Inflammatory and metabolic responses to an intramammary lipopolysaccharide challenge in early lactating cows supplemented with conjugated linoleic acid

Comparing oral versus intravenous calcium administration on alleviating markers of production, metabolism, and inflammation during an intravenous lipopolysaccharide challenge in mid-lactation dairy cows

Animals, including dairy cows, develop hypocalcemia during infection. Prior independent research suggests supplementing oral Ca, but not i.v. Ca, improves multiple health metrics after immune activation. Therefore, study objectives were to directly compare the effects of administering an oral Ca bolus versus i.v. Ca on mineral and energetic metabolism variables and inflammatory parameters following an i.v. LPS challenge. Mid-lactation cows (124 ± 43 DIM) were assigned to 1 of 4 treatments: (1) saline control (CON; 4 mL of saline; n = 4), (2) LPS control (CON-LPS; 0.375 µg/kg BW; n = 6), (3) LPS with oral Ca bolus (OCa-LPS; 0.375 µg/kg BW and a 192-g bolus of Bovikalc [Boehringer Ingelheim Animal Health USA Inc., Duluth, GA] containing 43 g of Ca [71% CaCl2 and 29% CaSO4] supplemented at -0.5 and 6 h relative to LPS administration; n = 8), and (4) LPS with i.v. Ca (IVCa-LPS; 0.375 µg/kg BW and 500 mL of Ca-gluconate, 23% [VetOne, Boise, ID]) supplemented at -0.5 and 6 h relative to LPS infusion; n = 8). During period (P) 1 (4 d), baseline data were obtained. At the initiation of P2 (5 d), LPS and Ca supplements were administered. As anticipated, CON-LPS became hypocalcemic, but OCa-LPS and IVCa-LPS had increased ionized Ca compared with CON-LPS cows (1.11 and 1.28 vs. 0.95 ± 0.02 mmol/L, respectively). Rectal temperature increased after LPS and was additionally elevated in IVCa-LPS from 3 to 4 h (38.9 and 39.8 ± 0.1°C in CON-LPS and IVCa-LPS, respectively). Administering LPS decreased DMI and milk yield relative to CON. Circulating glucose was decreased in OCa-LPS compared with CON-LPS and IVCa-LPS during the initial hyperglycemic phase at 1 h (75.1 vs. 94.9 and 95.7 ± 3.4 mg/dL, respectively, but all LPS infused cows regardless of treatment had similar glucose concentrations thereafter, which were decreased relative to baseline during the first 12 h. Blood urea nitrogen increased after LPS but this was attenuated in OCa-LPS compared with CON-LPS and IVCa-LPS cows (8.7 vs. 10.0 and 10.4 ± 0.3 mg/dL). Glucagon increased in OCa-LPS and IVCa-LPS compared with CON-LPS cows (459 and 472 vs. 335 ± 28 pg/mL, respectively), and insulin markedly increased over time regardless of LPS treatment. Lipopolysaccharide substantially increased serum amyloid A, LPS-binding protein (LBP), and haptoglobin in all treatments, but OCa-LPS tended to have increased LBP concentrations relative to IVCa-LPS (10.7 vs. 8.6 ± 0.7 µg/mL, respectively). Several cytokines increased after LPS administration, but most temporal cytokine profiles did not differ by treatment. In summary, LPS administration intensely activated the immune system and both Ca delivery routes successfully ameliorated the hypocalcemia. The i.v. and oral Ca treatments had differential effects on multiple metabolism variables and appeared to mildly influence production responses to LPS.

Intramammary lipopolysaccharide challenge in early- versus mid-lactation dairy cattle: Immune, production, and metabolic responses

Study objectives were to compare the immune response, metabolism, and production following intramammary LPS (IMM LPS) administration in early and mid-lactation cows. Early (E-LPS; n = 11; 20 ± 4 DIM) and mid- (M-LPS; n = 10; 155 ± 40 DIM) lactation cows were enrolled in an experiment consisting of 2 periods (P). During P1 (5 d) cows were fed ad libitum and baseline data were collected, including liver and muscle biopsies. At the beginning of P2 (3 d) cows received 10 mL of sterile saline containing 10 µg of LPS from Escherichia coli O111:B4/mL into the left rear quarter of the mammary gland, and liver and muscle biopsies were collected at 12 h after LPS. Tissues were analyzed for metabolic flexibility, which measures substrate switching capacity from pyruvic acid to palmitic acid oxidation. Data were analyzed with the MIXED procedure in SAS 9.4. Rectal temperature was assessed hourly for the first 12 h after LPS and every 6 h thereafter for the remainder of P2. All cows developed a febrile response following LPS, but E-LPS had a more intense fever than M-LPS cows (0.7°C at 5 h after LPS). Blood samples were collected at 0, 3, 6, 9, 12, 24, 36, 48, and 72 h after LPS for analysis of systemic inflammation and metabolism parameters. Total serum Ca decreased after LPS (26% at 6 h nadir) but did not differ by lactation stage (LS). Circulating neutrophils decreased, then increased after LPS in both LS, but E-LPS had exaggerated neutrophilia (56% from 12 to 48 h) compared with M-LPS. Haptoglobin increased after LPS (15-fold) but did not differ by LS. Many circulating cytokines were increased after LPS, and IL-6, IL-10, TNF-α, MCP-1, and IP-10 were further augmented in E-LPS compared with M-LPS cows. Relative to P1, all cows had reduced milk yield (26%) and DMI (14%) on d 1 that did not differ by LS. Somatic cell score increased rapidly in response to LPS regardless of LS and gradually decreased from 18 h onwards. Milk component yields decreased after LPS. However, E-LPS had increased fat (11%) and tended to have increased lactose (8%) yield compared with M-LPS cows throughout P2. Circulating glucose was not affected by LPS. Nonesterified fatty acids (NEFA) decreased in E-LPS (29%) but not M-LPS cows. β-Hydroxybutyrate slightly increased (14%) over time after LPS regardless of LS. Insulin increased after LPS in all cows, but E-LPS had blunted hyperinsulinemia (52%) compared with M-LPS cows. Blood urea nitrogen increased after LPS, and the relative change in BUN was elevated in E-LPS cows compared with M-LPS cows (36% and 13%, respectively, from 9 to 24 h). During P1, metabolic flexibility was increased in liver and muscle in early lactating cows compared with mid-lactation cows, but 12 h after LPS, metabolic flexibility was reduced and did not differ by LS. In conclusion, IMM LPS caused severe immune activation, and E-LPS cows had a more intense inflammatory response compared with M-LPS cows, but the effects on milk synthesis was similar between LS. Some parameters of the E-LPS metabolic profile suggest continuation of metabolic adjustments associated with early lactation to support both a robust immune system and milk synthesis.

Conjugated linoleic acid (CLA) modulates bovine peripheral blood mononuclear cells (PBMC) proteome in vitro

Conjugated linoleic acid (CLA) is a group of natural isomers of the n-6 polyunsaturated fatty acid (PUFA) linoleic acid, exerting biological effects on cow physiology. This study assessed the impact of the mixture 50:50 (vol:vol) of CLA isomers (cis-9, trans-11 and trans-10, cis-12) on bovine peripheral blood mononuclear cells (PBMC) proteome, identifying 1608 quantifiable proteins. A supervised multivariate statistical analysis, sparse variant partial least squares - discriminant analysis (sPLS-DA) for paired data identified 407 discriminant proteins (DP), allowing the clustering between the CLA and controls. The ProteINSIDE workflow found that DP with higher abundance in the CLA group included proteins related to innate immune defenses (PLIN2, CD36, C3, C4, and AGP), with antiapoptotic (SERPINF2 and ITIH4) and antioxidant effects (HMOX1). These results demonstrated that CLA modulates the bovine PBMC proteome, supports the antiapoptotic and immunomodulatory effects observed in previous in vitro studies on bovine PBMC, and suggests a cytoprotective role against oxidative stress. SIGNIFICANCE: In this study, we report for the first time that the mixture 50:50 (vol:vol) of cis-9, trans-11, and trans-10, cis-12-CLA isomers modulates the bovine PBMC proteome. Our results support the immunomodulatory and antiapoptotic effects observed in bovine PBMC in vitro. In addition, the present study proposes a cytoprotective role of CLA mixture against oxidative stress. We suggest a molecular signature of CLA treatment based on combining a multivariate sparse discriminant analysis and a clustering method. This demonstrates the great value of sPLS-DA as an alternative option to identify discriminant proteins with relevant biological significance.

Conjugated linoleic acid (CLA) as a functional food: Is it beneficial or not?

Conjugated linoleic acid (CLA) has attracted great attention in recent years as a popular class of functional food that is broadly used. It refers to a group of geometric and positional isomers of linoleic acid (LA) with a conjugated double bond. The main natural sources of CLA are dairy products, beef and lamb, whereas only trace amounts occur naturally in plant lipids. CLA has been shown to improve various health issues, having effects on obesity, inflammatory, anti-carcinogenicity, atherogenicity, immunomodulation, and osteosynthesis. Also, compared to studies on humans, many animal researches reveal more positive benefits on health. CLA represents a nutritional avenue to improve lifestyle diseases and metabolic syndrome. Most of these effects are attributed to the two major CLA isomers [conjugated linoleic acid cis-9,trans-11 isomer (c9,t11), and conjugated linoleic acid trans-10,cis-12 isomer (t10,c12)], and their mixture (CLA mix). In contrast, adverse effects of CLA have been also reported, such as glucose homeostasis, insulin resistance, hepatic steatosis and induction of colon carcinogenesis in humans, as well as milk fat inhibition in ruminants, lowering chicken productivity, influencing egg quality and altering growth performance in fish. This review article aims to discuss the health benefits of CLA as a nutraceutical supplement and highlight the possible mechanisms of action that may contribute to its outcome. It also outlines the feasible adverse effects of CLA besides summarizing the recent peer-reviewed publications on CLA to ensure its efficacy and safety for proper application in humans.

Review: Effect of essential fatty acids and conjugated linoleic acid on the adaptive physiology of dairy cows during the transition period

Cows fed total mixed rations (silage-based) may not receive as much essential fatty acids (EFAs) and conjugated linoleic acids (CLAs) as cows fed pasture-based rations (fresh grass) containing rich sources of polyunsaturated fatty acids. CLA-induced milk fat depression allows dairy cows to conserve more metabolisable energy, thereby shortening the state of negative energy balance and reducing excessive fat mobilisation at early lactation. EFAs, particularly α-linolenic acid, exert anti-inflammatory and antioxidative properties, thereby modulating immune functions. Thus, combined EFA and CLA supplementation seems to be an effective nutritional strategy to relieve energy metabolism and to improve immune response, which are often compromised during the transition from late pregnancy to lactation in high-yielding dairy cows. There has been extensive research on this idea over the last two decades, and despite promising results, several interfering factors have led to varying findings, making it difficult to conclude whether and under what conditions EFA and CLA supplementations are beneficial for dairy cows during the transition period. This article reviews the latest studies on the effects of EFA and CLA supplementation, alone or in combination, on dairy cow metabolism and health during various stages around parturition. Our review article summarises and provides novel insights into the mechanisms by which EFA and/or CLA influence markers of metabolism, energy homeostasis and partitioning, immunity, and inflammation revealed by a deep molecular phenotyping.

Cis-9, Trans-11 CLA Alleviates Lipopolysaccharide-Induced Depression of Fatty Acid Synthesis by Inhibiting Oxidative Stress and Autophagy in Bovine Mammary Epithelial Cells

Lipopolysaccharide (LPS) is the dominating endotoxin of Gram-negative bacteria, which can cause mastitis. Bovine mammary epithelial cells (BMECs), as major components of the mammary gland, usually suffer LPS challenge. Cis-9, trans-11 conjugated linoleic acid (CLA) has been reported to have anti-inflammatory characteristics, while its anti-oxidative ability to maintain cellular homeostasis in BMECs under LPS challenge is limited. Therefore, we studied whether cis-9, trans-11 CLA can restore the disturbance of cellular homeostasis indicated by the redox status and autophagy level caused by LPS and have an effect on cellular function- milk fat metabolism. For oxidative stress, LPS challenge promoted the formation of reactive oxygen species (ROS) and thiobarbituric acid reactive substances (TBARS) and decreased the concentration of glutathione. Anti-oxidative signaling regulated by transcription factor nuclear factor, erythroid 2 like 2 (Nrf2) was also depressed by LPS at the mRNA and protein level. However, cis-9, trans-11 CLA pretreatment downregulated the formation of ROS and TBARS and upregulated the expression of antioxidative enzymes. As a part of innate immunity, autophagy was also motivated by LPS challenge, while CLA decreased the autophagy level. LPS and H₂O₂ inhibited milk fat synthesis-related transcription factor sterol regulatory element binding protein (SREBP1), peroxisome proliferator activated receptor gamma (PPARG) and their downstream enzymes. Furthermore, 50 uM cis-9, trans-11 CLA promoted the mRNA and protein abundance of milk fat synthesis-related genes and lipid droplet formation in BMECs. In conclusion, LPS challenge disturbed the cellular homeostasis and depressed milk fat synthesis in BMECs; while cis-9, trans-11 CLA alleviated oxidative stress and decreased autophagy level, thus promoting milk fat synthesis, which offers a natural therapeutic strategy for mastitis.

Response of lactating dairy cows fed different supplemental zinc sources with and without evaporative cooling to intramammary lipopolysaccharide infusion: metabolite and mineral profiles in blood and milk

The objective of this study was to determine the effect of evaporative cooling and dietary supplemental Zn source on blood metabolites, insulin and mineral concentrations, and milk mineral concentrations following intramammary lipopolysaccharide (LPS) infusion. Seventy-two multiparous Holstein cows were assigned to one of four treatments with a 2 × 2 factorial arrangement. Treatments included two environments: with or without evaporative cooling using fans and misters over the freestall and feedbunk, and two dietary sources of supplemental Zn: 75 mg/kg of dry matter (DM) supplied by Zn hydroxychloride (inorganic Zn; IOZ) or Zn hydroxychloride (35 mg of Zn/kg of DM) + Zn-Met complex (ZMC; 40 mg of Zn/kg of DM). A subset of cows (n = 16; 263 ± 63 d in milk) was infused with 10 μg of LPS or a saline control in the left or right rear quarters on day 34 of the environmental treatment. Individual milk samples collected from LPS-infused quarters at -4, 0, 6, 12, 24, 48, 72, 96, and 144 h relative to infusion were analyzed for minerals. Blood samples were collected at the same time with an additional sample collected at 3 h post-infusion to analyze glucose, nonesterified fatty acids (NEFA), insulin, and minerals. Cooling by time interactions (P ≤ 0.07) were observed for plasma glucose, NEFA, and serum insulin. Compared with cooled cows, non-cooled cows had lower concentrations of plasma glucose except at 3 h following intramammary LPS infusion, greater serum insulin at 3 and 12 h, and lower plasma NEFA at 24 and 48 h after infusion. Relative to cooled cows, non-cooled cows tended (P = 0.07) to have lower serum K concentration and had lower (P < 0.01) serum Zn 6 h following infusion (cooling by time interaction: P < 0.01). Relative to ZMC cows, IOZ cows had greater (P ≤ 0.09) concentrations of plasma Se, skim milk Na and Se, and skim milk Na to K ratio. Regardless of treatment, intramammary LPS infusion reduced (P < 0.01) serum or plasma concentrations of Ca, Mg, Zn, Fe, and Se, but increased (P < 0.01) their concentration in skim milk. In conclusion, deprivation of cooling resulted in more rapid and prolonged insulin release and influenced the systemic and mammary mineral metabolism during mammary inflammation induced by LPS of lactating dairy cows. Dietary supplementation of Zn-Met complex reduced blood and milk Se concentrations compared with cows fed Zn from an inorganic source.

Free and bound cortisol, corticosterone, and metabolic adaptations during the early inflammatory response to an intramammary lipopolysaccharide challenge in dairy cows

Glucocorticoids, particularly cortisol and corticosterone, are key homeostatic regulators during metabolic and endocrine adaptations including inflammatory responses. Besides the established response of total cortisol (TC) concentrations during inflammatory processes in dairy cows, we investigated changes of corticosterone, free cortisol (FC), and serum albumin as the main protein of unspecific cortisol binding, in response to an intramammary lipopolysaccharide (LPS) challenge. Furthermore, we evaluated relationships of glucocorticoid responses with concomitant alterations of metabolites and their endocrine regulators, insulin and glucagon. Blood samples of 10 multiparous Holstein dairy cows (26.8 ± 3.4 d in milk, previous lactation yield: 7,601 ± 938 kg; mean ± SD) were obtained every 30 min up to 5 h after the LPS instillation, and rectal temperature and heart rate were measured in parallel. Corticosterone was measured by enzyme immunoassay, TC by radioimmunoassay, and the proportion of FC by ultrafiltration. A mixed model was used to evaluate differences within the investigated parameters among selected time points (0, 3.5, and 5 h relative to the intramammary LPS administration). Rectal temperature increased up to 41.6 ± 0.1°C at 5 h after the LPS application. Concentrations of TC and corticosterone increased until 3.5 h, and the proportion of FC relative to TC more than doubled until 3.5 h after LPS administration. Serum albumin concentration was reduced at 5 h compared with initial values, whereas concentrations of insulin, glucagon, and glucose were increased after 5 h compared with 0 h. In conclusion, the stimulation of the immune system by the intramammary LPS administration is accompanied by distinct metabolic and endocrine changes. Corticosterone and TC concentrations react similarly in response to the LPS challenge and earlier compared with metabolic adaptations. The increased need of active cortisol is covered by both increased secretion and a higher percentage of FC.

Changes in fatty acids in plasma and association with the inflammatory response in dairy cows abomasally infused with essential fatty acids and conjugated linoleic acid during late and early lactation

Dairy cows are exposed to increased inflammatory processes in the transition period from late pregnancy to early lactation. Essential fatty acids (EFA) and conjugated linoleic acid (CLA) are thought to modulate the inflammatory response in dairy cows. The present study investigated the effects of a combined EFA and CLA infusion on the fatty acid (FA) status in plasma lipids, and whether changes in the FA pattern were associated with the acute phase and inflammatory response during late pregnancy and early lactation. Rumen-cannulated Holstein cows (n = 40) were assigned from wk 9 antepartum to wk 9 postpartum to 1 of 4 treatment groups. Cows were abomasally supplemented with coconut oil (CTRL, 76 g/d), linseed and safflower oil (EFA, 78 g/d of linseed oil and 4 g/d of safflower oil; ratio of oils = 19.5:1; n-6:n-3 FA ratio = 1:3), Lutalin (CLA, 38 g/d; isomers cis-9,trans-11 and trans-10,cis-12; each 10 g/d), or both (EFA+CLA). Blood samples were taken to measure changes in FA in blood plasma on d -63, -42, 1, 28, and 56, and in plasma lipid fractions (cholesterol esters, free fatty acids, phospholipids, and triglycerides) on d -42, 1, and 56 relative to calving, and in erythrocyte membrane (EM) on d 56 after calving. Traits related to the acute phase response and inflammation were measured in blood throughout the study. Liver samples were obtained for biopsy on d -63, -21, 1, 28, and 63 relative to calving to measure the mRNA abundance of genes related to the inflammatory response. The concentrations of α-linolenic acid and n-3 FA metabolites increased in lipid fractions (especially phospholipids) and EM due to EFA supplementation with higher α-linolenic acid but lower n-3 metabolite concentrations in EFA+CLA than in EFA treatment only. Concentration of linoleic acid decreased in plasma fat toward calving and increased during early lactation in all groups. Concentration of plasma arachidonic acid was lower in EFA- than in non-EFA-treated groups in lipid fractions and EM. The cis-9,trans-11 CLA increased in all lipid fractions and EM after both CLA treatments. Plasma haptoglobin was lowered by EFA treatment before calving. Plasma bilirubin was lower in EFA and CLA than in CTRL at calving. Plasma concentration of IL-1β was higher in EFA than in CTRL and EFA+CLA at certain time points before and after calving. Plasma fibrinogen dropped faster in CLA than in EFA and EFA+CLA on d 14 postpartum. Plasma paraoxonase tended to be elevated by EFA treatment, and was higher in EFA+CLA than in CTRL on d 49. Hepatic mRNA abundance revealed time changes but no treatment effects with respect to the inflammatory response. Our data confirmed the enrichment of n-3 FA in EM by EFA treatment and the inhibition of n-3 FA desaturation by CLA treatment. The elevated n-3 FA status and reduced n-6:n-3 ratio by EFA treatment indicated a more distinct effect on the inflammatory response during the transition period than the single CLA treatment, and the combined EFA+CLA treatment caused minor additional changes on the anti-inflammatory response.

Mismatch of Glucose Allocation between Different Life Functions in the Transition Period of Dairy Cows

Immune cell functions such as phagocytosis and synthesis of immunometabolites, as well as immune cell survival, proliferation and differentiation, largely depend on an adequate availability of glucose by immune cells. During inflammation, the glucose demands of the immune system may increase to amounts similar to those required for high milk yields. Similar metabolic pathways are involved in the adaptation to both lactation and inflammation, including changes in the somatotropic axis and glucocorticoid response, as well as adipokine and cytokine release. They affect (i) cell growth, proliferation and activation, which determines the metabolic activity and thus the glucose demand of the respective cells; (ii) the overall availability of glucose through intake, mobilization and gluconeogenesis; and (iii) glucose uptake and utilization by different tissues. Metabolic adaptation to inflammation and milk synthesis is interconnected. An increased demand of one life function has an impact on the supply and utilization of glucose by competing life functions, including glucose receptor expression, blood flow and oxidation characteristics. In cows with high genetic merits for milk production, changes in the somatotropic axis affecting carbohydrate and lipid metabolism as well as immune functions are profound. The ability to cut down milk synthesis during periods when whole-body demand exceeds the supply is limited. Excessive mobilization and allocation of glucose to the mammary gland are likely to contribute considerably to peripartal immune dysfunction.

Metabolic status is associated with the recovery of milk somatic cell count and milk secretion after lipopolysaccharide-induced mastitis in dairy cows

Infections of the mammary gland in dairy cows are commonly accompanied by reduced milk production and feed intake and poor milk quality. The metabolic status of early-lactating cows is known to affect immune response to pathogens and imposed immune challenges. We investigated the extent to which metabolic status before an intramammary lipopolysaccharide (LPS) challenge (LPS-CH) is associated with immune response, milk production, and feed intake and the recovery thereof. In 15 Holstein cows, weekly blood sampling and daily recording of dry matter intake, milk yield, milk composition, and body weight (to calculate energy balance) was started immediately after parturition. In wk 4 after parturition, cows underwent an intramammary LPS-CH (50 μg of LPS into 1 quarter). Blood and milk samples were taken in parallel at 30- and 60-min intervals, respectively, until 10 h after the LPS application. Plasma concentrations of glucose, nonesterified fatty acids, β-hydroxybutyrate (BHB), cortisol, and insulin were analyzed. In milk, serum albumin, IgG concentration, somatic cell count (SCC), and lactate dehydrogenase (LDH) activity were determined. Dry matter intake and milk yield were recorded for an additional 6 d. Milk of the LPS-treated quarter was sampled at every milking for 8 d after the challenge. Based on plasma glucose concentrations in wk 1 to 4 after parturition before the LPS-CH, cows were retrospectively grouped into a high-glucose group (HG; 3.34-3.93 mmol/L, n = 7) and a low-glucose group (LG; 2.87-3.31 mmol/L, n = 8). Data were evaluated using mixed models with time, group, and time × group interaction as fixed effects and cow as repeated subject. Glucose was lower and BHB was higher in LG compared with HG before LPS-CH, whereas dry matter intake, energy balance, and SCC did not differ. During LPS-CH, SCC and LDH increased similarly in HG and LG, body temperature increased less in HG, and BHB and nonesterified fatty acids were higher in LG compared with HG. Dry matter intake declined in both groups during the day of the LPS-CH but recovered to prechallenge values faster in HG. Milk yield recovered within 2 d after the LPS-CH with no differences in morning milkings, whereas evening milk yield increased faster in HG. During 8 d after LPS-CH, SCC, LDH, IgG, and serum albumin in milk were lower in HG compared with LG. In conclusion, the level of circulating glucose and BHB concentrations in cows was associated with metabolic responses during an LPS-CH as well as the recovery of udder health and performance thereafter.

Milk yield, milk composition, and milk metabolomics of dairy goats intramammary-challenged with lipopolysaccharide under heat stress conditions

Heat stress and mastitis are major economic issues in dairy production. The objective was to test whether goat’s mammary gland immune response to E. coli lipopolysaccharide (LPS) could be conditioned by heat stress (HS). Changes in milk composition and milk metabolomics were evaluated after the administration of LPS in mammary glands of dairy goats under thermal-neutral (TN; n = 4; 15 to 20 °C; 40 to 45% humidity) or HS (n = 4; 35 °C day, 28 °C night; 40% humidity) conditions. Milk metabolomics were evaluated using ¹H nuclear magnetic resonance spectroscopy, and multivariate analyses were carried out. Heat stress reduced feed intake and milk yield by 28 and 21%, respectively. Mammary treatment with LPS resulted in febrile response that was detectable in TN goats, but was masked by elevated body temperature due to heat load in HS goats. Additionally, LPS increased milk protein and decreased milk lactose, with more marked changes in HS goats. The recruitment of somatic cells in milk after LPS treatment was delayed by HS. Milk metabolomics revealed that citrate increased by HS, whereas choline, phosphocholine, N-acetylcarbohydrates, lactate, and ß-hydroxybutyrate could be considered as putative markers of inflammation with different pattern according to the ambient temperature (i.e. TN vs. HS). In conclusion, changes in milk somatic cells and milk metabolomics indicated that heat stress affected the mammary immune response to simulated infection, which could make dairy animals more vulnerable to mastitis.

Effects of abomasal infusion of essential fatty acids and conjugated linoleic acid on performance and fatty acid, antioxidative, and inflammatory status in dairy cows

The objective of this study was to test the effects of essential fatty acids (EFA), particularly α-linolenic acid, and conjugated linoleic acid (CLA) supplementation on fatty acid (FA) composition, performance, and systemic and hepatic antioxidative and inflammatory responses in dairy cows. Four cows (126 ± 4 d in milk) were investigated in a 4 × 4 Latin square and were abomasally infused with 1 of the following for 6 wk: (1) coconut oil (control treatment, CTRL; 38.3 g/d; providing saturated FA), (2) linseed and safflower oil (EFA treatment; 39.1 and 1.6 g/d, respectively; providing mainly α-linolenic acid), (3) Lutalin (BASF, Ludwigshafen, Germany; CLA treatment; cis-9,trans-11 and trans-10,cis-12 CLA, 4.6 g/d each), (4) or EFA+CLA. The initial dosage was doubled every 2 wk, resulting in 3 dosages (dosage 1, 2, and 3). Cows were fed a corn silage-based total mixed ration with a high n-6/n-3 FA ratio. Dry matter intake and milk yield were recorded daily, and milk composition was measured weekly. The FA compositions of milk fat and blood plasma were analyzed at wk 0, 2, 4, and 6. The plasma concentration and hepatic mRNA abundance of parameters linked to the antioxidative and inflammatory response were analyzed at wk 0 and 6 of each treatment period. Infused FA increased in blood plasma and milk of the respective treatment groups in a dose-dependent manner. The n-6/n-3 FA ratio in milk fat was higher in CTRL and CLA than in EFA and EFA+CLA. The sum of FA <C16 in milk fat decreased in CLA and EFA+CLA in a dosage-dependent manner. Energy-corrected milk and milk fat decreased in CLA and EFA+CLA in a dosage-dependent manner and were higher in EFA and CTRL than in CLA at dosages 2 and 3. Energy balance tended to be highest in CLA cows. Milk protein content was lower in CLA and EFA+CLA than in CTRL. Milk urea concentration decreased in CLA and EFA+CLA in a dosage-dependent manner and was lower in CLA and EFA+CLA than in EFA and CTRL at dosages 2 and 3. Milk citrate concentration increased in CLA in a dosage-dependent manner and was higher in CLA and EFA+CLA than in EFA and CTRL. Glutathione peroxidase activity in blood plasma was lower in CTRL than in EFA, and plasma concentration of β-carotene increased in EFA and EFA+CLA with dosage. Increased milk citrate pointed at reduced de novo FA synthesis and a better antioxidative status in milk due to CLA treatment. Supplementation with CLA may also affect milk protein synthesis, but EFA and CLA treatment did not influence the inflammatory status in a consistent manner in mid-lactating cows.

Invited review: Metabolic challenges and adaptation during different functional stages of the mammary gland in dairy cows: Perspectives for sustainable milk production

Milk production of dairy cows has increased markedly during recent decades and continues to increase further. The evolutionarily conserved direction of nutrients to the mammary gland immediately after calving provided the basis for successful selective breeding toward higher performance. Considerable variation in adaptive responses toward energy and nutrient shortages exists; however, this variation in adaptability recently gained interest for identifying more metabolically robust dairy cows. Metabolic challenges during periods of high milk production considerably affect the immune system, reproductive performance, and product quality as well as animal welfare. Moreover, growing consumer concerns need to be taken into consideration because the public perception of industrialized dairy cow farming, the high dependency on feed sources suitable for human nutrition, and the apparently abundant use of antibiotics may affect the sales of dairy products. Breeding for high yield continues, but the metabolic challenges increasingly come close to the adaptational limits of meeting the mammary gland's requirements. The aim of the present review is to elucidate metabolic challenges and adaptational limitations at different functional stages of the mammary gland in dairy cows. From the challenges and adaptational limitations, we derive perspectives for sustainable milk production. Based on previous research, we highlight the importance of metabolic plasticity in adaptation mechanisms at different functional stages of the mammary gland. Metabolic adaptation and plasticity change among developing, nonlactating, remodeling, and lactational stages of the mammary gland. A higher metabolic plasticity in early-lactating dairy cows could be indicative of resilience, and a high performance level without an extraordinary occurrence of health disorders can be achieved.