Effect of fish oil in Iberian sow diets on fatty acid, oxylipins and immune traits of colostrum and milk, and suckling piglets' growth performance

Iberian sow productivity is characterised by a low number of weaned piglets with higher within-litter variation in piglet birth BW compared with conventional breeds. To overcome this, nutritional strategies, such as the dietary addition of n-3 fatty acids (FAs), are being studied to improve sow performance, as well as colostrum and milk composition. In addition, n-3 FAs and their derived oxylipins could also be beneficial for the offspring due to their anti-inflammatory roles. The present study was conducted in an outdoor production system where sows were group-fed during the mating and gestation periods, while feed intake was provided individually during lactation. The study aimed to evaluate the effects of including fish oil rich in eicosapentaenoic and docosahexaenoic acids (EPA and DHA, respectively) in Iberian sow diets on litter size, piglet growth during lactation, and the concentrations of anti-inflammatory molecules in colostrum and milk. Forty sows were randomly assigned to either a control or fish oil diet during pregnancy and lactation. Sow performance and litter traits were monitored until weaning. Colostrum and milk were collected after the birth of the first piglet and at weaning, respectively. Their FA composition, oxylipin profile, and immune indicators were analysed. Despite the piglets from the control group having greater average birth BW than those from the fish oil litters (P = 0.016), the fish oil piglets were heavier at weaning (P < 0.028). Total n-3 FA concentration was increased in the colostrum and milk of fish oil-fed sows (all P < 0.001), mainly due to increases in EPA and DHA concentrations (all P < 0.001). In the same way, most of their oxygenated derivatives were also increased in both colostrum and milk (P ≤ 0.045). The colostrum from fish oil-fed sows also presented higher concentrations of immunoglobulins (Ig) G and A than that from control sows (P = 0.025 and P = 0.026, respectively). In conclusion, the inclusion of fish oil in sow diets increased the levels of IgG and IgA in colostrum, n-3 FAs and their derived oxylipins in colostrum and milk, and piglet BW at weaning.

Effect of weaning strategies on biosynthesis of oxylipids in Holstein dairy calves

The aim of this study was to determine the effect of the weaning calves at 2 ages (early vs. late) and 2 weaning paces (abrupt over 3 d vs. gradual over 14 d) on plasma oxylipids. Seventy-one dairy calves (38.8 ± 4.4 kg, BW ± SD), blocked by sex and BW at birth, were randomly assigned in a 2 × 2 factorial arrangement of treatments. The factors were weaning age (early: 6-7 wk vs. late: 8-9 wk) and weaning pace (abrupt: 3 weaning steps over 2 d vs. gradual: 7 weaning steps over 14 d), generating 4 treatment groups: early-abrupt, early-gradual, late-abrupt, and late-gradual. Blood samples were collected from the jugular vein 1 d preweaning, and one day postweaning. Oxylipids concentration was measured by liquid chromatography-tandem MS. Fatty acid profile (including nonesterified fatty acids) was also assessed. Weaning pace, age, pace × age, BW at birth, and sex were included as fixed effect and cohort was included as random effect in the model. Linoleic acid derivatives 13- oxooctadecadienoic (OxoODE) and 9-OxoODE had a greater concentration in calves abruptly weaned when compared with those for gradually weaned calves. Calves weaned gradually showed a greater concentration of 9-hydroxyoctadecadienoic (HODE), 13-HODE, 12,13-dihydroxyoctadecenoic (DiHOME), 9,10-DiHOME, all linoleic acid-derived compared with that for abruptly weaned calves. Anti-inflammatory oxylipid 17,18-dihydroxyeicosatrienoic, an eicosapentaenoic acid derivative, was greater in calves abruptly weaned compared with those gradually weaned. Overall, the pace of weaning affected the plasma concentration of oxylipids, demonstrating that weaning pace affects the oxylipids status involved in inflammation in dairy calves.

Oxylipin dynamics in dairy cows during clinical ketosis and after treatment with niacin and flunixin meglumine

Dairy cows with clinical ketosis (CK) exhibit metabolic changes, including intense adipose tissue (AT) lipolysis and systemic insulin resistance, that increase plasma BHB and free fatty acids (FFA). Cows with CK also have systemic inflammation, predisposing them to inflammatory and infectious diseases. This inflammatory process is modulated in part by oxidized fatty acids (oxylipins) that regulate all aspects of inflammation. Oxylipin profiles have been characterized in healthy periparturient cows, but their dynamics during CK are unknown. Clinical ketosis is an acute metabolic disease requiring clinical therapy, commonly including propylene glycol (PG) as a gluconeogenic agent. Recently, we showed that including lipolysis inhibitors such as niacin (NIA) and flunixin meglumine (FM) improved CK recovery. These drugs may modulate oxylipin biosynthesis by regulating the release of PUFA (oxylipin substrates) and cyclooxygenase activity. However, their impact on oxylipin profiles in cows with CK is unknown. The objective of this study was to determine the dynamics of specific linoleic and arachidonic acid-derived oxylipins during CK and following therapy with PG, NIA, and FM. Multiparous Jersey cows (n = 72; 7.1 DIM) with CK from a commercial dairy were sampled. Inclusion criteria were CK symptoms (lethargy, depressed appetite, and reduced rumen fill) and blood BHB ≥ 1.2 mmol/L. The CK cows (n = 24/treatment) were randomly assigned to one of the 3 treatments: (1) PG: 310 g orally once daily for 5 d, (2) PG + NIA (PGNIA): 24 g orally once daily for 3 d, (3) PG + NIA + FM (PGNIAFM): 1.1 mg/kg i.v. once daily for 3 d. Healthy control cows (HC; n = 24) matched by lactation and DIM (±2 d) were also included. Plasma oxylipins were quantified at enrollment and 7 d later using HPLC-MS/MS. At enrollment, CK had higher concentrations of arachidonic acid (ARA)-derived 5- and 20-HETE, 8,9-, 11,12-, and 14-15-DHET, and lower concentrations of linoleic acid (LA)-derived 12,13-EpOME, 13-oxoODE, 9,10- and 12,13-DiHOME. Integrated analysis of biological pathways and oxylipin profiles using Ingenuity Pathway Analysis revealed ARA metabolism as the top pathway activated during CK. By d 7, treatment with PGNIAFM restored plasma PUFA and oxylipins to profiles similar to HC. Ingenuity Pathway Analysis showed that PGNIAFM activated the zinc transporter SLC30A7, associated with reduced activation of the ARA pathway. Results indicate that higher FA availability during CK, driven in part by dysregulated lipolysis, increases the pool of substrates for oxylipin biosynthesis. These oxylipins may play a role in both metabolic dysregulation and restoring homeostasis during CK. Inhibiting lipolysis and cyclooxygenase activity with NIA and FM can alter ARA- and LA-derived oxylipin biosynthesis. These findings underscore the potential use of lipolysis inhibitors NIA and FM in CK therapeutics and highlight the importance of understanding oxylipin pathways in the pathogenesis of CK.

Role of Acyl-CoA Thioesterase 7 in Regulating Fatty Acid Metabolism and Its Contribution to the Onset and Progression of Bovine Clinical Mastitis

Clinical mastitis (CM) is a prevalent and severe inflammatory disease in dairy cows affecting the mammary glands. Fatty acid (FA) metabolism and associated enzymes are crucial for many physiological and pathological processes in dairy cows. However, the relationships among FA metabolism, FA-associated enzymes, and CM, as well as the mechanisms underlying their interactions, in dairy cows are not fully understood. The aim of this study was to characterize biological process (BP) terms, pathways, and differentially expressed proteins (DEPs) related to FA metabolism from our previous data-independent acquisition proteomic study. Six BPs involving 14 downregulated and 20 upregulated DEPs, and four pathways involving 10 downregulated and 11 upregulated DEPs related to FA synthesis and metabolism were systematically identified. Associated analysis suggested that 12 candidate DEPs obtained from BPs and pathways, especially acyl-CoA thioesterase 7 (ACOT7), regulate long-chain FA (LCFA) elongation and the biosynthesis of unsaturated FAs. Immunohistochemical and immunofluorescence staining results showed that ACOT7 was present mainly in the cytoplasm of mammary epithelial cells. The qRT-PCR and Western blotting results showed that ACOT7 mRNA and protein levels in the mammary glands of the CM group were significantly upregulated compared to those in the healthy group. This evidence indicates that ACOT7 is positively correlated with CM onset and progression in Holstein cows. These findings offer novel insights into the role of FA metabolism and related enzymes in CM and offer potential targets for the development of therapeutic strategies and biomarkers for the prevention and treatment of CM in dairy cows.

A randomized control trial to test the effect of pegbovigrastim treatment at dry-off on plasma and milk oxylipid profiles during early mammary gland involution and the postparturient period

The early period of mammary gland involution is a critical juncture in the lactation cycle that can have significant effects on milk production and mammary gland health. Pegbovigrastim (PEG) administered 1 wk prior and on the day of parturition can enhance immune function and reduce the incidence of mastitis in the early postpartum period. Oxylipids are potent metabolites of polyunsaturated fatty acids (PUFA) and are important mediators of inflammation. The objective of this study was to evaluate effects of PEG given 1 wk before and at the day of dry-off (D0) on concentrations of oxylipids in plasma and milk from 7 d before D0 to 14 d after, as well as the effects during the first 14 d of the subsequent lactation. We hypothesized that both pro- and anti-inflammatory oxylipids would vary based on initiation of mammary gland involution and that pegbovigrastim would affect oxylipid concentrations, particularly those related to leukocytes. A complete randomized blocked design was used to enroll cows into either a PEG treatment group (n = 10) or control group (n = 10; CON). Blood samples were collected -7, -2, -1, 0, 1, 2, 4, 7, and 14 d relative to dry-off and 5, 10, and 14 d postcalving. Samples were analyzed for PUFA and oxylipids in milk and plasma by ultra-performance mass spectrometry and liquid chromatography tandem quadrupole mass spectrometry, respectively. Overall, 30 lipid mediators were measured in both milk and plasma. Repeated measures analyses revealed a significant interaction of treatment by time for milk 8-iso-keto-15-prostaglandin E2, prostaglandin F2α, plasma 8,12-iso-prostaglandin Fα-VI, 11-hydroxyeicosatetraenoic acid, and 12-hydroxyheptadecatienoic acid. The majority of milk PUFA and oxylipids differed significantly during early mammary gland involution and into the early postpartum period. This study demonstrated changes in oxylipids in milk secretions and plasma during early involution, and further investigation may illuminate multiple complex processes and reveal targets for optimization of mammary gland involution.

Potential Role of Lauric Acid in Milk Fat Synthesis in Chinese Holstein Cows Based on Integrated Analysis of Ruminal Microbiome and Metabolome

The composition and metabolic profile of the ruminal microbiome have an impact on milk composition. To unravel the ruminal microbiome and metabolome affecting milk fat synthesis in dairy cows, 16S rRNA and internal transcribed spacer (ITS) gene sequencing, as well as ultra-high performance liquid chromatography-mass spectrometry (UHPLC-MS/MS) methods were used to investigate the significant differences in ruminal bacterial and fungal communities as well as metabolome among Chinese Holstein cows with contrasting milk fat contents under the same diet (H-MF 5.82 ± 0.41% vs. L-MF 3.60 ± 0.12%). Another objective was to culture bovine mammary epithelial cells (BMECs) to assess the effect of metabolites on lipid metabolism. Results showed that the acetate-to-propionate ratio and xylanase activity in ruminal fluid were both higher in H-MF. Microbiome sequencing identified 10 types of bacteria and four types of fungi differently abundant at the genus level. Metabolomics analysis indicated 11 different ruminal metabolites between the two groups, the majority of which were lipids and organic acids. Among these, lauric acid (LA) was enriched in fatty acid biosynthesis with its concentration in milk fat of H-MF cows being greater (217 vs. 156 mg per 100 g milk), thus, it was selected for an in vitro study with BMECs. Exogenous LA led to a marked increase in intracellular triglyceride (TG) content and lipid droplet formation, and it upregulated the mRNA abundance of fatty acid uptake and activation (CD36 and ACSL1), TG synthesis (DGAT1, DGAT2 and GPAM), and transcriptional regulation (SREBP1) genes. Taken together, the greater relative abundance of xylan-fermenting bacteria and fungi, and lower abundance of bacteria suppressing short-chain fatty acid-producing bacteria or participating in fatty acid hydrogenation altered lipids and organic acids in the rumen of dairy cows. In BMECs, LA altered the expression of genes involved in lipid metabolism in mammary cells, ultimately promoting milk fat synthesis. Thus, it appears that this fatty acid plays a key role in milk fat synthesis.

Oxylipins biosynthesis and the regulation of bovine postpartum inflammation

Uncontrolled or dysregulated inflammation has adverse effects on the reproduction, production and health of animals, and is a major pathological cause of increased incidence and severity of infectious and metabolic diseases. To achieve successful transition from a non-lactation pregnant state to a non-pregnant lactation state, drastic metabolic and endocrine alteration have taken place in dairy cows during the periparturient period. These physiological changes, coupled with decreased dry matter intake near calving and sudden change of diet composition after calving, have the potential to disrupt the delicate balance between pro- and anti-inflammation, resulting in a disordered or excessive inflammatory response. In addition to cytokines and other immunoregulatory factors, most oxylipins formed from polyunsaturated fatty acids (PUFAs) via enzymatic and nonenzymatic oxygenation pathways have pro- or anti-inflammatory properties and play a pivotal role in the onset, development and resolution of inflammation. However, little attention has been paid to the possibility that oxylipins could function as endogenous immunomodulating agents. This review will provide a detailed overview of the main oxylipins derived from different PUFAs and discuss the regulatory role that oxylipins play in the postpartum inflammatory response in dairy cows. Based on the current research, much remains to be illuminated in this emerging field. Understanding the role that oxylipins play in the control of postpartum inflammation and inflammatory-based disease may improve our ability to prevent transition disorders via Management, pharmacological, genetic selection and dietary intervention strategies.

Intramammary calcitriol treatment of mastitis alters profile of milk somatic cells and indicators of redox activity in milk

The objective of this experiment was to determine the effect of intramammary calcitriol treatment on indicators of inflammation during an intramammary bacterial infection. Lactating Holstein cows were challenged with intramammary Streptococcus uberis. At the onset of mild or moderate mastitis, cows were randomly assigned to receive 10 µg of intramammary calcitriol (CAL, n = 7) or placebo control (CON; n = 6) after every milking for 5 days. Data were analyzed by ANOVA with mixed models using the MIXED procedure of SAS with significance declared at P ≤ 0.05. Milk somatic cells, mastitis severity scores, rectal temperatures, and milk bacterial counts did not differ between treatments. Calcitriol decreased the percentage of CD11b+CD14- cells in milk compared with CON (CON = 81 vs. CAL = 61 ± 5%). Antioxidant potential and concentrations of 15-F2t- isoprostanes in milk of infected quarters also were lower in CAL compared with CON. Transcripts for the 25-hydroxyvitamin D 24-hydroxylase and inducible nitric oxide synthase were greater in milk somatic cells of CAL compared with CON, but those for β-defensin 7, metallothionein 1 A and 2 A, thioredoxin and thioredoxin reductase did not differ between treatments. Although clinical signs of severity did not differ, CAL influenced the composition of milk somatic cells and redox activity in milk of infected quarters.

Effects of Anemoside B4 on Plasma Metabolites in Cows with Clinical Mastitis

Anemoside B4 has a good curative effect on cows with CM; however, its impact on their metabolic profiles is unclear. Based on similar somatic cell counts and clinical symptoms, nine healthy dairy cows and nine cows with CM were selected, respectively. Blood samples were collected from cows with mastitis on the day of diagnosis. Cows with mastitis were injected with anemoside B4 (0.05 mL/kg, once daily) for three consecutive days, and healthy cows were injected with the same volume of normal saline. Subsequently, blood samples were collected. The plasma metabolic profiles were analyzed using untargeted mass spectrometry, and the concentrations of interleukin (IL)-1β, IL-6, and tumor necrosis factor-α (TNF-α) in serum were evaluated via ELISA. The cows with CM showed increased concentrations of IL-1β, IL-6, and TNF-α (p < 0.05). After treatment with anemoside B4, the concentrations of IL-1β, IL-6, and TNF-α were significantly decreased (p < 0.01). Untargeted metabolomics analysis showed that choline, glycocholic acid, PC (18:0/18:1), 20-HETE, PGF3α, and oleic acid were upregulated in cows with CM. After treatment with anemoside B4, the concentrations of PC (16:0/16:0), PC (18:0/18:1), linoleic acid, eicosapentaenoic acid, phosphorylcholine, and glycerophosphocholine were downregulated, while the LysoPC (14:0), LysoPC (18:0), LysoPC (18:1), and cis-9-palmitoleic acid were upregulated. This study indicated that anemoside B4 alleviated the inflammatory response in cows with CM mainly by regulating lipid metabolism.

Comparative analysis of total protein, casein, lactose, and fat content in milk of cows suffering from subclinical and clinical mastitis caused by Streptococcus spp

Introduction

The aim of the study was to analyse the total protein (TP), casein (CAS), lactose (LAC), and fat content of milk from cows with subclinical (SCM) and clinical mastitis (CM) caused by Streptococcus spp.

Material and Methods

A total of 60 milk samples from diseased cows and 30 milk samples from healthy cows were included in the study. Milk samples were taken from Holstein-Friesian cows from four dairy farms in Lublin Province. The bacteriological examination of the milk was performed and the somatic cells count in 1 mL of milk was determined using a SomaCount FC automatic cell counter. Determination of TP, CAS, LAC, FAT and FA levels in milk was carried out using a DairySpec FT automated Fourier transform infrared spectrometer.

Results

Total protein in milk from HE was significantly higher than in milk from cows with mastitis (4.04% vs 3.57% in milk from SCM cows and 3.7% in milk from CM cows, P = 0.001). The CAS level was 2.73% in milk from CM cows and 2.92% in milk from SCM cows vs 3.30% in milk from HE cows, P = 0.001. The changes in CAS and TP in milk resulted in a significant difference in the CAS/TP ratio (81.7% in milk from HE cows vs 73.8% in milk from CM cows). A decrease in levels was also recorded for LAC (4.8% in milk from HE cows vs 4.51% in milk from SCM cows and 4.01% in milk from CM cows, P = 0.001). The fat level was significantly higher in milk from healthy cows than in milk from cows with mastitis (4.0% vs 2.3% in milk from SCM cows and 1.64% in milk from CM cows, P = 0.001).

Conclusion

It should be emphasised that the decrease in the levels of TP, LAC and FAT was significant not only in milk from CM cows but also in milk from SCM cows. This is very unfavourable, because the reduction in the main milk components results in poor quality dairy products and impairs line processes.

The Focus on Core Genetic Factors That Regulate Hepatic Injury in Cattle Seems to be Important for the Dairy Sector’s Long-Term Development

The cattle during the perinatal period, as well as malnutrition, generate oxidative stress which leads to high culling rates of calves after calving across the world. Although metabolic diseases have such a negative impact on the welfare and economic value of dairy cattle, that becomes a serious industrial concern across the world. According to research, genetic factors have a role or controlling fat deposition in the liver by influencing the biological processes of hepatic lipid metabolism, insulin resistance, gluconeogenesis, oxidative stress, endoplasmic reticulum stress, and inflammation, all of which contribute to hepatic damage. This review focuses on the critical regulatory mechanisms of VEGF, mTOR/AKT/p53, TNF-alpha, Nf-kb, interleukin, and antioxidants that regulate lipid peroxidation in the liver via direct or indirect pathways, suggesting that they could be a potential critical therapeutic target for hepatic disease.

Immune defenses of the mammary gland epithelium of dairy ruminants

The epithelium of the mammary gland (MG) fulfills three major functions: nutrition of progeny, transfer of immunity from mother to newborn, and its own defense against infection. The defense function of the epithelium requires the cooperation of mammary epithelial cells (MECs) with intraepithelial leucocytes, macrophages, DCs, and resident lymphocytes. The MG is characterized by the secretion of a large amount of a nutrient liquid in which certain bacteria can proliferate and reach a considerable bacterial load, which has conditioned how the udder reacts against bacterial invasions. This review presents how the mammary epithelium perceives bacteria, and how it responds to the main bacterial genera associated with mastitis. MECs are able to detect the presence of actively multiplying bacteria in the lumen of the gland: they express pattern recognition receptors (PRRs) that recognize microbe-associated molecular patterns (MAMPs) released by the growing bacteria. Interactions with intraepithelial leucocytes fine-tune MECs responses. Following the onset of inflammation, new interactions are established with lymphocytes and neutrophils recruited from the blood. The mammary epithelium also identifies and responds to antigens, which supposes an antigen-presenting capacity. Its responses can be manipulated with drugs, plant extracts, probiotics, and immune modifiers, in order to increase its defense capacities or reduce the damage related to inflammation. Numerous studies have established that the mammary epithelium is a genuine effector of both innate and adaptive immunity. However, knowledge gaps remain and newly available tools offer the prospect of exciting research to unravel and exploit the multiple capacities of this particular epithelium.

Oxylipins as Potential Regulators of Inflammatory Conditions of Human Lactation

Chronic low-grade inflammation can be associated with obesity or subclinical mastitis (SCM), which is associated with poor infant growth in low- to middle-income country settings. It is unknown what physiological mechanisms are involved in low milk supply, but our research group has shown that mothers with low milk supply have higher inflammatory markers. Studies investigating oxylipin signaling have the potential to help explain mechanisms that mediate the impacts of inflammation on milk production. Animal studies have reported various elevated oxylipins during postpartum inflammation, mastitis, and mammary involution in ruminant models. Several investigations have quantified oxylipins in human milk, but very few studies have reported circulating oxylipin concentrations during lactation. In addition, there are technical considerations that must be addressed when reporting oxylipin concentrations in human milk. First, the majority of milk oxylipins are esterified in the triglyceride pool, which is not routinely measured. Second, total milk fat should be considered as a covariate when using milk oxylipins to predict outcomes. Finally, storage and handling conditions of milk samples must be carefully controlled to ensure accurate milk oxylipin quantitation, which may be affected by highly active lipases in human milk.

Pomegranate (Punica granatum) By-Product Extract Influences the Oxylipids Profile in Primary Bovine Aortic Endothelial Cells in a Model of Oxidative Stress

Aerobic metabolism produces reactive oxygen species (ROS) as a natural by-product that can play a significant role in cell signaling and homeostasis. Excessive and uncontrolled production of ROS, however, can lead to oxidative stress that causes damage to immune cells and is related to several diseases in dairy cattle. Endothelial cells are essential for optimal immune and inflammatory responses but are especially sensitive to the damaging effects of ROS. Accordingly, investigating antioxidant strategies that can mitigate the detrimental impact of ROS on endothelial functions could impact compromised host defenses that lead to increased disease susceptibility. The objective of this study was to test the antioxidant effect of different concentrations (20, 40, 60, 80 μg/ml) of pomegranate by-product extract (PBE) on bovine aortic endothelial cells (BAECs). A model of oxidative stress was developed using in vitro exposure of BAEC to 2,2′-azobis (2-amidinopropane) dihydrochloride (AAPH) to induce the formation of ROS. The BAEC were then analyzed for cell viability, ROS production, fatty acids profile, and oxylipids formation. The BAECs viability did not change after different concentrations of PBE and remained up to 80% over control; whereas, intracellular ROS showed a reduction passing from 20 to 50% with increasing PBE concentration from 20 to 80 μg/ml, respectively. The PBE extract clearly demonstrated efficacy in reducing the concentrations of pro-inflammatory oxylipids with a concomitant enhancement of anti-inflammatory oxylipids. In particular, the pro-inflammatory 13-hydroxyoctadecadienoic acid and its derived anti-inflammatory 13-hydroperoxoctadecaienoic acid were found lower and higher, respectively, in PBE+AAPH treated cells than AAPH treatment. Data from the present study support in vivo future experimental use of pomegranate by-product extract to study its potential beneficial effect against oxidative stress conditions in dairy cattle.

Role of Selenium and Vitamins E and B9 in the Alleviation of Bovine Mastitis during the Periparturient Period

Mastitis (inflammation of the mammary gland) commonly occurs in dairy cattle during the periparturient period (transition period), in which dairy cattle experience physiological and hormonal changes and severe negative energy balance, followed by oxidative stress. To maintain successful lactation and combat negative energy balance (NEB), excessive fat mobilization occurs, leading to overproduction of reactive oxygen species (ROS). Excessive fat mobilization also increases the concentrations of nonesterified fatty acids (NEFA) and β-hydroxybutyric acid (BHB) during the periparturient period. In addition, the excessive utilization of oxygen by cellular respiration in the mammary causes abnormal production of oxidative stress (OS). OS impairs the immunity and anti-inflammatory efficiency of periparturient dairy cattle, increasing their susceptibility to mastitis. To alleviate oxidative stress and subsequent mastitis, antioxidants are supplemented to dairy cattle from an external source. Extensive studies have been conducted on the supplementation of selenium (Se) and vitamins E and B9 to mitigate mastitis during the transition period in dairy cattle. Altogether, in the current review, we discuss the research development on bovine mastitis and its major causes, with special emphasis on oxidative stress during the transition period. Moreover, we discuss the antioxidant, immunoregulatory, and anti-inflammatory properties of Se and vitamins E and B9 and their role in the control of bovine mastitis in periparturient dairy cattle.

Oxylipids are associated with higher disease risk in postpartum cows

Postpartum diseases are a major animal welfare and economic concern for dairy producers. Dysregulated inflammation, which may begin as soon as the cessation of lactation, contributes to the development of postpartum diseases. The ability to regulate inflammation and mitigate postpartum health diseases relies, in part, on the production of inflammatory mediators known as oxylipids. The objective of this study was to examine associations between oxylipids and postpartum diseases. Plasma samples were collected from 16 cattle via coccygeal venipuncture at the following time points: 6 d before dry-off; dry-off (d 0); 1, 2, 6, and 12 d after dry-off; 14 ± 3 d before the expected calving date; and 7 ± 2 d after calving. After calving, cows were grouped according to if clinical disease was undetected throughout the sampling period (n = 7) or if they developed a disease postpartum (n = 9). Liquid chromatography-tandem mass spectrometry was used to analyze plasma concentrations of 63 oxylipid species. Of the 32 oxylipids detected, concentrations of 7 differed between cows with no detected disease and diseased cows throughout the sampling period. Thus, a variable oxylipid profile was demonstrated through 2 major physiological transitions of a lactation cycle. Further, the information gained from this pilot study using a small number of animals with diverse diseases from a single herd suggests that it may be possible to use oxylipids at early mammary involution to alert dairy producers of cows at risk for disease after calving. Future studies should be performed in larger populations of animals, including cows from diverse geographies and dairying styles, and focus on specific diseases to evaluate the utility of oxylipids as biomarkers. Furthermore, it is important to determine the clinical implications of variable oxylipid concentrations throughout the lactation cycle and if the oxylipid profile can be modulated to improve inflammatory outcomes.

Fish oil rich in eicosapentaenoic acid and docosahexaenoic acid in sow diets modifies oxylipins and immune indicators in colostrum and milk

Colostrum and milk are the first nutrient sources for newborn piglets. In addition, n-3 fatty acids (FAs) and their oxygenated derivatives (oxylipins) have the capacity to modulate immune components. The aim of the current study was to include a fish oil rich in eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) in sow diets to promote an increase of anti-inflammatory molecules in colostrum and milk to benefit piglets. Thirty-six sows were randomly assigned from insemination to the end of lactation to either a control diet with animal fat (15 g/kg in gestation and 30 g/kg in lactation) or an n-3 diet in which animal fat was totally (gestation) or half (lactation) replaced by an equivalent amount of solid fish oil. Performance of sows and piglets was monitored during the study. Colostrum and milk samples were obtained after the birth of the first piglet and at weaning, respectively. From all samples (n = 18 per treatment), FAs were quantified by gas chromatography and immunoglobulins and cytokines by ELISA. Three samples per treatment were randomly selected to analyse oxylipin composition by liquid chromatography-tandem mass spectrometry. In colostrum and in milk, the n-3 FA (P = 0.020 and P < 0.001), particularly EPA (P < 0.001 and P < 0.001) and DHA (P < 0.001 and P < 0.001), and also their oxygenated derivatives were increased in samples from sows fed n-3 diet. Fish oil had no effect on immunoglobulin concentrations, but reduced tumour necrosis factor α (TNFα) (P = 0.011) and a tendency to reduce interleukin 10 (IL10) (P = 0.059) were observed in milk. In conclusion, fish oil in sow diets increased n-3 FA, particularly EPA and DHA, and their oxygenated derivatives in colostrum and milk, reducing TNFα and IL10 in milk.

MILK LIPIDS AND SUBCLINICAL MASTITIS

This article deals with the process of obtaining quality raw milk by analyzing its lipid composition. The lipid composition of raw milk depends on many factors, among which, first of all, is the species, the composition of the diet and the physiological state of the breast. In recent years, a large amount of data has accumulated on the fluctuations of certain lipid parameters of milk depending on the type, age, lactation, diet, time of year, exercise, animal husbandry technology, physiological state of the lactating organism in general and breast status in particular. Factors of regulation of fatty acid composition of raw milk: genetically determined parameters of quality and safety; fatty acid composition of the diet; synthesis of fatty acids by microorganisms of the digestive tract; synthesis of fatty acids in the breast; physiological state of the breast. The milk of each species of productive animals has its own specific lipid profile and is used in the formulation of certain dairy products to obtain the planned technological and nutritional parameters. Diagnosis of productive animals for subclinical mastitis involves the use of auxiliary (thermometry, thermography, electrical conductivity) and laboratory research methods: counting the number of somatic cells; use of specialized tests; microbiological studies of milk; biochemical studies of milk. The biochemical component in the diagnosis of subclinical forms of mastitis is underestimated. An increase in body temperature implies an increase in the intensity of heat release during the oxidation of substrates, sometimes due to a decrease in the intensity of synthesis of energy-intensive compounds. There are simply no other sources of energy in the body. The situation is the same with certain parts of the metabolism, which are aimed at the development of protective reactions to the etiological factor aimed at the defeat of the breast. That is why the biochemical composition of breast secretions in the absence of clinical signs of mastitis undergoes biochemical changes and the task of scientists is to develop mechanisms for clear tracking of such changes, identification of animals with subclinical forms of mastitis and effective treatment.

Serum Vitamin D Is Associated with Antioxidant Potential in Peri-Parturient Cows

Dairy cows experience increased oxidative stress during periods of transition such as at the cessation of lactation and around the periparturient period, thus increasing disease risk. Despite routine supplementation of transition cow diets with certain vitamins in an attempt to mitigate oxidative stress, there is no currently available data directly linking vitamin supplementation with antioxidant potential (AOP) in transition cows. The objective of this study was to determine the association between serum vitamins and biomarkers of oxidative stress in healthy cows. Blood samples were collected from 240 cows at dry off (DO), close up (CU), and 2-10 days post-calving (DIM2-10). Blood samples were analyzed for vitamins (A, D, E), β-carotene, reactive oxygen species (ROS), and AOP. Spearman correlations and mixed linear regression models were used to assess associations between vitamins and measures of oxidant status. Vitamin D concentrations were positively associated with AOP at the CU and DIM2-10. Based on the positive association with AOP, additional in-vitro studies were conducted that showed vitamin D mitigated barrier integrity loss in endothelial cells during oxidative stress. These results indicate for the first time that vitamin D may have a role in promoting antioxidant potential in transition dairy cows.

Specialized Pro-Resolving Lipid Mediators in Neonatal Cardiovascular Physiology and Diseases

Cardiovascular disease remains a leading cause of mortality worldwide. Unresolved inflammation plays a critical role in cardiovascular diseases development. Specialized Pro-Resolving Mediators (SPMs), derived from long chain polyunsaturated fatty acids (LCPUFAs), enhances the host defense, by resolving the inflammation and tissue repair. In addition, SPMs also have anti-inflammatory properties. These physiological effects depend on the availability of LCPUFAs precursors and cellular metabolic balance. Most of the studies have focused on the impact of SPMs in adult cardiovascular health and diseases. In this review, we discuss LCPUFAs metabolism, SPMs, and their potential effect on cardiovascular health and diseases primarily focusing in neonates. A better understanding of the role of these SPMs in cardiovascular health and diseases in neonates could lead to the development of novel therapeutic approaches in cardiovascular dysfunction.

Flunixin Meglumine Reduces Milk Isoprostane Concentrations in Holstein Dairy Cattle Suffering from Acute Coliform Mastitis

Dysfunctional inflammation contributes significantly to the pathogenesis of coliform mastitis and the classical pro-inflammatory enzyme cyclooxygenase-2 (COX-2) is the target of medical intervention using the non-steroidal anti-inflammatory drug (NSAID) flunixin meglumine (FM). Inhibition of COX-2 by FM can decrease concentrations of pro-inflammatory fatty acid-based mediators called eicosanoids, providing antipyretic and analgesic effects in dairy cows suffering from coliform mastitis. However, approximately 50% of naturally occurring coliform mastitis with systemic involvement results in death of the animal, even with NSAID treatment. Inadequate antioxidant potential (AOP) to neutralize reactive oxygen species (ROS) produced during excessive inflammation allows for oxidative stress (OS), contributing to tissue damage during coliform mastitis. Biomarkers of lipid peroxidation by ROS, called isoprostanes (IsoP), were used in humans and cattle to quantify the extent of OS. Blood IsoP were shown to be elevated and correlate with oxidant status during acute coliform mastitis. However, the effect of FM treatment on oxidant status and markers of OS has not been established. Blood IsoP concentrations were used to quantify systemic OS, whereas milk was used to assess local OS in the mammary gland. Results indicate that FM treatment had no effect on blood markers of inflammation but reduced the oxidant status index (OSi) by increasing blood AOP from pre- to post-FM treatment. Milk AOP significantly increased from pre- to post-FM treatment, whereas ROS decreased, resulting in a decreased OSi from pre- to post-FM treatment. The only blood IsoP concentration that was significantly different was 5-iso-iPF2α-VI, with a decreased concentration from pre- to post-FM treatment. Conversely, milk 5-iso-iPF2α-VI, 8,12-iso-iPF2α-VI, and total IsoP concentrations were decreased following FM treatment. These results indicated that administration of FM did improve systemic and local oxidant status and reduced local markers of OS. However, differential effects were observed between those animals that survived the infection and those that died, indicating that pre-existing inflammation and oxidant status greatly affect efficacy of FM and may be the key to reducing severity and mortality associated with acute coliform infections. Supplementation to improve AOP and anti-inflammatory mediator production may significantly improve efficacy of FM treatment.

Peripheral markers of oxidative stress in Labrador retrievers with copper-associated hepatitis

OBJECTIVES

To evaluate biomarkers of oxidative stress in dogs with copper-associated hepatitis (CAH) as compared with healthy controls, and to evaluate if these markers correlate with hepatic copper concentrations and hepatic histopathologic features.

MATERIALS AND METHODS

Prospective study. Plasma reactive metabolite concentrations, plasma antioxidant potential, and plasma and urine isoprostane concentrations were determined in Labrador retrievers with copper-associated hepatitis (n=9) as well as in breed- and sex-matched (n=9) and age- and sex-matched (n=9) healthy control populations. Possible correlations between markers of oxidative stress and hepatic histopathological features also were investigated.

RESULTS

Reactive metabolites (median, range) were over twofold greater in dogs with copper-associated hepatitis (87.2 RFU/μL, 60.9 to 185.6 RFU/μL) as compared to breed- and sex-matched (38.2 RFU/μL, 22.4 to 116.8 RFU/μL) and age- and sex-matched controls (32.0 RFU/μL, 18.5 to 127.4 RFU/μL). Antioxidant potential was decreased in copper-associated hepatitis dogs (6.5 TE/μL, 5.1 to 7.7 TE/μL) as compared to breed- and sex-matched controls (8.2 TE/μL, 5.3 to 11.8 TE/μL). Both reactive metabolite concentrations and the reactive metabolite to antioxidant potential ratio were positively correlated with hepatic copper concentrations. Plasma and urine isoprostanes were variable and not significantly different between populations.

CLINICAL SIGNIFICANCE

Labrador retrievers with copper-associated hepatitis have altered oxidant status. Plasma reactive metabolite concentrations and the reactive metabolite to antioxidant potential ratio could be useful biomarkers. However, neither plasma nor urine isoprostanes were useful biomarkers for copper-associated hepatitis.

Activity of sEH and Oxidant Status during Systemic Bovine Coliform Mastitis

Bovine coliform mastitis presents treatment challenges because of systemic inflammation and oxidative stress. Soluble epoxide hydrolase (sEH) is a promising therapeutic target in conditions characterized by inflammation and oxidative stress but has not been evaluated in cattle. We compared sEH activity and oxidant status in healthy Holstein dairy cows to those with systemic coliform mastitis (n = 5/group) using complementary approaches. First, the activity of sEH on [³H]-trans-diphenyl-propene oxide (tDPPO) was assessed ex vivo using tissue homogenates (mammary, liver, and kidney). Second, the concentrations of sEH substrates and metabolites in plasma, milk, and urine were determined as an index of in vivo sEH activity. Oxidant status was assessed in serum and milk. Data were analyzed by non-parametric methods. Metabolism of tDPPO was greater in mammary tissues from cows with coliform mastitis compared to controls. In contrast, ratios of sEH substrates and metabolites predicted lower sEH activity in cows with coliform mastitis than controls. Milk oxidant status showed greater prooxidant levels in coliform mastitis cows. Cows with coliform mastitis exhibit increased sEH activity in mammary tissue; at the same time, milk oxidant status is increased. Future studies should characterize sEH activity and oxidant status patterns and explore therapies targeting sEH during coliform mastitis.

Method optimization of oxylipin hydrolysis in nonprocessed bovine milk indicates that the majority of oxylipins are esterified

The oxidation of polyunsaturated fatty acids produces bioactive primary oxidation products known as oxylipins. In many biological matrices, the majority of oxylipins are bound (i.e. esterified), and a relatively small proportion (<10%) exists in the free form. The present study tested whether this extends to bovine milk following method evaluation of various extraction and base hydrolysis protocols for measuring bound oxylipins. Free (unbound) oxylipins were also measured. Folch extraction followed by sodium carbonate hydrolysis in the presence of methanol containing 0.1% of acetic acid and 0.1% of butylated hydroxytoluene resulted in greater oxylipin concentrations and better surrogate standard recoveries compared to other methods that did not involve Folch extraction or the addition of methanol with hydrolysis base. Sodium hydroxide was better than sodium carbonate in hydrolyzing bound oxylipins under the same conditions. Milk analysis of oxylipins with mass-spectrometry following Folch extraction and sodium hydroxide hydrolysis revealed that 95% of oxylipins in bovine milk were esterified. Most of the detected oxylipins were derived from linoleic acid, which accounted for 92 and 88% of oxylipins in the free and esterified pools, respectively. These results demonstrate that the majority of bovine milk oxylipins are bound, and that linoleic-acid derived metabolites are the most abundant oxylipin species in free and bound lipid pools. Additional studies are needed to understand the role of different oxylipin pools in both calf and human nutrition. PRACTICAL APPLICATION: A method involving Folch lipid extraction and sodium hydroxide hydrolysis was validated for esterified oxylipin measurements in bovine milk. Application of the method revealed that the majority (∼95%) of oxylipins in bovine milk were bound. Linoleic-acid derived oxylipins were the most abundant species in both bound and free milk fractions (88-92%). The results highlight the presence of a new pool of oxidized lipids in milk, potentially involved in modifying its sensory and nutritional properties.

Plasma metabolome alteration in dairy cows with left displaced abomasum before and after surgical correction

Left displaced abomasum (LDA) leads to substantial changes in the metabolism of dairy cows. Surgical correction of LDA can rapidly improve the health of cows; however, changes in metabolism following surgery are rarely described. To investigate the changes of plasma metabolome in cows with LDA before and after surgical correction, blood samples were collected from 10 healthy postpartum cows and 10 cows with LDA on the day of diagnosis, then again from the LDA cows 14 d after surgery. Serum nonesterified fatty acid, β-hydroxybutyric acid, cortisol and histamine concentration, and antioxidant enzyme (superoxide dismutase and glutathione peroxidase) activities were evaluated, and the metabolic profile in plasma was analyzed using ultra-high-performance liquid chromatography time-of-flight mass spectrometry. The results demonstrated that cows with LDA experienced severe negative energy balance and oxidative stress, which can be improved by surgical correction. The metabolic profile was analyzed using multidimensional and univariate statistical analyses, and different metabolites were identified. In total, 102 metabolites differed between cows with LDA and healthy cows. After surgical correction, 65 metabolites changed in cows with LDA, compared with these cows during the LDA event. Following surgical correction, AA levels tended to increase, and lipid levels tended to decrease in cows with LDA. Pathway analysis indicated marked changes in linoleic acid metabolism, Arg biosynthesis, and Gly, Ser, and Thr metabolism in cows at the onset of LDA and following surgical correction. Surgical treatment reversed the changes in AA and lipid metabolism in cows with LDA.

Inhibition of 20-hydroxyeicosatetraenoic acid biosynthesis by vitamin E analogs in human and bovine cytochrome P450 microsomes

Dairy cattle are predisposed to disease around the time of calving due to dysfunctional inflammatory responses. Oxylipids are lipid-derived mediators that regulate all aspects of the inflammatory response, and shifts in oxylipid profiles are correlated with disease risk. For example, 20-hydroxyeicosatetraenoic acid (HETE) is an oxylipid derived from cytochrome P450 enzymes (CYP450) found at significantly greater concentrations around calving and during clinical disease. Biosynthesis of 20-HETE occurs almost exclusively from two specific CYP450 of which CYP450 family four sub-family F member two (CYP4F2) is the major contributor to 20-HETE production in humans. To further study the activities of 20-HETE and potentially reduce its production in vivo, mitigation methods must be explored. Additional substrates of CYP4F2, such as vitamin E, are known to both increase and decrease the metabolism of other CYP4F2 substrates. This study aimed to determine whether vitamin E analogs may reduce the production of 20-HETE through competition for CYP4F2 activity in human CYP4F2, bovine-kidney and bovine-mammary microsomes. Gamma-tocopherol reduced 20-HETE production from human and bovine-kidney microsomes (35.3% and 27.5%, respectively) whereas γ-tocotrienol only reduced 20-HETE production from human microsomes (40.1%). Finally, bovine-mammary microsomes did not produce a quantifiable amount of 20-HETE, suggesting basal mammary CYP4F2 activity may not be a significant contributor to 20-HETE found in milk. Together, these data show that analogs of vitamin E can reduce the production of 20-HETE, potentially through competition with arachidonic acid for metabolism by CYP4F2, posing a potential means for limiting 20-HETE production during clinical diseases of dairy cattle.

Feeding a Saccharomyces cerevisiae fermentation product improves udder health and immune response to a Streptococcus uberis mastitis challenge in mid-lactation dairy cows

Background

We aimed to characterize the protective effects and the molecular mechanisms of action of a Saccharomyces cerevisiae fermentation product (NTK) in response to a mastitis challenge. Eighteen mid-lactation multiparous Holstein cows (n = 9/group) were fed the control diet (CON) or CON supplemented with 19 g/d NTK for 45 d (phase 1, P1) and then infected in the right rear quarter with 2500 CFU of Streptococcus uberis (phase 2, P2). After 36-h, mammary gland and liver biopsies were collected and antibiotic treatment started until the end of P2 (9 d post challenge). Cows were then followed until day 75 (phase 3, P3). Milk yield (MY) and dry matter intake (DMI) were recorded daily. Milk samples for somatic cell score were collected, and rectal and udder temperature, heart and respiration rate were recorded during the challenge period (P2) together with blood samples for metabolite and immune function analyses. Data were analyzed by phase using the PROC MIXED procedure in SAS. Biopsies were used for transcriptomic analysis via RNA-sequencing, followed by pathway analysis.

Results

DMI and MY were not affected by diet in P1, but an interaction with time was recorded in P2 indicating a better recovery from the challenge in NTK compared with CON. NTK reduced rectal temperature, somatic cell score, and temperature of the infected quarter during the challenge. Transcriptome data supported these findings, as NTK supplementation upregulated mammary genes related to immune cell antibacterial function (e.g., CATHL4, NOS2), epithelial tissue protection (e.g. IL17C), and anti-inflammatory activity (e.g., ATF3, BAG3, IER3, G-CSF, GRO1, ZFAND2A). Pathway analysis indicated upregulation of tumor necrosis factor α, heat shock protein response, and p21 related pathways in the response to mastitis in NTK cows. Other pathways for detoxification and cytoprotection functions along with the tight junction pathway were also upregulated in NTK-fed cows.

Conclusions

Overall, results highlighted molecular networks involved in the protective effect of NTK prophylactic supplementation on udder health during a subclinical mastitic event.

Supplementary Information

The online version contains supplementary material available at 10.1186/s40104-021-00560-8.

Isoprostanes in Veterinary Medicine: Beyond a Biomarker

Oxidative stress has been associated with many pathologies, in both human and animal medicine. Damage to tissue components such as lipids is a defining feature of oxidative stress and can lead to the generation of many oxidized products, including isoprostanes (IsoP). First recognized in the early 1990s, IsoP are formed in numerous biological fluids and tissues, chemically stable, and easily measured by noninvasive means. Additionally, IsoP are highly specific indicators of lipid peroxidation and thereby are regarded as excellent biomarkers of oxidative stress. Although there have been many advancements in the detection and use of IsoP as a biomarker, there is still a paucity of knowledge regarding the biological activity of these molecules and their potential roles in pathology of oxidative stress. Furthermore, the use of IsoP has been limited in veterinary species thus far and represents an avenue of opportunity for clinical applications in veterinary practice. Examples of clinical applications of IsoP in veterinary medicine include use as a novel biomarker to guide treatment recommendations or as a target to mitigate inflammatory processes. This review will discuss the history, biosynthesis, measurement, use as a biomarker, and biological action of IsoP, particularly in the context of veterinary medicine.

Invited review: Cytochrome P450 enzyme involvement in health and inflammatory-based diseases of dairy cattle

Dairy cattle are at the greatest risk of developing diseases around the time of calving because of compromised immune responses and the occurrence of oxidative stress. Both the development of compromised immunity and oxidative stress are influenced directly or indirectly by the metabolism of polyunsaturated fatty acids (PUFA) and fat-soluble vitamins. The cytochrome P450 (CYP450) family of enzymes is central to the metabolism of both classes of these compounds, but to date, the importance of CYP450 in the health of dairy cattle is underappreciated. As certain CYP450 isoforms metabolize both PUFA and fat-soluble vitamins, potential interactions may occur between PUFA and fat-soluble vitamins that are largely unexplored. For example, one CYP450 that generates anti-inflammatory oxylipids from arachidonic acid additionally contributes to the activation of vitamin D. Other potential substrate interactions between PUFA and vitamins A and E may exist as well. The intersection of PUFA and fat-soluble vitamin metabolism by CYP450 suggest that this enzyme system could provide an understanding of how immune function and oxidant status interconnect, resulting in increased postpartum disease occurrence. This review will detail the known contributions of bovine CYP450 to the regulation of oxylipids with a focus on enzymes that may also be involved in the metabolism of fat-soluble vitamins A, D, and E that contribute to antioxidant defenses. Although the activity of specific CYP450 is generally conserved among mammals, important differences exist in cattle, such as the isoforms primarily responsible for activation of vitamin D that makes their specific study in cattle of great importance. Additionally, a CYP450-driven inflammatory positive feedback loop is proposed, which may contribute to the dysfunctional inflammatory responses commonly found during the transition period. Establishing the individual enzyme isoform contributions to oxylipid biosynthesis and the regulation of vitamins A, D, and E may reveal how the CYP450 family of enzymes can affect inflammatory responses during times of increased susceptibility to disease. Determining the potential effect of each CYP450 on disease susceptibility or pathogenesis may allow for the targeted manipulation of the CYP450 pathways to influence specific immune responses and antioxidant defenses during times of increased risk for health disorders.

Analysis of oxylipins to differentiate between organic and conventional UHT milks

Nowadays, there is a strong interest in analytical approaches for assessing organic farming practices. Here, we propose that oxylipins, a group of oxidised metabolites derived from various polyunsaturated fatty acids, could be promising biomarkers for organic milk assessment because their biosynthesis is modulated by both precursor fatty acid availability and physiological or pathological status. Thus, we determined 31 fatty acids, 53 triacylglycerols and 37 oxylipins in one hundred commercial UHT milks by chromatographic methods coupled to mass spectrometry. Of these, 52 milks were conventional (34 whole milk, 11 semi-skimmed milk and 7 skimmed milk) and 48 were organic (31 whole milk, 11 semi-skimmed milk and 6 skimmed milk). Several oxylipins (8-HEPE, 5-HEPE, 11-HEPE, 9-HEPE, 18-HEPE, 9-HOTrE, 13-HOTrE, 12,13-DiHODE and 15,16-DiHODE) could distinguish between organic and conventional milks. Within these oxylipins, arachidonic and linoleic acid derived do not correlate with their fatty acid precursors; therefore these oxylipins could be promising as not only diet-dependent biomarkers for organic milk assessment.

Colostrum supplementation with n-3 fatty acids alters plasma polyunsaturated fatty acids and inflammatory mediators in newborn calves

Calves may experience increased oxidative stress at birth through activation of metabolic and respiratory processes. Reducing oxidative stress may enhance calf viability in early life. Our objective was to determine the dose response to fish and flaxseed oil when supplemented in colostrum on concentrations of plasma fatty acid (FA), FA metabolites, and index of oxidative stress during the critical first week of life in calves to understand how supplementing n-3 FA may decrease oxidative stress. We hypothesized that n-3 FA supplemented in colostrum in a linear dose-dependent fashion would associate with increased plasma n-3 FA concentrations and decreased oxidative stress. Twenty-four male and female Holstein calves were randomly assigned to receive 0, 30, 60, or 120 mL of a 1:1 fish to flaxseed oil supplement in colostrum. All calves received 2.8 L of previously frozen colostrum (≥22% Brix) with their respective treatment within 6 h after birth. Blood was sampled before first feeding after birth and on d 1, 2, 4, 7, and 14 d of age to assess oxidant status and plasma free PUFA, phospholipid FA, and oxylipid concentrations. Health indicators were observed daily. Indicators of general health and growth were unaffected by treatment. Supplemented calves exhibited greater concentrations of n-3 FA in plasma as free and phospholipid FA and some n-3 and n-6 FA-derived oxylipids in the first week of life in a linear fashion with increasing supplemental dose. Fish and flaxseed oil treatments did not alter oxidant status but overall decreased isoprostane concentrations in plasma, indicating oxidative stress was decreased. Together, these responses indicate that the fish and flaxseed oil supplement was antiinflammatory. In conclusion, supplementing colostrum with 30, 60, and 120 mL of a 1:1 mixture of fish and flaxseed oil linearly increased plasma concentrations of n-3 FA and metabolites and decreased biomarkers of oxidative stress, but did not alter oxidant status or affect health or growth. Our findings suggest neonatal calves may benefit from n-3 FA supplementation in colostrum to encourage a greater antiinflammatory state.

Mass spectrometry-based determination of lipids and small molecules composing adipose tissue with a focus on brown adipose tissue

Adipose tissue has been the subject of research for a very long time. Many studies perform a comprehensive analysis of different types of adipose tissue with an emphasis on brown adipose tissue. Mass spectrometry-based approaches are particularly useful in the exploration not only of the metabolic composition of adipose tissue but also its function. In the presented review, a complex and critical overview of publications devoted to the analysis of adipose tissue by means of mass spectrometry was performed. Detailed investigation of analytical aspects related to either untargeted or targeted analysis of adipose tissue was performed, leading to the formation of a collection of hints at the available analytical methods. Moreover, a profound analysis of the metabolic composition of brown adipose tissue was performed. Brown adipose tissue metabolome was characterized on structural and functional levels, providing information about its exact metabolic composition but also connecting these molecules and placing them into biochemical pathways. All our work resulted in a very broad picture of the analysis of adipose tissue, starting from the analytical aspects and finishing on the current knowledge about its composition.

Selection of Potent Inhibitors of Soluble Epoxide Hydrolase for Usage in Veterinary Medicine

The veterinary pharmacopeia available to treat pain and inflammation is limited in number, target of action and efficacy. Inhibitors of soluble epoxide hydrolase (sEH) are a new class of anti-inflammatory, pro-resolving and analgesic drugs being tested in humans that have demonstrated efficacy in laboratory animals. They block the hydrolysis, and thus, increase endogenous concentrations of analgesic and anti-inflammatory signaling molecules called epoxy-fatty acids. Here, we screened a library of 2,300 inhibitors of the sEH human against partially purified feline, canine and equine hepatic sEH to identify inhibitors that are broadly potent among species. Six very potent sEH inhibitors (IC50 < 1 nM for each enzyme tested) were identified. Their microsomal stability was then measured in hepatic extracts from cat, dog and horse, as well as their solubility in solvents suitable for the formulation of drugs. The trans-4-{4-[3-(4-trifluoromethoxy-phenyl)-ureido]-cyclohexyloxy}-benzoic acid (t-TUCB, 1,728) appears to be the best compromise between stability and potency across species. Thus, it was selected for further testing in veterinary clinical trials of pain and inflammation in animals.

Postpartum meloxicam administration alters plasma haptoglobin, polyunsaturated fatty acid, and oxylipid concentrations in postpartum ewes

Background

Postpartum inflammation is a natural and necessary response; however, a dysfunctional inflammatory response can be detrimental to animal productivity. The objective of this study was to determine the effects of a non-steroidal anti-inflammatory drug (meloxicam) on ewe postpartum inflammatory response, ewe plasma polyunsaturated fatty acid and oxylipid concentrations, and lamb growth.

Results

After lambing, 36 Hampshire and Hampshire × Suffolk ewes were sequentially assigned within type of birth to control (n = 17) or meloxicam orally administered on d 1 and 4 of lactation (MEL; 90 mg, n = 19). Milk and blood samples were collected on d 1 (prior to treatment) and d 4. Milk glucose-6-phosphate was not affected by MEL. Plasma haptoglobin (Hp) concentrations were less for MEL ewes; control ewes with greater d 1 Hp concentrations had elevated Hp on d 4, but this was not the case for MEL-treated ewes. Treatment with MEL increased plasma arachidonic acid concentration by more than 4-fold in ewes rearing singles but decreased concentrations of 9,10-dihydroxyoctadecenoic acid, prostaglandin F_2α, 8-iso-prostaglandin E₂, and 8,9-dihydroxyeicosatetraenoic acid. Nine oxylipids in plasma had interactions of treatment with d 1 Hp concentration, all of which revealed positive associations between d 1 Hp and d 4 oxylipid concentrations for CON, but neutral or negative relationships for MEL. MEL decreased 13-hydroxyoctadecadienoic acid:13-oxooctadecadienoic acid ratio and tended to increase 9-hydroxyoctadecadienoic acid:9-oxooctadecadienoic acid ratio (both dependent on d 1 values), indicating progressive metabolism of linoleic acid-derived oxylipids occurred by enzymatic oxidation after MEL treatment. Meloxicam reduced oxylipids generated across oxygenation pathways, potentially due to an improved redox state.

Conclusions

Postpartum MEL treatment of ewes decreased plasma concentrations of Hp and several oxylipids, with the greatest impact in ewes with biomarkers reflecting a greater inflammatory state before treatment. Anti-inflammatory strategies may help resolve excessive postpartum inflammation in some dams.

Review: Following the smoke signals: inflammatory signaling in metabolic homeostasis and homeorhesis in dairy cattle

Inflammatory cascades are a critical component of the immune response to infection or tissue damage, involving an array of signals, including water-soluble metabolites, lipid mediators and several classes of proteins. Early investigation of these signaling pathways focused largely on immune cells and acute disease models. However, more recent findings have highlighted critical roles of both immune cells and inflammatory mediators on tissue remodeling and metabolic homeostasis in healthy animals. In dairy cattle, inflammatory signals in various tissues and in circulation change rapidly and dramatically, starting just prior to and at the onset of lactation. Furthermore, several observations in healthy cows point to homeostatic control of inflammatory tone, which we define as a regulatory process to balance immune tolerance with activation to keep downstream effects under control. Recent evidence suggests that peripartum inflammatory changes influence whole-body nutrient flux of dairy cows over the course of days and months. Inflammatory mediators can suppress appetite, even at levels that do not induce acute responses (e.g. fever), thereby decreasing nutrient availability. On the other hand, inhibition of inflammatory signaling with non-steroidal anti-inflammatory drug (NSAID) treatment suppresses hepatic gluconeogenesis, leading to hypoglycemia in some cases. Over the long term, though, peripartum NSAID treatment substantially increases peak and whole-lactation milk synthesis by multiparous cows. Inflammatory regulation of nutrient flux may provide a homeorhetic mechanism to aid cows in adapting to rapid changes in metabolic demand at the onset of lactation, but excessive systemic inflammation has negative effects on metabolic homeostasis through inhibition of appetite and promotion of immune cell activity. Thus, in this review, we provide perspectives on the overlapping regulation of immune responses and metabolism by inflammatory mediators, which may provide a mechanistic underpinning for links between infectious and metabolic diseases in transition dairy cows. Moreover, we point to novel approaches to the management of this challenging phase of the production cycle.

Colostrum supplementation with n-3 fatty acids and α-tocopherol alters plasma polyunsaturated fatty acid profile and decreases an indicator of oxidative stress in newborn calves

Our objective was to characterize the effects of supplementing newborn calves with n-3 fatty acids (FA) and α-tocopherol on blood lipid profiles and oxidant status in early life. Sixteen calves received 0 or 60 mL of 1:1 fish and flaxseed oil with 200 mg of α-tocopherol in 2.8 L of colostrum within 6 h after birth. Colostrum was >22% on the Brix scale. Blood was sampled on d 1, 2, 4, 7, 14, and 21 after birth for assessment of plasma polyunsaturated FA, α-tocopherol, total serum protein, and oxidant status index, an indirect indicator of oxidative stress that examines the balance between the concentration of reactive oxygen and nitrogen species and antioxidant capacity in serum. Health was observed daily. Weight and hip height were recorded at birth, 3 wk, and 8 wk. Data were analyzed with a Mixed procedure of SAS 9.4 (SAS Institute Inc., Cary, NC). Treatment did not alter concentration of total protein in blood serum, prevalence of diarrhea or other signs of disease, or rate of growth. Feeding n-3 FA and α-tocopherol increased plasma concentrations of the n-3 FA, including α-linolenic, eicosapentaenoic, and docosahexaenoic acids, with a concomitant decrease in oxidant status index during the first week of life. Concentrations of α-tocopherol decreased with supplementation, but all calves maintained adequate concentrations. Oxidant status index of treated calves returned to the level of control calves by d 14. We conclude that a colostrum supplement of n-3 FA and α-tocopherol is safe to administer to newborn calves, reduces oxidant status in the first week of life, and may improve health and performance.

20-hydroxyeicosatetraenoic acid alters endothelial cell barrier integrity independent of oxidative stress and cell death

Unregulated inflammation during bovine mastitis is characterized by severe mammary tissue damage with systemic involvement. Vascular dysfunction underlies tissue pathology because of concurrent oxidative stress mediated by several inflammatory mediators. We recently demonstrated increased production of 20-hydroxyeicosatetraenoic acid (20-HETE), a cytochrome P450-derived (CYP) oxylipid that correlated with oxidative stress during severe bovine coliform mastitis. The hypothesis for this study was that 20-HETE-induced oxidative stress disrupts barrier function of endothelial cells. Primary endothelial cells from the bovine aorta were utilized to investigate the effects of 20-HETE on barrier integrity in an in-vitro model of oxidative stress. The effects of various antioxidants on modulating the 20-HETE barrier integrity effects also were investigated. Our results showed that 20-HETE decreased endothelial barrier integrity, which was associated with increased reactive metabolite production and decreased total glutathione. The antioxidant, vitamin E, partially delayed the loss of endothelial resistance upon exposure to 20-HETE but did not prevent complete loss of barrier integrity. The decrease in barrier resistance due to 20-HETE was neither associated with oxidative stress as assessed by oxidative protein or lipid damage nor endothelial cell apoptosis; however, selenium supplementation conferred resistance to loss of barrier integrity suggesting a role for shifts in redox status. Specific mechanisms by which 20-HETE alters vascular barrier integrity require further investigation to identify targets for therapy during inflammatory conditions with enhanced CYP450 activity.

Effects of industrial heat treatments on bovine milk oxylipins and conventional markers of lipid oxidation

The effects of industrial heat treatments of raw bovine milk subjected to Batch Pasteurization (BP), High Temperature Short Time (HTST) and Ultra High Temperature (UHT) on the formation of primary (hydroperoxide content and oxylipins) and secondary lipid oxidation products (thiobarbituric acid reactive species -TBARS) were evaluated. Total fatty acid content, percent of free fatty acids (FFA), and total antioxidant capacity (TAC) were also measured. Except for a 30% reduction in capric acid (C10:0) after UHT compared to BP, no significant differences in total fatty acid concentrations were detected amongst the heat treatments. Compared to raw bovine milk, no statistically significant effects of heat treatment were observed on percent FFA (0.29-0.31%), hydroperoxide concentration (0.0558-0.0624 mmol L^-1), and TBARS values (13.4-18.9 µg MDA kg^-1). HTST and UHT led to significant reductions (50-65%) in linoleic and alpha-linolenic acid oxidized metabolites compared with raw milk and batch pasteurized milk. Compared to raw milk (2943.7 μmol of TEAC L^-1), TAC was significantly reduced by all heat treatments (2245 - 2393 μmol of TEAC L^-1), although no statistically significant differences were observed amongst the treatments. The results demonstrate that heat processing reduces milk oxylipin content and antioxidant capacity and that oxylipin and TAC measurements provide a new sensitive approach to assess the impact of milk processing on lipid oxidation. The nutritional, shelf life and sensory implications of reduced oxylipins in HTST and UHT processed bovine milk merit further investigation.

Widespread basal cytochrome P450 expression in extrahepatic bovine tissues and isolated cells

Periparturient cattle face increased risk of both metabolic and infectious diseases. Factors contributing to this predisposition include oxidized polyunsaturated fatty acids, also known as oxylipids, whose production is altered during the periparturient period and in diseased cattle. Alterations in the production of oxylipids derived from cytochrome P450 (CYP450) enzymes are over-represented during times of increased disease risk and clinical disease, such as mastitis. Many of these same CYP450 enzymes additionally regulate metabolism of fat-soluble vitamins, such as A, D, and E. These vitamins are essential to maintaining immune health, yet circulating concentrations are diminished near calving. Despite this, a relatively small amount of research has focused on the roles of CYP450 enzymes outside of the liver. The aim of this paper is to describe the relative gene expression of 11 CYP450 in bovine tissues and common in vitro bovine cell models. Eight tissue samples were collected from 3 healthy dairy cows after euthanasia. In vitro samples included primary bovine aortic and mammary endothelial cells and immortalized bovine kidney and mammary epithelial cells. Quantitative real-time-PCR was carried out to assess basal transcript expression of CYP450 enzymes. Surprisingly, CYP450 mRNA was widely expressed in all tissue samples, with predominance in the liver. In vitro CYP450 expression was less robust, with several cell types lacking expression of specific CYP450 enzymes altogether. Overall, cell culture models did not reflect expression of tissue CYP450. However, when CYP450 were organized by activity, certain cell types consistently expressed specific functional groups. These data reveal the widespread expression of CYP450 in individual organs of healthy dairy cows. Widespread expression helps to explain previous evidence of significant changes in CYP450-mediated oxylipid production and fat-soluble vitamin metabolism in organ microenvironments during periods of oxidative stress or disease. As such, these data provide a foundation for targeted functional experiments aimed at understanding the activities of specific CYP450 and associated therapeutic potential during times of increased disease risk.

Arachidonic acid-derived hydroxyeicosatetraenoic acids are positively associated with colon polyps in adult males: a cross-sectional study

Oxylipids are potent lipid mediators associated with inflammation-induced colon carcinomas and colon tumor survival. Therefore, oxylipid profiles may be useful as novel biomarkers of colon polyp presence. The aim of this study was to investigate the relationship between plasma non-esterified oxylipids and the presence of colon polyps. A total of 123 Caucasian men, ages 48 to 65, were categorized into three groups: those with no polyps, those with one or more hyperplastic polyps, and those with one or more adenomas. Plasma non-esterified oxylipids were analyzed using solid phase extraction and quantified using a targeted HPLC tandem mass spectrometric analysis. Statistical analyses included Kruskal-Wallis one-way ANOVA with Dunn's test for multiple comparison and generalized linear models to adjust for confounding factors such as age, anthropometrics, and smoking status. In general, monohydroxy omega-6-derived oxylipids were significantly increased in those with polyps. Concentrations of 5-hydroxyeicosatetraenoic acid (HETE) and 11-HETE were significantly higher in those with hyperplastic polyps and adenomas compared to those with no polyps. Arachidonic acid-derived HETEs were significantly associated with colon polyp types, even after adjusting for age, smoking, and body mass index or waist circumference in regression models. Since many of these oxylipids are formed through oxygenation by lipoxygenases (i.e., 5-, 12-, and 15-HETE, and 15- hydroxyeicosatrienoic acid [HETrE]) or auto-oxidative reactions (i.e., 11-HETE), this may indicate that lipoxygenase activity and lipid peroxidation are increased in those with colon polyps. In addition, since oxylipids such as 5-, 12-, and 15-HETE are signaling molecules involved in inflammation regulation, these oxylipids may have important functions in inflammation-associated polyp presence. Future studies should be performed in a larger cohorts to investigate if these oxylipids are useful as potential biomarkers of colon polyps.

Omega-3 fatty acids and docosahexaenoic acid oxymetabolites modulate the inflammatory response of equine recombinant interleukin1β-stimulated equine synoviocytes

Omega-3 fatty acid (n-3 PUFA) supplementation may have beneficial effects in certain chronic diseases, potentially including osteoarthritis. Favorable effects are attributed, in part, to downstream pro-resolving oxylipid metabolites. We investigated the role of n-3 PUFA and docosahexaenoic acid (DHA)-derived oxylipids (docosanoids) on equine synoviocyte metabolism. We hypothesized that n-3 PUFA and selected docosanoids would modulate inflammatory mediator gene expression by recombinant equine (re)IL-1β-stimulated synovial fibroblasts. Synoviocyte monolayer cultures were prepared from grossly normal equine carpal synovium. Cellular incorporation of eicosapentaenoic acid (EPA) and DHA was determined using LC-MS and docosanoid biosynthesis by LC-MS-MS. The influence of n-3 PUFA and docosanoids on osteoarthritis marker gene expression was determined by quantitative real time polymerase chain reaction (qPCR). Synoviocytes incorporated EPA and DHA in significant amounts and DHA treatment augmented the synthesis of several docosanoids. Synoviocyte cultures pre-treated with EPA or DHA followed by reIL-1β stimulation had significant reductions in expression of ADAMTS4, MMP-1, MMP-13, IL-1β, IL-6 and COX-2. The docosanoids resolvin D1 and D2, maresin 1 and protectin DX, alone and in combination, abrogated ADAMTS4, MMP-1, MMP-13, and IL-6 gene expression in reIL-1β-stimulated synoviocytes. Similarly, both resolvins and maresin 1 stifled COX-2 expression. Our results demonstrate that synoviocytes readily incorporate n-3 PUFA. DHA incorporation was sufficient for biosynthesis of significant concentrations of several docosanoids which modulated the synovial inflammatory response in vitro. These data indicate n-3 PUFA supplementation may prove useful in the prevention or treatment of osteoarthritis.

Plasma metabolite changes in dairy cows during parturition identified using untargeted metabolomics

The metabolic responses of cows undergo substantial changes during the transition from late pregnancy to early lactation. However, the molecular mechanisms associated with these changes in physiological metabolism have not been clearly elucidated. The objective of this study was to investigate metabolic changes in transition cows from the perspective of plasma metabolites. Plasma samples collected from 24 multiparous dairy cows on approximately d 21 prepartum and immediately postpartum were analyzed using ultra-high-performance liquid chromatography/time-of-flight mass spectrometry in positive and negative ion modes. In conjunction with multidimensional statistical methods (principal component analysis and orthogonal partial least squares discriminant analysis), differences in plasma metabolites were identified using the t-test and fold change analysis. Sixty-seven differential metabolites were identified consisting of AA, lipids, saccharides, and nucleotides. The levels of 32 plasma metabolites were significantly higher and those of 35 metabolites significantly lower after parturition than on d 21 prepartum. Pathway analysis indicated that the metabolites that increased from late pregnancy to early lactation were primarily involved in lipid metabolism and energy metabolism, whereas decreased metabolites were related to AA metabolism.

Production of 15-F2t-isoprostane as an assessment of oxidative stress in dairy cows at different stages of lactation

Oxidative stress contributes to dysfunctional immune responses and predisposes dairy cattle to several metabolic and inflammatory-based diseases. Although the negative effects of oxidative stress on transition cattle are well established, biomarkers that accurately measure oxidative damage to cellular macromolecules are not well defined in veterinary medicine. Measuring 15-F_2t-isoprostane, a lipid peroxidation product, is the gold standard biomarker for quantifying oxidative stress in human medicine. The aim of our study was to determine whether changes in 15-F_2t-isoprostane concentrations in plasma and milk could accurately reflect changes in oxidant status during different stages of lactation. Using liquid chromatography-tandem mass spectrometry, 15-F_2t-isoprostane concentrations were quantified in milk and plasma of 12 multiparous Holstein-Friesian cows that were assigned to 3 different sampling periods, including the periparturient period (1-2 d in milk; n = 4), mid lactation (80-84 d in milk; n = 4), and late lactation (183-215 d in milk; n = 4). Blood samples also were analyzed for indicators of oxidant status, inflammation, and negative energy balance. Our data revealed that 15-F_2t-isoprostane concentrations changed at different stages of lactation and coincided with changes in other gauges of oxidant status in both plasma and milk. Interestingly, milk 15-F_2t-isoprostane concentrations and other indices of oxidant status did not follow the same trends as plasma values at each stage of lactation. Indeed, during the periparturient period, systemic 15-F_2t-isoprostane increased significantly accompanied by an increase in the systemic oxidant status index. Milk 15-F_2t-isoprostane was significantly decreased during the periparturient period compared with other lactation stages in conjunction with a milk oxidant status index that trended lower during this period. The results from this study indicate that changes in 15-F_2t-isoprostane concentrations in both milk and plasma may be strong indicators of an alteration in redox status both systemically and within the mammary gland.

Docosahexaenoic acid-derived oxidized lipid metabolites modulate the inflammatory response of lipolysaccharide-stimulated macrophages

Docosahexaenoic acid (DHA) supplementation has demonstrated beneficial effects in a number of inflammatory diseases. Increasingly, important contributions to its favorable effects are attributed downstream metabolites called docosanoids. Herein, we investigated the role of DHA-derived oxidized lipid metabolites on inflammatory mediator expression by RAW 264.7 murine macrophages. Specifically, macrophage incorporation of DHA, and the resultant biosynthesis of selected pro-resolving docosanoids was quantified. Docosanoid effects on the expression of selected pro-inflammatory cytokines in LPS-stimulated cultures was determined. Macrophages incorporated DHA in significant amounts. In the presence of DHA macrophages produced statistically significant amounts of several putative pro-resolving docosanoids compared to untreated controls. Among them, resolvins D1 and D2 and maresin 1 abrogated COX-2 and IL-1β gene expression in LPS-stimulated macrophages. In addition to these mediators, protectin DX inhibited LPS-stimulated macrophage expression of IL-6. Our results demonstrate that macrophages incorporate DHA in quantities sufficient for the biosynthesis of biologically-relevant concentrations of a number of pro-resolving docosanoids, certain of which modulate the inflammatory response of macrophages under conditions mimicking acute inflammation. These data provide further information on the mechanism(s) by which DHA exerts salutary effects on the inflammatory response of macrophages.

Periparturient lipolysis and oxylipid biosynthesis in bovine adipose tissues

The periparturient period of dairy cows is characterized by intense lipolysis in adipose tissues (AT), which induces the release of free fatty acids (FFA) into circulation. Among FFA, polyunsaturated fatty acids are susceptible to oxidation and can modulate inflammatory responses during lipolysis within AT. Linoleic and arachidonic acid oxidized products (oxylipids) such as hydroxy-octadecadienoic acids (HODE) and hydroxy-eicosatetraenoic acids (HETE), were recently identified as products of lipolysis that could modulate AT inflammation during lipolysis. However, the effect of lipolysis intensity during the transition from gestation to lactation on fatty acid substrate availability and subsequent AT oxylipid biosynthesis is currently unknown. We hypothesized that in periparturient dairy cows, alterations in AT and plasma fatty acids and oxylipid profiles coincide with changes in lipolysis intensity and stage of lactation. Blood and subcutaneous AT samples were collected from periparturient cows at -27±7 (G1) and -10±5 (G2) d prepartum and at 8±3 d postpartum (PP). Targeted lipidomic analysis was performed on plasma and AT using HPLC-MS/MS. We report that FFA concentrations increased as parturition approached and were highest at PP. Cows exhibiting high lipolysis rate at PP (FFA>1.0 mEq/L) had higher body condition scores at G1 compared to cows with low lipolysis rate (FFA<1.0 mEq/L). Concentrations of plasma linoleic and arachidonic acids were increased at PP. In AT, 13-HODE, and 5-, 11- and 15-HETE were increased at PP compared to G1 and G2. Concentrations of beta hydroxybutyrate were positively correlated with those of 13-HODE and 15-HETE in AT. Plasma concentrations of 5- and 20-HETE were increased at PP. These data demonstrate that prepartum adiposity predisposes cows to intense lipolysis post-partum and may exacerbate AT inflammation because of increased production of pro-inflammatory oxylipids including 5- and 15-HETE and 13-HODE. These results support a role for certain linoleic and arachidonic acid-derived oxylipids as positive and negative modulators of AT inflammation during periparturient lipolysis.

Role of lipid mediators in the regulation of oxidative stress and inflammatory responses in dairy cattle

Periparturient dairy cows experience an increased incidence and severity of several inflammatory-based diseases such as mastitis and metritis. Factors associated with the physiological adaptation to the onset of lactation can impact the efficiency of the inflammatory response at a time when it is most needed to eliminate infectious pathogens that cause these economically important diseases. Oxidative stress, for example, occurs when there is an imbalance between the production of oxygen radicals during periods of high metabolic demand and the reduced capabilities of the host's antioxidant defenses. The progressive development of oxidative stress in early lactation cows is thought to be a significant underlying factor leading to dysfunctional inflammatory responses. Reactive oxygen species (ROS) are also produced by leukocytes during inflammation resulting in positive feedback loops that can further escalate oxidative stress during the periparturient period. During oxidative stress, ROS can modify polyunsaturated fatty acids (PUFA) associated with cellular membranes, resulting in the biosynthesis of oxidized products called oxylipids. Depending on the PUFA substrate and oxidation pathway, oxylipids have the capacity of either enhancing or resolving inflammation. In mediating their effects, oxylipids can directly or indirectly target sites of ROS production and thus control the degree of oxidative stress. This review discusses the evidence supporting the roles of oxylipids in the regulation of oxidative stress and the subsequent development of uncontrolled inflammatory responses. Further, the utility of some of the oxylipids as oxidative stress markers that can be exploited in developing and monitoring therapies for inflammatory-based diseases in dairy cattle is discussed. Understanding of the link between some oxylipids and the development or resolution of oxidative stress could provide novel therapeutic targets to limit immunopathology, reduce antibiotic usage, and optimize the resolution of inflammatory-based diseases in periparturient dairy cows.

Differences in the Oxylipid Profiles of Bovine Milk and Plasma at Different Stages of Lactation

Mastitis is caused by a bacterial infection of the mammary gland, which reduces both milk quality and quantity produced for human consumption. The incidence and severity of bovine mastitis are greatest during the periparturient period that results from dysfunctional inflammatory responses and causes damage to milk synthesizing tissues. Oxylipids are potent fatty acid-derived mediators that control the onset and resolution of the inflammatory response. The purpose of this study was to investigate how oxylipid profiles change in bovine milk at different stages of the lactation cycle. Results showed significantly lower concentrations of both milk polyunsaturated fatty acid content and total oxylipid biosynthesis during early lactation when compared to mid- or late-lactation. The only oxylipid that was higher during early lactation was 20-hydroxyeicosatetraenoic acid (HETE), which is often associated with inflammatory-based diseases. Milk oxylipid profiles during the different stages of lactation differed from plasma profiles. As such, plasma fatty acid and oxylipid concentrations are not a proxy for local changes in the mammary gland during the lactation cycle.