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ABSTRACT: The efficacy of an intramammary antibiotic dry cow preparation with significant gram-negative spectrum (product A; Leo Red Dry Cow, Leo Animal Health, UK) was compared with a product with no gram-negative efficacy (product B; Orbenin Extra DC, Pfizer Ltd, UK) as assessed by control of coliform mastitis in the first 100 d of the lactation. The efficacy of both products was also compared for control of noncoliform mastitis and for the ability to control existing and new intramammary infections as measured by individual cow somatic cell counts. Cows treated with product A were significantly less likely to develop clinical Escherichia coli or coliform mastitis during the dry period or the first 100 d of lactation than cows treated with product B. Cows treated with product A were no more likely to develop clinical mastitis due to a noncoliform organism than were cows treated with product B. There was no significant difference between the two groups as measured by individual cow somatic cell count changes across the dry period. This study is the first to have demonstrated the clinical efficacy of an intramammary antibiotic dry cow preparation, as measured by reduction in gram-negative clinical mastitis in the subsequent lactation. These findings demonstrate that selection of a dry cow intramammary preparation with a significant gram-negative spectrum can influence the incidence of clinical coliform mastitis in the subsequent lactation. This finding should be one of the factors taken into account when selecting products.
Journal of Dairy Science 08/2001; 84(7):1632-9. · 2.56 Impact Factor
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ABSTRACT: Clinical mastitis was monitored in six Somerset dairy herds for one year. The herds all had three-month geometric mean bulk milk somatic cell counts of less than 250,000 cells/ml. Escherichia coli was the predominant pathogen isolated on all the farms and in all months of the year. Environmental pathogens accounted for 61.4 per cent of all cases of clinical mastitis and for 79.3 per cent of the mastitis cases in which an aetiological agent was identified. The mean annual incidence was 41.6 cases per 100 cows (range 14 to 75). Affected cows suffered a mean of 1.5 cases and 16.4 per cent of quarters suffered at least one repeat case. Mastitis due to E. coli was more severe than mastitis due to other causes and it tended to be more severe in early lactation and during the housing period. Mastitis was significantly more severe (grades 2 and 3) in the herd with the lowest bulk milk somatic cell count and in the herd which was kept indoors throughout the year than in the other four herds. Mastitis was fatal in 2.2 per cent of cases and resulted in the death of 0.6 per cent of the lactating cows.
The Veterinary record 07/2001; 148(22):683-6. · 1.25 Impact Factor
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ABSTRACT: Clinical mastitis in six Somerset dairy herds was monitored over a 12-month period. Escherichia coli was implicated in 34.7% of all clinical cases. Forty-one percent of all clinical E. coli mastitis cases occurred in just 2.2% of the population. A total of 23.9% of clinical E. coli cases occurred in quarters suffering recurrent cases of E. coli mastitis. The genotypes of strains involved in recurrent cases of clinical E. coli mastitis were compared by DNA fingerprinting with enterobacterial repetitive intergenic consensus primers. In 85.7% of cases of recurrent quarter E. coli mastitis, the same genotype was implicated as the cause of disease, suggesting persistence of the organism within the mammary environment. The same genotype as that in the original case was also implicated in 8.5% of recurrent cases occurring in different quarters of the same cow, suggesting spread between quarters. These findings challenge our current understanding of the epidemiology of E. coli mastitis and suggest that pathogen adaptation and host susceptibility may be playing a part in the changing pattern of clinical mastitis experienced in the modern dairy herd.
Journal of Clinical Microbiology 06/2001; 39(5):1845-9. · 4.15 Impact Factor
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ABSTRACT: A cross-sectional survey of dairy farms with low bulk milk somatic cell counts was carried out to assess the level of clinical mastitis and to quantify risk factors associated with the incidence rate of clinical mastitis. Questionnaires were sent to 3009 milk operations with an annual mean bulk milk somatic cell count of less than 100,000 cells/ml during 1997. A response rate was 61%. The mean incidence of clinical mastitis reported was 22.8 cases per 100 cows/yr. Negative binomial regression models were used to assess statistically significant risk factors associated with the incidence of clinical mastitis. The incidence increased when farmers reported that they had straw yard housing for milking cows (compared with cubicle housing), mucked out the calving area less frequently than once per month, kept cows standing in a yard after milking, always practiced postmilking teat disinfection, had greater than 50% replacement rate, had some cows that leaked milk on entry to the parlor, had some cows that leaked milk at other times, and foremilked before cluster attachment. The incidence of clinical mastitis was lower on farms when the gathering yard used before milking was scraped at least twice a day, cows were offered feed after both milkings, rubber gloves were not worn during milking, teat liners were changed after 6000 milkings, and the average dry period was less than 40 d. The study has identified areas of the environment in which efforts to improve hygiene should be focused.
Journal of Dairy Science 12/2000; 83(11):2464-72. · 2.56 Impact Factor
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ABSTRACT: We assessed the incidence of enterobacterial infection of the mammary glands of 629 cows, from six commercial herds in Somerset, during the nonlactating period; samples were collected from all clinical quarters of these cows during the subsequent lactation. A rise in the incidence of intramammary enterobacterial infection was detected between drying off and before calving. Quarters infected with an enterobacterial organism during the dry period were more likely to develop mastitis due to that pathogen than were uninfected quarters. Of all enterobacterial mastitis occurring in the first 100 d of lactation, 52.6% arose in quarters previously infected, during the dry period, with the same strain of bacteria, as identified by DNA fingerprinting using enterobacterial repetitive intergenic consensus primers. When compared with unsampled controls, quarters sampled during the dry period did not show a higher incidence of infection at calving or of subsequent clinical mastitis. These findings suggest that chronic infections are important in the epidemiology of enterobacterial mastitis and that environmental management during the dry period may greatly impact the incidence of enterobacterial mastitis in the subsequent lactation.
Journal of Dairy Science 10/2000; 83(9):1957-65. · 2.56 Impact Factor
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ABSTRACT: Escherichia coli O26:K60, with genetic attributes consistent with a potentially human enterohaemorrhagic E. coli was isolated from the faeces of an eight-month-old heifer with dysentery. Attaching and effacing lesions were identified in the colon of a similarly affected heifer examined postmortem, and shown to be associated with E. coli O26 by specific immunolabelling.
The Veterinary record 10/1999; 145(13):370-3. · 1.25 Impact Factor
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The Veterinary record 05/1999; 144(17):484. · 1.25 Impact Factor
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ABSTRACT: During a three-year study, 54 cows with toxic mastitis were examined and a number of clinical and laboratory measurements were taken. Twenty-five (46.3 per cent) of the cows died, and in comparison with those which survived, they had a significantly higher packed cell volume (PCV) (P < 0.01), longer eyelid skin tent time (P < 0.01) and lower rectal temperature (P < 0.01). In a model designed to predict the probability of survival, these variables correctly predicted survival in 84 per cent of cases and death in 73 per cent of cases. The cows with toxic mastitis had a significantly higher PCV than a normal cohort of cows sampled at the end of the study.
The Veterinary record 09/1998; 143(5):127-30. · 1.25 Impact Factor
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ABSTRACT: A retrospective case control study of farm level risk factors for toxic mastitis was carried out in November and December 1996. Twenty-six farms from mid-Somerset were visited: 13 case farms (had had a cow with toxic mastitis in the previous year) and 13 geographically matched controls (no case of toxic mastitis). The farmers were interviewed and the buildings were examined. Information was collected on the type and quality of housing, usual milking routines, milk quality and mastitis prevalence in the previous year. All the data were collected on to pretested recording sheets and loaded into a database. Simple and complex analysis was done. The following variable were significantly (P < 0.05) associated with an increased risk of toxic mastitis in the simple analysis: housing cows in October rather than November; a low number of calving boxes per cow; a high proportion of cows with intermediate body condition and low herd bulk milk somatic cell counts (HBMSCC). In the final model low HBMSCC and a high proportion of cows with intermediate body condition remained significant. The authors conclude that, despite the small size sample, the results of this study are consistent, plausible and support the information from previous experimental and observational studies about the role of somatic cell counts in toxic mastitis.
The Veterinary record 09/1998; 143(13):362-5. · 1.25 Impact Factor
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The Veterinary record 09/1997; 141(7):179-80. · 1.25 Impact Factor
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ABSTRACT: During a three-year study, 54 cows with toxic mastitis were allocated randomly to one of three treatment groups (A, B and C). Each cow was re-examined within 24 hours of the initial examination, and, during this time, group A received fluid therapy (45 liters of intravenous isotonic electrolyte solution) and flunixin meglumine (2000 mg), group B received fluid therapy only, and group C received flunixin meglumine only. In addition all the cases were treated with parenteral and intramammary tetracyclines, oxytocin and calcium boroglucoanate. There was no significant difference in the rate of survival between the treatment groups and 29 of the cows (53.7 per cent, 95 per cent confidence interval of 39 to 67 per cent) survived.
The Veterinary record 03/1997; 140(6):149-52. · 1.25 Impact Factor
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The Veterinary record 04/1996; 138(13):305-6. · 1.25 Impact Factor
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ABSTRACT: The purpose of the research was to investigate cow characteristics, farm facilities, and herd management strategies during the dry period to examine their joint influence on the rate of clinical mastitis after calving. Data were collected over a 2-yr period from 52 commercial dairy farms throughout England and Wales. Cows were separated for analysis into those housed for the dry period (8,710 cow-dry periods) and those at pasture (9,964 cow-dry periods). Multilevel models were used within a Bayesian framework with 2 response variables, the occurrence of a first case of clinical mastitis within the first 30 d of lactation and time to the first case of clinical mastitis during lactation. A variety of cow and herd management factors were identified as being associated with an increased rate of clinical mastitis and these were found to occur throughout the dry period. Significant cow factors were increased parity and at least one somatic cell count 200,000 cells/mL in the 90 d before drying off. A number of management factors related to hygiene were significantly associated with an increased rate of clinical mastitis. These included measures linked to the administration of dry-cow treatments and management of the early and late dry-period accommodation and calving areas. Other farm factors associated with a reduced rate of clinical mastitis were vaccination with a leptospirosis vaccine, selection of dry-cow treatments for individual cows within a herd rather than for the herd as a whole, routine body condition scoring of cows at drying off, and a pasture rotation policy of grazing dry cows for a maximum of 2 wk before allowing the pasture to remain nongrazed for a period of 4 wk. Models demonstrated a good ability to predict the farm incidence rate of clinical mastitis in a given year, with model predictions explaining over 85% of the variability in the observed data. The research indicates that specific dry-period management strategies have an important influence on the rate of clinical mastitis during the next lactation.
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ABSTRACT: This study investigated cow characteristics, farm facilities, and herd management strategies during the dry period to examine their joint influence on somatic cell counts (SCC) in early lactation. Data from 52 commercial dairy farms throughout England and Wales were collected over a 2-yr period. For the purpose of analysis, cows were separated into those housed for the dry period (6,419 cow-dry periods) and those at pasture (7,425 cow-dry periods). Bayesian multilevel models were specified with 2 response variables: ln SCC (continuous) and SCC >199,000 cells/mL (binary), both within 30 d of calving. Cow factors associated with an increased SCC after calving were parity, an SCC >199,000 cells/mL in the 60 d before drying off, increasing milk yield 0 to 30 d before drying off, and reduced DIM after calving at the time of SCC estimation. Herd management factors associated with an increased SCC after calving included procedures at drying off, aspects of bedding management, stocking density, and method of pasture grazing. Posterior predictions were used for model assessment, and these indicated that model fit was generally good. The research demonstrated that specific dry-period management strategies have an important influence on SCC in early lactation.
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ABSTRACT: Assessing the fit of a model is an important final step in any statistical analysis, but this is not straightforward when complex discrete response models are used. Cross validation and posterior predictions have been suggested as methods to aid model criticism. In this paper a comparison is made between four methods of model predictive assessment in the context of a three level logistic regression model for clinical mastitis in dairy cattle; cross validation, a prediction using the full posterior predictive distribution and two “mixed” predictive methods that incorporate higher level random effects simulated from the underlying model distribution. Cross validation is considered a gold standard method but is computationally intensive and thus a comparison is made between posterior predictive assessments and cross validation. The analyses revealed that mixed prediction methods produced results close to cross validation whilst the full posterior predictive assessment gave predictions that were over-optimistic (closer to the observed disease rates) compared with cross validation. A mixed prediction method that simulated random effects from both higher levels was best at identifying the outlying level two (farm-year) units of interest. It is concluded that this mixed prediction method, simulating random effects from both higher levels, is straightforward and may be of value in model criticism of multilevel logistic regression, a technique commonly used for animal health data with a hierarchical structure.
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ABSTRACT: Researchers have reported that as milk yield increases composite milk somatic cell count (SCC) is diluted in cattle with no intramammary infection (IMI) and as a consequence, estimates of SCC from high yields are lower than estimates of SCC from low yields in dairy cows without an IMI. To date, estimates of reduced milk yield associated with high SCC because of intramammary infection have not been adjusted for any dilution of SCC. Ignoring dilution is therefore likely to lead to an overestimate of reduction in yield with increasing SCC. This paper investigates scenarios of the possible impact of dilution and inflammation on the association between somatic cell count and yield. The data used to investigate this relationship come from 8373 monthly records of milk yield and composite somatic cell count, together with incidence of clinical mastitis, which were recorded on 850 cows from five dairy cattle farms in Gloucestershire, UK. Two sets of models were used to investigate dilution and inflammation using two-level hierarchical models. The first set of models was used to estimate the linear (dilution) and log 10-linear (inflammation) impact of SCC on the outcome variable milk yield. Five general linear models with increasing inclusion of higher test day SCC values were run. The cumulative categories were test day SCC values of up to and inclusive of 30, 50, 100, 200 and 400 × 103 cells/ml. Linear and log linear SCC influences on milk yield were estimated. At low SCC values the linear SCC predictor was dominant, while at higher values the log linear predictor was dominant. Up to 100 × 103 cells/ml there was mostly a slightly negative linear relationship between SCC and yield, potentially indicating a dilution effect.In the second set of models, three approaches to adjust milk loss for dilution were compared with an unadjusted model. In general, dilution-adjusted SCC values fitted the data better and resulted in a slightly lower milk loss per SCC category compared with unadjusted SCC. In all models with a dilution term there was a significant reduction in yield with SCC > 200 × 103 cells/ml.
Preventive Veterinary Medicine.
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ABSTRACT: Knowledge of the efficacy of an intervention for disease control on an individual farm is essential to make good decisions on preventive healthcare, but the uncertainty in outcome associated with undertaking a specific control strategy has rarely been considered in veterinary medicine. The purpose of this research was to explore the uncertainty in change in disease incidence and financial benefit that could occur on different farms, when two effective farm management interventions are undertaken. Bovine mastitis was used as an example disease and the research was conducted using data from an intervention study as prior information within an integrated Bayesian simulation model. Predictions were made of the reduction in clinical mastitis within 30 days of calving on 52 farms, attributable to the application of two herd interventions previously reported as effective; rotation of dry cow pasture and differential dry cow therapy. Results indicated that there were important degrees of uncertainty in the predicted reduction in clinical mastitis for individual farms when either intervention was undertaken; the magnitude of the 95% credible intervals for reduced clinical mastitis incidence were substantial and of clinical relevance. The large uncertainty associated with the predicted reduction in clinical mastitis attributable to the interventions resulted in important variability in possible financial outcomes for each farm. The uncertainty in outcome associated with farm control measures illustrates the difficulty facing a veterinary clinician when making an on-farm decision and highlights the importance of iterative herd health procedures (continual evaluation, reassessment and adjusted interventions) to optimise health in an individual herd.
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ABSTRACT: Individual cow somatic cell count (SCC) patterns were explored over a one year period in 33 dairy herds to investigate the reason for a summer rise in bulk milk somatic cell counts (BMSCC). Cow test day somatic cell counts were categorised according to the magnitude of change since the previous test day reading, to examine which categories were responsible for the summer increase. Multilevel models using Markov chain Monte Carlo methods were specified to estimate the number of somatic cells/ml produced by different cell count categories. Stage of lactation and parity were accounted for in the models. There was an increase in the proportion of cows that remained above 200,000 cells/ml for two consecutive recordings in summer and this group of cows were responsible for 70.8% of the increase in somatic cells/ml produced from May to September compared with October to March. There was no evidence that a greater new infection rate (somatic cell counts moving from below 100,000 cells/ml to over 200,000 cells/ml) contributed to the increased summer bulk milk somatic cell counts. There was no indication that a general small increase in all somatic cell counts played an important role in the increased summer somatic cell counts. Markov chain Monte Carlo methods provided a valuable and flexible platform for parameter estimation in reasonably complex multilevel models.
Preventive Veterinary Medicine.
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ABSTRACT: Two analytical approaches were used to investigate the relationship between somatic cell concentrations in monthly quarter milk samples and subsequent, naturally occurring clinical mastitis in three dairy herds. Firstly, cows with clinical mastitis were selected and a conventional matched analysis was used to compare affected and unaffected quarters of the same cow. The second analysis included all cows, and in order to overcome potential bias associated with the correlation structure, a hierarchical Bayesian generalised linear mixed model was specified. A Markov chain Monte Carlo (MCMC) approach, that is Gibbs sampling, was used to estimate parameters.The results of both the matched analysis and the hierarchical modelling suggested that quarters with a somatic cell count (SCC) in the range 41,000–100,000 cells/ml had a lower risk of clinical mastitis during the next month than quarters <41,000 cell/ml. Quarters with an SCC >200,000 cells/ml were at the greatest risk of clinical mastitis in the next month. There was a reduced risk of clinical mastitis between 1 and 2 months later in quarters with an SCC of 81,000–150,000 cells/ml compared with quarters below this level. The hierarchical modelling analysis identified a further reduced risk of clinical mastitis between 2 and 3 months later in quarters with an SCC 61,000–150,000 cells/ml, compared to other quarters.We conclude that low concentrations of somatic cells in milk are associated with increased risk of clinical mastitis, and that high concentrations are indicative of pre-existing immunological mobilisation against infection. The variation in risk between quarters of affected cows suggests that local quarter immunological events, rather than solely whole cow factors, have an important influence on the risk of clinical mastitis. MCMC proved a useful tool for estimating parameters in a hierarchical Bernoulli model. Model construction and an approach to assessing goodness of model fit are described.
Preventive Veterinary Medicine.
