PSIV-9 A Multistate Evaluation of an Additional Iron Injection Administered to Piglets Before Weaning

A cooperative study utilizing 514 weanling pigs from 7 experiment stations was conducted to determine the effects of an additional iron injection administered to piglets before weaning on growth performance and hematological measures. All pigs received an initial iron injection at the time of processing postfarrowing. At each station, pigs were assigned to either the control or an added-injection treatment by pairing two same-sex pigs with a BW difference ≤ 0.453 kg within a litter. One pig within each pair received the additional iron injection (same dose received at processing) 3 to 5 days preweaning. Once weaned, both the control and added-injection group received common station-specific nursery diets. Body weight was recorded weekly by all stations. Blood samples were also collected at second injection, weaning, 14 and 28 days postweaning by 3 of the 7 stations. All data were subjected to ANOVA with the model containing the terms treatment, station, and treatment by station interaction. Average daily gain (Table 1) was greater for the added-injection group during d 0 to 14 (212.5 vs. 202.6 g, P = 0.03) which resulted in an increase in d 14 BW (P = 0.05). Although there was no treatment effect for overall ADG (d -4 to d 28), the tendency for a treatment by station interaction (P = 0.09) illustrated both responsive and nonresponsive stations, indicating that iron status was not the most limiting factor for growth at all stations. Hemoglobin concentration was greater (P < 0.0001) for the added-injection group at weaning and d 14 postweaning. In conclusion, an additional iron injection administered before weaning may lead to early success in the nursery resulting in a heavier BW in subsequent periods; however, the beneficial effects of an additional iron injection are likely dependent on herd status and characteristics.

A large-scale transcriptome-wide association study (TWAS) of ten blood cell phenotypes reveals complexities of TWAS fine-mapping

Hematological measures are important intermediate clinical phenotypes for many acute and chronic diseases. Hematological measures are highly heritable, and although genome-wide association studies (GWAS) have identified thousands of loci containing trait-associated variants, the causal genes underlying these associations are often uncertain. To better understand the underlying genetic regulatory mechanisms, we performed a transcriptome-wide association study (TWAS) using PrediXcan to systematically investigate the association between genetically-predicted gene expression and hematological measures in 54,542 individuals of European ancestry from the Genetic Epidemiology Research on Adult Health and Aging (GERA) cohort. We found 239 significant gene-trait associations with hematological measures. Among this set of 239 associations, we replicated 71 at p < 0.05 with same direction of effect for the blood cell trait in a meta-analysis of TWAS results consisting of up to 35,900 European ancestry individuals from the Women’s Health Initiative (WHI), the Atherosclerosis Risk in Communities Study (ARIC), and BioMe Biobank. We further attempted to refine this list of candidate genes by performing conditional analyses, adjusting for individual variants previously associated with these hematological measures, and performed further fine-mapping of TWAS loci. To assist with the interpretation of TWAS findings, we designed an R Shiny application to interactively visualize TWAS results, one genomic locus at a time, by integrating our TWAS results with additional genetic data sources (GWAS, TWAS from other gene expression reference panels, conditional analyses, known GWAS variants, etc.). Our results and R Shiny application highlight frequently overlooked challenges with TWAS and illustrate the complexity of TWAS fine-mapping efforts.Author SummaryTranscriptome-wide association studies (TWAS) have shown great promise in furthering our understanding of the genetic regulatory mechanisms underlying complex trait variation. However, interpreting TWAS results can be incredibly complex, especially in large-scale analyses where hundreds of signals appear throughout the genome, with multiple genes often identified in a single chromosomal region. Our research demonstrates this complexity through real data examples from our analysis of hematological traits, and we provide a useful web application to visualize TWAS results in a broadly approachable format. Together, our results and web application illustrate the importance of interpreting TWAS studies in context and highlight the need to carefully examine results in a region-wide context to draw reasonable conclusions and formulate mechanistic hypotheses.

Physical condition of Black-capped Chickadees (Poecile atricapillus) in relation to road disturbance

Roads and their associated low-frequency noise have been linked with a reduction in abundance and density for many songbird species. However, a handful of species remain equally abundant in roadside habitats and nondisturbed areas. Abundance is a valuable baseline indicator of a species’ ability to adapt to habitats altered by roads, but does not directly ascertain whether health is affected in these species. Here we examine whether Black-capped Chickadees (Poecile atricapillus (L., 1766)), a species that remains abundant near roads, exhibit higher levels of chronic stress or reduced physical condition when residing near roads. Neither hematological measures of chronic stress, nor any of our measures of physical condition, differed significantly between Black-capped Chickadees inhabiting areas near or far from roads. Our results suggest that health and physical condition, like abundance, are not significantly affected by roads in the Black-capped Chickadee. This species may be an ideal model for understanding how some songbird species adapt to roads and the noise that they produce.