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1.
The pharmacokinetics of erythromycin was studied in five lactating dairy cows following single intramammary infusion of 300 mg erythromycin in each of two quarters per cow with specific mastitis. Levels of erythromycin in plasma and quarter milk samples were measured by agar plate diffusion assay using Micrococcus luteus (ATCC 9341) as the test organism. Erythromycin level in plasma reached a peak concentration value (C max) of 0.07 ± 0.01 μg/ml at 30 min; thereafter, levels declined gradually to reach 0.05 ± 0.00 μg/ml 12 h post drug administration. The pharmacokinetic profile of the drug revealed mean absorption half life (t 1/2ka) as 0.26 ± 0.05 h. The drug was eliminated slowly with elimination half-life (t 1/2β) of 13.75 ± 0.35 h and elimination rate constant (k el) of 0.04 ± 0.00 h−1. The volume of distribution based on the zero-time plasma concentration intercept of the least-squares regression line of the elimination phase (V d(B)) was 0.032 L/kg. The drug crossed to untreated quarters also; mean drug levels of 0.20 ± 0.07, 0.23 ± 0.07, 0.17 ± 0.04, and 0.17 ± 0.04 μg/ml were found at 3, 6, 8 and 12 h, respectively. The mean drug concentration for treated quarters was measured as 22.97 ± 2.31 μg/ml milk at first milking (12 h) following drug infusion. No apparent adverse reaction was seen in cows administered erythromycin. It is concluded that following intramammary infusion erythromycin diffuses readily and extensively in various body fluids and tissues and adequate concentration is maintained in udder tissues for at least 12 h post intramammary administration. Thus, erythromycin may be recommended for local therapy of acute mastitis caused by Gram-positive bacteria in lactating dairy cows.  相似文献   

2.
Pharmacokinetics of polymyxin B administered via the bovine mammary gland   总被引：2，自引：0，他引：2  
Polymyxin B was infused into normal, chronically inflamed, and acutely inflamed quarters of the mammary gland of lactating cows at dosages ranging between 1 and 2 million units (100–200 mg) per quarter. Samples of milk from treated and non-treated quarters, jugular venous blood, subcutaneous abdominal (mammary) venous blood, and urine were collected at intervals after treatment and were assayed using microbiological test methods for polymyxin B concentrations. The drug was not absorbed from normal and chronically inflamed quarters; more than 90% of the infused dose was recovered in milk within 24 h after treatment, and drug residues were detected up to the ninth milking. Drug concentrations in milk from acutely inflamed quarters were significantly lower than in milk from normal quarters; 55% of the infused dose was recovered in the milk within 24 h after treatment. The drug was detected in milk from non-treated quarters, in blood from the subcutaneous abdominal vein, and in the urine during 36–48 h after acutely inflamed quarters were infused with the drug. These data indicate that polymyxin B is well distributed throughout, and is absorbed to a significant degree into the systemic circulation from the acutely inflamed udder.  相似文献   

3.
The infusion of ozone into the inflamed quarter of cows with clinical mastitis was performed and the efficacy of ozone therapy was evaluated. Ozone was infused into the inflamed quarter via a teat canal using ozone gas generating equipment. Nineteen Holstein cows with acute clinical mastitis were divided into two groups: 15 cows treated with ozone therapy, and 4 cows treated with antibiotic therapy. Systemic and local clinical signs, California Mastitis Test scores, the mastitis causing pathogens, electronic conductivity of milk, and somatic cell counts in milk from ozone- and antibiotic-treated quarters, were compared between the groups. Sixty percent (9/15) of cows with acute clinical mastitis treated with ozone therapy, did not require any antibiotics for recovery. This newly developed ozone therapy method was proven to be effective, safe, and cost effective, and carries no risk of drug residues in milk.  相似文献   

4.
Eleven lactating dairy cows were used to evaluate the response of bovine mammary glands to increasing doses of recombinant bovine interferon (rBoIFN)-gamma. Right front and rear quarters were intramammarily infused with eight different doses (10(2) U to 2 x 10(8) U/quarter) of rBoIFN-gamma; each dose was tested in at least two quarters. Left udder halves served as within animal controls in which quarters were injected with a saline placebo or were not infused at all. Milk secretion samples for compositional analysis were collected from each quarter prior to infusion and at 6, 24, 36 and 48 h following infusion. Animals were slaughtered immediately following the 48 h sampling period and mammary tissue was obtained for morphometric analyses. Milk composition was similar between control quarters and those quarters infused with up to 10(5) U of rBo-IFN-gamma during the entire sampling period. Quarters infused with 10(6) U and 10(7) U of rBoIFN-gamma had higher milk somatic cell counts (SCC) following treatment compared with preinfusion values. Changes in the composition of mammary secretion were most dramatic in quarters infused with greater than or equal to 10(8) U of rBoIFN-gamma as indicated by the significant increase in SCC and milk pH with a concomitant decrease in lactose concentration when compared with pre-infusion values or with control quarters. Morphometric analysis of tissue demonstrated an increase in stroma, a decrease in luminal area, and a marked increase in the number of infiltrating leukocytes in those quarters infused with the higher doses of rBoIFN-gamma.(ABSTRACT TRUNCATED AT 250 WORDS)  相似文献   

5.
The milk excretion of group B streptococci (Streptococcus agalactiae) from the udder quarters was examined in thirty cows of a heavily infected herd. Six samplings were performed in ten- to fourteen-day intervals. With respect to excretion rate, the set of cows could be divided into three groups: 1. group of cows excreting S. agalactiae from all udder quarters permanently and absolutely regularly; 2. cows excreting S. agalactiae regularly only from some quarters, certain quarter being negative at all samplings; 3. cows excreting streptococci from all quarters absolutely irregularly, without any conclusive order or dependence. The cytological picture of all samples exhibited no signs of inflammation. The discussion deals with some factors that may influence the excretion of streptococci with milk.  相似文献   

6.
The pharmacodynamics of carprofen and its pharmacokinetics in plasma and milk of healthy cows and cows with endotoxin-induced mastitis were studied after a single intravenous dose of 0.7 mg/kg body weight. Carprofen was administered to five clinically healthy cows and to the same cows 3 weeks later, 2 h after intramammary infusion of endotoxin. Mastitis developed in all endotoxin-infused quarters. The pharmacokinetic characteristics of carprofen in healthy cows were a small volume of distribution (0.09 l/kg), a relatively low systemic clearance (2.4 ml/h kg), and a long elimination half-life (30.7 h). In the mastitic cows, systemic clearance (1.4 ml/h kg) was significantly lower (P less than 0.01), and elimination half-life (43.0 h) was significantly longer (P less than 0.01) than in the normal animals. Concentrations of carprofen in milk from healthy quarters were below the limit of detection for the assay (0.022 micrograms/ml). In milk from mastitic quarters, concentrations of carprofen increased up to 0.164 micrograms/ml during the first 12 h after induction of mastitis, but were less than 0.022 micrograms/ml at 24 to 48 h. Compared with the untreated mastitic controls, carprofen treatment significantly reduced heart rate (P less than 0.01), rectal temperature (P less than 0.001), quarter swelling (P less than 0.01) and other parameters measured. Local and systemic adverse reactions to carprofen were not observed.  相似文献   

7.
Infection of the mammary gland (mastitis) was produced by infusing ten quarters 2/cow x 5 cows) with Staphylococcus aureus strain 305. Mastitic and normal quarters were then infused with a preparation containing two levels of penicillin G (100,000 and 200,000 IU) in 10 mL of 3% aluminum monostearate and peanut oil. Milk penicillin levels were determined prior to treatment and twice daily for eight milkings after treatment. Normal and mastitic quarters infused with 200,000 IU had higher peak levels than those infused with 100,000 IU. Milk penicillin levels were similar in mastitic and normal quarters for the first three milkings after treatment. However, residues persisted for a longer time in milk from mastitic quarters. Penicillin was not detected in milk from the untreated control quarters nor in serum samples assayed during the experiment. The in vitro penicillin G sensitivity of the udder pathogen (MIC=0.039 and MBC=0.078 IU) was well below the milk penicillin levels for the first five milkings in all cases. However, infection recurred in two of the ten quarters (one receiving 100,000 IU and one receiving 200,000 IU).  相似文献   

8.

Background

Subclinical mastitis is of concern in veterinary hospitals because contagious mastitis pathogens might be unknowingly transmitted to susceptible cows and then back to their farm of origin.

Objectives

To evaluate the California mastitis test (CMT) as an indicator of intramammary infection (IMI) in lactating dairy cows admitted to a veterinary hospital.

Animals

A total of 139 admissions of 128 lactating dairy cows admitted to the University of Illinois Veterinary Teaching Hospital over a 2‐year period.

Methods

A retrospective study with a convenience sample was conducted. Medical records of cows with CMT results and milk culture results for the day of admission were reviewed. Breed, age, season, maximum CMT score for the 4 quarters, maximum CMT score difference, and clinical diagnosis were evaluated as predictors of IMI by the chi‐square test and stepwise logistic regression.

Results

An IMI was identified in 51% of quarters. For cows admitted without evidence of clinical mastitis, the sensitivity of a CMT score ≥trace in predicting an IMI on a quarter or cow basis was 0.45 and 0.68, respectively. The distributions of maximal quarter CMT score and the maximum difference in quarter CMT score for cows without evidence of clinical mastitis did not differ (P = 0.28, P = 0.84, respectively) for cows with and without IMI. Stepwise logistic regression did not identify significant predictors of IMI in cows without clinical mastitis.

Conclusions

Lactating dairy cattle admitted to a veterinary hospital should be managed as if they have an IMI, even in the absence of clinical mastitis.  相似文献   

9.
OBJECTIVE: To determine the elimination kinetics of ceftiofur hydrochloride in milk after intramammary administration in lactating dairy cows. DESIGN: Prospective study. ANIMALS: 5 lactating dairy cows. PROCEDURE: After collection of baseline milk samples, 300 mg (6 mL) of ceftiofur was infused into the left front and right rear mammary gland quarters of each cow. Approximately 12 hours later, an additional 300 mg of ceftiofur was administered into the same mammary gland quarters after milking. Milk samples were collected from each mammary gland quarter every 12 hours for 10 days. Concentrations of ceftiofur and its metabolites in each milk sample were determined to assess the rate of ceftiofur elimination. RESULTS: Although there were considerable variations among mammary gland quarters and individual cows, ceftiofur concentrations in milk from all treated mammary gland quarters were less than the tolerance (0.1 microg/mL) set by the FDA by 168 hours (7 days) after the last intramammary administration of ceftiofur. No drug concentrations were detected in milk samples beyond this period. Ceftiofur was not detected in any milk samples from nontreated mammary gland quarters throughout the study. CONCLUSIONS AND CLINICAL RELEVANCE: Ceftiofur administered by the intramammary route as an extra-label treatment for mastitis in dairy cows reaches concentrations in milk greater than the tolerance set by the FDA. Results indicated that milk from treated mammary gland quarters should be discarded for a minimum of 7 days after intramammary administration of ceftiofur. Elimination of ceftiofur may be correlated with milk production, and cows producing smaller volumes of milk may have prolonged withdrawal times.  相似文献   

10.
The objective of the study was to estimate the prevalence and losses associated with subclinical mastitis (SCM) caused by Staphylococcus aureus in Ethiopian crossbred dairy cows. A split-udder trial was carried out to determine milk yield losses in udder quarter with S. aureus-caused SCM. Each quarter of the study cows was examined using the California Mastitis Test (CMT) and quarter milk production was measured over a period of 8 days. Milk yield losses for CMT positive quarters were estimated by comparing production of quarters with CMT score 0. Mean milk yield for uninfected healthy quarters was 1.66 kg per milking (95% CI, 1.66–1.55 kg per milking), and the rate of milk reduction for quarters with CMT scores of 1+, 2+, and 3+ was 25%, 33%, and 48%, respectively. Economic losses at different farm-size levels were calculated by multiplying the prevalence of CMT scores with milk yield losses associated with respective CMT scores. In Debre Ziet dairy herds, a quarter with SCM due to S. aureus lost an average of 34.5% of its potential milk production while the total milk yield loss per cow was estimated at 6.8%. Losses were highest in large-scale (13%) farms and lowest (3.7%) in small-scale. Based on the prevalence, the overall financial loss for each cow per lactation was 984.64 Eth Birr (US78.65) and losses in large farms (1,882.40 Eth Birr or US78.65) and losses in large farms (1,882.40 Eth Birr or US150.35) were over 3.5 times the loss in small-size farms. These figures possibly underestimate the potential benefits of mastitis control program as they do not include other direct and indirect costs.  相似文献   

11.
Eighteen Holstein dairy cows ranging in body weight from 500–700 kg and with an average milk yield of 37 ± 6 kg/day were used to investigate the depletion of florfenicol (FFL) in milk and plasma of dairy cows. Three groups of six were administered FFL: Group A, intramammary (IMM) infusion of ~2.5 mg FFL/kg BW at three consecutive milking intervals (total amount of ~7.5 mg/kg BW); Group B, one IMM infusion (20 mg/kg BW) into one quarter and Group C, one subcutaneous (SC) treatment (40 mg/kg BW). IMM infusions were into the right front quarter. Cows were milked daily at 06:00 and 18:00 h. The highest concentrations (Cmax) and time to Cmax (Tmax) were: 1.6 ± 2.2 μg·FFL/mL milk at 22 h (Group A), 5.5 ± 3.6 μg·FFL/mL milk at 12 h (Group B), and 1.7 ± 0.4 μg·FFL/mL milk at 12 h (Group C). The half‐lives (t1/2) were ~19, 5.5, and 60 h, for Groups A, B, and C, respectively. FFL was below the limit of detection (LOD) by 60 h in three Group B cows, but above the LOD at 72, 84, and 120 h in three cows. FFL was above the LOD in milk from Group C's cows for 432–588 h. Plasma values followed the same trends as milk. The results demonstrate that IMM‐infused FFL is bioavailable and below the LOD within 72–120 h. The concentration of FFL was detectable in both plasma and milk over the course of 2–3 weeks after SC administration. The absence of residue depletion data presents problems in determining safe levels of FFL residues in milk and edible tissues. The data presented here must not be construed as approval for extra‐label use in food animals.  相似文献   

12.
OBJECTIVE: To evaluate the elimination kinetics of chlorhexidine in milk when used as an intramammary infusion to stop lactation in cows. DESIGN: Prospective study. ANIMALS: 6 cows. PROCEDURE: The study was performed in 2 phases. Three cows were studied in each phase. All cows were treated with chlorhexidine suspension by infusion into a mastitic mammary gland quarter after 2 milkings 24 hours apart. Foremilk samples (100 mL) were collected from treated and untreated (controls) mammary gland quarters of each cow. Chlorhexidine was extracted from raw milk, and residue concentrations were quantified by use of high-performance liquid chromatography. Foremilk samples from days 2, 5, and 8 were analyzed in phase I, and samples from time 0 and days 3, 7, 14, 21, 28, 35, and 42 were analyzed in phase II. RESULTS: In phases I and II, there was no quantifiable transference of chlorhexidine to milk in untreated mammary gland quarters. Measurable chlorhexidine residues were found in milk from treated mammary gland quarters of 2 cows throughout the 42-day sample period in phase II. Estimated mean elimination half-life for chlorhexidine in milk was 11.5 days. CONCLUSIONS AND CLINICAL RELEVANCE: On the basis of the long elimination half-life of chlorhexidine in milk from treated mammary gland quarters, the lack of human dietary exposure data to suggest a food tolerance for chlorhexidine in food products, and the Food and Drug Administration's published zero tolerance for chlorhexidine in uncooked edible calf tissues, we do not recommend extralabel use of chlorhexidine suspension as a treatment to stop lactation in mastitic mammary gland quarters of cows.  相似文献   

13.
Quarter Milking for Improved Detection of Increased SCC   总被引：1，自引：0，他引：1  
The aim of the present study was to investigate whether milk composition and milk yield are changed in relation to a moderate increase in milk somatic cell count (SCC) in separate udder quarters. During a period of 13 weeks, 4158 bulk quarter milk samples from 68 cows were collected and analysed for milk SCC and milk composition. The sampling was done twice weekly. The cows were in different stages of lactation and in different lactation numbers. For calculations, three groups of cows were formed according to their SCC value. Group 1 cows, where all quarters had an SCC <100,000 cells/ml at all sampling occasions, were considered to be non-affected. Group 2 cows had one udder quarter with an increased SCC >100,000 cells/ml and 1.5-fold higher than the opposite quarter at one sampling occasion. For group 3 cows, the increase in SCC remained for several consecutive sampling occasions. Data from group 1 cows revealed that front and rear quarters were similar when compared with each other. For group 3 cows, the lactose content in milk decreased significantly, simultaneously with the increase in SCC and remained decreased for two sampling occasions after the initial increase in SCC. It was concluded that deviations in lactose content within front and rear quarters, respectively, may be a useful tool for detection of moderately increased SCC in separate udder quarters.  相似文献   

14.
Data from a randomized controlled field study of selective dry cow therapy were used in which 686 cows had been allocated to 2 control groups (sampling only or placebo) or 2 therapy groups. Possible factors from previous lactation were assessed in determining their association with the probability of 'failure', designated as a cow milk somatic cell count (CMSCC) of greater than 399,000 per ml in geometric mean of several measurements during subsequent lactation. Success cows were those with a CMSCC of less than 200,000 per ml. For our analyses, this targeted 187 success cows and 186 failure cows. Therapy was given as a total dose of 400,000 IU penicillin and 100 mg neomycin per infected quarter as dry cow preparation once, or as a lactation formula with a total dose of 1.2 million IU penicillin and 1,200 mg dihydrostreptomycin per infected quarter during a 1-week period. Significant factors in the predictive model for success included therapy, low level of CMSCC (geometric mean of the 3 last tests) in previous lactation, low level of CMSCC (weighted by daily milk yield mean) in the herd, young cows, and not having had a case of treatment for chronic clinical mastitis. Additional information on the probability of failure in treated and untreated cows can be predicted by number of quarters infected with Staphylococcus aureus approximately 1.5 months before drying off. The models derived are considered for use as tools in selective treatment and culling decisions.  相似文献   

15.
Quarter foremilk samples were taken at 2–3 weekly intervals for several years in a experimental herd comprising about 45 cows. The samples were submitted to bacteriological analysis and somatic cell counting. The most prevalent quarter infections from 1982 to 1988 were by coagulase-negative staphylococci (15–20% of all the quarters sampled). Most of these (75.6%) persisted until drying-off Dry cow therapy eliminated 86.5% of these infections. Comparison of udder quarters within cows, involving 775 samples from pairs of non-infected quarters and quarters infected by coagulase-negative staphylococci, yielded geometric means of somatic cell counts of 210 000 and 420 000 cells/ml, respectively. The correlation (r=0.87) between the herd bulk milk somatic cell count (SCC) and its estimation from the quarter milk somatic cell count performed on the same day allowed us to evaluate the contribution of the different categories of quarters, according to their infection status, to the herd bulk milk SCC. Quarters infected by a major pathogen (8.5% of samples) gave rise to 46.6% of the total number of cells, while quarters infected by coagulase-negative staphylococci (17.8% of samples) gave rise to 18.1%. Although coagulase-negative staphylococci represented only a secondary source of somatic cells as compared to major pathogens, they were not a negligible source considering the threshold of 300 000 somatic cells advocated for herd milk of good quality.  相似文献   

16.
It was the objective of this study to analyse shedding patterns and somatic cell counts in cows and quarters infected with Prototheca spp. and to evaluate two approaches to identify infected animals by somatic cell count (SCC) or by bacteriological analysis of pooled milk samples. Five lactating dairy cows, chronically infected with Prototheca spp. in at least one quarter were studied over 11 weeks to 13 months. Quarter milk samples and a pooled milk sample from 4 quarters were collected aseptically from all quarters of the cows on a weekly basis. Culture results of quarter milk and pooled samples were compared using cross tabulation. SCC of quarter milk samples and of pooled samples were related to the probability of detection in the infected quarters and cows, respectively. Shedding of Prototheca spp. was continuous in 2 of 8 quarters. In the other quarters negative samples were obtained sporadically or over a longer period (1 quarter). Overall, Prototheca spp. were isolated from 83.6% of quarter milk samples and 77.0% of pooled milk samples of infected quarters and cows. Somatic cell counts were higher in those samples from infected quarters that contained the algae than in negative samples (p < 0.0001). The same applied for composite samples from infected cows. Positive samples had higher SCC than negative samples. However, Prototheca spp. were also isolated from quarter milk and pooled samples with physiological SCC (i.e. < 10(5)/ml). Infected quarters that were dried off did not develop acute mastitis. However, drying off had no effect on the infection, i.e. samples collected at calving or 8 weeks after dry off still contained Prototheca spp. Results indicate that pre-selection of cows to be sampled for Prototheca spp. by SCC and the use of composite samples are probably inadequate in attempts to eradicate the disease. However, due to intermittent shedding of the algae in some cows, single herd sampling using quarter milk samples probably also fails to detect all infected cases. Therefore, continuous monitoring of problem cows with clinical mastitis or increased SCC in herds during eradication programs is recommended.  相似文献   

17.

Background

Studies outside the Nordic countries have indicated that subclinical mastitis (measured by milk somatic cell count or the California Mastitis Test), intramammary infections (IMI), or blind quarters in beef cows may have negative effects on beef calf growth. Knowledge on prevalence of such udder health problems in Swedish beef cows is scarce. Therefore, the main aim of this study was to investigate subclinical mastitis, IMI and udder conformation in a number of beef cow herds. Production of β-lactamase in staphylococci was also investigated. Associations between certain cow factors and subclinical mastitis and IMI, and associations between cow and calf factors and 200 day calf weaning weight were also studied. The herds were visited once within a month after calving and once at weaning. Udder examination and quarter milk sampling, for somatic cell count and bacteriology, were performed in 8 to 12 cows per herd and occasion.

Results

Approximately 50%, 40% and 10% of the cows had subclinical mastitis, IMI, and at least one blind quarter, respectively, but the prevalence varied markedly between herds. Intramammary infections (mainly due to staphylococci) were identified in 13-16% of the milk samples. Less than 5% of the staphylococcal isolates produced β-lactamase. Approximately 11% of the cows sampled twice had the same IMI (mostly Staphylococcus aureus) at both samplings. Cow factors of importance for subclinical mastitis and/or IMI were teat and udder shape, breed, parity, presence of blind quarters, and cow hygiene. No significant associations were found between udder health parameters studied and calf weaning weights.

Conclusions

Subclinical mastitis and IMI, but not blind quarters, were common in beef cows, but the prevalence varied markedly between herds. Most IMI were caused by staphylococci and more than 95% of those were sensitive to penicillin. Cows with large funnel-shaped teats or pendulous udder after calving, and cows with blind quarters were at risk of having subclinical mastitis and/or IMI. Poor hygiene was also a risk factor for udder health problems. No significant associations were found between udder health and calf weaning weight. More studies on risk factors are warranted to improve advisory services on awareness and prevention of mastitis in beef cows.  相似文献   

18.
The excretion rate of dicloxacillin from milk was studied after intramammary administration of a suspension of the drug active in vegetable oil. Eight cows and eight sheep, four of each group in low and four in high milk production, were dosed with 200 mg dicloxacillin/quarter in cows and 100 mg dicloxacillin/quarter in sheep, three times at 12 h intervals. The dicloxacillin concentrations in milk were quantified by high performance liquid chromatography (HPLC). In cows, time until dicloxacillin was undetectable was 48 h and no difference was observed between the groups. In sheep, dicloxacillin was undetectable 72 h and 84 h after the treatment in low and in high milk production groups, respectively. The implications of several factors affecting the possible milk withdrawal period were studied. The results indicated that the pharmaceutical vehicle and the coefficient of lipid solubility exerted major effects on depletion time.  相似文献   

19.
The excretion rates of sodium penicillin and sodium cloxacillin from treated and untreated quarters of normal and mastitic cows were studied. Penicillin was detected in normal and infected quarters for 72 hours after treatment. Cloxacillin was detected in normal and infected quarters for 64 and 48 hours, respectively, after treatment. Differences in the excretion rates of both antibiotics from normal and infected treated quarters were not significant. Penicillin was detected in the untreated quarters of both normal and mastitic cows but cloxacillin was only detected in the untreated quarters of mastitic cows.  相似文献   

20.

Background

The objective of this study was to characterize the changes in various metabolic parameters in blood and milk during IMI challenge with Escherichia coli (E. coli) for dairy cows during early lactation. Thirty, healthy primiparous Holstein cows were infused (h = 0) with ~20-40 cfu of live E. coli into one front mammary quarter at ~4-6 wk in lactation. Daily feed intake and milk yield were recorded. At –12, 0, 3, 6, 12, 18, 24, 36, 48, 60, 72, 96, 108, 120, 132, 144, 156, 168, 180 and 192 h relative to challenge rectal temperatures were recorded and quarter foremilk was collected for analysis of shedding of E. coli. Composite milk samples were collected at -180, -132, -84, -36, -12, 12, 24, 36, 48, 60, 72, 84, 96, 132 and 180 h relative to challenge (h = 0) and analyzed for lactate dehydrogenase (LDH), somatic cell count, fat, protein, lactose, citrate, beta-hydroxybutyrate (BHBA), free glucose (fglu), and glucose-6-phosphate (G6P). Blood was collected at -12, 0, 3, 6, 12, 18, 24, 36, 60, 72, 84, 132 and 180 h relative to challenge and analyzed for plasma non-esterified fatty acids (NEFA), BHBA and glucose concentration. A generalized linear mixed model was used to determine the effect of IMI challenge on metabolic responses of cows during early lactation.

Results

By 12 h, E. coli was recovered from challenged quarters and shedding continued through 72 h. Rectal temperature peaked by 12 h post-challenge and returned to pre-challenge values by 36 h post-IMI challenge. Daily feed intake and milk yield decreased (P <0.05) by 1 and 2 d, respectively, after mastitis challenge. Plasma BHBA decreased (12 h; P <0.05) from 0.96 ± 1.1 at 0 h to 0.57 ± 0.64 mmol/L by 18 h whereas concentration of plasma NEFA (18 h) and glucose (24 h) were significantly greater, 11 and 27%, respectively, after challenge. In milk, fglu, lactose, citrate, fat and protein yield were lower whereas yield of BHBA and G6P were higher after challenge when compared to pre-challenge values.

Conclusions

Changes in metabolites in blood and milk were most likely associated with drops in feed intake and milk yield. However, the early rise in plasma NEFA may also signify enhanced adipose tissue lipolysis. Lower concentrations of plasma BHBA may be attributed to an increase transfer into milk after IMI. Decreases in both milk lactose yield and % after challenge may be partly attributed to reduced conversion of fglu to lactose. Rises in G6P yield and concentration in milk after challenge (24 h) may signify increased conversion of fglu to G6P. Results identify changes in various metabolic parameters in blood and milk after IMI challenge with E. coli in dairy cows that may partly explain the partitioning of nutrients and changes in milk components after IMI for cows during early lactation.  相似文献   

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