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Measures of heifer fertility are economi-cally relevant traits for beef production systems and knowledge of candidate genes could be incorporated into future genomic selection strategies. Ten traits related to growth and fertility were measured in 890 Brangus heif-ers (3/8 Brahman x 5/8 Angus, from 67 sires). These traits were: BW and hip height adjusted to 205 and 365 d of age, postweaning ADG, yearling assessment of carcass traits (i.e., back fat thickness, intramuscular fat, and LM area), as well as heifer pregnancy and first service con-ception (FSC). These fertility traits were collected from controlled breeding seasons initiated with estrous syn-chronization and Al targeting heifers to calve by 24 mo of age. The BovineSNP50 BeadChip was used to ascertain 53,692 SNP genotypes for -802 heifers. Associations of genotypes and phenotypes were performed and SNP effects were estimated for each trait. Minimally associ-ated SNP (P < 0.05) and their effects across the 10 traits formed the basis for an association weight matrix and its derived gene network related to FSC (57.3% success and heritability = 0.06 ± 0.05). These analyses yielded 1,555 important SNP, which inferred genes linked by 113,873 correlations within a network. Specifically, 1,386 SNP were nodes and the 5,132 strongest correlations (|r| > 0.90) were edges. The network was filtered with genes queried from a transcriptome resource created from deep sequencing of RNA (i.e., RNA-Seq) from the hypothala-mus of a prepubertal and a postpubertal Brangus heifer. The remaining hypothalamic-influenced network con-tained 978 genes connected by 2,560 edges or predicted gene interactions. This hypothalamic gene network was enriched with genes involved in axon guidance, which is a pathway known to influence pulsatile release of LHRH. There were 5 transcription factors with 21 or more connections: ZMAT3, STAT6, RFX4, PLAGL1, and NR6A1 for FSC. The SNP that identified these genes were intragenic and were on chromosomes 1, 5, 9, and 11. Chromosome 5 harbored both STAT6 and RFX4. The large number of interactions and genes observed with network analyses of multiple sources of genomic data (i.e., GWAS and RNA-Seq) support the concept of FSC being a polygenic trait. [ABSTRACT FROM AUTHOR]

The technological properties of milk have significant importance for the dairy industry. Citrate, a normal constituent of milk, forms one of the main buffer systems that regulate the equilibrium between Ca2+ and H+ ions. Higher-than-normal citrate content is associated with poor coagulation properties of milk. To identify the genes responsible for the variation of citrate content in milk in dairy cattle, the metabolic steps involved in citrate and fatty acid synthesis pathways in ruminant mammary tissue using RNA sequencing were studied. Genetic markers that could influence milk citrate content in Holstein cows were used in a marker-trait association study to establish the relationship between 74 single nucleotide polymorphisms (SNP) in 20 candidate genes and citrate content in 250 Holstein cows. This analysis revealed 6 SNP in key metabolic pathway genes [isocitrate dehydrogenase 1 (NADP+), soluble (IDH1); pyruvate dehydrogenase (lipoamide) β (PDHB); pyruvate kinase (PKM2); and solute carrier family 25 (mitochondrial carrier; citrate transporter), member 1 (SLC25A1)] significantly associated with increased milk citrate content. The amount of the phenotypic variation explained by the 6 SNP ranged from 10.1 to 13.7%. Also, genotype-combination analysis revealed the highest phenotypic variation was explained combining IDH1_23211, PDHB_5562, and SLC25A1_4446 genotypes. This specific genotype combination explained 21.3% of the phenotypic variation. The largest citrate associated effect was in the 3' untranslated region of the SLC25A1 gene, which is responsible for the transport of citrate across the mitochondrial inner membrane. This study provides an approach using RNA sequencing, metabolic pathway analysis, and association studies to identify genetic variation in functional target genes determining complex trait phenotypes. [ABSTRACT FROM AUTHOR]

The objective was to identify single nucleotide polymorphisms (SNP) associated to fertility in cows raised under a subtropical environment. Re-sequencing of nine genes associated to GH-IGF endocrine pathway, which are located in bovine chromosomes 5, 16 and 20, identified 73 SNP useful for associative genetic studies; however, only seven resulted as polymorphic and unique to the Romosinuano breed. Then, DNA samples were extracted from 129 beef heifers and used to determine genotypes corresponding to each SNP. Mixed model analysis identified one SNP from the PAPP-A2 gene (C/T, rs110490898) as predictor (P<0.05) of reproductive performance. The allele T was the most favorable allele (P<0.05), because it was associated with lower age at first calving (-37.1 ± 14.4 d) and age at second calving (-65.43 ± 30.8 d). In the contrast analysis, the linear term resulted as significant and quadratic term as non significant, which suggested an additive effect of the alleles. These results provide evidence to support the PAPP-A2 gene as a candidate gene associated to reproductive performance in heifers and first-calf cows from the Romosinuano breed, raised under a subtropical environment. [ABSTRACT FROM AUTHOR]

El objetivo fue identificar polimorfismos de un solo nucleótido (SNP) asociados a la fertilidad en hembras bovinas criadas en subtropico. La re-secuenciación de nueve genes relacionados al eje endocrino GH-IGF, localizados en los cromosomas 5, 16 y 20 del bovino, identificó 73 SNP útiles para estudios genéticos asociativos; sin embargo, sólo siete resultaron polimórficos y exclusivos de la raza Romosinuano. Muestras de ADN se extrajeron de 129 vaquillas Romosinuano y usadas para determinar los genotipos correspondientes a cada SNP. Un análisis de modelos mixtos identificó únicamente a un polimorfismo del gen PAPP-A2 (C/T, rs110490898) como predictor (P<0.05) del comportamiento reproductivo. El alelo T fue el más favorable (P<0.05) ya que éste se asoció a una reducción tanto en la edad al primer parto (-37.1 ± 14.4 días), como en la edad al segundo parto (-65.43 ± 30.8 días). En el análisis de contrastes el término lineal resultó significativo (P<0.05), pero no el quadrático, lo cual sugiere un efecto aditivo de los alelos. Los resultados proporcionan evidencia para proponer al gen PAPP-A2, como candidato asociado al comportamiento reproductivo en vaquillas y vacas primerizas de la raza Romosinuano. [ABSTRACT FROM AUTHOR]