Development And Implementation Of A Pathogen Specific Clinical Mastitis Economic Decision Model

Clinical mastitis (CM) is a production limiting disease affecting dairy cattle worldwide. Cows suffering from CM may experience a loss in milk production, reduction in rate of conception an increased risk of mortality and culling. Direct costs to the dairy farmer include costs due to compromised milk quality, treatment and discarded milk costs if antibiotics are used. Given these effects, dairy farmers are often faced with the decision of what to do with their diseased cows; whether to keep or replace with a younger heifer. The economic model developed to assist dairy farmers with these decisions is based on dynamic programming. It was necessary to develop a pathogen specific model for several reasons: (1) The previous framework did not separate CM into the different pathogens that are causative, hence, in the past, the effects of pathogen specific CM were pooled while decisions may be pathogen specific and (2) Discarded milk due to treatment after adjusting for the loss of milk from disease was not accounted. Further, the previous framework did not have the flexibility to include additional pathogens easily. In developing this model, we estimated the effects of pathogen specific CM for inclusion in the model (i.e., risk of pathogen specific CM and risk of mortality (and culling)). Further, prior to developing a pathogen specific model, we expanded an existing generic CM model (i.e., where all CM pathogens were combined) to study the cost of 3 different types of CM i.e., grampositive, gram-negative and other CM. Cows with more cases of CM in the previous lactation were at greater risk of bacteria specific CM in the current lactation, e.g., among multiparous cows in wim [GREATER-THAN OR EQUAL TO] 3, cows were 2.2 times more at risk of a first case of E. coli if they had 2 cases of CM (of any type) in the previous lactation compared with no cases in the previous lactation. Among multiparous cows, cows were at greater risk of a recurrent case within the first month after the previous case of CM, unlike primipara, where these cows were at greater risk of a recurrent case within 2 months of the previous case. 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, where cows were 4.57 (exp(1.52)= 4.57 [95% CI (2.75, 7.61)]) times more at risk of mortality, and with a first case of E. coli with cows 3.32 times more at risk (i.e., relative risk = exp(1.20)= 3.32, [95% CI (2.46, 4.48)]. In general the presence of a first or second case resulted in cows in parity [GREATER-THAN OR EQUAL TO]2 with a greater risk of mortality (compared with cows with no first or second case of bacteria specific CM in the current month in milk). In first parity cows, the risk of culling generally increased with the presence of a case of bacteria specific CM. Among cows of parity [GREATER-THAN OR EQUAL TO]2, when a cow contracted a case of Streptococcus spp., she was more likely to be culled one month after the case of CM (regardless of whether it was a first, second or third case of Streptococcus spp.). The average costs per case (USD) 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 of gram-positive CM was treatment cost (51.5% of the total cost per case), milk loss for gram-negative CM (72.4%) and treatment cost for other CM (49.2%). From the pathogen specific economic model, we determined the net returns per cow and year, with an incidence of CM (cases per 100-cow years) of 35.5 was 500 US$, of which 90.6% of cases were recommended to be treated under an optimal replacement policy. The cost per case of CM was 233.41. The average cost per case was greatest for Klebsiella (416), followed by other not treated cases (e.g., Trueperella pyogenes) (316), other treated cases (e.g. pseudomonas) (310), Escherichia coli (309), Staphylococcus aureus (298), Staphylococcus spp. (275), Streptococcus spp. (257) and Negative culture cases (151). Optimal recommended time for replacement was as great as 5 months earlier for cows with CM compared with cows without CM. This model provides economically optimal decisions depending on the individual characteristics of the cow and the specific pathogen causing CM. The parameter estimates may be altered so that the results are specific to a given far

Evidence of no protection for a recurrent case of pathogen specific clinical mastitis from a previous case

The objective of this study was to determine whether the occurrence of a previous case of pathogen-specific clinical mastitis (CM) protects Holstein dairy cows against a recurrent case. Pathogens studied were Escherichia coli, Staphylococcus aureus, Staphylococcus spp., Streptococcus spp., Klebsiella spp., and Trueperella pyogenes. A total of 40 864 lactations (17 265 primiparous and 23 599 multiparous) from 19 835 cows from 5 large, high milk producing New York State dairy herds were analysed. We estimated the effects of parity, calving diseases, milk yield, current season and number of CM cases in the previous lactation on the risk of a first CM case using generalised linear mixed models with a log link and Poisson error distribution. The aforementioned risk factors and the occurrence of previous cases of pathogen-specific CM within the current lactation were evaluated as risks for second and third cases of pathogen-specific CM. Cows with more CM cases in the previous lactation were at greater risk of pathogen-specific CM in the current lactation. Multiparous cows were at greater risk of a second CM case if they had suffered from a first CM case that was caused by the same pathogen as the second case. In contrast, a second CM case generally put cows at greater risk of a third case, irrespective of whether the third case was caused by the same or a different pathogen. Our results showed that a previous case of pathogen specific CM does not generally protect against a recurrent case

Evidence of no protection for a recurrent case of pathogen specific clinical mastitis from a previous case

The objective of this study was to determine whether the occurrence of a previous case of pathogen-specific clinical mastitis (CM) protects Holstein dairy cows against a recurrent case. Pathogens studied were Escherichia coli, Staphylococcus aureus, Staphylococcus spp., Streptococcus spp., Klebsiella spp., and Trueperella pyogenes. A total of 40 864 lactations (17 265 primiparous and 23 599 multiparous) from 19 835 cows from 5 large, high milk producing New York State dairy herds were analysed. We estimated the effects of parity, calving diseases, milk yield, current season and number of CM cases in the previous lactation on the risk of a first CM case using generalised linear mixed models with a log link and Poisson error distribution. The aforementioned risk factors and the occurrence of previous cases of pathogen-specific CM within the current lactation were evaluated as risks for second and third cases of pathogen-specific CM. Cows with more CM cases in the previous lactation were at greater risk of pathogen-specific CM in the current lactation. Multiparous cows were at greater risk of a second CM case if they had suffered from a first CM case that was caused by the same pathogen as the second case. In contrast, a second CM case generally put cows at greater risk of a third case, irrespective of whether the third case was caused by the same or a different pathogen. Our results showed that a previous case of pathogen specific CM does not generally protect against a recurrent case

The value of pathogen information in treating clinical mastitis

The objective of this study was to determine the economic value of obtaining timely and more accurate clinical mastitis (CM) test results for optimal treatment of cows. Typically CM is first identified when the farmer observes recognisable outward signs. Further information of whether the pathogen causing CM is Gram-positive, Gram-negative or other (including no growth) can be determined by using on-farm culture methods. The most detailed level of information for mastitis diagnostics is obtainable by sending milk samples for culture to an external laboratory. Knowing the exact pathogen permits the treatment method to be specifically targeted to the causation pathogen, resulting in less discarded milk. The disadvantages are the additional waiting time to receive test results, which delays treating cows, and the cost of the culture test. Net returns per year (NR) for various levels of information were estimated using a dynamic programming model. The Value of Information (VOI) was then calculated as the difference in NR using a specific level of information as compared to more detailed information on the CM causative agent. The highest VOI was observed where the farmer assumed the pathogen causing CM was the one with the highest incidence in the herd and no pathogen specific CM information was obtained. The VOI of pathogen specific information, compared with non-optimal treatment of Staphylococcus aureus where recurrence and spread occurred due to lack of treatment efficacy, was $20.43 when the same incorrect treatment was applied to recurrent cases, and$30.52 when recurrent cases were assumed to be the next highest incidence pathogen and treated accordingly. This indicates that negative consequences associated with choosing the wrong CM treatment can make additional information cost-effective if pathogen identification is assessed at the generic information level and if the pathogen can spread to other cows if not treated appropriately

The value of pathogen information in treating clinical mastitis

The objective of this study was to determine the economic value of obtaining timely and more accurate clinical mastitis (CM) test results for optimal treatment of cows. Typically CM is first identified when the farmer observes recognisable outward signs. Further information of whether the pathogen causing CM is Gram-positive, Gram-negative or other (including no growth) can be determined by using on-farm culture methods. The most detailed level of information for mastitis diagnostics is obtainable by sending milk samples for culture to an external laboratory. Knowing the exact pathogen permits the treatment method to be specifically targeted to the causation pathogen, resulting in less discarded milk. The disadvantages are the additional waiting time to receive test results, which delays treating cows, and the cost of the culture test. Net returns per year (NR) for various levels of information were estimated using a dynamic programming model. The Value of Information (VOI) was then calculated as the difference in NR using a specific level of information as compared to more detailed information on the CM causative agent. The highest VOI was observed where the farmer assumed the pathogen causing CM was the one with the highest incidence in the herd and no pathogen specific CM information was obtained. The VOI of pathogen specific information, compared with non-optimal treatment of Staphylococcus aureus where recurrence and spread occurred due to lack of treatment efficacy, was $20.43 when the same incorrect treatment was applied to recurrent cases, and$30.52 when recurrent cases were assumed to be the next highest incidence pathogen and treated accordingly. This indicates that negative consequences associated with choosing the wrong CM treatment can make additional information cost-effective if pathogen identification is assessed at the generic information level and if the pathogen can spread to other cows if not treated appropriately.</p

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