The cost of generic clinical mastitis in dairy cows as estimated by using dynamic programming

The objective of this study was to estimate the cost of generic clinical mastitis (CM) in high-yielding dairy cows given optimal decisions concerning handling of CM cases. A specially structured optimization and simulation model that included a detailed representation of repeated episodes of CM was used to study the effects of various factors on the cost of CM. The basic scenario was based on data from 5 large herds in New York State. In the basic scenario, 92% of the CM cases were recommended to be treated. The average cost of CM per cow and year in these herds was $71. The average cost of a CM case was $179. It was composed of $115 because of milk yield losses, $14 because of increased mortality, and $50 because of treatment-associated costs. The estimated cost of CM was highly dependent on cow traits: it was highest ($403) in cows with high expected future net returns (e.g., young, high-milk-yielding cows), and was lowest ($3) in cows that were recommended to be culled for reasons other than mastitis. The cost per case of CM was 18% higher with a 20% increase in milk price and 17% lower with a 20% decrease in milk price. The cost per case of CM was affected little by a 20% change in replacement cost or pregnancy rate. Changes in CM incidence, however, resulted from changes in these factors, thus affecting whole-farm profitability. The detailed results obtained from this insemination and replacement optimization model can assist farmers in making CM treatment decisions.     

The effect of repeated episodes of bacteria-specific clinical mastitis on mortality and culling in Holstein dairy cows

The objective of this study was to estimate the effect of a first and repeated cases of bacteria-specific clinical mastitis (CM) on the risk of mortality and culling in Holstein dairy cows. The pathogens studied were Streptococcus spp., Staphylococcus aureus, Staphylococcus spp., Escherichia coli, Klebsiella spp., Trueperella pyogenes, others, and no growth on aerobic culture. A total of 50,166 lactations were analyzed from 5 large, high-milk-producing dairy herds in New York State from 2003/2004 to 2011. Generalized linear mixed models with a Poisson error distribution were used to study the effects of parity, month of lactation, CM, calving diseases, pregnancy status, current season, and economic values on the risk of mortality and culling. Among first-lactation cows, the presence of a first CM case generally exposed cows to a greater risk of mortality in the current month (compared with the absence of a first case). This was especially acute with a first case of Klebsiella spp., where cows were 4.5 times more at risk [95% confidence interval (CI): 2.7–7.6] of mortality, and with a first case of E. coli were 3.3 times more at risk (95% CI: 2.5–4.5). In first-parity cows, the risk of culling generally increased with a case of bacteria-specific CM. This was observed among cows with a first case of T. pyogenes [relative risk = 10.4 (95% CI: 8.4–12.8)], a first case of Klebsiella spp. [relative risk = 6.7 (95% CI: 5.5–8.1)], a first case of Staph. aureus [relative risk = 4.8 (95% CI: 2.7–8.4)], a first case of E. coli [relative risk = 3.1 (95% CI: 2.7–3.6)], and a third case of Klebsiella spp. [relative risk = 5.0 (95% CI: 3.1–8.0)]. In general, the presence of a first or second/third case resulted in cows in parity ≥2 with a greater risk of mortality. This was greatest for cows with a first case of Klebsiella spp. [relative risk = 3.7 (95% CI: 3.3–4.3)], followed by a second/third case of Klebsiella spp. [relative risk = 3.2 (95% CI: 2.5–4.0)], a first case of E. coli [relative risk = 3.0 (95% CI: 2.7–3.3)], and a first case of other CM [relative risk = 1.8 (95% CI: 1.6–2.0)]. Among cows of parity ≥2, the risk of culling was greater for cows as they progressed through lactations [i.e., cows in parity 4+ were 2.1 (95% CI: 2.0–2.2) times more likely to be culled compared with cows in lactation 2 (the baseline)]. The risk of culling dependent on the cow's characteristics can be easily calculated from the parameter estimates in the provided tables.     

Effects of pathogen-specific clinical mastitis on probability of conception in Holstein dairy cows

The objective of this study was to estimate the effects of pathogen-specific clinical mastitis (CM), occurring in different weekly intervals before or after artificial insemination (AI), on the probability of conception in Holstein cows. Clinical mastitis occurring in weekly intervals from 6 wk before until 6 wk after AI was modeled. The first 4 AI in a cow’s lactation were included. The following categories of pathogens were studied: Streptococcus spp. (comprising Streptococcus dysgalactiae, Streptococcus uberis, and other Streptococcus spp.); Staphylococcus aureus; coagulase-negative staphylococci (CNS); Escherichia coli; Klebsiella spp.; cases with CM signs but no bacterial growth (above the level that can be detected from our microbiological procedures) observed in the culture sample and cases with contamination (≥3 pathogens in the sample); and other pathogens [including Citrobacter, yeasts, Trueperella pyogenes, gram-negative bacilli (i.e., gram-negative organisms other than E. coli, Klebsiella spp., Enterobacter, and Citrobacter), Corynebacterium bovis, Corynebacterium spp., Pasteurella, Enterococcus, Pseudomonas, Mycoplasma, Prototheca, and others]. Other factors included in the model were parity (1, 2, 3, 4 and higher), season of AI (winter, spring, summer, autumn), day in lactation of first AI, farm, and other non-CM diseases (retained placenta, metritis, ketosis, displaced abomasum). Data from 90,271 AI in 39,361 lactations in 20,328 cows collected from 2003/2004 to 2011 from 5 New York State dairy farms were analyzed in a generalized linear mixed model with a Poisson distribution. The largest reductions in probability of conception were associated with CM occurring in the week before AI or in the 2 wk following AI. Escherichia coli and Klebsiella spp. had the greatest adverse effects on probability of conception. The probability of conception for a cow with any combination of characteristics may be calculated based on the parameter estimates. These findings may be helpful to farmers in assessing reproduction in their dairy cows for more effective cow management.     

Milk production change following clinical mastitis and reproductive performance compared among J5 vaccinated and control dairy cattle

Naturally occurring cases of bovine clinical mastitis (CM) were studied among J5 vaccinates and controls on 3 commercial dairy farms. Milk production change and reproductive performance following CM were compared between the 2 groups. Among 306 controls and 251 vaccinates, there were 221 new cases of CM affecting 120 cows; 437 lactations never had a case of CM. Environmental pathogens made up 90% (159/176) of etiologic agents isolated. Change in daily milk production following CM was associated with J5 vaccination, days in milk (DIM) at onset of CM, and herd effect as well as each 2-way interaction between the 3 factors. The adjusted daily milk for 21 d following CM was 7.6 kg greater among J5 vaccinates than controls; however, this protective effect of vaccination waned with increasing DIM at onset of CM. A mixed linear model with autoregressive order 1 [AR(1)] correlation structure estimated the daily milk production of any cow (whether or not she had CM) on a given DIM. Cows with CM caused by nonagalactiae streptococci, Staphylococcus aureus, Escherichia coli, or Klebsiella lost significant daily milk production for the entire lactation relative to nonmastitic cows. Another mixed linear model for only coliform CM cases (E. coli, Klebsiella, and Enterobacter) within the first 50 DIM showed milk loss for 21 d following coliform CM to be significantly less for J5 vaccinates than for controls, by 6 to 15 kg per day. Cows were significantly less likely to become pregnant if they had CM caused by E. coli (42% pregnant) or Streptococcus spp. (38% pregnant), whereas 78% (342/437) of cows with no mastitis conceived. Days open (number of days from calving until pregnancy) averaged 131 d for cows with no CM and 162 d for cows that had at least one case of CM. Days until conception, days until last breeding, days open, times bred, and percentage of cows pregnant by 200 DIM were not changed with J5 vaccination. Nonetheless, an important benefit of the use of J5 bacterin appears to be reduction of the loss of daily milk production following CM, whether all cases or only those caused by coliform bacteria were considered.     

The effect of recurrent episodes of clinical mastitis caused by gram-positive and gram-negative bacteria and other organisms on mortality and culling in Holstein dairy cows

The objective of this study was to estimate the effects of recurrent episodes of different types of clinical mastitis (CM) caused by gram-positive (Streptococcus spp., Staphylococcus aureus, Staphylococcus spp.) and gram-negative (Escherichia coli, Klebsiella, Citrobacter, Enterobacter, Pseudomonas) bacteria, and other organisms (Arcanobacterium pyogenes, Mycoplasma, Corynebacterium bovis, yeast, miscellaneous) on the probability of mortality and culling in Holstein dairy cows. Data from 30,233 lactations in cows of 7 dairy farms in New York State were analyzed. Cows were followed for the first 10 mo in lactation, or until death or culling occurred, or until the end of our study period. Generalized linear mixed models with a Poisson error distribution were used to study the effects of recurrent cases of the different types of CM and several other factors (herd, parity, month of lactation, current year and season, profitability, net replacement cost, other diseases) on cows’ probability of death (model 1) or being culled (model 2). Primiparous and multiparous cows were modeled separately because they had different risks of mortality and culling and potentially different CM effects on mortality and culling. Approximately 30% of multiparous cows had at least one case of CM in lactation compared with 16.6% of primiparous cows. Multipara also had higher lactational incidence risks of second (10.7%) and third (4.4%) cases than primipara (3.7% and 1.1%, respectively). For primipara, CM increased the probability of death, with each successive case occurring in a month being increasingly lethal. In multipara, gram-negative CM increased the probability of death, especially when the gram-negative case was the first or second CM case in lactation. Primiparous cows with CM were more likely to be culled after CM than if they did not have CM, particularly after a second or third case. In multipara, any type of CM increased the probability of being culled. Gram-negative CM cases were associated with the numerically highest risk of culling.     

Incidence of clinical mastitis and distribution of pathogens on large Chinese dairy farms

Knowledge of the incidence of clinical mastitis (CM) and the distribution of pathogens involved is essential for development of prevention and control programs as well as treatment protocols. No country-wide study on the incidence of CM and the distribution of pathogens involved has been conducted in China. Core objectives of this study were, therefore, to determine the cumulative incidence of CM and the distribution of pathogens causing CM on large Chinese (>500 cows) dairy farms. In addition, associations between the distribution of CM pathogens and bedding materials and seasonal factors were also investigated. Bacterial culture was done on a total of 3,288 CM quarter milk samples from 161 dairy herds (located in 21 provinces) between March 2014 and September 2016. Additional data, including geographical region of herds, herd size, bedding types, and number of CM cases during the last month, were also recorded. Mean cumulative incidence of CM was 3.3 cases per 100 cows per month (range = 1.7 to 8.1). The most frequently isolated pathogens were Escherichia coli (14.4%), Klebsiella spp. (13.0%), coagulase-negative staphylococci (11.3%), Streptococcus dysgalactiae (10.5%), and Staphylococcus aureus (10.2%). Streptococcus agalactiae was isolated from 2.8% of CM samples, whereas Streptococcus uberis were isolated from 2.1% of samples, and 15.8% of 3,288 samples were culture-negative. Coagulase-negative staphylococci, E. coli, and other Enterobacter spp. were more frequently isolated in the northwest than the northeast or south of China. Streptococcus dysgalactiae, other streptococci, and Strep. agalactiae were more frequently isolated in winter (October–March), whereas E. coli and Klebsiella spp. were mostly isolated in summer (April–September). Streptococcus dysgalactiae was more often isolated from CM cases of herds using sand bedding, whereas Klebsiella spp. and other streptococci were more common in herds using organic bedding. The incidence of CM and distribution of pathogens differed among herds and better mastitis management is needed. Furthermore, geography, bedding materials, and season should be included when designing mastitis control and prevention schemes for Chinese dairies.     

The cost and management of different types of clinical mastitis in dairy cows estimated by dynamic programming

The objective of this study was to estimate the cost of 3 different types of clinical mastitis (CM) (caused by gram-positive bacteria, gram-negative bacteria, and other organisms) at the individual cow level and thereby identify the economically optimal management decision for each type of mastitis. We made modifications to an existing dynamic optimization and simulation model, studying the effects of various factors (incidence of CM, milk loss, pregnancy rate, and treatment cost) on the cost of different types of CM. The average costs per case (US$) of gram-positive, gram-negative, and other CM were $133.73, $211.03, and $95.31, respectively. This model provided a more informed decision-making process in CM management for optimal economic profitability and determined that 93.1% of gram-positive CM cases, 93.1% of gram-negative CM cases, and 94.6% of other CM cases should be treated. The main contributor to the total cost per case was treatment cost for gram-positive CM (51.5% of the total cost per case), milk loss for gram-negative CM (72.4%), and treatment cost for other CM (49.2%). The model affords versatility as it allows for parameters such as production costs, economic values, and disease frequencies to be altered. Therefore, cost estimates are the direct outcome of the farm-specific parameters entered into the model. Thus, this model can provide farmers economically optimal guidelines specific to their individual cows suffering from different types of CM.     

Pathogen-specific effects on milk yield in repeated clinical mastitis episodes in Holstein dairy cows

The objective of this study was to estimate the effects of clinical mastitis (CM) cases due to different pathogens on milk yield in Holstein cows. The first 3 CM cases in a cow’s lactation were modeled. Eight categories of pathogens were included: Streptococcus spp.; Staphylococcus aureus; coagulase-negative staphylococci (CNS); Escherichia coli; Klebsiella spp.; cases with CM signs but no bacterial growth (above the level detectable by our microbiological procedures) observed in the culture sample, and cases with contamination (≥3 pathogens in the sample); other pathogens that may be treated with antibiotics (included Citrobacter, Corynebacterium bovis, Enterobacter, Enterococcus, Pasteurella, Pseudomonas; “other treatable”); and other pathogens not successfully treated with antibiotics (Trueperella pyogenes, Mycoplasma, Prototheca, yeasts; “other not treatable”). Data from 38,276 lactations in cows from 5 New York State dairy herds, collected from 2003–2004 until 2011, were analyzed. Mixed models with an autoregressive correlation structure (to account for correlation among the repeated measures of milk yield within a lactation) were estimated. Primiparous (lactation 1) and multiparous (lactations 2 and 3) cows were analyzed separately, as the shapes of their lactation curves differed. Primiparas were followed for up to 48 wk of lactation and multiparas for up to 44 wk. Fixed effects included parity, calving season, week of lactation, CM (type, case number, and timing of CM in relation to milk production cycle), and other diseases (milk fever, retained placenta, metritis, ketosis, displaced abomasum). Herd was modeled as a random effect. Clinical mastitis was more common in multiparas than in primiparas. In primiparas, Streptococcus spp. occurred most frequently as the first case. In multiparas, E. coli was most common as the first case. In subsequent cases, CM cases with no specific growth or contamination were most common in both parity groups. The hazard of CM increased with case number. Mastitic cows were generally higher producers before the CM episode than their nonmastitic herdmates. Milk loss varied with pathogen and case number. In primiparas, the greatest losses were associated with E. coli and “other not treatable” organisms. In multiparas, the greatest losses were associated with Klebsiella spp. and “other not treatable” organisms. Milk loss was not associated with occurrence of CNS. The findings may help farmers to make optimal management decisions for their cows.     

Cow-specific treatment of clinical mastitis: an economic approach

Under Dutch circumstances, most clinical mastitis (CM) cases of cows on dairy farms are treated with a standard intramammary antimicrobial treatment. Several antimicrobial treatments are available for CM, differing in antimicrobial compound, route of application, duration, and cost. Because cow factors (e.g., parity, stage of lactation, and somatic cell count history) and the causal pathogen influence the probability of cure, cow-specific treatment of CM is often recommended. The objective of this study was to determine if cow-specific treatment of CM is economically beneficial. Using a stochastic Monte Carlo simulation model, 20,000 CM cases were simulated. These CM cases were caused by Streptococcus uberis and Streptococcus dysgalactiae (40%), Staphylococcus aureus (30%), or Escherichia coli (30%). For each simulated CM case, the consequences of using different antimicrobial treatment regimens (standard 3-d intramammary, extended 5-d intramammary, combination 3-d intramammary + systemic, combination 3-d intramammary + systemic + 1-d nonsteroidal antiinflammatory drugs, and combination extended 5-d intramammary + systemic) were simulated simultaneously. Finally, total costs of the 5 antimicrobial treatment regimens were compared. Some inputs for the model were based on literature information and assumptions made by the authors were used if no information was available. Bacteriological cure for each individual cow depended on the antimicrobial treatment regimen, the causal pathogen, and the cow factors parity, stage of lactation, somatic cell count history, CM history, and whether the cow was systemically ill. Total costs for each case depended on treatment costs for the initial CM case (including costs for antibiotics, milk withdrawal, and labor), treatment costs for follow-up CM cases, costs for milk production losses, and costs for culling. Average total costs for CM using the 5 treatments were (US) $224, $247, $253, $260, and $275, respectively. Average probabilities of bacteriological cure for the 5 treatments were 0.53, 0.65, 0.65, 0.68, and 0.75, respectively. For all different simulated CM cases, the standard 3-d intramammary antimicrobial treatment had the lowest total costs. The benefits of lower costs for milk production losses and culling for cases treated with the intensive treatments did not outweigh the higher treatment costs. The stochastic model was developed using information from the literature and assumptions made by the authors. Using these information sources resulted in a difference in effectiveness of different antimicrobial treatments for CM. Based on our assumptions, cow-specific treatment of CM was not economically beneficial.     

Risk factors associated with short-term post-treatment outcomes of clinical mastitis

The objectives of this study were to characterize 60-d outcomes after treatment of mild (abnormal milk) and moderate (abnormal milk and abnormal udder) cases of clinical mastitis (CM) occurring in a single quarter of cows on Wisconsin farms (n = 4) and to determine risk factors associated with those outcomes. Duplicate milk samples were collected from the affected quarter of each cow for microbiological analysis at the onset of CM (PRE) and 21 d later (POST). Cows were treated only in the affected quarter using an intramammary product containing 125 mg of ceftiofur. Bacteriological cure was defined as absence of pathogens in the POST sample obtained from the enrolled quarter. Recurrence was defined for the cow when CM occurred after the milk-withholding period for the enrolled case of CM. Retention in the herd was defined when a cow was retained within the herd for the 60-d follow-up period. Somatic cell count reduction (SCCR) was defined at the cow level as somatic cell count (SCC) below 200,000 cells/mL at the Dairy Herd Improvement Association test day occurring between 21 to 55 d post-treatment. The effects of farm, days in milk, parity, severity, microbiological diagnosis at PRE, previous milk yield, previous SCC, previous occurrence of CM and treatment duration on selected post-treatment outcomes were assessed using Chi-squared analysis and logistic regression. Microbiological results at PRE were distributed as: Escherichia coli (n = 14), Klebsiella spp. (n = 11), Enterobacter spp. (n = 8), Serratia spp. (n = 7), other gram-negative species (n = 3), Streptococcus spp. (n = 25), coagulase-negative staphylococci (n = 4); Staphylococcus aureus (n = 1); Streptococcus agalactiae (n = 1), other gram-positive species (n = 9), and culture negative (n = 60). Treated quarters were more likely to experience bacteriological cure when the cow experienced CM for the first time in the lactation and when no pathogen was recovered from PRE milk samples obtained from the enrolled quarter. Parity and bacteriological cure were associated with the probability of recurrence. Greater milk yield at previous Dairy Herd Improvement test was the most important predictor for retention within the herd. When SCC before CM was >200,000 cells/mL the probability of having SCCR after treatment was decreased. When the case experienced bacteriological cure, the cow was less likely to experience recurrent cases and was more likely to have SCCR below 200,000 cells/mL. Post-treatment outcomes, such as recurrence and SCCR, are strongly associated with bacteriological cure and, when monitored, can be used to help determine if a treatment has been successful. Information about the etiology of CM, history of clinical and subclinical mastitis, and parity are useful to review when making strategic treatment decisions.     

Comparison of J5 vaccinates and controls for incidence, etiologic agent, clinical severity, and survival in the herd following naturally occurring cases of clinical mastitis

Holstein dairy cattle in 3 commercial herds were randomly allocated to J5 vaccination (n = 251) or untreated control (n = 306) groups. There were 221 new cases of clinical mastitis (CM) affecting 120 cows. Coliform mastitis cases had a higher percentage of severe quarter swelling or signs of systemic illness among control cows but not among J5 vaccinates, in comparison to noncoliform cases. Culling or death from CM affected 13 controls (4.3%) and 4 vaccinates (1.6%), with losses occurring earlier in lactation among controls, a higher hazard (probability of a cow dying on each day of lactation) for controls than vaccinates. The J5 vaccination was significantly associated with protection from culling for mastitis among the 15 Klebsiella cases; 2 out of 10 (20%) Klebsiella-infected controls were culled and 0 out of 5 vaccinates were culled. Cows in second lactation were at reduced hazard of culling for mastitis compared with older animals, even when adjusting for effects of J5 vaccination. When all CM cases (including subsequent new cases during the same lactation and multiple quarters or pathogens within the same cow on the same day) were evaluated, for the 221 cases of CM, the rate was significantly higher among vaccinates than controls (0.10 and 0.07 cases/30 d in milk, respectively). This was because J5 vaccinates had more subsequent new cases of CM in the same cow than controls. Pathogens isolated, which included mainly environmental bacteria, were not different among J5 vaccinates and controls. Immunization with J5 was associated with protection against severe clinical coliform mastitis signs, culling, and death loss from CM but not with any reduction in overall CM.     

Immunization with a novel recombinant protein (YidR) reduced the risk of clinical mastitis caused by Klebsiella spp. and decreased milk losses and culling risk after Escherichia coli infections

The primary objective of this study was to evaluate the protective efficacy of a novel recombinant subunit vaccine containing the protein YidR (rYidR) against clinical mastitis (CM) caused by Klebsiella spp. and Escherichia coli. Given that E. coli infection is known to cause metritis, we also evaluated the effect of rYidR vaccination on the incidence of metritis and conception at the first artificial insemination. Retained placenta and abortion incidence, milk production and composition, and serological responses to specific antigens were also evaluated. In total, 3,107 cows were blocked by parity and randomly allocated into 1 of 3 treatment groups: experimental recombinant subunit vaccine containing the YidR protein (rYidR); commercial vaccine composed of Klebsiella pneumoniae siderophore receptors and porin protein (Kleb-SRP; KlebVax, Epitopix, Willmar, MN); and sterile water adjuvanted with aluminum hydroxide (20%; placebo). Vaccinations were performed at the dry-off for cows, and at 223 ± 3 d of pregnancy for pre-fresh heifers. A second administration was given at 21 ± 3 d after the first injection. Vaccination with rYidR significantly reduced the incidence of CM caused by Klebsiella spp. (3.2%) when compared with the placebo (5.1%) group. No difference was observed on risk of Klebsiella CM between Kleb-SRP (5.9%) and placebo groups. Cows in the rYidR group that experienced E. coli CM had a lower risk of death or culling (12.5%) compared with the Kleb-SRP (27.6%) and placebo groups (27.8%). Furthermore, among cows that developed E. coli CM, rYidR-immunized cows produced more milk than did cows in the placebo and Kleb-SRP groups. Regardless of CM occurrence, rYidR-immunized cows tended to have higher milk production up to the eighth month of lactation than cows in the other groups. No significant effect of treatment was observed on the overall incidence of abortion and metritis; however, the risk of retained placenta tended to be lower for the rYidR group (4.7%) compared with the placebo group (6.7%). In addition, primiparous cows in the rYidR group had the highest conception risk at the first artificial insemination (48.3%) compared with the placebo (39.5%) group, and no significant difference was observed when the Kleb-SRP (40.1%) group was compared with the placebo group. Generally, higher antibody serum titers (IgM and IgG) were observed for the immunized groups compared with the placebo. In conclusion, the rYidR vaccine reduced the risk of CM caused by Klebsiella spp. and the mortality or culling of cows with E. coli infections. Other benefits of the novel vaccine include maintenance of milk production after CM caused by E. coli, and higher conception risk at the first service in primiparous cows compared with cows in the placebo and Kleb-SRP groups.     

The economic cost of metritis in dairy herds

The objective of this study was to estimate the cost of metritis in dairy herds. Data from 11,733 dairy cows from 16 different farms located in 4 different regions of the United States were compiled for up to 305 d in milk, and 11,581 cows (2,907 with and 8,674 without metritis) were used for this study. Metritis was defined as fetid, watery, red-brownish vaginal discharge that occurs ≤21 d in milk. Continuous outcomes such as 305-d milk production, milk sales ($/cow), cow sales ($/cow), metritis treatment costs ($/cow), replacement costs ($/cow), reproduction costs ($/cow), feeding costs ($/cow), and gross profit per cow ($/cow) were analyzed using mixed effect models using the MIXED procedure of SAS (SAS Institute Inc., Cary, NC). Gross profit was also compared using the Kruskal–Wallis test. Dichotomous outcomes such as pregnant and culling by 305 d in milk were analyzed using the GLIMMIX procedure of SAS. Time to pregnancy and culling were analyzed using the PHREG procedure of SAS. Models included the fixed effects of metritis, parity, and the interaction between metritis and parity, and farm as the random effect. Variables were considered significant when P ≤ 0.05. Metritis cost was calculated by subtracting the gross profit of cows with metritis from the gross profit of cows without metritis. A stochastic analysis was performed with 10,000 iterations using the observed results from each group. Milk yield and proportion of cows pregnant were lesser for cows with metritis than for cows without metritis, whereas the proportion of cows leaving the herd was greater for cows with metritis than for cows without metritis. Milk sales, feeding costs, residual cow value, and gross profit were lesser for cows with metritis than for cows without metritis. Cow sales and replacement costs were greater for cows with metritis than for cows without metritis. The mean cost of metritis from the study herds was $511 and the median was $398. The stochastic analysis showed that the mean cost of a case of metritis was $513, with 95% of the scenarios ranging from $240 to $884, and that milk price, treatment cost, replacement cost, and feed cost explained 59%, 19%, 12%, and 7%, respectively, of the total variation in cash flow differences. In conclusion, metritis caused large economic losses to dairy herds by decreasing milk production, reproduction, and survival in the herd.     

Evaluation of chromogenic culture media for rapid identification of microorganisms isolated from cows with clinical and subclinical mastitis

This study aimed to evaluate the diagnostic performance (specificity, Sp; sensitivity, Se; accuracy; positive predictive value; negative predictive value; and Cohen's kappa coefficient, κ, of agreement) of chromogenic culture media for rapid identification of microorganisms isolated from cows with clinical (CM) and subclinical mastitis (SCM). For this, 2 experiments were carried out: evaluation of (1) biplate, and (2) triplate of chromogenic culture media for rapid identification of mastitis-causing microorganisms. For the evaluation of diagnostic performance, identification of microorganisms by MALDI-TOF mass spectrometry was considered the standard methodology. In experiment 1, 476 milk samples collected from cows with CM and 660 from cows with SCM were evaluated by inoculation in 2 selective chromogenic culture media (CHROMagar) for gram-positive bacteria and another for gram-negative bacteria. In experiment 2, 476 milk samples from cows with CM and 500 from cows with SCM were evaluated by inoculation in triplate chromogenic culture media (Smartcolor2, Onfarm), selective for Streptococcus and Strep-like organisms, Staphylococcus, and gram-negative bacteria. In experiment 1 for the CM samples, the use of biplates with gram-positive and gram-negative culture media showed Se that ranged from 0.56 (0.32–0.81; Staphylococcus aureus) to 0.90 (0.80–0.99 Streptococcus uberis), Sp varied from 0.94 (0.92–0.96; Strep. uberis) to 1.00 (Prototheca spp. or yeast), and κ ranged from 0.47 (0.26–0.67; Staph. aureus) to 0.84 (0.78–0.9; Escherichia coli). The Se of biplates for SCM samples ranged from 0.50 (0.15–0.85; E. coli) to 0.94 (0.87–1.00; Staph. aureus), Sp varied from 0.95 (0.93–0.97; Strep. uberis) to 0.99 (0.98–1.00; Staph. aureus and Strep. Agalactiae or dysgalactiae), and κ ranged from 0.18 (0.00–0.40; Escherichia coli) to 0.88 (0.80–0.95; Staph. aureus). In experiment 2, the Se of the triplate chromogenic media in CM samples ranged from 0.09 (0.00–0.26; Serratia spp.) to 0.94 (0.85–1.00; Klebsiella spp. and Enterobacter spp.), Sp varied from 0.94 (0.92–0.96; Strep. agalactiae and Strep. dysgalactiae) to 1.00 (Serratia spp.) and κ ranged from 0.07 (0.00–0.24; Serratia spp.) to 0.85 (0.75–0.94; Klebsiella spp. and Enterobacter spp.). For SCM samples, the use of the triplate with the chromogenic culture media showed Se that varied from 0.25 (0.10–0.40; Lactococcus spp.) to 1.00 (Strep. Agalactiae or dysgalactiae), Sp ranged from 0.92 (0.90–0.94; Strep. Agalactiae and Strep. dysgalactiae) to 0.99 (0.98–1.00; Klebsiella spp. and Enterobacter spp.), and κ varied from 0.28 (0.00–0.72; E. coli) to 0.72 (0.60–0.82; Staph. aureus). Our results suggest that the diagnostic accuracy of the biplate and triplate of chromogenic culture media varies according to pathogen, and the results of chromogenic culture media may be useful for rapid decision-making on mastitis treatment protocols of the main mastitis-causing microorganisms, but their use for implementation of mastitis control measures will depend on each farm specific needs.     

Loss of income from cows shedding Mycobacterium avium subspecies paratuberculosis prior to calving compared with cows not shedding the organism on two Minnesota dairy farms

Quantification of the financial effect of Mycobacterium paratuberculosis infection on lactation performance is essential to encourage participation of dairy cattle producers in Johne's disease (JD) control programs. The objective of this study was to evaluate the differences in net income per lactation of cows shedding Mycobacterium paratuberculosis before calving compared with test-negative cows. Two Minnesota dairies were enrolled in the study and fecal samples were collected from 1,048 cows during the close-up period. Milk production, clinical diseases (other than clinical JD), and reproductive performance data were recorded for each cow. Overall, fecal-culture-positive (FCP) cows produced 1,355 kg less than fecal-culture-negative (FCN) cows. Fecal-culture-positive cows that survived their current lactation produced $276 less in milk income than cows that were FCN ($1,956 vs. $1,680; SD $526, $570). Fecal-culture-positive cows were 3.0 (95% confidence interval: 1.6-5.8) times more likely to be culled than FCN cows. The mean days open (number of days from calving to conception) was not statistically significant and the cost differences for clinical disease other than JD were small and neither statistically nor economically significant between FCP and FCN cows. Among all FCP cows, income over feed costs losses were $366 per cow per lactation compared with FCN cows. Among FCP nonculled cows, income over feed costs losses were $276 more compared with FCN cows and this difference was statistically significant. There was a total loss of $155 per lactation for nonculled FCP cows retained in the herd compared with FCN cows retained in the herd. Among culled cows, FCP cow losses were $50 less because of age at culling and $120 for reduced beef value. This totaled a loss of $441 for culled FCP cows compared with culled FCN cows. The losses as a result of lower lactation performance and early culling from the herd should alarm dairy producers and motivate them to implement the appropriate control measures for the disease.     

Cleanliness scores as indicator of Klebsiella exposure in dairy cows

This study was designed to explore the relationship between cow and udder cleanliness scores and the risk of isolation of Klebsiella spp. from lower hind legs and teat ends, respectively. The distribution of Klebsiella species was compared among isolates from teat ends, legs, and cases of clinical mastitis obtained from 2 dairy farms in New York State, with 850 and 1,000 cows, respectively. Farms were visited twice approximately 4 wk apart in August and September 2007 to obtain cleanliness scores and swabs from legs and teats. Isolates of Klebsiella clinical mastitis from each farm were collected from July through October 2007. Two studies were conducted. In the first study, whole-cow cleanliness of a purposive sample of 200 lactating cows was scored using a 4-point scale, and swabs were taken from their lower hind legs. In the second study, udder cleanliness of a separate convenience sample of 199 lactating cows was scored in the milking parlor, and swabs were taken from their teat ends before and after premilking udder preparation. Prevalence of Klebsiella spp. on legs and teat ends before udder preparation was 59 and 60%, respectively. Logistic regression was used to explore the association between isolation of Klebsiella spp. and cleanliness scores. Cow cleanliness scores and udder cleanliness scores were not associated with detection of Klebsiella on legs and on teats before udder preparation, respectively. After udder preparation, 43% of previously Klebsiella positive teat end samples remained positive, with significant differences between farms and months. Teats from dirty udders were significantly more likely to test positive for Klebsiella after udder preparation than teats from clean udders. The proportion of Klebsiella pneumoniae and Klebsiella oxytoca isolates was similar for isolates from teat end swabs and clinical mastitis cases, supporting the notion that the presence of Klebsiella on teat ends may lead to opportunistic intramammary infections. Udder cleanliness scores could be used as a management tool to monitor the risk of exposure to Klebsiella spp. on teat ends.     

Practical challenges and potential approaches to predicting low-incidence diseases on farm using individual cow data: A clinical mastitis example

Clinical mastitis (CM) incidence is considerable in terms of cows affected per year, but cases are much less common in terms of detections per cow per milking. From a modeling perspective, where predictions are made every time any cow is milked, low CM incidence per cow day makes training, evaluating, and applying CM prediction models a challenge. The objective of this study was to build models for predicting CM incidence using time-series sensor data and choose models that maximize net return based on a cost matrix. Data collected from 2 university dairy farms, the University of Florida and Virginia Polytechnic Institute and State University, were used to gather representative data, including 110,156 milkings and 333 CM cases. Variables used in the models were milk yield, protein, lactose, fat, electrical conductivity, days in milk, lactation number, and activity as the number of steps, lying time, lying bouts, and lying bout duration. Models that predicted either likelihood of CM caused by gram-negative (GN) or gram-positive (GP) bacteria on each day were derived using extreme gradient boosting with weighting favoring true-positive cases, logistic responses, and log-loss errors. Model accuracies were determined using data randomly held out from the training set on each run. All variables considered were in terms of change (slope) over previous days, including the day CM was visually detected. The GN models had a median sensitivity (Se) of 52.6% and specificity (Sp) of 99.8%, whereas the GP models had a median Se of 37.5% and Sp of 99.9% when tested on the held-out data. In our models optimized to reduce cost from predictions, the Se was much less than Sp, suggesting that CM models might benefit from greater model weighting placed on Sp. Results also highlight the importance of positive predictive value (true positive cases per predicted positive case) along with Sp and Se, as models built on sparse data tend to predict too many false-positive cases. The calculated partial net return of our GN and GP models were ?$0.15 and ?$0.10 per cow per lactation, respectively, whereas International Organization for Standardization (ISO) standard models with Se of 80% and Sp of 99% would return ?$1.32 per cow per lactation. Models chosen that minimized the cost to the farmer differed markedly from models that met ISO guidelines, showing asymmetry in targets between Sp and Se when the disease incidence rate is low. Because of the unique challenges that low-incidence diseases like CM present, we recommend that future CM predictive models consider the economic and practical implications in addition to the traditional model evaluation metrics.     

Relationships between milk culture results and treatment for clinical mastitis or culling in Norwegian dairy cattle

In quarter milk samples from 2,492 randomly sampled cows that were selected without regard to their current or previous udder health status, the relationships between the following outcome variables were studied: treatment of clinical mastitis; the joint event of either treatment or culling for mastitis; culling for all reasons; culling specifically for mastitis; and the covariates of positive milk culture for Staphylococcus aureus, Streptococcus spp., and coagulase-negative Staphylococcus spp., or other pathogens, or of negative culture for mastitis pathogens. Microbiological diagnoses were assigned at the cow level, and altogether 3,075 diagnoses were related to the outcome variables. The relation between the absence of pathogens and rich (>1,500 cfu/mL of milk) or sparse (≤1,500 cfu/mL of milk) growth of Staph. aureus were also assessed separately for each outcome variable. The hazard of treatment of clinical mastitis was greater for cows diagnosed with Staph. aureus compared with cows with no pathogens in all analyses. Cows with sparse growth of Staph. aureus upon microbiological analysis were more likely to be treated for clinical mastitis, and cows with rich growth of the bacteria experienced a higher overall risk of culling when the models adjusted for cow composite milk somatic cell count. No difference between rich and sparse growth of Staph. aureus was found when mastitis was defined as the joint event of either culling for mastitis or treatment of clinical mastitis, and when the relationship with culling specifically for mastitis was assessed. The combined outcome of treatment and culling for mastitis was related to a positive diagnosis of Strep. spp. after cow composite milk somatic cell count was omitted from the model. Presence of Streptococcus spp. was also related to culling specifically for mastitis, whereas culling for all reasons and treatment of clinical mastitis was not related to a positive culture of Strep. spp. Presence of coagulase-negative Staph. spp. or other pathogens was not associated with either of the outcome variables.     

Acute-phase inter-alpha-trypsin inhibitor heavy chain 4 (ITIH4) levels in serum and milk of cows with subclinical mastitis caused by Streptococcus species and coagulase-negative Staphylococcus species

The aim of the study was to investigate the concentrations of acute-phase inter-α-trypsin inhibitor heavy chain 4 (ITIH4) in serum and milk of cows with subclinical mastitis caused by Streptococcus spp. (STR) and coagulase-negative Staphylococcus spp. (CNS) and healthy cows. The blood and milk samples were obtained from 60 mid-lactation, multiparous Holstein-Friesian cows from 7 herds in the Lublin region of Poland. In the milk samples from 40 cows with subclinical mastitis, Streptococcus spp. and CNS were isolated. The ITIH4 was significantly higher in serum of cows with subclinical mastitis caused both by STR and CNS compared with healthy cows. One hundred percent of animals infected with Streptococcus spp. and 89% of animals infected with Staphylococcus spp. showed ITIH4 concentration in sera higher than 0.5 mg/mL. The concentration of ITIH4 in milk also was significantly higher in cows with subclinical mastitis caused by Streptococcus spp. and Staphylococcus spp. compared with the control group. Seventy percent of cows infected by STR and CNS showed ITIH4 concentration in milk higher than 2.5 μg/mL. Milk ITIH4 concentration higher than 5 µg/mL was found in 55% of animals infected with Streptococcus spp. and in 40% of animals infected with Staphylococcus spp. No statistically significant differences were observed in ITIH4 concentrations both in serum and in milk between the studied unhealthy animal groups. These results suggest that ITIH4 may be used in the future as a novel diagnostic marker in serum and in milk of subclinical mastitis in cows.