William Raphael

Significance of Metabolic Stress, Lipid Mobilization, and Inflammation on Transition Cow Disorders

The incidence and severity of disease in cows is greatest during the transition period, when immune functions are impaired. Intense lipid mobilization is associated with both metabolic and infectious diseases in the transition cow. Significant increases in plasma nonesterified fatty acids contribute to oxidative stress and uncontrolled inflammatory responses. A dysfunctional inflammatory response is the common link between metabolic and infectious diseases around the time of calving. Intervention strategies that can reduce lipid mobilization may improve inflammatory responses and reduce the economic losses associated with health disorders during the transition period.

Dietary Polyunsaturated Fatty Acids and Inflammation: The Role of Phospholipid Biosynthesis

The composition of fatty acids in the diets of both human and domestic animal species can regulate inflammation through the biosynthesis of potent lipid mediators. The substrates for lipid mediator biosynthesis are derived primarily from membrane phospholipids and reflect dietary fatty acid intake. Inflammation can be exacerbated with intake of certain dietary fatty acids, such as some ω-6 polyunsaturated fatty acids (PUFA), and subsequent incorporation into membrane phospholipids. Inflammation, however, can be resolved with ingestion of other fatty acids, such as ω-3 PUFA. The influence of dietary PUFA on phospholipid composition is influenced by factors that control phospholipid biosynthesis within cellular membranes, such as preferential incorporation of some fatty acids, competition between newly ingested PUFA and fatty acids released from stores such as adipose, and the impacts of carbohydrate metabolism and physiological state. The objective of this review is to explain these factors as potential obstacles to manipulating PUFA composition of tissue phospholipids by specific dietary fatty acids. A better understanding of the factors that influence how dietary fatty acids can be incorporated into phospholipids may lead to nutritional intervention strategies that optimize health.

Effects of cloprostenol sodium at final prostaglandin F2α of Ovsynch on complete luteolysis and pregnancy per artificial insemination in lactating dairy cows

Luteolysis is a key event in Ovsynch programs of lactating dairy cows. Studies indicate that as many as 20% of cows treated with a Presynch/Ovsynch program have delayed or incomplete luteolysis using dinoprost tromethamine. Cows must have complete luteolysis to have a chance to become pregnant. Dinoprost tromethamine has a short half-life of approximately 7 to 8min. Cloprostenol sodium is more resistant to endogenous metabolism and is maintained in circulation for a longer time (half-life=3h). The objective was to determine if cloprostenol sodium could increase the percentage of cows with complete luteolysis and subsequent pregnancy per artificial insemination (P/AI) in lactating dairy cows compared with dinoprost tromethamine when administered within a presynchronization plus Ovsynch program for first artificial insemination (n=652) and an Ovsynch resynchronization program for second or later AI (second+; n=394). Blood samples were collected daily for 5 d beginning at the PGF(2α) of Ovsynch in a subset of cows (n=680) for first and second+ AI to measure circulating concentrations of progesterone (P(4)) and estradiol (E(2)). Complete luteolysis was defined as cows with functional corpus luteum (CL) at time of treatment and serum concentrations of P(4) <0.5 ng/mL at 56, 72, and 96 h after treatment. Percentage of cows with functional CL that had complete luteolysis after treatment was not greater for cloprostenol sodium compared with dinoprost tromethamine in first (79 vs. 80%, respectively) or second+ AI (70 vs. 72%, respectively). In addition, mean serum concentrations of P(4) were not less for cows treated with cloprostenol sodium following treatment. Pregnancy per AI of cows treated with cloprostenol sodium tended to be greater than dinoprost tromethamine for first (40 vs. 35%; respectively) but not second+ AI (23 vs. 21%, respectively). Cows with greater serum P(4) concentrations at time of PGF(2α) of Ovsynch had a greater probability of undergoing complete luteolysis after PGF(2α) of Ovsynch and pregnancy at 39 d after timed AI (i.e., 50% pregnant at 8 vs. 28% pregnant at 4 ng/mL P(4)). Serum concentrations of E(2) at 56 h after PGF(2α) of Ovsynch were a positive predictor of pregnancy at 39 d after timed AI. In summary, cloprostenol sodium tended to improve P/AI. Cows with greater serum concentrations of P(4) at time of PGF(2α) of Ovsynch had a greater chance of luteolysis and pregnancy.

Nonesterified fatty acids modify inflammatory response and eicosanoid biosynthesis in bovine endothelial cells

Intense lipid mobilization during the transition period in dairy cows is associated with increased disease susceptibility. The potential impact of altered plasma nonesterified fatty acids (NEFA) concentrations and composition on host inflammatory responses that may contribute to disease incidence and severity are not known. The objective of this study was to evaluate if increased NEFA concentrations could modify vascular inflammatory responses in vitro by changing the expression of important inflammatory mediators that are important in the pathogenesis of infectious diseases of transition cows such as mastitis and metritis. Bovine aortic endothelial cells (BAEC) were cultured with different concentrations of a NEFA mixture that reflected the plasma NEFA composition during different stages of lactation. The expression of cytokines, adhesion molecules, and eicosanoids were measured to assess changes in BAEC inflammatory phenotype. Addition of NEFA mixtures altered the fatty acid profile of BAEC by increasing the concentration of stearic acid (C18:0) and decreasing the content of arachidonic acid (C20:4n6c) and other long-chain polyunsaturated fatty acids in the phospholipid fraction. A significant increase also occurred in mRNA expression of cytokine and adhesion molecules that are associated with increased inflammatory responses during the transition period. Expression of cyclooxygenase 2, an important enzyme associated with eicosanoid biosynthesis, was increased in a NEFA concentration-dependent manner. The production of linoleic acid-derived eicosanoids 9- and 13-hydroxyoctadecadienoic acids also was increased significantly after treatment with NEFA mixtures. This research described for the first time specific changes in vascular inflammatory response during in vitro exposure to NEFA mixtures that mimic the composition and concentration found in cows during the transition period. These findings could explain, in part, alterations in inflammatory responses observed during intense lipid mobilization stages such as in the transition period of dairy cows. Future studies should analyze specific mechanisms by which high NEFA concentrations induce a vascular proinflammatory phenotype including the effect of 9 and 13-hydroxyoctadecadienoic acids and other lipid mediators.

Association between polyunsaturated fatty acid-derived oxylipid biosynthesis and leukocyte inflammatory marker expression in periparturient dairy cows

Peripheral blood mononuclear leukocytes from periparturient cows can have exacerbated inflammatory responses that contribute to disease incidence and severity. Oxylipids derived from the oxygenation of polyunsaturated fatty acids (PUFA) can regulate the magnitude and duration of inflammation. Although PUFA substrate for oxylipid biosynthesis in leukocytes is known to change across the periparturient period, the plasma oxylipid profile and how this profile relates to leukocyte inflammatory phenotype is not clear. The objective of this study was to determine if a relationship exists between the profile of pro- and antiinflammatory plasma oxylipids and the inflammatory phenotype of peripheral blood leukocytes during the periparturient period. Seven multiparous Holsteins were sampled from the prepartum period through peak lactation. Plasma oxylipids were measured by liquid chromatography-mass spectrometry, peripheral leukocyte mRNA expression was measured by quantitative PCR, and PUFA content of peripheral blood mononuclear cells was measured by gas chromatography-mass spectrometry. Concentrations of several hydroxyl products of linoleic and arachidonic acid changed over time. Linoleic acid and arachidonic acid concentrations in leukocytes increased during early lactation, suggesting that substrate availability for hydroxyoctadecadienoic and hydroxyeicosatetraenoic acid biosynthesis may influence the oxylipid profile. Leukocyte mRNA expressions of IL-12B, IL-1B, inducible nitric oxide synthase 2, and cyclooxygenase 2 were correlated with several plasma oxylipids. These are the first observations linking leukocyte inflammatory gene responses to shifts in oxylipid biosynthesis in periparturient dairy cows.

Enhanced n-3 phospholipid content reduces inflammatory responses in bovine endothelial cells

Uncontrolled inflammation contributes to the increased incidence and severity of infectious diseases in periparturient dairy cattle. The objective of this study was to determine if increasing n-3 fatty acid (FA) content and altering the profile of vasoactive eicosanoids could attenuate endothelial cell inflammatory responses. Bovine aortic endothelial cells (BAEC) were cultured with free FA mixtures that mimic the plasma NEFA composition during the first week of lactation of dairy cows or with a free FA mixture supplemented with a higher proportion of n-3 FA, including eicosapentaenoic and docosahexaenoic acids. The effects of increasing the docosahexaenoic and eicosapentaenoic acid content of BAEC on the expression of proinflammatory mediators and eicosanoid biosynthesis was assessed. Culturing BAEC with enriched concentrations of n-3 FA decreased the expression of proinflammatory cytokines, adhesion molecules, and reactive oxygen species with a concomitant increase in the biosynthesis of proresolving eicosanoids, including resolvins, protectins, and lipoxins. This study showed for the first time that increasing the n-3 FA content of endothelial cell phospholipids could alter the expression of eicosanoids and control the magnitude of inflammatory responses. Future studies are necessary to elucidate the mechanisms by which resolvins, protectins, and lipoxins may modify endothelial inflammatory pathways necessary to reduce the severity and duration of disease in periparturient cows.

Adipose tissue lipolysis and remodeling during the transition period of dairy cows

Elevated concentrations of plasma fatty acids in transition dairy cows are significantly associated with increased disease susceptibility and poor lactation performance. The main source of plasma fatty acids throughout the transition period is lipolysis from adipose tissue depots. During this time, plasma fatty acids serve as a source of calories mitigating the negative energy balance prompted by copious milk synthesis and limited dry matter intake. Past research has demonstrated that lipolysis in the adipose organ is a complex process that includes not only the activation of lipolytic pathways in response to neural, hormonal, or paracrine stimuli, but also important changes in the structure and cellular distribution of the tissue in a process known as adipose tissue remodeling. This process involves an inflammatory response with immune cell migration, proliferation of the cellular components of the stromal vascular fraction, and changes in the extracellular matrix. This review summarizes current knowledge on lipolysis in dairy cattle, expands on the new field of adipose tissue remodeling, and discusses how these biological processes affect transition cow health and productivity.

Adipose tissue remodeling in late-lactation dairy cows during feed-restriction-induced negative energy balance

Excessive rates of demand lipolysis in the adipose tissue (AT) during periods of negative energy balance (NEB) are associated with increased susceptibility to disease and limited lactation performance. Lipolysis induces a remodeling process within AT that is characterized by an inflammatory response, cellular proliferation, and changes in the extracellular matrix (ECMT). The adipose tissue macrophage (ATM) is a key component of the inflammatory response. Infiltration of ATM-forming cellular aggregates was demonstrated in transition cows, suggesting that ATM trafficking and phenotype changes may be associated with disease. However, it is currently unknown if ATM infiltration occurs in dairy cows only during NEB states related to the transition period or also during NEB-induced lipolysis at other stages of lactation. The objective of this study was to evaluate changes in ATM trafficking and inflammatory phenotypes, and the expression of genetic markers of AT remodeling in healthy late-lactation cows during feed restriction-induced NEB. After a 14-d (d -14 to d -1) preliminary period, Holstein cows were randomly assigned to 1 of 2 feeding protocols, ad libitum (AL) or feed restriction (FR), for 4 d (d 1-4). Caloric intake was reduced in FR to achieve a targeted energy balance of -15 Mcal/d of net energy for lactation. Omental and subcutaneous AT samples were collected laparoscopically to harvest stromal vascular fraction (SVF) cells on d -3 and 4. The FR induced a NEB of -14.1±0.62 Mcal/d of net energy for lactation, whereas AL cows remained in positive energy balance (3.2±0.66 Mcal/d of NEL). The FR triggered a lipolytic response reflected in increased plasma nonesterified fatty acids (0.65±0.05 mEq/L on d 4), enhanced phosphorylation of hormone sensitive lipase, and reduced adipocyte diameter. Flow cytometry and immunohistochemistry analysis revealed that on d 4, FR cows had increased numbers of CD172a+, an ATM (M1 and M2) surface marker, cells in SVF that were localized in aggregates. However, FR did not alter the number of SVF cells expressing M1 markers (CD14 and CD11c) or M2 markers (CD11b and CD163). This finding contrasts with the predominately M1 phenotype observed previously in ATM from clinically diseased cows. No changes were observed in the expression of ECMT-related or cell proliferation markers. In summary, an acute 4-d lipolytic stimulus in late-lactation dairy cows led to ATM infiltration with minimal changes in inflammatory phenotype and no changes in ECMT. These results underscore that physiological changes related to parturition, the onset of lactation, extended periods of lipolysis, or a combination of these can induce intense AT remodeling with enhanced ATM inflammatory phenotype expression that may impair the metabolic function of AT in transition dairy cattle.

Efficacy of oral administration of a modified-live Salmonella Dublin vaccine in calves.

OBJECTIVE To determine the efficacy a modified-live Salmonella Dublin vaccine administered PO in an extralabel manner in the prevention of diseases associated with Salmonella Dublin infection. DESIGN Randomized clinical trial. ANIMALS 288 preweaned Holstein dairy calves on a commercial dairy farm. PROCEDURES Calves were orally administered either 2 mL of a commercially available, modified-live Salmonella Dublin vaccine (n = 140) or a placebo (148) at 3 and 10 days of age. Signs of diarrhea and depression were recorded daily. Weight gain between 3 days of age and time of weaning was measured. Fecal samples from clinically depressed or diarrheic calves and fresh tissues samples from calves that died were submitted for bacterial culture of Salmonella organisms. RESULTS Salmonella organisms were isolated from samples of 1.4% (2/140) and 3.4% (5/148) of calves receiving the vaccine and placebo, respectively. Additionally, 57.1% (80/140) and 60.1 % (89/148) of the vaccinated and control calves, respectively, had at least 1 day with an abnormal fecal score. Calves receiving the vaccine and placebo were not significantly different in terms of overall morbidity rate, Salmonella-specific morbidity rate, or average daily gain. Adverse reactions related to administration of the vaccine were not seen. The attenuated vaccine strain was not isolated from any fecal or tissue samples. CONCLUSIONS AND CLINICAL RELEVANCE This method of vaccination was safe in young Holstein calves, although it was not effective in reducing the incidence of disease or improving weight gain on this farm. However, the power of this study was limited by a low incidence of clinical salmonellosis.

Fetuin-A: A negative acute-phase protein linked to adipose tissue function in periparturient dairy cows

Fetuin-A (FetA) is a free fatty acid transporter and an acute-phase protein that enhances cellular lipid uptake and lipogenesis. In nonruminants, FetA is involved in lipid-induced inflammation. Despite FetA importance in lipid metabolism and inflammation, its expression and dynamics in adipose tissue (AT) of dairy cows are unknown. The objectives of this study were to (1) determine serum and AT FetA dynamics over the periparturient period and in mid-lactation cows in negative energy balance (NEB) after a feed restriction protocol and (2) characterize how an inflammatory challenge affects adipocyte FetA expression. Blood and subcutaneous AT were collected from 16 cows with high (≥3.75, n = 8) or moderate (≤3.5, n = 8) body condition score (BCS) at -26 ± 7 d (far off) and -8 ± 5 d (close up) before calving and at 10 ± 2 d after parturition (early lactation) and from 14 nonpregnant mid-lactation cows (>220 d in milk) after a feed restriction protocol. Serum FetA concentrations were 0.89 ± 0.13 mg/mL at far off, 0.96 ± 0.13 mg/mL at close up, and 0.77 ± 0.13 mg/mL at early lactation and were 1.09 ± 0.09 and 1.17 ± 0.09 mg/mL in feed-restricted and control cows, respectively. Serum and AT FetA contents decreased at the onset of lactation when lipolysis was higher. No changes in AT and serum FetA were observed after feed restriction induced NEB in mid-lactation cows. Prepartum BCS had no effect on serum FetA, but AT expression of AHSG, the gene encoding FetA, was reduced in periparturient cows with high BCS at dry-off throughout all time points. Circulating FetA was positively associated with serum albumin and calcium and with BCS variation over the periparturient period. The dynamics of AHSG expression were analogous to the patterns of lipogenic markers ABDH5, ELOVL6, FABP4, FASN, PPARγ, and SCD1. Expression of AHSG and FetA protein in AT was inversely correlated with AT proinflammatory markers CD68, CD44, SPP1, and CCL2. In vitro, bovine adipocytes challenged with lipopolysaccharide downregulated FetA protein expression. Adipocytes treated with FetA had lower CCL2 expression compared with those exposed to lipopolysaccharide. Overall, FetA is a systemic and local AT negative acute-phase protein linked to AT function in periparturient cows. Furthermore, FetA may support physiological adaptations to NEB in periparturient cows.