Weighted single-step genome-wide association study and pathway analyses for feed efficiency traits in Nellore cattle.

The aim was to conduct a weighted single-step genome-wide association study to detect genomic regions and putative candidate genes related to residual feed intake, dry matter intake, feed efficiency (FE), feed conversion ratio, residual body weight gain, residual intake and weight gain in Nellore cattle. Several protein-coding genes were identified within the genomic regions that explain more than 0.5% of the additive genetic variance for these traits. These genes were associated with insulin, leptin, glucose, protein and lipid metabolisms; energy balance; heat and oxidative stress; bile secretion; satiety; feed behaviour; salivation; digestion; and nutrient absorption. Enrichment analysis revealed functional pathways (p-value < .05) such as neuropeptide signalling (GO:0007218), negative regulation of canonical Wingless/Int-1 (Wnt) signalling (GO:0090090), bitter taste receptor activity (GO:0033038), neuropeptide hormone activity (GO:0005184), bile secretion (bta04976), taste transduction (bta0742) and glucagon signalling pathway (bta04922). The identification of these genes, pathways and their respective functions should contribute to a better understanding of the genetic and physiological mechanisms regulating Nellore FE-related traits.

Improving genomic prediction accuracy for meat tenderness in Nellore cattle using artificial neural networks.

The goal of this study was to compare the predictive performance of artificial neural networks (ANNs) with Bayesian ridge regression, Bayesian Lasso, Bayes A, Bayes B and Bayes Cπ in estimating genomic breeding values for meat tenderness in Nellore cattle. The animals were genotyped with the Illumina Bovine HD Bead Chip (HD, 777K from 90 samples) and the GeneSeek Genomic Profiler (GGP Indicus HD, 77K from 485 samples). The quality control for the genotypes was applied on each Chip and comprised removal of SNPs located on non-autosomal chromosomes, with minor allele frequency <5%, deviation from HWE (p < 10-6 ), and with linkage disequilibrium >0.8. The FImpute program was used for genotype imputation. Pedigree-based analyses indicated that meat tenderness is moderately heritable (0.35), indicating that it can be improved by direct selection. Prediction accuracies were very similar across the Bayesian regression models, ranging from 0.20 (Bayes A) to 0.22 (Bayes B) and 0.14 (Bayes Cπ) to 0.19 (Bayes A) for the additive and dominance effects, respectively. ANN achieved the highest accuracy (0.33) of genomic prediction of genetic merit. Even though deep neural networks are recognized to deliver more accurate predictions, in our study ANN with one single hidden layer, 105 neurons and rectified linear unit (ReLU) activation function was sufficient to increase the prediction of genetic merit for meat tenderness. These results indicate that an ANN with relatively simple architecture can provide superior genomic predictions for meat tenderness in Nellore cattle.

Association of methamidophos and sleep loss on reproductive toxicity of male mice.

This study investigated the effects of organophosphate exposure on the male reproductive system of mice submitted to chronic sleep loss condition. Adult Swiss mice were distributed into 4 groups: control; methamidophos (MTP); sleep restriction (SR); and MTP+SR. The dose of methamidophos was 0.002 mgkg(-1)day(-1) (half of the Acceptable Daily Intake). Sleep restriction condition was 21 h day(-1) during 15 days. In relation to control group, MTP treatment induced a significant reduction of 12% on morphologically normal spermatozoa in both MTP and MTP+SR groups. In addition, the absolute and relative weights of the seminal vesicles were decreased (MTP, -34%; MTP+SR, -45%). Epididymal fat was reduced in SR groups (SR, -64%; MTP+SR, -58%). Plasma testosterone levels were significantly decreased in MTP and SR groups, and progesterone levels were increased 8 times in MTP+SR in comparison with the control group. The corticosterone levels were unaffected by MTP or SR conditions. Thus, low dose MTP exposure resulted in deleterious effects on the male reproductive system. Sleep loss associated with MTP potentiated the effect on steroidogenesis, mainly in terms of progesterone levels.