Mastitis remains a substantial challenge for the dairy industry. Producers strive to maximize dairy cow production, health, and well-being, while also reducing antibiotic usage. Limitations to current mastitis measures have led to the exploration of the use of differential SCC (DSCC). Rather than evaluating the total cell population within milk (i.e., SCC), DSCC focuses on the distribution of individual white blood cell (WBC) types. During an infection, the number of WBC will change dramatically as a result of inflammation. Predominant WBC consist of neutrophils, macrophages, and lymphocytes. A more in-depth assessment of the immune response provided by DSCC may address limitations of other diagnostic parameters. Multiple methods exist to enumerate DSCC, with the most common being fluorescence microscopy and flow cytometry. However, there is still much unknown about the biological factors that affect DSCC. In order for DSCC to be appropriately used in the dairy industry, there must be a consensus on how DSCC is reported and a greater understanding of the physiological and environmental factors that affect cell populations. This review brings together current information on the performance of DSCC in IMI detection and related factors to help guide future directions for research.

Foodborne pathogenic bacteria are often found in the gut of cattle, including those which pose significant concerns to human consumers such as E. coli O157:H7 and other Shiga-toxin producing E. coli (STEC) which are classified as adulterants in ground beef. High starch-containing diets have been linked to the intestinal proliferation of E. coli, while forages caused decreases in E. coli fecal shedding However, the effects of an abrupt dietary shift and different forage qualities on E. coli shedding in beef cattle remains unknown. The study aimed to evaluate the influence of changing diets from high grain to high-quality and low-quality forage rations on fecal E. coli and coliform shedding. Twenty-seven (n =27) crossbred beef steers and heifers from the University of Georgia Double Bridges Farm were enrolled in a 43-day randomized design block design. Cattle were blocked based on weight and sex and on Day 0 assigned to 1 of 3 treatments: 1) Finishing-high grain Diet (CTRL), 2) Low-Quality Forage (LQF), and 3) High-Quality Forage (HQF). The initial 21 days cattle were adapted to the high-grain diet, followed by an abrupt shift to their respective treatments for an additional 22 days. Fecal samples were collected via rectal fecal grabs on days 0, 21, 23, 25, 29, and 43. Samples were serially diluted (10-fold increments), plated on Petrifilm® E. coli/Coliform Count Plates, and incubated for 24 hours at 35° C for enumeration. Across all time points, a TRT´DAY interaction was observed for both E. coli (P = 0.0022) and Coliforms (P = 0.0036) populations. Eight days post-shift (day 29), E. coli populations in the LQF group were decreased by 1.15 log10 CFU/g compared to CTRL as well as a reduction in coliforms. On day 43, E. coli populations in the LQF group remained lower than in the HQF group but were not different from CTRL. Coliform populations in the LQF group remained lower than both the CTRL and HQF groups on day 43. While abruptly transitioning finishing beef cattle to hay remains impractical, a >1 log10 CFU/g reduction in E. coli and coliforms suggests that LQF may hold the key to understanding which specific chemical nutrient components drive E. coli and coliform shedding and will indicate which feeds can practically be used in beef cattle finishing rations. Further research is needed to identify these components to decrease contamination risks to the public.

Abstract Blanket dry cow therapy accounts for approximately one third of antibiotic use on dairies. Selective dry cow therapy (SDCT) is a management strategy that selects quarters or cows to be treated with antibiotics based on herd and/or cow-level criteria. Options for implementing SDCT include both cow-side tests (low-cost, rapid tests and higher cost culture-based SDCT) and historical data (algorithm-based SDCT), or a combination. Considerations made when exploring SDCT options include differences in diagnostic efficacy, cost, etc. The objective of this study is to evaluate the accuracy of common low-cost cow-side tests for diagnosing infection in the development of a SDCT program relative culture-based SCDT. In particular, the California Mastitis Test (CMT) and milk conductivity as measured by Mas-D-Tec were selected given their low input and per cow cost ($17 kit at < $0.10/cow and $400 device with negligible per cow cost, respectively). Late-lactation dairy cows (n = 47) at the University of Georgia Teaching Dairy were enrolled 48 h prior to dry off. On enrollment day, quarter milk samples were aseptically collected, tested utilizing CMT and milk conductivity was recorded. Milk samples were then plated on blood agar, following which, plates were evaluated for microbial growth 48 h later. Quarters were identified as bacteriologically infected or uninfected based on microbial growth. Cow-based SDCT, rather than quarter-based SDCT, was evaluated in this study. Overall, 23.40% of cows were infected at collection. Relative to culture-based selection, the sensitivity and specificity of CMT was 90.9% and 13.9% whereas the sensitivity and specificity conductivity was 81.8% and 27.8%. However, analysis indicated effects seen were not significant (P > 0.05). As a result of CMT and conductivity not yielding a significant effect, a third, yet more costly, cow-side test was evaluated. Selecting cows based on increased milk somatic cell count (SCC) is a central piece in algorithm-based SDCT. Relative to culture-based selection, SCC as a diagnostic indicator was significant (P = 0.01) with a sensitivity of 90.1% and specificity of 55.6%. The accuracy of SCC as a diagnostic tool was 63.8%. Additional data are needed to fully evaluate the applicability of CMT and conductivity as measured by the Mas-D-Tec, especially when considering the perceived economic benefits of implementing SCDT with rapid, low-cost cow-side tests. Utilization of SCC is a viable option given our findings however initial input costs (>$3,000), per cow screening costs ($3 to $12), and labor are all examples of barriers to implementation. In conclusion, the low-cost, rapid cow-side tests assessed in the current study were not effective as diagnostic tools for SDCT. Considering another cow-side test (SCC) may be necessary for producers interested in reducing antibiotic usage and costs. Dairy producers would realize a 45% decrease in dry cow therapy costs and 42% reduction in antibiotic use.

The objective of this study was to determine the effect of dietary manganese on the reproductive performance of sows. Sows (n = 39; 231 ± 8 kg) were randomly assigned to one of three dietary levels of supplemented Mn (CON: 0 ppm Mn; PRO20: 20 ppm Mn; PRO40: 40 ppm Mn). The experimental treatments were initiated at breeding and continued through two parities. The sows were blocked by parity within each farrowing group. The data were analyzed as a randomized complete block design using the MIXED procedure of SAS with diet as a fixed effect and block as a random effect. The lactation feed intake increased in the PRO20 sows compared to the CON and PRO40 sows (p < 0.05). The PRO20 and PRO40 sows farrowed piglets with improved average daily gain from birth to weaning (CON 214 g/day; PRO20 237 g/day; 220 g/day; p < 0.05) compared to the CON sows. The milk fat content was lower in the PRO20 (5.5%) and PRO40 sows (6.1%; p < 0.05) compared to the CON sows (7.8%), possibly due to increased milk demand. Supplementary dietary Mn throughout two gestation and lactation cycles led to improved birth weights and pre-weaning growth of piglets.

Antibiotic administration is crucial to ensure the health and productivity of dairy cattle. Mastitis is a disease that is typically a result of an intramammary infection (IMI), and antibiotic regimens are implemented to aid in curing IMI. Diagnosis is usually by detection of elevated milk somatic cell counts (SCC) and/or presence of culturable pathogens in the milk. Antibiotic treatment success is associated with the SCC at the time of treatment, though this correlation is still poorly understood. The objective of this project was to evaluate pre-treatment SCC and its association with IMI cure incidence following a standard antibiotic treatment. We hypothesized that pre-treatment SCC would be significantly lower in cases where the IMI ultimately cured compared to cases where the IMI failed to cure. Milk samples were collected aseptically from lactating cow quarters experiencing clinical or subclinical mastitis (n = 52). Clinical mastitis was diagnosed by a trained milking technician and subclinical mastitis was diagnosed at the quarter level as a SCC > 200,000 cells/mL and presence of bacterical growth in milk at time of treatment. After collection of the day 0 (D0) milk samples, the SCC was enumerated, and the milk sample cultured. Intramammary antibiotic therapy Cetftiofur hydrochloride (Spectramast® LC) was administered once/day for 5 days. Post-treatment samples were collected 14 d (D14) and 28 d (D28) later. A bacteriological cure was confirmed when both the D14 and D28 samples were free of culturable pathogens. The overall cure rate was 46.2%. Interestingly, the cure rates of antibiotic therapy decreased as pre-treatment SCC increased. Quarters that experienced bacteriological cure demonstrated a lower pre-treatment SCC (507,041 cells/mL ± 127.86 SEM, P = 0.01) compared to cows that did not cure, which had high pre-treatment SCC (1,640,392 cells/mL ± 333.28 SEM). Quarters that failed to cure had higher SCC values 28 days post-treatment in comparison to quarters that cured (P < 0.001). Future studies should investigate whether we can develop unique SCC-dependent mastitis treatment protocols which increase mastitis cure rates and enhance overall mammary health.

The objective of this study was to determine the effect of dietary manganese (ProPath Mn, Zinpro Corporation) on the reproductive performance of sows. Sows (N = 39; 231 ± 8 kg) were randomly assigned to 1 of three dietary levels of Mn (CON: 0 ppm Mn; PRO20: 20 ppm Mn; PRO40: 40 ppm Mn). Experimental treatments were initiated at breeding and continued through 2 parities. Sows were blocked by parity within each farrowing group and dietary treatments were represented within each block. Data were analyzed as a randomized complete block design using the MIXED procedure of SAS with diet as a fixed effect and block as a random effect. Dietary treatment did not affect sow body weights (P > 0.10). Lactation feed intake was increased in PRO20 sows compared with CON and PRO40 sows (P < 0.05). PRO20 and PRO40 sows farrowed heavier piglets (CON 1.23 kg; PRO20 1.57 kg; PRO40 1.40 kg; P = 0.001) with improved average daily gain to weaning (CON 213 g/day; PRO20 237 g/day; 220 g/day; P < 0.05), compared with CON sows. Milk fat content (average from d 7 and 14 of lactation) was reduced in PRO20 (5.5%) and PRO40 sows (6.1%; P < 0.05) compared with CON sows (7.8%), possibly due to increased milk demand from the piglets. There were no significant differences in milk mineral concentrations during lactation or piglet tissue Mn-superoxide dismutase (MnSOD) activity at weaning (P > 0.10). On day 3 of lactation, prolactin concentrations were similar across treatments (P > 0.10), whereas progesterone concentrations tended to differ in response to Mn level (CON 23.70 ng/mL; PRO20 26.15 ng/mL; PRO40 22.10 ng/ml; P = 0.09). Supplementary dietary Mn throughout 2 gestation and lactation cycles led to increased birth weights and pre-weaning growth of piglets.

Mastitis is a costly disease in dairy cattle as a result of decreased milk production, discarded milk, and other economic drivers such as treatment costs. Although it can be costly, effective antibiotic therapy is useful to ensure the health and productivity of dairy cattle. Antibiotic usage to treat mastitis can be implemented after diagnosis based upon detection of increased milk somatic cell counts (SCC). Previous work demonstrated antibiotic treatment tends to be more effective when milk SCC are lower prior to treatment. An approach to increasing the cure rates of mastitis may be evaluating milk SCC prior to administering treatment. In order to investigate this potential tool, an effective and reliable method to enumerate SCC is critical. In this review, we (a) dissect the different definitions of cure, (b) review the methods available for enumerating SCC, and (c) discuss factors that are associated with intramammary infection cure with an emphasis on SCC.

The microorganisms inhabiting the gastrointestinal tract (GIT) of ruminants have a mutualistic relationship with the host that influences the efficiency and health of the ruminants. The GIT microbiota interacts with the host immune system to influence not only the GIT, but other organs in the body as well. The objective of this review is to highlight the importance of the role the gastrointestinal microbiota plays in modulating the health of a host through communication with different organs in the body through the microbiome-gut-organ axes. Among other things, the GIT microbiota produces metabolites for the host and prevents the colonization of pathogens. In order to prevent dysbiosis of the GIT microbiota, gut microbial therapies can be utilized to re-introduce beneficial bacteria and regain homeostasis within the rumen environment and promote gastrointestinal health. Additionally, controlling GIT dysbiosis can aid the immune system in preventing disfunction in other organ systems in the body through the microbiome-gut-brain axis, the microbiome-gut-lung axis, the microbiome-gut-mammary axis, and the microbiome-gut-reproductive axis.

Targeting the gastrointestinal microbiome for improvement of feed efficiency and reduction of production costs is a potential promising strategy. However little progress has been made in manipulation of the gut microbiomes in dairy cattle to improve milk yield and milk quality. Even less understood is the milk microbiome. Understanding the milk microbiome may provide insight into how the microbiota correlate with milk yield and milk quality. The objective of this study was to characterize similarities between rumen, fecal, and milk microbiota simultaneously, and to investigate associations between microbiota, milk somatic cell count (SCC), and milk yield. A total of 51 mid-lactation, multiparous Holstein dairy cattle were chosen for sampling of ruminal, fecal, and milk contents that were processed for microbial DNA extraction and sequencing. Cows were categorized based on low, medium, and high SCC; as well as low, medium, and high milk yield. Beta diversity indicated that ruminal, fecal, and milk populations were distinct (p < 0.001). Additionally, the Shannon index demonstrated that ruminal microbial populations were more diverse (p < 0.05) than were fecal and milk populations, and milk microbiota was the least diverse of all sample types (p < 0.001). While diversity indices were not linked (p > 0.1) with milk yield, milk microbial populations from cows with low SCC demonstrated a more evenly distributed microbiome in comparison to cows with high SCC values (p = 0.053). These data demonstrate the complexity of host microbiomes both in the gut and mammary gland. Further, we conclude that there is a significant relationship between mammary health (i.e., SCC) and the milk microbiome. Whether this microbiome could be utilized in efforts to protect the mammary gland remains unclear, but should be explored in future studies.

Staphylococcus aureus is one of the most concerning mastitis-causing pathogens in dairy cattle. Using basic microbiological techniques, S. aureus is typically identified by colony characteristics and hemolysis on blood agar where isolates without hemolysis are typically considered to be coagulase-negative staphylococci (CNS) isolates. Herein, we present a decade-long case study where suspected S. aureus isolates from one Georgia dairy farm were further tested to confirm presumptive identification. Presumptive identification of bacterial growth from 222 mammary secretions from bred Holstein heifers and lactating cows was conducted at the time of collection. Presumptive identification of S. aureus on blood agar was based on observation of colony morphology, color, and presence or absence of a broad zone of incomplete hemolysis and a smaller zone of complete hemolysis at 48 h. Those without hemolysis were presumptively characterized as CNS. All isolates were further plated on mannitol salt agar and a coagulase test was performed. A positive for both of these tests together was deemed to be S. aureus. A selection of isolates was tested using API® Staph to biochemically confirm S. aureus identification. Data showed that 63.96% of isolates presumed to be CNS isolates were identified as S. aureus, 9.46% of isolates presumed to be CNS isolates were identified as coagulase-positive staphylococci (CPS) species (but not S. aureus), and 26.58% of samples that were presumed to be CNS isolates were identified correctly.

Teat disinfection, both before and after milking, is the most important mastitis management tool for reducing the incidence of new intramammary infections in dairy cows. Between milkings, cows are exposed to pathogenic mastitis-causing microorganisms in the environment in which they are managed that are present in soil, manure, bedding materials, water, and mud. These pathogens contaminate the teat skin of the udder, and include environmental bacteria such as Streptococcus uberis and Escherichia coli. The practice of pre-dipping reduces the bacterial load with these environmental pathogens, which subsequently reduces the new infection rate. During the milking process, teats are exposed to the contagious organisms such as Streptococcus agalactiae, Staphylococcus, aureus, and Mycoplasma species. Post-dipping by immersion of teats in a disinfectant immediately after milking cluster removal kills the majority of contagious bacteria, thereby preventing the establishment of new infections during the post-milking period. Whether preand/or post-dipping are used, dairy producers must ensure that they are using products that have been proven effective against mastitis-causing bacteria through valid scientific testing. In this study, the germicidal efficacies of Forticept Udder Wash (pre-dip) and Forticept Udder Forte (post-dip) (Lidan, Inc., NY, NY) in reducing the new intramammary infection rate under natural exposure to mastitis pathogens were evaluated and compared with a proven iodine preand post-dip product as a positive control. Results of the 6-month trial demonstrated a new infection rate of 10.5% among mammary quarters pre-dipped and post-dipped in Forticept products, and a rate of 5.8% among quarters pre-dipped and post-dipped in the positive control iodine product; the difference was not significant (P < 0.06). In addition, average somatic cell count (SCC) was 304,000/ml among mammary quarters pre-dipped and post-dipped in Forticept products, and 239,000/ml among quarters pre-dipped and post-dipped in the positive control product; the difference was not significant (P < 0.06). Average teat condition scores were very similar (P < 0.96) among quarters pre-dipped and post-dipped in Forticept products (Score = 1.40), and quarters pre-dipped and post-dipped in the positive control (Score = 1.46). Findings suggest that under the conditions of this study, the new mammary quarter infection rate, SCC, and teat condition scores were similar among quarters dipped in Forticept products and quarters dipped in the positive control product.

[This corrects the article DOI: 10.1371/journal.ppat.1007696.].

Background:Why resistance to specific antibiotics emerges and spreads rapidly in some bacteria confronting these drugs but not others remains a mystery. Resistance to erythromycin in the respiratory pathogens Staphylococcus aureus and Streptococcus pneumoniae emerged rapidly and increased problematically. However, resistance is uncommon amongst the classic Bordetella species despite infections being treated with this macrolide for decades.Objectives:We examined whether the apparent progenitor of the classic Bordetella spp., Bordetella bronchiseptica, is able to rapidly generate de novo resistance to antibiotics and, if so, why such resistance might not persist and propagate.Methods:Independent strains of B. bronchiseptica resistant to erythromycin were generated in vitro by successively passaging them in increasing subinhibitory concentrations of this macrolide. Resistant mutants obtained were evaluated for their capacity to infect mice, and for other virulence properties including adherence, cytotoxicity and induction of cytokines.Results:B. bronchiseptica rapidly developed stable and persistent antibiotic resistance de novo. Unlike the previously reported trade-off in fitness, multiple independent resistant mutants were not defective in their rates of growth in vitro but were consistently defective in colonizing mice and lost a variety of virulence phenotypes. These changes rendered them avirulent but phenotypically similar to the previously described growth phase associated with the ability to survive in soil, water and/or other extra-mammalian environments.Conclusions:These observations raise the possibility that antibiotic resistance in some organisms results in trade-offs that are not quantifiable in routine measures of general fitness such as growth in vitro, but are pronounced in various aspects of infection in the natural host.

Multiple lines of evidence suggest that Bordetella species have a significant life stage outside of the mammalian respiratory tract that has yet to be defined. The Bordetella virulence gene (BvgAS) two-component system, a paradigm for a global virulence regulon, controls the expression of many “virulence factors” expressed in the Bvg positive (Bvg+) phase that are necessary for successful respiratory tract infection. A similarly large set of highly conserved genes are expressed under Bvg negative (Bvg-) phase growth conditions; however, these appear to be primarily expressed outside of the host and are thus hypothesized to be important in an undefined extrahost reservoir. Here, we show that Bvg- phase genes are involved in the ability of Bordetella bronchiseptica to grow and disseminate via the complex life cycle of the amoeba Dictyostelium discoideum. Unlike bacteria that serve as an amoeba food source, B. bronchiseptica evades amoeba predation, survives within the amoeba for extended periods of time, incorporates itself into the amoeba sori, and disseminates along with the amoeba. Remarkably, B. bronchiseptica continues to be transferred with the amoeba for months, through multiple life cycles of amoebae grown on the lawns of other bacteria, thus demonstrating a stable relationship that allows B. bronchiseptica to expand and disperse geographically via the D. discoideum life cycle. Furthermore, B. bronchiseptica within the sori can efficiently infect mice, indicating that amoebae may represent an environmental vector within which pathogenic bordetellae expand and disseminate to encounter new mammalian hosts. These data identify amoebae as potential environmental reservoirs as well as amplifying and disseminating vectors for B. bronchiseptica and reveal an important role for the Bvg- phase in these interactions.

Oxylipids are derived from polyunsaturated fatty acids (PUFA) in cellular membranes and the relative abundance or balance may contribute to disease pathogenesis. Previous studies documented unique oxylipid profiles from cows with either coliform or Streptococcus uberis mastitis, suggesting that lipid mediator biosynthesis may be dependent on the type of microbial-derived agonist. Changing the fatty acid content of peripheral blood leukocytes also may be critical to the relative expression of oxylipid profiles and the outcome of bacterial infection. No information is available in dairy cows describing how changing cellular PUFA content will modify oxylipids in the context of a microbial agonist challenge. Therefore, the hypothesis for the current study was that PUFA supplementation would change bovine leukocyte fatty acid content and respective oxylipid profiles from ex vivo microbial agonist-challenged leukocytes. Fatty acid content of leukocytes and plasma was quantified in (1) samples from cows not supplemented with PUFA, (2) cows supplemented with linoleic acid (LnA), and (3) cows supplemented with α-linolenic acid (ALA). Plasma oxylipids were assessed after S. uberis or lipopolysaccharide exposure and was compared with unstimulated oxylipid profiles. Fatty acid supplementation with ALA significantly increased ALA content of blood leukocytes and plasma relative to LnA. Fatty acid supplementation affected several S. uberis-induced oxylipids, but only S. uberis-induced 15-oxoETE was greater with ALA supplementation compared with LnA. Notably, only LPS-induced 5,6 LXA4 was altered with fatty acid supplementation, but no significant effect of LnA vs. ALA treatment was identified. Future studies are needed to understand how leukocyte activation and membrane PUFA availability collectively contribute to differential oxylipid profiles.

Inflammation is an essential host response during bacterial infections such as bovine mastitis. Endothelial cells are critical for an appropriate inflammatory response and loss of vascular barrier integrity is implicated in the pathogenesis of Streptococcus uberis-induced mastitis. Previous studies suggested that accumulation of linoleic acid (LA) oxygenation products derived from 15-lipoxygenase-1 (15-LOX-1) metabolism could regulate vascular functions. The initial LA derivative from the 15-LOX-1 pathway, 13-hydroperoxyoctadecadienoic acid (HPODE), can induce endothelial death, whereas the reduced hydroxyl product, 13-hydroxyoctadecadienoic acid (HODE), is abundantly produced during vascular activation. However, the relative contribution of specific LA-derived metabolites on impairment of mammary endothelial integrity is unknown. Our hypothesis was that S. uberis-induced LA-derived 15-LOX-1 oxygenation products impair mammary endothelial barrier integrity by apoptosis. Exposure of bovine mammary endothelial cells (BMEC) to S. uberis did not increase 15-LOX-1 LA metabolism. However, S. uberis challenge of bovine monocytes demonstrated that monocytes may be a significant source of both 13-HPODE and 13-HODE during mastitis. Exposure of BMEC to 13-HPODE, but not 13-HODE, significantly reduced endothelial barrier integrity and increased apoptosis. Changing oxidant status by coexposure to an antioxidant during 13-HPODE treatment prevented adverse effects of 13-HPODE, including amelioration of apoptosis. A better understanding of how the oxidant status of the vascular microenvironment impacts endothelial barrier properties could lead to more efficacious treatments for S. uberis mastitis.

The balance of n-3 and n-6 fatty acids (FA) in immune system tissues can influence the degree of inflammatory responses in dairy cattle. Linoleic acid (C18:2 n-6) and linolenic acid (C18:3 n-3) are the most abundant n-6 and n-3 FA in lactating dairy cow rations, and are associated with pro-inflammatory and anti-inflammatory responses, respectively. Our objective was to evaluate the incorporation of these FA, and their downstream oxidized FA (oxylipids), into plasma and white blood cells (WBC) following supplementation. Six mid-lactation dairy cows were abomasally infused 4x/d for 7-d treatment periods with 7-d washout intervals in a replicated balanced Latin square design with 3 treatments: 1) CON = ethanol carrier, 2) LA = 45 g/d C18:2 n-6, and 3) LNA = 45 g/d C18:3 n-3. Blood was collected on d 7 of the treatment periods and analyzed for WBC and plasma lipid fraction FA and plasma oxylipid composition. Yields of milk and milk components were calculated for d 6 and d 7 of the treatment periods. Statistical analysis was performed using linear mixed models. Dry matter intake was not affected by treatment (P = 0.68). LA treatment increased the yield of milk and milk protein compared to CON and LNA (P ≤ 0.05). LNA treatment increased milk fat concentration compared to CON and LA (P ≤ 0.05). The concentration of C18:3 n-3 in WBC was increased by LNA (0.86 g/100 g FA; P ≤ 0.05), compared to LA (0.39 g/100 g FA) and CON (0.34 g/100 g FA), but C18:2 n-6 was unaffected by treatment (P = 0.15). LNA increased C18:3 n-3 (3.17 g/100 g FA) and C20:5 n-3 (0.43 g/100 g FA) in the phospholipid fraction of plasma, compared to CON and LA (P ≤ 0.01), while LA increased C18:2 n-6 (38.7 g/100 g FA), compared to the other treatments (P < 0.01). Plasma phospholipid C20:4 n-6 concentration was not altered by treatment (P = 0.65). LNA decreased C20:4 n-6-derived 8,9-DiHETrE (P < 0.01) and tended to decrease C18:2 n-6-derived 12,13 EpOME in plasma (P = 0.09). When C18:3 n-3 and C18:2 n-6 were abomasally infused at the same dose, C18:3 n-3 had a greater influence on the profile of plasma FA and oxylipids and the FA composition of WBC. These changes have the potential to mediate inflammatory responses in cattle at risk of infection.