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Transmission ratio distortion ( TRD) is the departure from the expected Mendelian ratio in offspring, a poorly investigated biological phenomenon in livestock species. Given the current availability of specific parametric methods for the analysis of segregation data, this study focused on the screening of TRD in 602 402 single nucleotide polymorphisms covering all autosomal chromosomes in seven Spanish beef cattle breeds. On average, 0.13% ( n = 786) and 0.01% ( n = 29) of genetic markers evidenced sire- or dam-specific TRD respectively. There were no single nucleotide polymorphisms accounting for both sire- and dam-specific TRD at the same time, and only one marker (rs43147474) accounted for (sire-specific) TRD in all seven breeds. It must be noted that rs43147474 is located in the fourth intronic region of the GTP-binding protein 10 gene, and this locus has been previously linked to the maintenance of mitochondria and nucleolar architectures. Alternatively, other candidate genes surround this hot-spot for sire-specific TRD in the cattle genome, and they are related to embryonic and postnatal lethality as well as prostate cancer, among others. This research characterized the distribution of TRD in the bovine genome, highlighting heterogeneous results when comparing across breeds. [ABSTRACT FROM AUTHOR]

Haplotype probabilities have been implemented in association analyses performed between three candidate genes and the preweaning survival of F2 Iberian × Meishan piglets, under a categorical proportional hazard model. The additive effect of substitution of each haplotype was estimated using information of parental genotypes for non-genotyped piglets. Analysed loci were the bone morphogenetic protein type 1B receptor ( BMPR1B) gene at 8q25 (three SNPs; haplotypes BMPR1BA, BMPR1BB, BMPR1BC and BMPR1BD), the dopamine β-hydroxylase ( DBH) gene at 1q2.13 (two SNPs; haplotypes DBHX, DBHY and DBHZ), and the prolactin receptor ( PRLR) gene at 16q1.4-q2.3 (six SNPs; haplotypes PRLRA, PRLRB, PRLRC, PRLRD and PRLRE). The number of analysed records were 899 ( BMPR1B), 850 ( DBH) and 822 ( PRLR) with a censoring percentage ranged between 87 and 89%. Associations with preweaning survival were suggested for BMPR1B (p < 0.10) and associations were clearly significant for DBH haplotypes (p < 0.05), whereas the PRLR locus did not reach statistical significance (p > 0.10). The BMPR1BA haplotype could increase piglet survivability in relation to the BMPR1BB haplotype with a hazard ratio of 0.751 and a confidence interval (CI) between 0.550 and 1.025 (p < 0.10). The two remaining haplotypes did not differ significantly from the BMPR1BB haplotype, with a hazard ratio higher than 0.90 (p > 0.10). For the DBH locus, the DBHX and the DBHZ haplotypes were associated with an improved preweaning survival in relation to the DBHY haplotype. The advantage for DBHX in terms of hazard ratio was 0.789 (CI = 0.625 to 0.994; p < 0.05) and differences between DBHY and DBHZ reached a hazard ratio of 0.770 (CI = 0.606 to 0.977; p < 0.05). Although further researches are required, BMPR1B and DBH genes could be a useful tool to improve piglet survival under a marker assisted selection strategy. [ABSTRACT FROM AUTHOR]

The recent development of the Bayes factor methodology to test between nested competing models has allowed to evaluate the genetic component of continuous traits through a methodology based on the reparameterization of a variance component model in terms of intra-class correlation. In this study, we present a modification of that procedure to compare between threshold models that only differ in a bounded variable. An extra data-augmentation step is required to sample liability, an underlying continuous variable related with phenotypic records through an adequate number of thresholds. In this context, we describe a procedure to sample from a truncated multivariate normal distribution with non-null covariances between records, taking as starting point the Cholesky factorization and the inclusion of linear restrictions. The method was tested by computer simulations with satisfactory results. [ABSTRACT FROM AUTHOR]

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