods. Reproductive traits of 185 Brown Swiss x Zebu and Simmental x Zebu crossbred cows with diverse percentages of European breed were evaluated. Grazing of cows was rotational. The milking was twice daily with the help (suckling) of the calf, which was kept tied next to the dam while she was milked. Traits were evaluated fitting a repeated measures model (except for age at first calving). Calving interval, age at first calving, days open, interval from calving to first service, and weight at calving were analyzed with PROC MIXED of SAS. Pregnancy rate at first service and services per conception were analyzed with PROC GENMOD of the same software. Results. Simmental x Zebu cows started to re-bred 39 days earlier after calving (p, Objetivo. Comparar la fertilidad de vacas cruzadas Suizo Pardo x Cebú y Simmental x Cebú criadas en un ambiente tropical. Materiales y métodos. Se evaluaron características reproductivas de 185 vacas cruzadas Suizo Pardo x Cebú y Simmental x Cebú con diversos porcentajes de raza europea. El pastoreo de las vacas fue rotacional. El ordeño fue dos veces al día con la ayuda (amamantamiento) del becerro, el cual se mantuvo atado cerca de la vaca mientras ella se ordeñaba. Las características se evaluaron ajustando un modelo de mediciones repetidas (excepto para edad a primer parto). Periodo interparto, edad a primer parto, días abiertos, periodo parto-primer servicio y peso al parto fueron analizados con PROC MIXED de SAS. Tasa de gestación a primer servicio y servicios por concepción, se analizaron con PROC GENMOD del mismo programa. Resultados. Las vacas Simmental x Cebú se sirvieron después del parto 39 días antes (p

Mexican Creole Cattle (MCC) derived from cattle of the Iberian Peninsula, mainly from Andalucia and Extremadura, and were introduced in central America the 16th century. Copy Number Variants (CNVs) are structural variants contributing to the genetic diversity among populations and related to variation in phenotypic expression. More than half of the identified CNVs regions in human and livestock include protein-coding genes involved in essential function, as cellular functionality, metabolic pathways and disease susceptibility. The aim of this study is to investigate the CNVs genomic variation in the MCC population. A total of 48 unrelated individuals (5 males and 43 females) were genotyped with the BovineHD Genotyping BeadChip Illumina, containing 7,77,962 polymorphic SNPs. A total of 2170 CNVs were detected in 40 individuals, summarized into 733 CNV regions, covering 32.1 Mb of the bovine autosome genome. Functional analysis of the CNVRs identified 131 genes mainly involved in immune response and inflammation, and 923 overlapping QTL classified in six difference QTL-term categories. Cluster and PCA analyses showed a samples distribution in concordance with the geographical origins of the sub-populations, highlighting both a sharing genetic background together with a diversification of populations as a response to adaptation to different and adverse environments.

El objetivo del presente estudio fue evaluar la resistencia a la infección natural por Cooperia spp. en bovinos jóvenes cruzados Cebú x Holstein, en trópico. Catorce (14) becerros de cuatro meses de edad fueron tratados con desparasitante y trasladados a potreros naturalmente contaminados con nematodos gastrointestinales bajo condiciones de trópico sub-húmedo. Muestras de heces se colectaron cada siete días durante tres meses por individuo, para cuantificar el número de huevos por gramo de heces (HPG) e identificar el género por PCR de punto final. Se colectaron muestras de pelo para llevar a cabo estudios de asociación genómica utilizando la plataforma GeneSeek Genomic Profiler HD-V3 que contiene139,376 marcadores SNP. Los resultados obtenidos indican variación en el número de HPG por individuo (mínimo 7+7 y máximo 4657+1886 HPG). En los análisis de componentes principales se identificaron diferencias raciales entre los animales con genes de las razas Cebú y Holstein. Los estudios de asociación del genoma completo detectaron 5 haplotipos estadísticamente significativos (P

This research assessed the dose/response to Duddingtonia flagrans chlamydospores (Df-C) administered to calves naturally infected with gastrointestinal nematodes (GINs), and its effect in reducing the infective larvae (L3) population in faeces in a farm in the Mexican tropics. Forty zebu calves, between 6 and 12 months of age, were randomly distributed into four groups of 10 calves. One control and three groups treated with different oral doses of Df-C based on their body weight (BW) were established as follows: group 1 (control); group 2, 0.250 × 106 Df-C per kg/BW; group 3, 0.5 × 106 Df-C per kg/BW and group 4, 1 × 106 Df-C per kg/BW. The fungal doses were administered daily for 10 days. Every group was confined to individual pens, and they received a nutritional regime based on Buffel grass, concentrated supplement and water ad libitum. Every third day, starting one week before treatments, faeces were taken from the rectum of each animal to determine the number of eggs per g of faeces (epg) through the McMaster technique. Four coprocultures of 20 g each from each individual faecal sample were prepared and incubated for 14 days. The efficacy of the treatments was based on the mean of the GIN L3 recovered from coprocultures of the different groups. Data were analysed using a completely randomized design through an ANOVA analysis, followed by a Duncan multiple range test. The efficacy of treatments was expressed as the larval reduction rate. High variation in the epg in the different groups along the experiment was recorded. The reduction in the GIN L3 population was observed from the 4 to 11 day post-treatment in the three assessed doses. Results in group 2 (lowest fungal dose), showed 88.5, 57.6, 55.9 and 30% (58% overall reductions) in the GIN L3 in the faeces of animals 4, 7, 9 and 11 days post-treatment, respectively. In group 3 (medium fungal dose), 95.8, 80.4, 63.4 and 52.7% GIN L3 reductions (73% overall reduction) were recorded, respectively. At the highest Df-C dose used (1 × 106 per kg/BW), the results were 88.9, 78.0, 59.3 and 67.3% (73.5% overall reduction), respectively (p

Background: Knowledge of genetic correlations and the economics of traits are essential to decide which traits should be used as selection criteria. Objective: To estimate heritabilities and genetic, environmental, and phenotypic correlations, and direct (DRS) and correlated (CRS) responses to selection by scrotal circumference (SC), frame score (FS), and yearling weight (YW) of Mexican Charolais (CH), and Charbray (CB) Young bulls. Methods: Actual SC, height and YW records (10,078 for CH, and 500 for CB) were adjusted to 365 d. The 0.0505 adjustment factor recommended by the Beef Improvement Federation was used to obtain the 365-d adjusted SC for both breeds. Height and age records were used to obtain FS. Data were analyzed using a three-trait animal model. The animal model for each trait included bull breed, contemporary group (groups of young bulls born in the same herd, year, and season of the year), and age of dam as a linear covariate as fixed effects, and direct additive genetic and residual as random effects. Results: Heritability estimates for SC, FS and YW were 0.21 ± 0.04, 0.25 ± 0.04, and 0.29 ± 0.04, respectively. The genetic correlation between YW with SC was 0.37 ± 0.16, and between YW with FS was 0.42 ± 0.16. The estimate of genetic correlation between SC and FS was low and positive (0.15 ± 0.14). The DRS was 0.38 cm, 0.18 units, and 8.30 kg for SC, FS and YW. The CRS was 0.16 cm, and 0.08 units for SC and FS from indirect selection on YW. Conclusions: Direct selection for YW is expected to be effective. Indirect selection for SC and FS based on YW would not be expected to be as effective as direct selection for improving SC and FS. Keywords: Beef cattle, genetic correlations, heritability, males, phenotypic correlations, response to selection. Resumen Antecedentes: el conocimiento de las correlaciones geneticas y el aspecto economico de las caracteristicas son necesarios para decidir que caracteristicas usar como criterios de seleccion. Objetivo: estimar las heredabilidades y correlaciones geneticas, ambientales y fenotipicas, y respuesta directa (DRS) y correlacionada (CRS) a la seleccion por circunferencia escrotal (SC), talla corporal (FS), y peso al ano (YW) de toros jovenes mexicanos Charolais (CH), y Charbray (CB). Metodos: registros (10.078 para CH y 500 para CB) de SC, altura y YW se ajustaron a 365 d. El factor de ajuste de 0,0505 recomendado por la Beef Improvement Federation se uso para obtener la SC ajustada a 365 d para ambas razas. Registros de altura y edad del animal se usaron para calcular FS. Los datos se analizaron usando un modelo animal para tres caracteristicas. El modelo animal para cada caracteristica incluyo raza del toro, grupo contemporaneo (grupos de toros jovenes nacidos en el mismo hato, ano y epoca del ano) y edad de la madre como covariable lineal como efectos fijos, y el genetico aditivo directo y el error como efectos aleatorios. Resultados: los estimadores de heredabilidad de SC, FS y YW fueron 0,21 ± 0,04, 0,25 ± 0,04 y 0,29 ± 0,04, respectivamente. La correlacion genetica de YW con SC fue 0,37 ± 0,16, y de YW con FS fue 0,42 ± 0,16. El estimador de la correlacion genetica entre SC y FS fue bajo y positivo (0,15 ± 0,14). La DRS fue 0,38 cm, 0,18 unidades, y 8,30 kg para SC, FS y YW. La CRS fue 0,16 cm y 0,08 unidades para SC y FS al seleccionar YW. Conclusiones: se espera que la seleccion directa de YW sea efectiva. La seleccion indirecta de SC y FS basada en YW no se espera que sea tan efectiva como la seleccion directa para mejorar SC y FS. Palabras clave: correlaciones fenotipicas, correlaciones geneticas, ganado de carne, heredabilidad, machos, respuesta a la seleccion. Resumo Antecedentes: o conhecimento das correlacoes geneticas, e aspecto economico de as caracteristicas sao necessario para decidir que caracteristicas usar como criterios de selecao. Objetivo: estimar herdabilidades e correlacoes geneticas, ambientais e fenotipicas, e resposta direta (DRS), e correlacionada (CRS) a selecao do perimetro escrotal (SC), escore de frame (FS), e peso ao ano de idade (YW) de touros jovens mexicanos Charoles (CH), e Charbray (CB). Metodos: registros (10.078 para CH e 500 para CB) de SC, altura e YW foram ajustados a 365 d. O fator de ajuste 0,0505 recomendado por a Beef Improvement Federation foi usado para obter o SC ajustado aos 365 d para ambas racas. Registros de altura na garupa e idade do animal foram usados para obter o FS. Os dados foram analisados usando um modelo animal para tres caracteristicas. O modelo animal para cada caracteristica incluiu raca do touro, grupo contemporâneo (grupos de touros jovens nascidos no mesmo fazenda, ano e epoca do ano) e idade materna como covariavel linear como efeitos fixos, e genetico aditivo direto e o erro como efeitos aleatorios. Resultados: as estimativas de herdabilidade para SC, FS e YW foram 0,21 ± 0,04, 0,25 ± 0,04 e 0,29 ± 0,04, respetivamente. A correlacao genetica do YW com SC foi 0,37 ± 0,16, e de YW com FS foi 0,42 ± 0,16. A estimativa da correlacao genetica entre SC e FS foi baixa e positiva (0,15 ± 0,14). A DRS foi 0,38 cm, 0,18 unidades, e 8,30 kg para SC, FS e YW. A CRS foi 0,16 cm e 0,08 unidades para SC e FS al selecionar YW. Conclusoes: espera-se que a selecao direta do YW seja eficaz. A selecao indireta de SC e FS com base no YW nao se espera que seja tao efetiva como a selecao direta para melhorar SC e FS. Palavras-chave: bovinos de corte, correlacoes fenotipicas, correlacoes geneticas, herdabilidade, machos, resposta a selecao.

The aim of this study was to compare alternative models for the genetic evaluation of heifer fertility in Simmental–Simbrah cattle. The analyses were conducted using a database with 37,390 female birth information recorded from 1984 to 2007, and 59,018 individuals in the pedigree. Three generalized mixed models were adjusted for a single trait in a multiracial population: linear animal, linear sire and logistic sire. The models were analysed by restricted maximum likelihood procedure with Average Information algorithm. Two strategies of cross-validation were carried out to evaluate the predict ability of the models. The heritability from linear animal and sire models had lower values than that estimated with the logistic model, 0.04 ± 0.00, 0.05 ± 0.00 and 0.20 ± 0.03, respectively. High Spearman and Kendall correlations were observed between the ranks of breeding values (BV) estimated from the linear and logistic sire models, 0.99 and 0.94, respectively. In contrast, these correlations were lower between the animal and sire models, 71% and 54%, respectively. The logistic sire model was the best estimating the BV with ancestors’ information, while the linear animal model (LAM) was the best predicting with scattered information. In general, it was considered that best fit and prediction was produced with the LAM.

Objective. Compare the fertility of Brown Swiss x Zebu and Simmental x Zebu crossbred cows reared in a tropical environment. Materials and methods. Reproductive traits of 185 Brown Swiss x Zebu and Simmental x Zebu crossbred cows with diverse percentages of European breed were evaluated. Grazing of cows was rotational. The milking was twice daily with the help (suckling) of the calf, which was kept tied next to the dam while she was milked. Traits were evaluated fitting a repeated measures model (except for age at first calving). Calving interval, age at first calving, days open, interval from calving to first service, and weight at calving were analyzed with PROC MIXED of SAS. Pregnancy rate at first service and services per conception were analyzed with PROC GENMOD of the same software. Results. Simmental x Zebu cows started to re-bred 39 days earlier after calving (p

This study aims at investigating genomic diversity of several turkey populations using Copy Number Variants (CNVs). A total of 115 individuals from six Italian breeds (Colle Euganei, Bronzato Comune Italiano, Parma e Piacenza, Brianzolo, Nero d’Italia, and Ermellinato di Rovigo), seven Narragansett, 38 commercial hybrids, and 30 Mexican turkeys, were genotyped with the Affymetrix 600K single nucleotide polymorphism (SNP) turkey array. The CNV calling was performed with the Hidden Markov Model of PennCNV software and with the Copy Number Analysis Module of SVS 8.4 by Golden Helix®. CNV were summarized into CNV regions (CNVRs) at population level using BEDTools. Variability among populations has been addressed by hierarchical clustering (pvclust R package) and by principal component analysis (PCA). A total of 2,987 CNVs were identified covering 4.65% of the autosomes of the Turkey_5.0/melGal5 assembly. The CNVRs identified in at least two individuals were 362—189 gains, 116 losses, and 57 complexes. Among these regions the 51% contain annotated genes. This study is the first CNV mapping of turkey population using 600K chip. CNVs clustered the individuals according to population and their geographical origin. CNVs are known to be indicators also of adaptation, as some researches in different species are suggesting.

Se usó la metodología de análisis de supervivencia con un modelo de riesgos proporcionales de Weibull para estudia la duración de vida productiva funcional (DVPF) de ganado Holstein en México, usando un modelo padre-abuelo materno con el software Survival Kit V3.12. La DVPF se calculó como el número de días entre la fecha de primer parto y la fecha de desecho o censura, con un crédito máximo de 305 días por lactación. Los datos analizados se obtuvieron de la Asociación Holstein de México. El archivo final constó de 36,507 registros para DVPF de vacas que parieron por primera vez entre 1995 y 2008. El modelo incluyó la función de riesgo basal de Weibull y los siguientes efectos fijos: edad al primer parto, número de lactación por fase de lactación con cortes en los días 29, 249 y 305 y nivel de producción estandarizado con 10 clases con cambios en cada lactación, incluidas como variables tiempo dependientes y los efectos aleatorios de hato-año de parto y efectos genéticos de padre y abuelo materno. El porcentaje de censura fue de 25.54 %. Todos los efectos fijos analizados fueron significativos (P

Genetic variation enables both adaptive evolutionary changes and artificial selection. Genetic makeup of populations is the result of a long-term process of selection and adaptation to specific environments and ecosystems. The aim of this study was to characterize the genetic variability of México's chicken population to reveal any underlying population structure. A total of 213 chickens were sampled in different rural production units located in 25 states of México. Genotypes were obtained using the Affymetrix Axiom ® 600 K Chicken Genotyping Array. The Identity by Descent (IBD) and the principal components analysis (PCA) were performed by SVS software on pruned single nucleotide polymorphisms (SNPs). ADMIXTURE analyses identified 3 ancestors and the proportion of the genetic contribution of each of them has been determined in each individual. The results of the Neighbor-Joining (NJ) analysis resulted consistent with those obtained by the PCA. All methods utilized in this study did not allow a classification of Mexican chicken in distinct clusters or groups. A total of 3,059 run of homozygosity (ROH) were identified and, being mainly short in length (

Background Copy number variations are genome polymorphism that influence phenotypic variation and are an important source of genetic variation in populations. The aim of this study was to investigate genetic variability in the Mexican Creole chicken population using CNVs. Results The Hidden Markov Model of the PennCNV software detected a total of 1924 CNVs in the genome of the 256 samples processed with Axiom® Genome-Wide Chicken Genotyping Array (Affymetrix). The mapped CNVs comprised 1538 gains and 386 losses, resulting at population level in 1216 CNV regions (CNVRs), of which 959 gains, 226 losses and 31 complex (i.e. containing both losses and gains). The CNVRs covered a total of 47 Mb of the whole genome sequence length, corresponding to 5.12% of the chicken galGal4 autosome assembly. Conclusions This study allowed a deep insight into the structural variation in the genome of unselected Mexican chicken population, which up to now has not been genetically characterized. The genomic study disclosed that the population, even if presenting extreme morphological variation, cannot be organized in differentiated genetic subpopulations. Finally this study provides a chicken CNV map based on the 600 K SNP chip array jointly with a genome-wide gene copy number estimates in a native unselected for more than 500 years chicken population. Electronic supplementary material The online version of this article (doi:10.1186/s12863-017-0524-4) contains supplementary material, which is available to authorized users.

Records from Charolais, Charbray and Charolais-Zebu crosses provided by Charolais–Charbray Herd Book de Mexico, were used to estimate heritabilities and genetic correlations between scrotal circumference (SC, n = 18,972), heifer fertility (HF, n = 91,250), and stayability (STAY, n = 17,696). Measurements of SC were adjusted to 365 days limiting the age range from 320 to 410 days of age. The trait HF was coded as 1 if the heifer calved before 1,281 d of age and 0 otherwise. The trait STAY was defined as the probability of whether or not a cow calved a second calf before the six years of age given that, at least, the cow had calved a calf at three years of age or before. A three trait animal model and a Bayesian linear-threshold-threshold analysis were used to estimate (co)variance components. Heritability estimates were 0.18 ± 0.02, 0.11 ± 0.01, and 0.26 ± 0.03 for SC, HF and STAY, respectively. Strong genetic correlations were detected between SC and STAY (0.76 ± 0.04), and between HF and STAY (0.57 ± 0.07), suggesting that selection of sires based on SC, and HF could lead to an improvement of STAY of cows in the Charolais–Charbray population of Mexico. A weak genetic correlation was found between SC and HF (−0.08 ± 0.10). Overall, the heritabilities and genetic correlations estimated for the three traits evaluated in this study support the feasibility of improving by selection the reproductive performance of the Charolais–Charbray population of Mexico.

Records of 354 Holstein Friesian (HF) and Brown Swiss (BS) cows born from 1986 to 2006 at Las Margaritas research station, under subtropical conditions of Mexico, were analyzed to estimate milk yield per lactation (MYL, n = 1229), milk yield per day (MYD, n = 1227), milk yield per calving interval (MYCI, n = 929), lactation length (LL, n = 1229), calving weight (CW, n = 1164) and efficiency of milk production (EMP, n = 890). The cows were daughters of 144 sires and 232 dams. Models included breed of cow (2 classes: HF and BS), calving year (22 classes: 1989-2010), calving season (3 classes: cold, from November to February; dry, from March to June; and rainy, from July to October), lactation number (4 classes: 1, 2, 3 and ≥4), linear (except for CW) and quadratic (except for MYD and CW) effect of lactation length and linear effect of calving weight (except for LL). The random effect, other than the error term, was sire of the cow nested within breed of cow. Holstein Friesian cows yielded 261, 0.8 and 0.7 kg more milk per lactation, per day and per calving interval, respectively, than BS cows. In addition, HF cows were more efficient (p 0.05). Cows that calved in the cold season had greater (p

Se estimaron parámetros genéticos para características de crecimiento en corderos Katahdin, usando seis variantes del modelo animal. Se usó información de pesos al nacimiento (BW; n= 13,099), al destete ajustado a 75 d (WW; n= 11,509) y posdestete ajustado a 120 d (AW; n= 6,886) tomada durante 7 años (2004-2010) en 20 estados de la República Mexicana. Los análisis se hicieron ignorando o incluyendo efectos maternos. El modelo más sencillo incluyó el efecto genético aditivo directo como el único efecto aleatorio. El modelo más completo incluyó los efectos genéticos directo y materno, la covarianza entre ellos, y el efecto del ambiente permanente materno. Para seleccionar el mejor modelo se usó la prueba de razón de verosimilitud. Cuando los efectos maternos no fueron incluidos en el modelo, los estimadores de la heredabilidad directa y de la varianza genética directa resultaron sobreestimados. Las heredabilidades directas con el mejor modelo fueron 0.18 ± 0.03, 0.30 ± 0.04 y 0.20 ± 0.05 para BW, WW y AW, respectivamente. Las heredabilidades maternas también variaron dependiendo del modelo, de 0.05 a 0.23, 0.00 a 0.12, y 0.09 a 0.25 para BW, WW y AW. El ignorar los efectos maternos en el modelo resultaría en una evaluación genética equivocada para las características de crecimiento en borregos Katahdin.

║*Facultad de Medicina Veterinaria y Zootecnia, Universidad Nacional Autonoma de Mexico, Ciudad Universitaria, Distrito Federal, Mexico, 04510; †National Animal Disease Center, Agricultural Research Service, US Department of Agriculture (USDA), 1920 Dayton Ave., Ames, IA 50010; ‡Faculdade de Zootecnia e Engenharia de Alimentos, Universidade de Sao Paulo (USP), Rua Duque de Caxias Norte, 225–Campus da USP, Piras-sununga, Sao Paulo, Brazil 13635-900; §Centro de Investigacion Regional Golfo-Centro, Instituto Nacional de Investigaciones Forestales Agricolas y Pecuarias (INIFAP), Medellin de Bravo, Veracruz, Mexico 94277; #Dipartimento di Scienze e Tecnologie Veterinarie per la Sicurezza Alimentare, Universita degli Studi di Milano, Via Celoria 10, Milano, Italia 20133; and ║Campo Experimental Valles Centrales–Centro de Investigacion Regional Pacifi co Sur, INIFAP, Melchor Ocampo 7, Etla, Oaxaca, Mexico 68200

Con el objetivo de estimar las varianzas y covarianzas genéticas entre producción total de leche por lactación y crecimiento corporal en una población multirracial de bovinos de doble propósito en el trópico de México, se estimaron las varianzas y covarianzas genéticas entre la producción total de leche durante la primera (PTL1L), la segunda (PTL2L) y la tercera lactaciones (PTL3L), y las varianzas y covarianzas genéticas entre PTL1L con peso al nacimiento (PN) y los pesos ajustados a los 205 (P205) y 365 (P365) días de edad. Se utilizaron 1,349 registros de lactaciones de hembras de cruzas de razas cebuinas (CE) con Holstein (HS) [558], con Suizo Pardo (SP) [444] y con Simmental (SM) [357]. Se presentan las heredabilidades estimadas en ambos análisis. Las correlaciones genéticas encontradas en el primer análisis fueron 0.77 (± 0.16) entre PTL1L y PTL2L, 0.47 (± 0.25) entre PTL1L y PTL3L, y 0.73 (± 0.21) entre PTL2L y PTL3L. Las correlaciones genéticas encontradas en el segundo análisis fueron 0.10 (± 0.35) entre PTL1L y PN, 0.20 (± 0.25) entre PTL1L y P205 y 0.21 (± 0.32) entre PTL1L y P365. Se concluye que las correlaciones genéticas son positivas entre las tres primeras lactaciones y se sugiere una correlación positiva entre la primera lactación y características de crecimiento corporal, lo cual hace factible el planteamiento de programas de mejoramiento genético que tomen en cuenta ambas características de manera simultánea.

The aim of the present study was to estimate (co)variance components and genetic correlations of days open with milk yield per lactation, lactation length and metabolic weight in Holstein and Brown Swiss cows under subtropical conditions of Mexico. Cows were kept in an intensive rotational grazing system in which the principal feed was Star grass (Cynodon plectostachyus). Cows were milked twice daily, by machine. Analyses of data were made applying a series of bivariate animal models in the MTDFREML program. Models for days open, milk yield per lactation and metabolic weight included breed of cow, calving year, calving season and lactation number as fixed environmental effects, and animal direct genetic, cows permanent environmental, and residual as random effects. For lactation length the model included the same fixed and random effects, except cows permanent environmental effect. The estimates of genetic correlations of days open with milk yield per lactation and metabolic weight were moderate and positive (0.45 and 0.33, respectively), suggesting that genes that control milk yield per lactation and metabolic weight also control days open. Estimates of phenotypic and permanent environmental correlations were smaller than estimates of genetic correlations. Results of the present study evidence that poor genetic potential for reproductive performance is associated with high genetic potential for milk production and metabolic weight.

Specific phenotypic traits of the blood-feeder nematode Haemonchus contortus were characterized on Pelibuey native, cross-breed sheep in a tropical region of Mexico with background of anthelmintic problems. Data were collected on 4-month-old lambs (n= 63) and analyzed weekly in three stages: stage 1 (S1, not infected (0-3 weeks)); S2, first infection with 350 H. contortus infective larvae (L(3)) per kg of body weight by oral route (3-10 weeks); and S3, second infection with 175 H. contortus L(3) per kg of body weight by oral route (10-18 weeks). Once infection took place, sheep grazed in a free-nematode experimental paddock, and hemoncosis-related traits, such as the number of eggs per gram of feces (epg), packed cell volume (%pvc), and eosinophils (%eo), were measured each week. Results were analyzed on specific traits and stages using SAS statistics. Statistical differences of the main phenotypic traits (P0.05) were observed throughout S2 on Pelibuey high (hr) and low (lr) responders, respectively: epg mean, 475 +/- 340.5 and 1439 +/- 243.6; %pvc mean, 31 +/- 0.3 and 27 +/- 0.2; and %eo mean, 2.5 +/- 0.3 and 1.99 +/- 0.2. In addition, lr and hr sheep grazed for 3 months on an area infected with Haemonchus, Cooperia, and Strongyloides, and the hr sheep showed a low number of epg after being exposed to multiple infections, so that no further treatment was required. These results showed that the selection of animals resistant to nematodes can be an alternative method of control against anthelmintic resistance problems in order to improve animal health and avoid a negative environmental impact.

El objetivo fue estimar los componentes de (co)varianza, heredabilidades y correlaciones genéticas y fenotípicas para peso al año (YW), circunferencia escrotal (SC) y talla (FS) en toros jóvenes Simmental y Simbrah de México. Todas las características se ajustaron a 305 días acorde a los lineamientos descritos por la Federación para el Mejoramiento Genético de los Bovinos de Carne (BIF). El archivo final de datos incluyó 1,949 registros Simmental y 1,259 Simbrah. Para estimar los compones de (co)varianza y parámetros genéticos se usó un modelo animal de tres características. Para cada característica, el modelo incluyó los efectos fijos de hato-año-estación; como covariables se incluyeron la edad de la madre, proporción de genes de raza Simmental, heterocigosis y los efectos por pérdida de recombinación; los efectos de animal y residual se incluyeron como aleatorios. Las varianzas genéticas aditivas fueron 376.3±13 0.9 kg2, 2.89±0.69 cm2 y 0.37±0.08 unidades2; y las heredabilidades fueron 0.33±0.11, 0.35±0.08 y 0.42±0.08, para YW, SC y FS, respectivamente. Las correlaciones genéticas fueron 0.36±0.19, 0.47±0.17 y 0.59±0.12 para YW-SC, YW-FS, y SC-FS, respectivamente. Las estimaciones de heredabilidad muestran que puede existir una respuesta favorable en la selección para las características estudiadas. Las correlaciones genéticas indican que no existen antagonismos genéticos, sugiriendo que habría una respuesta correlacionada positiva en la selección de cualquiera de ellas.

Se analizaron los registros productivos y genealógicos de 354 vacas Holstein y Pardo Suizo, nacidas de 1986 a 2006 en el sitio experimental Las Margaritas (Instituto Nacional de Investigaciones Forestales, Agrícolas y Pecuarias), localizado en el estado de Puebla, México, para estimar componentes de varianza, la heredabilidad y la repetibilidad de la producción total de leche (PTL), producción de leche por día (PLD), producción de leche por día interparto (PDI), duración de la lactancia (DL), peso de la vaca al parto (PP), eficiencia productiva (EP) y duración de la gestación (DG). Las vacas fueron hijas de 144 sementales y 232 madres. Los parámetros genéticos fueron estimados con el programa MTDFREML, usando un modelo animal para una sola característica. Los modelos incluyeron los efectos genético directo y ambiental permanente de la vaca, y los efectos fijos de raza (2 clases: Holstein y Pardo Suizo), año de parto (22 clases: 1989-2010), época de parto (3 clases: noviembre- febrero, marzo-junio y julio-octubre) y la edad de la vaca al parto, como covariable (lineal y cuadrática). El estimado de heredabilidad para peso de la vaca al parto fue similar a los estimados de heredabilidad relacionados con la producción de leche, pero mayor que los estimados de heredabilidad para duración de la gestación y duración de la lactancia. El estimado de la varianza del ambiente permanente fue cero para PDI, DL, EP y DG; por lo tanto, los estimados de repetibilidad para estas tres características fueron iguales a sus correspondientes estimados de heredabilidad. Los estimados de heredabilidad y repetibilidad fueron: 0,28 y 0,40; 0,29 y 0,40; 0,32 y 0,32; 0,11 y 0,11; 0,30 y 0,49; 0,34 y 0,34; y 0,08 y 0,08 para PTL, PLD, PDI, DL, PP, EP y DG, respectivamente. La magnitud de los estimados de heredabilidad indica que existe suficiente variación genética para mejorar la producción de leche a través de selección.

Six models to estimate genetic parameters for birth weight (BW), weaning weight adjusted to 205 days (W205), and yearling weight adjusted to 365 days (W365) were compared. Model A included direct genetic effects. Model AP allowed for direct genetic and permanent environmental effect of the dam. Model AM included direct genetic and maternal genetic effects. Models AMC and AMP were the same as Model AM but they also allowed for the covariance between direct and maternal genetic effects, and the common environmental effect due to the dam, respectively; and Model AMCP was fitted for all three random effects plus the covariance between direct and maternal effects. Models were compared using the likelihood ratio text. The AMC model was selected to be the most appropriate for BW and W205, whereas Model A was chosen for W365. When maternal effects were included, direct genetic variance and direct heritability estimates were reduced for BW and W205. Direct heritability estimates with appropriate models were: 0.13, 0.21 and 0.20 for BW, W205 and W365. Heritability of maternal effects with appropriate models was: 0.15 and 0.32 for BW and W205, and direct-maternal genetic correlations with appropriate models were: -0.67 and -0.69 for BW and W205, respectively. Â

Studies were conducted to determine hen preference for and stress response to cage type. By using a plywood (1.25 cm) test apparatus with open- and solid-sided compartments and a plexiglass divider at the entrance for controlling passage, birds (n = 20) were evaluated as to their choice of compartment after training and acclimation. For each test, after training, an individual bird was placed in the start box and given 1 min to acclimate before making a choice. The experiment was repeated after rotating the apparatus 180 degrees. In Experiment 1, the open-sided compartment was chosen by 45% of the hens, and the solid-sided compartment by 25% (P = 0.02); 30% chose neither. In Experiment 2, the compartment with open sides was chosen by 70% of the hens, and that with solid sides was chosen by 15% (P = 0.004); 15% chose neither. The length of time required to choose one compartment over the other did not differ in either experiment (P = 0.29; P = 0.76). In Experiment 3, tests were videotaped from 0830 h to 1330 h, and tapes were scored for time spent in each compartment. Birds were observed to spend more time in open- compared with solid-sided compartments (P = 0.02). To assess stress level of birds exposed to each type of enclosure, blood was collected from 24 commercial Hy-Line W36 hens housed long-term in either open (n = 12) or solid (n = 12) cages, and heterophil:lymphocyte (H:L) ratios were determined. Birds in solid cages had higher H:L ratios than did birds in open cages (P = 0.02), indicating a greater stress response. These data would suggest that hens may prefer greater visual access to their surroundings afforded by open cages.