乳头管灌注脂多糖对兔血清酶活性的影响及病理组织学观察

探讨经乳头管灌注脂多糖(LPS)对兔血清酶活性的影响及乳腺病理组织学变化.12只泌乳兔(产后第7天)经乳头管灌注LPS(150 μg/kg体重)建立急性临床型乳房炎模型,在灌注前2 h,灌注后6、12、24、48、72 h以及5 d和7 d分别测定血清中乳酸脱氢酶(LDH)、髓过氧化物酶(MPO)、过氧化物酶(LP)及...     

Seasonal variations in the concentration of antimicrobial components in milk of dairy cows

The incidence of bovine mastitis and the bulk milk somatic cell count (BMSCC) are influenced by season, which may be associated with innate immune functions, including antimicrobial components in mammary glands. Therefore, the present study was conducted to examine the effect of season on antimicrobial components in milk. Rectal temperature and plasma cortisol, thyroxine, and derivatives of reactive oxygen metabolites (d‐ROMs) were measured as stress parameters. Concentrations of lactoferrin (LF), lingual antimicrobial peptide (LAP), psoriasin (S100A7), and Immunoglobulin A (IgA) in milk were measured as indicators of innate immune function. LF and LAP concentrations were significantly lower in summer than in winter and spring, respectively, whereas the concentration of S100A7 was significantly lower in winter than in spring and autumn. The rectal temperature was significantly higher in summer than in other seasons, whereas plasma cortisol, thyroxine, and d‐ROMs did not exhibit any seasonal variation. In conclusion, even though stress parameters were not changed, the concentration of antimicrobial components, such as LF and LAP, decreased in summer, which may explain the frequent occurrence of mastitis during this season.     

Short-term changes of mRNA expression of various inflammatory factors and milk proteins in mammary tissue during LPS-induced mastitis

During mammary gland infection, non-specific responses are the predominant ones. The goal of this study was to investigate the mRNA expression of various soluble immune components and of the major milk proteins during the acute phase of mammary inflammation. Five healthy lactating cows were intramammary infused in one quarter with 100 microg Escherichia coli-endotoxin (lipopolysaccharide, LPS) and the contralateral quarter with saline (9 g/l) serving as control. Mammary biopsy samples of both quarters were taken immediately before and at 3, 6, 9 and 12 h after infusion and mRNA expression of various factors was quantified via real-time RT-PCR. Blood samples for determination of leukocyte number were taken simultaneously with the biopsy samples and rectal temperature was measured at 1-h intervals. Rectal temperature increased until 5h (P < 0.05) after LPS administration and remained elevated until 9 h after LPS inoculation. Blood leukocyte number decreased (P < 0.05) from 0 to 3 h from 7.7 +/- 1.1 x 10(9)l(-1) to 5.7 +/- 1.0 x 10(9)l(-1) and thereafter recovered to pre-treatment levels until 12 h after LPS challenge. In LPS-treated quarters, tumor necrosis factor-alpha and cyclooxygenase-2-mRNA expression increased (P < 0.05) to highest values at 3h after LPS challenge. Lactoferrin, lysozyme, inducible nitric oxide synthase increased (P < 0.05) and peaked at 6 h after challenge, and platelet-activating factor acetylhydrolase-mRNA expression tended to increase (P = 0.07). mRNA expression of insulin-like growth factor-I and of alphaS1-casein (CN), alphaS2-CN, beta-CN and beta-lactoglobulin did not change significantly, whereas mRNA expression of 5-lipoxygenase and alpha-lactalbumin decreased (P < 0.05) in both quarters and that of kappa-CN only in the LPS quarter. mRNA expression of some investigated factors (tumor necrosis factor-alpha, lysozyme, 5-lipoxygenase, alpha-lactalbumin) changed in control quarters, however in all respective factors less than in the LPS quarters (P < 0.05). In conclusion, mRNA expression of most inflammatory factors increased within hours, whereas that of most milk proteins remained unchanged.     

Immunolocalization of lingual antimicrobial peptide (LAP) in the bovine mammary gland

Lingual antimicrobial peptide (LAP), a member of the β-defensin family in cows, is involved in the innate immune system and plays a crucial role in killing a large variety of microorganisms. The aim of the present study was to demonstrate the immunolocalization of LAP in the mammary glands of cows. A LAP antibody was raised in a rabbit by immunity with a synthetic 11 amino acid sequence out of a 42-amino acid sequence of the mature form of LAP. The specificity of the LAP antibody was checked using a competitive immunoassay and Western blotting. Paraffin sections of the mammary gland were immunostained with LAP antibody. In the competitive immunoassay, an increase of synthetic LAP concentration suppressed the optical density. Western blotting analysis for LAP revealed the presence of the LAP peptide in mammary alveolar tissue. When the mammary gland was immunostained with LAP antibody, epithelial cells of both infected and non-infected alveoli were immunopositive. These results indicate that LAP is localized in the epithelium of non-infected as well as infected alveolus in the mammary gland in cows.     

Glucose transport and milk secretion during manipulated plasma insulin and glucose concentrations and during LPS‐induced mastitis in dairy cows

In dairy cows, glucose is essential as energy source and substrate for milk constituents. The objective of this study was to investigate effects of long‐term manipulated glucose and insulin concentrations in combination with a LPS‐induced mastitis on mRNA abundance of glucose transporters and factors involved in milk composition. Focusing on direct effects of insulin and glucose without influence of periparturient endocrine adaptations, 18 dairy cows (28 ± 6 weeks of lactation) were randomly assigned to one of three infusion treatments for 56 h (six animals each). Treatments included a hyperinsulinemic hypoglycaemic clamp (HypoG), a hyperinsulinemic euglycaemic clamp (EuG) and a control group (NaCl). After 48 h of infusions, an intramammary challenge with LPS from E. coli was performed and infusions continued for additional 8 h. Mammary gland biopsies were taken before, at 48 (before LPS challenge) and at 56 h (after LPS challenge) of infusion, and mRNA abundance of genes involved in mammary gland metabolism was measured by RT‐qPCR. During the 48 h of infusions, mRNA abundance of glucose transporters GLUT1, 3, 4, 8, 12, SGLT1, 2) was not affected in HypoG, while they were downregulated in EuG. The mRNA abundance of alpha‐lactalbumin, insulin‐induced gene 1, κ‐casein and acetyl‐CoA carboxylase was downregulated in HypoG, but not affected in EuG. Contrary during the intramammary LPS challenge, most of the glucose transporters were downregulated in NaCl and HypoG, but not in EuG. The mRNA abundance of glucose transporters in the mammary gland seems not to be affected by a shortage of glucose, while enzymes and milk constituents directly depending on glucose as a substrate are immediately downregulated. During LPS‐induced mastitis in combination with hypoglycaemia, mammary gland metabolism was more aligned to save glucose for the immune system compared to a situation without limited glucose availability during EuG.     

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.     

Dynamics of lingual antimicrobial peptide,lactoferrin concentrations and lactoperoxidase activity in the milk of cows treated for clinical mastitis

The aim of the present study was to examine changes in innate immune factors in the milk of mastitic dairy cows treated with antibiotics. Cows in the antibiotics group (n = 13) were infused into the mammary gland with cefazolin on the sixth day after mastitis was diagnosed (the day of the mastitis diagnosis = day ?6). The control group (n = 12) was not treated. Milk samples were collected once every 2 days from days ?6 to 12 and somatic cell count (SCC), lingual antimicrobial peptide (LAP), and lactoferrin (LF) concentrations and lactoperoxidase (LPO) activity were measured. SCC and LF concentrations in the antibiotics group markedly decreased after the antibiotic treatment. When cows in the antibiotics group were divided according to SCC on day 0, LAP concentrations and LPO activity in cows with a lower SCC on day 0 (<5 × 10⁶ cell/mL) were significantly higher and lower than those in cows with a higher SCC, respectively. These results suggest that LF concentration decreased with decrease in SCC after treatment and that LAP concentration and LPO activity differed depending on the severity of mastitis. This is the first report to reveal the dynamics of innate immune factor in milk of cows treated for clinical mastitis.     

Translocation of intrauterine-infused bacterial lipopolysaccharides to the mammary gland in dexamethasone-treated goats

Our previous study showed that intrauterine-infused lipopolysaccharide (LPS) can be translocated to the mammary gland to induce weak inflammation. This study aimed to determine whether dexamethasone treatment facilitated the translocation of LPS from the uterus to the mammary gland to induce a heavy inflammatory response. Sixteen goats were divided into control and LPS groups, subjected to daily dexamethasone administration before saline or LPS infusion. Milk and blood samples were collected before and after LPS infusion to determine the milk yield and somatic cell count (SCC) and blood leucocyte count (BLC), cytokines, antimicrobial peptides and serum amyloid A (SAA) concentrations. Mammary gland tissues were collected from two goats before and 24 hr after LPS infusion for immunohistochemical analysis of LPS. The mean SCC in the LPS group was significantly higher, whereas the milk yield was significantly lower than that in the control group after LPS infusion. The mean BLC in the LPS group was significantly lower than in the control group after LPS infusion. Furthermore, milk concentrations of IL-1β, S100A8 and lactoferrin were higher in the LPS group than in the control group after infusion. LPS was detected in the connective tissues and inner alveolar spaces of the mammary glands 24 hr after LPS infusion. We concluded that dexamethasone administration facilitated the translocation of intrauterine-infused LPS to the mammary gland, where it induced an inflammatory response. Therefore, LPS translocated from other organs, such as the uterus, can induce heavy inflammation in the mammary gland under immunosuppressive conditions.     

Recombinant bovine soluble CD14 sensitizes the mammary gland to lipopolysaccharide

Standard therapies including administration of potent antibiotics, aggressive fluid resuscitation and metabolic support have not been successful in relieving symptoms and reducing mortality associated with acute coliform mastitis. It is important to understand the pathophysiological response of the mammary gland to coliform infections when designing preventive or therapeutic regimens for controlling coliform mastitis. Our laboratory has previously shown that macrophages and polymorphonuclear neutrophils in milk express CD14 on their cell surface. In this study, we found that soluble CD14 (sCD14) is present in milk whey as a 46kDa protein reacted with anti-ovine CD14 antibody. Additional functional studies found that: (1) under serum-free condition, complexes of LPS-recombinant bovine soluble CD14 (rbosCD14) induced activation of mammary ductal epithelial cells (as measured by changes in interleukin-8 (IL-8) mRNA level by competitive RT-PCR) at low concentrations of LPS after 6 or 24h incubation (1-1000ng/ml), whereas LPS alone did not induce activation of mammary ductal epithelial cells at the same concentrations, and (2) intramammary injection of low concentrations of LPS did not increase concentration of leukocytes in milk. In contrast, LPS-rbosCD14 complex containing the same concentration of LPS increased the concentration of leukocytes in the injected mammary gland at 12 and 24h post-injection. These results indicate that rbosCD14 sensitizes mammary epithelial cells to low concentrations of LPS in vitro and in vivo. Endogenous sCD14 in milk may be important in initiating host responses to Gram-negative bacterial infections.     

Effect of bovine lactoferrin feeding on lipopolysaccharide-induced metabolic and hormonal disturbances in preruminant calves

One of the biological functions of bovine lactoferrin (LF) is modulation of the host defense system, including cytokine production and immune response. The aim of the present study was to investigate the effect of oral administration of LF in calves on lipopolysaccharide (LPS)‐induced metabolic and hormonal changes in inflammatory response. Thirty Holstein calves at 4 day of age were given one of three oral doses of LF (0, 1, 3 g/day) for 10 days (?10 day to ?1 day). They were injected i.v. with LPS (50 ng/kg bodyweight) the day (day 0) after the end of LF treatment. Plasma samples were obtained on ?10, 0 day (immediately before LPS injection), and at 2, 6, 12, 24, 48, 72, and 96 h after LPS injection. Plasma tumor necrosis factor‐α concentrations at 2 h after LPS treatment were lower (P < 0.05) in LF 1 g/day‐fed claves compared with LF 0 g/day (control) calves. On day 0 there were no significant group differences in plasma LF concentration. Plasma concentration of haptoglobin in control calves was elevated by LPS injection. In LF groups, plasma haptoglobin concentrations slightly increased after LPS injection, but those levels at 6–24 h were lower (P < 0.05) than in the control group. The LF treatment inhibited (P < 0.05) the reduction of plasma ferrin concentration in calves following LPS challenge. The concentration of plasma aspartate aminotransferase in calves treated with LF was lower (P < 0.05) than in control calves at 24–96 h after LPS treatment. The concentration of plasma insulin‐like growth factor‐1 (IGF‐1) in all groups was decreased by LPS treatment, while in the LF groups the IGF‐1 level was higher (P < 0.05) than in the control group. Plasma adrenocorticotropic hormone and insulin concentrations in LF groups were lower (P < 0.05) than in control calves at 2 h after LPS injection. These data suggest that LF has a substantial anti‐inflammatory effect on the modulation of the host defense system in preruminant calves.     

脂多糖对泌乳奶牛乳中氨基酸组成及蛋白质代谢相关基因表达的影响

本试验旨在通过半体内和体外试验研究灌注脂多糖(lipopolysacchride,LPS)对泌乳奶牛乳中氨基酸组成和蛋白质代谢相关基因表达的影响。半体内试验选用6头经产的荷斯坦奶牛[泌乳天数为(186±30)d],随机分为对照组和试验组,每组3头。采用交叉试验设计,每期正试期7 d,间隔期14 d;试验组阴外动脉灌注LPS(大肠杆菌型O111∶B4,0.01μg/kg),对照组阴外动脉灌注生理盐水。体外试验以乳腺上皮细胞为模型,基础培养基中LPS添加水平分别为0、0.1和10.0 ng/mL,培养24 h后,采用实时定量-PCR(qRT-PCR)法检测目的基因的相对表达水平。结果表明,阴外动脉灌注LPS后,乳中必需氨基酸、支链氨基酸含量随着灌注时间的增加呈先升高后降低的趋势(P>0.05),灌注后6 h达到最高;乳中非必需氨基酸含量随着灌注时间的增加呈先降低后升高的趋势(P>0.05),灌注后6 h达到最低。LPS提高了乳腺上皮细胞中p70核糖体蛋白S6激酶-1(S6K1)和真核起始因子4E结合蛋白-1(4EBP1)mRNA的表达水平(P>0.05),且具有剂量效应。LPS对雷帕霉素靶点(mTOR)、Janus激酶2(JAK2)mRNA表达水平影响差异不显著(P>0.05),但有提高的趋势。与对照组相比,LPS显著提高了信号转导和转录激活因子5(STAT5)mRNA表达水平(P<0.05)。综上所述,LPS通过干扰mTOR通路和JAK2/STAT5通路影响了乳蛋白及氨基酸组成。     

Neutrophil recruitment in endotoxin-induced murine mastitis is strictly dependent on mammary alveolar macrophages

Mastitis, inflammation of the mammary tissue, is a common disease in dairy animals and mammary pathogenic Escherichia coli (MPEC) is a leading cause of the disease. Lipopolysaccharide (LPS) is an important virulence factor of MPEC and inoculation of the mammary glands with bacterial LPS is sufficient to induce an inflammatory response. We previously showed using adoptive transfer of normal macrophages into the mammary gland of TLR4-deficient C3H/HeJ mice that LPS/TLR4 signaling on mammary alveolar macrophages is sufficient to elicit neutrophil recruitment into the alveolar space. Here we show that TLR4-normal C3H/HeN mice, depleted of alveolar macrophages, were completely refractory to LPS intramammary challenge. These results indicate that alveolar macrophages are both sufficient and essential for neutrophil recruitment elicited by LPS/TLR4 signaling in the mammary gland. Using TNFα gene-knockout mice and adoptive transfer of wild-type macrophages, we show here that TNFα produced by mammary alveolar macrophages in response to LPS/TLR4 signaling is an essential mediator eliciting blood neutrophil recruitment into the milk spaces. Furthermore, using the IL8 receptor or IL1 receptor gene-knockout mice we observed abrogated recruitment of neutrophils into the mammary gland and their entrapment on the basal side of the alveolar epithelium in response to intramammary LPS challenge. Adoptive transfer of wild-type neutrophils to IL1 receptor knockout mice, just before LPS challenge, restored normal neutrophil recruitment into the milk spaces. We conclude that neutrophil recruitment to the milk spaces is: (i) mediated through TNFα, which is produced by alveolar macrophages in response to LPS/TLR4 signaling and (ii) is dependent on IL8 and IL1β signaling and regulated by iNOS-derived NO.     

Dynamics of leukocytes and cytokines during experimentally induced Streptococcus uberis mastitis

Streptococcus uberis causes a significant proportion of clinical and subclinical intramammary infections (IMI) in lactating and non-lactating dairy cows. In spite of this, its pathogenesis is incompletely understood. A study was conducted to determine leukocyte and cytokine dynamics during experimentally induced S. uberis mastitis. Five Jersey and five Holstein cows were challenged via intramammary inoculation of S. uberis into two uninfected mammary glands. Sixteen of 20 challenged mammary glands developed clinical mastitis with peak clinical signs observed at 144 h. The number of S. uberis in milk increased (P<0.05) 48 h after challenge, in spite of an increase in milk somatic cells that began at 18 h (P<0.001) and remained elevated throughout the study. Increased tumor necrosis factor-alpha (TNF-alpha), interleukin-1beta (IL-1beta) and interleukin-8 (IL-8) in milk were detected 66 h after challenge (P<0.05). Peak TNF-alpha and IL-8 concentrations occurred 120 h after challenge and preceded peak clinical signs. Experimental S. uberis IMI induced local production of TNF-alpha, IL-1beta and IL-8, which may play a role in the pathogenesis of S. uberis mastitis. Other mediators may be involved in initial leukocyte recruitment to the mammary gland, since increases in milk somatic cells occurred earlier than cytokine production.     

Effect of Intramammary Infusion of Tumour Necrosis Factor‐α on Milk Protein Composition and Induction of Acute‐Phase Protein in the Lactating Cow

The present study was designed to evaluate the effects of tumour necrosis factor‐α (TNF‐α) on lactating bovine mammary functions such as milk protein secretion and the integrity of the milk‐blood barrier. The effect on the induction of the systemic inflammatory response was also examined using concentrations of serum haptoglobin (Hp), a major inflammatory acute‐phase protein, as an index. One hundred micrograms per mammary gland of recombinant bovine (rBo) TNF‐α or placebo saline was individually infused into a rear mammary gland of each of four lactating cows, and milk and blood samples were collected before and 4, 8, 24, 32, 48, 96 and 168 h after infusion. In the rBoTNF‐α‐infused gland, increases of somatic cell counts were observed at 4–48 h. Although concentrations of total milk protein were not changed, compositions of milk proteins varied following rBoTNF‐α infusion. Concentrations of caseins, α‐lactalbumin and β‐lactoglobulin were significantly decreased at 4 and 8 h. Lactoferrin concentrations were significantly increased at 4 h. Significant infiltrations of serum albumin, immunoglobulin G1 (IgG1) and IgG2 were observed at 4 and 8 h. Elevations of the serum concentration of Hp were detected at 8‐32 h, but were very small in comparison with those reported in inflammatory diseases. Changes in rectal temperature and white blood cell counts were not significant. These results show that single rBoTNF‐α infusion into the lactating mammary gland suppresses the lactogenic function of the gland and influences the function of the milk‐blood barrier, with little effect on the generalized inflammatory response.     

Lingual antimicrobial peptide and lactoferrin concentrations and lactoperoxidase activity in bovine colostrum are associated with subsequent somatic cell count

The present study was undertaken to examine whether potential levels of innate immune factors (lingual antimicrobial peptide (LAP), lactoferrin (LF) and lactoperoxidase (LPO)) in colostrum are associated with subsequent milk somatic cell count (SCC) in dairy cows. Quarter milk samples were collected daily for 1 week postpartum to measure LAP and LF concentrations and LPO activity. SCC in milk was determined weekly for 2 months postpartum and its correlations to concentrations of LAP and LF and LPO activity were examined. Only small variations of all immune factors were found among four udders in each individual cow, whereas there were great differences in these factors among cows. Negative correlation was detected only between LPO activity and mean and maximum SCC, whereas its relationship was not significant. LAP and LF concentrations were significantly correlated positively to mean, maximum and minimum SCC. These results suggest that the great difference in innate immune factors among animals and high LAP and LF concentrations in colostrum may be associated with subsequent high incidence of SCC increase.     

LPS对小鼠乳腺组织中NF—KB、ACCa和β-CaseinmRNA表达的影晌

为探讨灌注不同质量浓度LPS对小鼠乳腺组织中NF-xB、ACCa和pCaseinmRNA表达的影响，选择30只雌性ICR小鼠为试验动物，受孕后随机分为试验组和对照组，试验组经第4对乳头灌注不同质量浓度LPS（0．1，5，10，50，100mg／L），对照组灌注生理盐水，于灌注后6h采集乳腺组织样品，组织学方法分析乳腺组织的病理变化；采用RT—PCR方法分析乳腺组织中NF_KB、ACCa和B—CaseinmRNA表达的变化。病理切片结果显示，随着LPS灌注浓度的增加，乳腺小叶间炎性细胞数量逐步增加，乳腺小叶内腺泡结构破坏程度也变大；对乳腺组织中NF-xB、ACCa和pCasein的mRNA表达水平进行分析时，发现灌注LPS小鼠乳腺组织中NF-KBmRNA的表达水平随着LPS灌注浓度的增加而逐步增加，而ACCa和pCaseinmRNA的表达水平则随着LPS灌注浓度的增加而逐步降低。结果表明，灌注LPS能够上调N-KBmRNA的表达，下调ACCa和肛CaseinmRNA的表达。     

Concentration patterns of antibacterial factors and immunoglobulin A antibody in foremilk fractions of healthy cows

Antibacterial factors act as innate immune components, which respond as soon as bacteria enter a living organism. To prevent and treat mastitis in cattle, understanding the concentrations of these substances inside the udder is important; however, they remain to be studied. In this investigation, the concentration of lingual antimicrobial peptide (LAP), S100 protein (S100A7), lactoferrin (LF), and immunoglobulin antibody were measured in the different fractions of foremilk. Lactating Holstein cows were examined, and 10 foremilk fractions were obtained from sequential samples up to 150 ml. The LAP concentrations in milk samples increased until 25 ml. The LF concentrations increased up to the 10 ml fraction, then stabilized at low level after the 50 ml fraction. For S100A7, some fractions had significantly higher (p < .05) concentrations than the 5 or 10 ml fractions. The IgA antibody concentration increased up to the 5 ml fraction, then after 50 ml fraction showed relatively low concentrations. This investigation determined the concentration patterns of LAP, LF, S100A7, and IgA antibody secreted in milk inside the udders of healthy lactating cows as baseline data. These distinct concentration patterns might indicate various protective responses.     

Effects of continuous low dose infusion of lipopolysaccharide on inflammatory responses,milk production and milk quality in dairy cows

The objective of this study was to evaluate the effects of continuous low dose infusion of lipopolysaccharide (LPS) on inflammatory responses and milk production and quality in lactating dairy cows. Eight Holstein cows were assigned to two treatments in a cross‐over experimental design. Cows were infused intravenously either with saline solution or with saline solution containing LPS from Escherichia coli O111:B4 at a dose of 0.01 μg LPS/kg body weight for approximately 6 hr each day during a seven‐day trial. The clinical symptoms and milk production performance were observed. Milk samples were analysed for conventional components, fatty acids and amino acids. And jugular vein and mammary vein plasma samples were analysed for concentrations of cytokines and acute phase proteins. LPS infusion decreased feed intake and milk yield. An increase in body temperature was observed after LPS infusion. LPS infusion also increased plasma concentrations of interleukin‐1β, serum amyloid A, LPS‐binding protein, C‐reactive protein and haptoglobin. LPS infusion decreased the contents of some fatty acids, such as C17:1, C18:0, C18:1n9 (trans) and C18:2n6 (trans), and most amino acids except for methionine, threonine, histidine, cysteine, tyrosine and proline in the milk. The results indicated that a continued low dose infusion of LPS can induce an inflammatory response, decrease milk production and reduce milk quality.