The major goal of the study isto improve animal welfare and farm profitability in dairy operations through developing an applicable and cost-effective disease prevention therapy. Blanket disease prevention therapies have been proposed to help cows cope with common physiological challenges during the post-partum period, such as high systemic inflammation, in order for them to maintain a strong health and perform properly. However, recent research has shown that in some groups of cows, such as over-conditioned cows (OVCOND), primiparous cows (PRIM) and cows that experience a difficult calving, known as dystocia (DYS), these physiological challenges may be exacerbated, suggesting that these high-priority groups of animals may benefit from disease prevention therapies the most, while other animals may not need it at all. Considering that around 40% of cows may be over-conditioned at dry off, and >15% of dairy cattle may experience dystocia in US dairy operations, developing selective disease prevention treatment strategies for these groups of animals is key to improve health in dairy farms.Anti-inflammatory treatment after calving has been proposed, and studied, as a proactive management strategy to reduce inflammation and alleviate discomfort after calving in dairy cattle. One of the most common family of drugs used for this purpose are non-steroidal anti-inflammatory drugs (NSAIDs). Several treatment approaches (e.g., number of doses, type of administration) using a variety of drugs from this family (e.g., carprofen, meloxicam) have been studied; however, results have been inconsistent. Notably, one of the promising NSAID drugs is acetylsalicylic acid (ASA) that has been shown to have consistently improved cow performance after calving (e.g., increased milk yield, improved fertility) regardless of the treatment approach used. As mentioned above, cows with higher inflammation at calving are at a higher risk of developing diseases during the first weeks after calving. Therefore, modulating the inflammatory response around calving could have the potential of decreasing diseases during the early lactation period. However, studies that have assessed variables related to cow health have shown inconsistent results on modulating inflammation or decreasing disease risk, suggesting that perhaps the treatment approach utilized (e.g., timing of treatment) may not be optimal. Although proposed ASA treatment approach features varied in the number of treatment administrations, drug use and dose, and route of administration, among others; administering treatment prior to calving has not yet been studied. To our knowledge there are no ASA studies focused on developing targeted pre-partum treatment approaches for the high-priority cow groups mentioned above.Efforts to elucidate the mechanisms involved on the observed benefits of ASA treatment have been focused on identifying specific effects of ASA treatment on cow metabolic stress and systemic inflammation variables, such as haptoglobin (HP) and β-hydroxybutyrate (BHB) concentrations, without being able to accurately explain the relationship between ASA treatment and cow health and performance. There is existing evidence that ewes fed willow trees, containing salicin, which is metabolized into ASA during absorption, not only showed similar animal performance benefits observed in dairy cattle treated with ASA, but also altered rumen aspects, such as rumen microbial profiles. Since most of the studies that showed positive results of ASA treatment administered this product orally, it remains to be determined if the possible mechanism of action of ASA is via modulating the rumen microbiome, metabolites and fermentation. To our knowledge till date, there is a lack of research reports investigating the direct effect of ASA on ruminal function.The proposed study will address these critical knowledge gaps and anticipate unravelling novel information on the mechanism of action of ASA in reducing inflammation during the pre-partum period by investigating the link between cow physiological parameters, inflammatory responses and the rumen microbiome and metabolites. By using this integrated approach in highly disease predisposed groups, we anticipate identifying factors that predispose to stress and cause inflammation that will eventually lead to developing targeted therapeutic applications. We hypothesize that early therapeutic treatment with ASA 14 d prior to calving date may modulate early pro-inflammatory responses, preventing the onset of an exacerbated inflammatory response around calving, and alter the rumen microbial composition and their metabolites, which may improve adaptation to dietary management changes during this period; thus, decreasing the likelihood of cows developing diseases and improving cow performance. This project brings together an interdisciplinary team of experts from Penn State University and University of Pennsylvania to fill these critical knowledge gaps and help in better serving the dairy industry. Drs. Barragan and Hovingh have extensive experience on the assessment of metabolic stress and systemic inflammation and Drs. Pitta and Bender, have been working on USDA-funded grants to investigate the role rumen microbiome and ruminal function in improving health, well-being, and productivity of dairy cattle.The long-term goal of this study is to uncover the underlying physiological mechanisms involved with improved performance observed in cows treated with ASA after calving and develop an applicable and targetable ASA treatment regimen aimed at preventing diseases and improving performance in high-priority cow groups. The specific objectives are to assess the effects of pre-partum oral ASA treatment 14±3 days from predicted calving date on:1) milk yield, milk components and milk quality (somatic cell counts) during the first 60 days in milk, number of clinical disease events during the first 60 days in milk, and cow fertility (i.e., days in milk [DIM] to conception, numbers of service to conceive, abortion rate) in high-priority cow groups (i.e., OVCOND, PRIM and DYS) during the peri-parturient period; 2) systemic inflammation (HP, cytokines [IL-6, IL-1β, TNF-α]) and metabolic stress (NEFA, BHB) in high-priority cow groups (i.e., OVCOND, PRIM and DYS) during the peri-parturient period; and 3) rumen microbial diversity and metagenomics in high-priority cow groups (i.e., OVCOND, PRIM and DYS) during the peri-parturient period.