First Case Of Clinical Mastitis Research Articles

Effect of pegbovigrastimon clinical mastitis and uterine disease during a full lactation in grazing dairy cows.

In this randomized controlled trial on four commercial grazing dairy farms, we investigated whether pegbovigrastim (PEG) treatment affects clinical mastitis (CM) and uterine disease (i.e. retained placenta (RP), metritis and endometritis) occurrence during a full lactation. The association of prepartum body condition score and prepartum non-esterified fatty acid (NEFA) concentration with disease occurrence was also evaluated. Holstein cows were randomly assigned to one of two treatments: first PEG dose approximately 7 d before the expected calving date and a second dose within 24 h after calving (PEG) compared to untreated controls (Control). In total, 2,153 animals were included in the study: 733 primiparous cows (Control = 391, PEG = 342) and 1420 multiparous cows (Control = 723, PEG = 697). Treatment effects were evaluated with generalized linear mixed models and Cox’s proportional hazard models. Treatment with PEG reduced the occurrence of a first case of CM during the first 30 days in milk (DIM) by 24.6% and reduced the hazard of a first case and the rate of total cases of CM during the full lactation. All PEG treatment effects were independent of parity. Prepartum body condition score interacted with PEG treatment: in over-conditioned cows, PEG reduced the occurrence of a first case of CM during the first 30 DIM by 49.5%. The hazard analysis of a first case of CM during the full lactation suggested that the preventive effect of PEG disappeared with increasing DIM. Treatment with PEG did not affect the occurrence of RP or metritis. Pegbovigrastim treated cows with metritis subsequently showed a reduced occurrence of endometritis compared to control cows with metritis. Pegbovigrastim reduces the occurrence of CM particularly in cows at risk of elevated lipid mobilization, and PEG ameliorates the uterine healing process in cows that experienced metritis.

Short communication: Cow- and quarter-level milking indicators and their associations with clinical mastitis in an automatic milking system

The aim of this study was to assess associations of cow-, udder-, and quarter-level factors with the risk of clinical mastitis (CM) in cows managed using an automatic milking system. The primary hypothesis was that quarter peak milk flow rate (QPMF) is associated with increased risk of CM. A retrospective, case-control study was undertaken using data from a 1,549 cow farm using 20 automatic milking system units. All data from cows milked during March to December 2015 was available for analysis. Cases (n = 82) were defined as cows diagnosed with their first case of CM between 24 and 300 d in milk in the current lactation. Healthy control cows (n = 6/case) were randomly matched based on identical parity, existence of milk records during the day in milk period corresponding to the 15-d window before case diagnosis, average conductivity of <5.5 mS/cm in that window, and no history of CM in the current lactation. Logistic regression was used to estimate effects of parity, quarter position, day in milk at diagnosis of CM, average of QPMF 15 d before CM diagnosis, udder milk yield, and milking interval on the probability of CM. Of the 6 predictor variables included in the model, only milking interval was significantly associated with the increased risk of quarter CM. We concluded that in a high-production, freestall-housed North American herd using automatic milking system, milking interval, but not QPMF, was associated with risk of CM.

An investigation of risk factors for two successive cases of clinical mastitis in the same lactation

The objective of this study was to identify risk factors for the occurrence of two successive cases of clinical mastitis (CM). Two farms were visited monthly during 10 months. Milk samples were collected from all cases of CM that occurred during the study. Cows were observed prospectively from the beginning of the study and a case cow was defined when she experienced the second case of CM within the same lactation. For each case cow, 3 control cows matched by days in milk (DIM) were randomly selected from the cohort of cows who did not experience CM. On each visit day, a series of udder and teat characteristics were recorded during milking time: teat-end hyperkeratosis scoring, milking ease scoring, teat length and diameter, teat-to-ground distance, and udder position in relation to the hock. A total of 113 case cows and 324 control cows were used for analyses. The median time to occurrence of the first case of CM was 84 DIM and the median interval between the first and second cases of CM was 39 days. Of all second cases, 49.6% (N=55) occurred in the same mammary gland. Of these 55 cases, 29.1% had identical milk culture results from both first and second cases. Most cases of CM were caused by coliforms and environmental streptococci. Teat-to-ground distance, teat-end hyperkeratosis, udder position in relation to the hock, milking ease, parity, and milk production at the first test of lactation were individually associated with the occurrence of two successive cases of CM. Of all explanatory variables, 3 remained in the final multivariable model. The odds of two successive cases of CM were 3.7 times greater for cows who were “very easy to milk”, as compared with cows who were “difficult to milk”. Cows who had their udders below the hock, and those of parity >2 were 3.6 and 2.5 times more likely to experience two successive cases of CM, as compared with cows whose udder was positioned above the hock, and cows of parity 1, respectively. Findings of this study highlight the importance of teat and udder characteristics as risk factors for two successive cases of CM. Further investigations are needed to elucidate the role of the teat canal in preventing mastitis for modern cows that have been selected for increased milk production, shorter teats, and greater milk flow rates.

0158 Effects of antibiotic dry cow therapy and internal teat sealant (Teatseal) on milk somatic cell counts, clinical, and subclinical mastitis in early lactation

A randomized multi-site clinical trial was performed to determine the efficacy of an internal teat sealant (TS; Teatseal; Zoetis Australia, Silverwater, NSW, Australia), when used in combination with antibiotic dry cow therapy (ADCT), on milk individual cow cell count (ICCC), milk production and components, and the incidence of clinical and subclinical mastitis in cows up to 60 d in milk (DIM), and when compared with ADCT only. Multiparous Holstein, Jersey, or Holstein cross cows (n = 2200) from 8 farms in Southern and Eastern Australia were randomly assigned to treatment in all 4 quarters with an ADCT alone or with ADCT + TS at dry-off. Individual milk yield, fat and protein percentage, and ICCC were measured at 14 ± 3 d intervals for the first 60 DIM for cows that calved 40 to 100 d after dry-off. The first measurement occurred between 10 and 24 DIM. Clinical mastitis and health events were recorded from dry-off to 60 DIM. Milk yield, ICCC weighted by milk yield, and fat and protein percentage were not affected by treatment or time or their interaction in a generalized linear model. Treatment with ADCT + TS decreased geometric mean ICCC (P = 0.021), compared with treatment with ADCT alone. Geometric mean ICCC (x1000 cells/mL) was 32.0 (95% CI: 26.8 to 38.3) and 43.5 (95% CI: 36.2 to 52.1), respectively. The odds of at least 1 case of subclinical mastitis (ICCC ≥ 250,000 cells/mL) were 1.9 times higher (95% CI: 1.4 to 2.6) with ADCT alone, compared with ADCT + TS. Four cows had a first case of clinical mastitis in the dry period; while, 5% of cows had a first case of clinical mastitis between 0 and 60 DIM. Of the 1528 cows included in this analysis, 43 cases (5.7%) and 33 (4.3%) were from the ADCT and ADCT + TS groups, respectively (P = 0.194). Proportional hazards estimates of survival showed no difference in the number of d post-calving to detection of first cases of clinical mastitis between treatments over the first 60 DIM (P = 0.153). The estimated hazard ratio for clinical mastitis over this period in the ADCT + TS cows (relative to ADCT alone) was 0.70 (95% CI: 0.43 to 1.14). The combination of ADCT and TS provides benefits over ADCT alone through improved prevention of subclinical mastitis and reduced ICCC in the first 60 DIM.

Short communication: Pre- and postmilking anatomical characteristics of teats and their associations with risk of clinical mastitis in dairy cows

The primary objective of this study was to describe and compare anatomical characteristics of teats before and after machine milking adjusted for parity and teat location (front versus rear). The second objective was to determine if selected milking and anatomical characteristics of teats were associated with occurrence of clinical mastitis. To address objective 1, a cross-sectional study was done to describe and compare teat dimensions before and after milking (n=1,751 teats from 445 cows). To fulfill objective 2, a case-control study was performed. Quarters having their first case of clinical mastitis in the current lactation from 2 mo before to 2 mo after the day the teats were measured were selected as cases (n=47), provided no other quarters from that cow were affected by clinical mastitis at that time. Three controls (n=141) were matched with each case; these were selected from quarters that did not experience any case of clinical mastitis during their current lactation. A conditional logistic regression model was used to determine associations between teat dimensions and occurrence of clinical mastitis. Primiparous and multiparous Holstein cows were enrolled in both studies. As compared with premilking dimensions, postmilking teats were longer and narrower at the barrel and the apex. Significant interactions between teat position and parity were identified for premilking teat length and diameter of the teat barrel. Premilking, teats were longer and wider with increasing parity. Front teats were longer and wider than rear teats premilking. Also during premilking, differences between the front and rear teat were less at increasing parity. Teat apex diameter was greater for premilking teats of cows in parity ≥3 and the apexes of front teats were wider than those of rear teats. Teats enrolled in the case-control study had twice as many clinical mastitis cases in front quarters compared with rear quarters. Premilking diameter of the teat apex was positively associated with risk of clinical mastitis (odds ratio=1.20 per 1-mm increase in the diameter of the apex of the teat, 95% confidence interval=1.05-1.37). Milking machine-related changes in teat dimensions had no association with occurrence of clinical mastitis.

Effects of antibiotic dry-cow therapy and internal teat sealant on milk somatic cell counts and clinical and subclinical mastitis in early lactation

The objective of this study was to determine the efficacy of an internal teat sealant (TS; Teatseal; Zoetis Australia, Silverwater, NSW, Australia), when used in combination with antibiotic dry-cow therapy (ADCT) administered at dry-off, on milk individual somatic cell count (ISCC), milk production and components, and the incidence of clinical and subclinical mastitis in dairy cows up to 60 d after calving, when compared with ADCT only. Multiparous Holstein, Jersey, or Holstein cross cows (n=2,200) from 8 farms in southern and eastern Australia were randomly assigned to treatment of all 4 quarters with ADCT alone or with ADCT plus TS (ADCT + TS) at dry-off in this randomized, multisite clinical trial. Individual milk yield, fat and protein percentages, and ISCC were measured at intervals of 14±3 d after calving for the first 60 d of lactation. The first measurement occurred between 10 and 24 d after calving. Clinical mastitis and health events were recorded from dry-off to 60 d of lactation. Milk samples were collected from first cases of clinical mastitis and subjected to bacteriology. Treatment and the interaction of treatment by time did not affect milk yield, ISCC weighted by milk yield, or fat and protein percentages. Treatment with ADCT + TS decreased geometric mean ISCC compared with treatment with ADCT alone over the first 60 d of lactation. Geometric mean ISCC (×103 cells/mL) was 32.0 [95% confidence interval (CI): 26.8 to 38.3] and 43.5 (95% CI: 36.2 to 52.1) for ADCT + TS and ADCT alone, respectively. The odds of at least 1 case of subclinical mastitis (ISCC ≥250,000 cells/mL) were 1.9 times higher (95% CI: 1.4 to 2.6) with ADCT alone in the first 60 d of lactation compared with ADCT + TS. Use of ADCT + TS reduced the estimated incidence of at least 1 case of subclinical mastitis on all 8 farms, compared with use of ADCT alone. Only 4 cows that calved 40 to 100 d after dry-off had a first case of clinical mastitis in the dry period. Five percent of cows (76 cases from 1,528 cows included in this analysis) that calved 40 to 100 d after dry-off had a first case of clinical mastitis between 0 and 60 d in milk. Of these first cases of clinical mastitis, 43 cases (5.7% of 761 cows) occurred in the ADCT group and 33 (4.3% of 767 cows) in the ADCT + TS group, but this was not significantly different. Proportional hazards estimates of survival showed no difference in the number of days postcalving to detection of first cases of clinical mastitis between the ADCT and ADCT + TS groups over the first 60 d postpartum. The estimated hazard ratio for clinical mastitis over this period in the ADCT + TS cows (relative to ADCT alone) was 0.70 (95% CI: 0.43 to 1.14). The combination of ADCT and TS provides benefits over ADCT use alone through improved prevention of subclinical mastitis and reduced ISCC in the first 60 d of lactation.

Comparison of cephalonium alone and in combination with an internal teat sealant for dry cow therapy in seasonally calving dairy cows

AIM: To assess the effect of combining an internal teat sealant (ITS) and a long-acting cephalonium-based dry cow therapy (DCT) on the prevalence of cows with a somatic cell count (SCC) >150,000 cells/mL 60–80 days after calving, and the incidence of clinical mastitis diagnosed by farm staff in the first 100 days after calving.METHODS: Cows from a spring-calving, pasture-based, dairy farm in the South Canterbury region of New Zealand were randomly allocated to receive cephalonium DCT (n=289) or cephalonium and internal teat sealant (n=304) at the end of lactation. Cows were inspected twice daily by farm staff during the dry period and following calving for signs of mastitis. Individual SCC were determined from herd tests conducted in the previous lactation and following calving. Logistic regression models were used to determine relationships with the prevalence of cows with a SCC >150,000 cells/mL after calving, and survival analysis was used to model time to the first case of clinical mastitis following calving at the cow and quarter level.RESULTS: The OR for a cow with a SCC >150,000 cells/mL after calving, including age and individual SCC in the preceding lactation in the model, was 0.53 (95% CI=0.32–0.89) for cows treated with combination therapy compared to cows receiving cephalonium (p=0.017). At the cow level, including age and preceding SCC in the model, the hazard ratio for diagnosis of clinical mastitis by farm staff in the first 100 days of lactation was 0.60 (95% CI=0.39–0.98) for cows treated with combination therapy compared to cows receiving cephalonium (p=0.04). At the quarter level, the hazard ratio for diagnosis of clinical mastitis, with age included in the model, was 0.41 (95% CI=0.23–0.74) for the combination therapy compared to cephalonium alone (p<0.001).CONCLUSIONS: The combination of internal teat sealant and cephalonium DCT was more effective than cephalonium alone at reducing clinical mastitis diagnosed by farm staff in the 100 days after calving, and the prevalence of cows with a SCC >150,000 cells/mL 60–80 days after calving.CLINICAL RELEVANCE: This study adds to the evidence that the prevention of intra mammary infections throughout the dry period and up to calving by using combination therapy is important in reducing the incidence of farmer-diagnosed clinical mastitis and prevalence of cows with a SCC >150,000 cells/mL 60–80 days after calving.

Economics of milk yield losses in one dairy farm in Macedonia associated with clinical mastitis

Mastitis remains one of the major disease in dairy herds, causing profound economic losses to the entire milk production chain due to changes in the milk quality and milk yield. A one year cross-sectional longitudinal survey was carried out to evaluate milk yield losses associated with occurrence of clinical mastitis cases in one dairy herd. Cows that had clinical mastitis and clinically healthy cows during lactation were included in the study. The traits analyzed were the average of the monthly test day milk yields, cow parities and days in lactation while first case of clinical mastitis was occurred. For these purpose there were recorded data for monthly test day milk yield of the cows at the 2nd, the 3rd and the 4th monthly test day (TD). TDs were chosen according to the average number of days in lactation to diagnose the first case of clinical mastitis. According these criteria, the 2nd and the 3rd TD were made before the diagnosis of the first lactation case of clinical mastitis, while the 4th TD was made after the diagnosis. Monthly test day milk yields were treated as repeated measurement within an animal in General Linear Model (GLM). Statistical model included fixed effect of cow parity and covariance of days in lactation when the first case of clinical mastitis was occurred. Estimated lactation incidence risk (LIR) for CM in observed population of dairy cows was 21.49%. Regardless parities, the first case of clinical mastitis in dairy herd occurred on the average 108.09±83.182 days in lactation. The LIR tended to significantly increased (p&lt;0.001) with increasing the cow parity, as risk factor for occurrence of clinical mastitis. Before contracting the disease, cows with clinical mastitis yielded more milk than did healthy cows. Mastitis clearly affected the milk yield and the difference between the milk yield of the healthy cows and the cows after clinical mastitis was statistically significant. There was a significant decrease in the milk yield before and after the diagnosis of clinical mastitis case (p&lt;0.001). The estimated daily milk yield losses per cow suffered from case of clinical mastitis, between the 3rd TD and the 4th TD, range from 0.9 kg to 26.0 kg, or average 9.6 kg/day. According this, the monthly milk yield losses per mastitic cow, between the 3rd TD and the 4th TD, were 288 kg. If we take in consideration the price of one kg milk of 0.32 euro, than the total daily economic losses per mastitic cow will be around 3 euro’s and monthly losses per cow will be around 92 euro. Regardless of the time of occurrence during the lactation, mastitis had a long-lasting effect on milk yield; cows with clinical mastitis did not reach their premastitis milk yields during the remainder of the lactation after onset of the disease. The daily milk yield must be taken in consideration for more rapid economic analysis of milk losses associated with occurrence of clinical mastitis in dairy herds.

Evaluation of selective dry cow treatment following on-farm culture: Risk of postcalving intramammary infection and clinical mastitis in the subsequent lactation

The objective of the study was to evaluate the utility of a Petrifilm-based on-farm culture system when used to make selective antimicrobial treatment decisions on low somatic cell count cows (<200,000 cells/mL) at drying off. A total of 729 cows from 16 commercial dairy herds with a low bulk tank somatic cell count (<250,000 cells/mL) were randomly assigned to receive either blanket dry cow therapy (DCT) or Petrifilm-based selective DCT. Cows belonging to the blanket DCT group were infused with a commercial dry cow antimicrobial product and an internal teat sealant (ITS) at drying off. Using composite milk samples collected on the day before drying off, cows in the selective DCT group were treated at drying off based on the results obtained by the Petrifilm on-farm culture system with DCT + ITS (Petrifilm culture positive), or ITS alone (Petrifilm culture negative). Quarters of all cows were sampled for standard laboratory bacteriology on the day before drying off, at 3 to 4d in milk (DIM), at 5 to 18 DIM, and from the first case of clinical mastitis occurring within 120 DIM. Multilevel logistic regression was used to assess the effect of study group (blanket or selective DCT) and resulting dry cow treatment (DCT + ITS, or ITS alone) on the risk of intramammary infection (IMI) at calving and the risk of a first case of clinical mastitis between calving and 120 DIM. According to univariable analysis, no difference was observed between study groups with respect to quarter-level cure risk and new IMI risk over the dry period. Likewise, the risk of IMI at calving and the risk of clinical mastitis in the first 120 DIM was not different between quarters belonging to cows in the blanket DCT group and quarters belonging to cows in the selective DCT group. The results of this study indicate that selective DCT based on results obtained by the Petrifilm on-farm culture system achieved the same level of success with respect to treatment and prevention of IMI over the dry period as blanket DCT and did not affect the risk of clinical mastitis in the first 120d of the subsequent lactation.

Clinical mastitis in Macedonian dairy herds

The purpose of this study is the determination of the occurrence and prevalence of clinical mastitis and lactation incidence risk on three dairy farms. A one year study on a total of 1031 black-white breed cows with a total of 1267 lactations was performed. Each dairy farm implemented a different technology of rearing and was of different herd size (farm A - tie-stalls, 162 cows; farm B - loose-housing system with open shed and deep bedding, 357 dairy cows; and farm C - loosehousing system with enclosed shed, 512 cows). Clinical mastitis in cows was detected by clinical examination of the udder and determination of abnormalities in the milk. To distinguish two consecutive cases of clinical mastitis within the same lactation a time period of nine days was used. Annual prevalence rate of clinical mastitis for the entire population of cows was 34.13% on cow level, and 30.07% on lactation level. There was a high prevalence rate of clinical mastitis in primiparous cows, 21.43%, 40.77% and 12.55%, on farms A, B and C, respectively. Lactation incident risk for cows on farm A was 25.00%, farm B 95.58% and farm C 21.49%. The prevalence of clinical mastitis and lactation incidence risk tended to increase with increasing parity. The annual lactation risk for the entire population of cows was 45.86%. All indicators for the determination of the occurrence of clinical mastitis in dairy farms, which were observed during the research, showed the greatest values on farm B. Most of the cows manifested one (68.24%) or two (18.63%) cases of clinical mastitis during lactation. There was a long period in lactation until the appearance of the first case of clinical mastitis (112.21 ± 92.04 days). Generally, clinical mastitis was registered during the whole period of the survey, with some fluctuations between different seasons. The method of GLM (General Linear Model), univariate procedure, was used to analyze associations between the incidence of clinical mastitis and farm management, parity of cows and season of the year. Pearson's coefficient of correlation was performed for analysis of interdependence on variables in the model. There was statistical significance (p<0,001) between the season and incidence of clinical mastitis. [Projekat Ministarstva nauke Republike Srbije, br. TR 31086]

Relationship between somatic cell count status and subsequent clinical mastitis in Dutch dairy cows

High composite somatic cell counts (CSCC) in dairy cows may develop into clinical mastitis (CM), suggesting that prevention or intervention of high CSCC may prevent CM later in lactation. The objective of this study was to quantify the relationship between high CSCC in dairy cows and the first subsequent case of CM in the same lactation. Farmer-diagnosed cases of CM and test day CSCC measurements during 1 year of 13,917 cows in 196 randomly selected Dutch dairy herds were available for analysis. Cows were followed in 1 lactation from the first test day postpartum until CM, drying off, culling or end of study. Cox proportional hazards models with time-varying CSCC levels were used to estimate the effect of high CSCC (≥200,000 cells/ml) on the time until the first case of CM. A shared frailty effect was included to adjust for clustering of cows within herds. The proportion of cows developing CM after a CSCC measurement was 11%. Primiparae with a high CSCC had a 4-fold higher hazard for subsequent CM than primiparae with a low CSCC; multiparae with a high CSCC had a 2-fold higher hazard than multiparae with a low CSCC. Additionally, multiparae with a low CSCC had a 2-fold higher hazard for CM occurrence than primiparae with a low CSCC. Increasing the threshold for high CSCC showed that the risk for CM increased. If the last CSCC before CM was low, CSCC information of 2 preceding test days was more predictive than CSCC information from only the last test day. When the last CSCC was high, CSCC information of 2 preceding test days did not have added predictive value. This study identified that approximately 25% of first subsequent CM cases after a CSCC measurement can potentially be prevented when cows are prevented to get high CSCC or when high CSCC cows are removed from the population. This corresponded with a decrease in the proportion of lactating cows with CM after a CSCC measurement from 11% to 7%.

Somatic cell count status across the dry period as a risk factor for the development of clinical mastitis in the subsequent lactation

The objective of this study was to determine the risk of clinical mastitis in the first 120d in lactation based on previous somatic cell count (SCC) history in a herd with a very low prevalence of contagious pathogens. A total of 218 cows from a university herd were enrolled at dry-off. Duplicate quarter milk samples were collected from all quarters at dry-off, postcalving (2 to 9 d in milk), and before treatment of all first cases of clinical mastitis that occurred during the first 120d of the subsequent lactation. Quarter SCC statuses across the dry period were defined based on comparison of quarter SCC between the date of dry-off and the postcalving sampling periods. The relationship between the probability of developing clinical mastitis in the first 120d of lactation and SCC status across the dry period and other explanatory variables was assessed using logistic regression. In the first 120d postcalving, 68 first cases of clinical mastitis occurred in 47 cows. Of quarters that experienced a microbiologically positive clinical case, the same microorganism was never isolated from milk samples obtained at dry-off or consistently isolated from milk samples collected at all sampling periods. Coagulase negative staphylococci were the most prevalent pathogens isolated from subclinical intramammary infection, whereas gram-negative pathogens were the most common pathogen associated with clinical cases. Quarters that had at least 1 case of mastitis during the previous lactation were 4.2 times more likely to have a first case of clinical mastitis in the current lactation than quarters that did not have clinical mastitis in the previous lactation [odds ratio (OR) = 4.2 (1.8, 10.0)]. Quarters of cows of greater than fourth parity were 4.2 times more likely to have a first case of clinical mastitis than quarters of cows of second parity [OR=4.2 (1.4, 10.0)]. Quarters with SCC ≥200,000cells/mL at dry-off and postcalving were 2.7 times more likely to experience a first case of mastitis than quarters with SCC <200,000cells/mL at both periods [OR=2.7 (0.97, 7.67)].

Use of a dynamic programming model to estimate the value of clinical mastitis treatment and prevention options utilized by dairy producers

This study discusses and demonstrates the construction and application of a specially structured dynamic programming replacement and insemination optimization and simulation model of the dairy cow that includes detailed representation of repeated episodes of clinical mastitis (CM). The application determined optimal individual cow decisions, which were then compared with mastitis culling rules of thumb to determine the deviation of these rules from optimality. Calculation of break-even values of applying a preventive measure to reduce CM incidence or severity in the form of two fictitious mastitis vaccines were also carried out. Model input parameters were based on data from five large dairy herds in New York State (about 16,000 lactations), but these parameters can be easily changed for other types of dairy operations. To demonstrate the usefulness of this model to assist individual cow CM treatment options, the cost of the decision to cull a third lactation cow, six months after calving, with the first case of CM, was negative $3 USD for a low milk producing open or pregnant cow (i.e. cull), and positive $850 USD for a high milk producing and pregnant cow (i.e. treat even with extremely high treatment cost). Compared with the model recommended optimal policy, a rule of thumb decision to routinely treat all cows with a first case of CM resulted in an additional cost of $2 per cow per year, a very low deviation from optimality and suggests all cows should be given a second chance. A policy of replacing all CM cows after their second CM case after treatment of the first CM incident resulted in an additional cost of $27 per cow per year. If the decision was to replace all cows only after their third CM case this cost estimate was $8. The cost-benefit of applying two fictitious vaccinations showed that a vaccination reducing the milk loss caused by Gram-negative CM by 50% had a break-even cost of $14 per cow per year. A vaccination that would result in additional reduction of the risk of CM by 50% had a break-even cost of $37 per cow per year.

Cow, Farm, and Management Factors During the Dry Period that Determine the Rate of Clinical Mastitis After Calving

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.