-The objective of this study was to estimate the genetic, phenotypic and environmental parameters for calving interval (CI), days open (DO), number of services per conception (NSC) and conception rate (CR) The results show that the genetic, phenotypic and permanent environmental correlations in the two evaluated breeds were favorable for CI × DO, CI × NSC and DO × NSC, but not for CI × CR, DO × CR and NSC × CR. Genetic and permanent environmental correlations were high in most cases in Holstein cattle, whereas in Jersey cattle they were moderate. In contrast, phenotypic correlations were very low in both breeds, except for CI × DO and NSC × CR, which were high. Overall, the genetic component found was very low (≤8%) in both evaluated breeds and this implies that their selection would take long time and that a good practical management of the herd will be essential in order to improve the reproductive performance.

ABSTRACT. The aim of this study was to determine the association between a polymorphism in intron 3 of the bovine growth hormone (BGH) gene and growth traits related to the start of the reproductive life of Holstein heifers. This research was conducted using 480 Holstein heifers belonging to eight herds in three municipalities in the Department of Antioquia (Colombia). The phenotypic information used corresponded to information that had been historically recorded for each of the herds and was supplemented with information obtained through bimonthly visits to the herds over a period of 24 months. Genotyping was performed using the PCR-RFLP technique with DNA extracted from peripheral blood using the salting out technique. To determine association, statistical analyses were performed using parametric methods. Allele frequencies for the alleles (+) and (-) were 0.91 and 0.09, respectively. The genotype frequencies were 0.77, 0.2 and 0.03 for the genotypes (+/+), (+/-) and (-/-), respectively. There was an association between genotype and weight at first estrus and first calving (P < 0.01). The regression coefficients for both characteristics were significant, indicating that for each (+) allele, weight at first estrus and first calving decreased by 9.24 and 16.07 kg, respectively. The results indicated the existence of an association between a polymorphism in intron 3 of the BGH gene and both weight at first estrus and first calving, which can be used to facilitate the selection of animals with these genotypes for use in breeding programs.

Antioxidants have been widely used during in vitro production to decrease the negative effect of reactive oxygen species. It was reported that the complex resveratrol-methyl β-cyclodextrin (RV-CD) improves resveratrol's stability and bioavailability and increases its antioxidant activity. This study evaluates the effect of RV-CD during in vitro oocyte maturation (IVM) or in vitro embryo culture (IVC) on developmental competence and quantitative changes in gene expression of developmental important genes. In experiment 1, RV-CD was added to IVM media and maturation level, embryo development and oocytes, cumulus cells, and blastocysts gene expression by RT-qPCR were examined. In experiment 2, presumptive zygotes were cultured in SOF supplemented with RV-CD and embryo development and blastocysts gene expression by RT-qPCR were studied. A group without RV-CD (control ) and a group with cyclodextrin (control ) were included. No differences were found in cleavage rate or blastocyst yield between groups. However, the expression of LIPE was higher in blastocysts derived from oocytes treated with resveratrol compared with control groups (p < .05). Blastocysts produced by IVC with resveratrol showed that RV-CD could modify the expression of genes related to lipid metabolism (CYP51A1, PNPLA2 and MTORC1) compared with control groups (p < .05). RV-CD in the IVM and IVC media could reduce accumulated fat by increasing lipolysis and suppressing lipogenesis of blastocysts.

El virus de la leucosis bovina (BLV) posee un genoma RNA de cadena sencilla, pertenece a la familia Retroviridae y presenta ocho genotipos diferentes. Los linfocitos B son la célula blanco del BLV, lo cual tiene un impacto negativo sobre el sistema inmune de los bovinos ya que los hace más susceptibles a otras enfermedades de origen infeccioso además las vacas lecheras presentan una menor producción respecto al hato (2,5 a 5 %). Esta enfermedad se transmite a través del consumo de leche y principalmente de forma iatrogénica. El objetivo del presente trabajo fue diagnosticar BLV por medio de la técnica PCR anidada, para lo cual se tomaron 500 muestras de sangre de vacas Holstein pertenecientes a varios hatos ubicados en los principales municipios con carácter lechero en el departamento de Antioquía, durante los meses de febrero a junio de 2013. Se realizó una PCR anidada para detectar el provirus amplificando una región del gen env viral. Se obtuvo un fragmento de 444 pb y se comprobó la identidad de la secuencia a través de la aplicación BLAST ®. La prevalencia para el departamento de Antioquía fue del 44 % (219/500). Uno de los productos de PCR fue secuenciado y clasificado como genotipo 1; se encontró un 99 % de identidad con la secuencia FJ808575.1. Se evaluaron tres subregiones lecheras Oriente, Norte y Valle de Aburra. La presencia del virus fue de 70 %, 45 %, 31 % respectivamente. La prevalencia molecular de BLV varió entre 16 y 88 % por municipio. Se encontró diferencia estadísticamente significativa (p

El objetivo de este estudio fue estimar parámetros genéticos y fenotípicos en características productivas y reproductivas en ganado Holstein y Jersey de Antioquia, Colombia. La información fue obtenida de 85 hatos lecheros de raza Holstein y 7 hatos de raza Jersey, ubicados en 18 municipios del Departamento de Antioquia. Las características productivas evaluadas fueron: producción de leche (PL), porcentaje de proteína (PP), porcentaje de grasa (PG) y puntaje de células somáticas (SCS) y las características reproductivas evaluadas fueron: intervalo entre partos (IEP), días abiertos (DA), número de servicios por concepción (NSC) y tasa de concepción (TC). Los componentes de (co)varianza, los parámetros genéticos y fenotípicos fueron estimados empleando modelos mixtos univariados y bivariados y las soluciones de las ecuaciones de los modelos mixtos fueron obtenidas mediante el método de máxima verosimilitud restricta libre de derivadas. Las heredabilidades obtenidas para características productivas oscilaron entre 0,22 y 0,35, excepto para SCS que fueron bajas (h2