Cost-benefit analysis

The following notes may be of interest. They tell you about some of the assumptions used in developing this website and provide links to further resources where appropriate.

The mastitis cost-benefit calculator was designed by Peter Gripper MRCVS and implemented by Mark Holmes MRCVS. If you have any comments or problems with this site, please contact us at support.uk@intervet.com

Bulk somatic cell count

Importance

High SCC results in a major economic loss to the unit.

• Financial penalties and bonuses are often based on herd SCC
• A bonus is often paid if SCC are less than the targets set by the milk buyer
• A penalty is incurred if the SCC is greater than the targets set by the milk buyer

• Raised SCC depresses milk yield
• The average lactation yield is reduced by about 2.5% for every 100,000 increase in SCC
• Losses are considered even greater in the 50,000-150,000 range. (Philpot, W.N 1984)

Areas to consider:

Individual cow SCC counts can help identify high SCC cows and SCC counts for individual quarters are even more useful in identifying the affected quarter or quarters.

A single high SCC in a cow is not a reason to cull a cow but is a reason to investigate that cow further.

Bactoscan and TBC

Importance

High bactoscans result in a major economic loss to the unit.

• Financial penalties are applied if mean bactoscan results become too high
• High bactoscan affects keeping quality of milk

Areas to consider:

Inadequate plant hygiene, wash procedures, plant maintenance and certain types of clinical mastitis can all lead to raised bactoscans.

When was the plant last serviced, when was rubberware changed, how often do liners get changed, is the wash cycle effective, is the temperature of circulation fluids checked, is the boiler furred up, what is the volume of circulation fluid used, how long is it circulated for?

Cases per 100 cows per year

Importance

Too many cases of mastitis are a major economic loss to the unit.

• Discarded milk
• Medicine and treatment costs
• Veterinary visits for severe cases
• Fatality costs
• Increased culling costs
• Reduced yield for the lactation
• It has been estimated that a mild case results in a loss of £60 and a severe case in £168 loss
• An average cost of £90 has been used in these calculations (Blowey and Edmonson 1995)

Areas to consider:

The number of cows in the herd and number of cases recorded over one year - regardless of whether all cases occur in a few cows. Inaccuracies can occur if all cases are not recorded correctly.

The lower the number of cases the better, as long as the SCC is also low and all cases are being identified. Clinical cases are also a risk to other cows in the herd.

Low cases per 100 cows per year but raised SCC may suggest that there is a subclinical mastitis problem or poor identification of cases.

Proportion of herd affected (%)

• Calculated from the number of cows in the herd that have had mastitis in the year and expressed as a percentage of the total number of cows in the herd
• Should be considered in conjunction with other parameters, such as recurrence rate and SCC

Areas to consider:

If the proportion of the herd affected is low but there is a high recurrence rate then infectious causes must be considered and individual cow cell counts would be a useful analytical tool.

A low proportion of the herd affected and a low recurrence rate may offer different strategies for long-term mastitis control in the herd.

Recurrence rate (%)

• The percentage of cows that have a second or subsequent case of mastitis in the same quarter
• A repeat treatment more than 7 days after a case is considered a recurrence. Accurate records are essential to measure recurrence rate
• Some people calculate the recurrence rate based on second or subsequent cases in the same cow, rather than in the same quarter

Areas to consider:

Certain organisms are difficult to treat and a high recurrence rate indicates that treatment regimes should be reviewed.

Bacteriological examination results will help in the selection of the best treatment protocols for each cow with recurrent mastitis and for the herd as a whole.

Recurrent cases can produce large numbers of cells and just a few cows can be responsible for a large proportion of the overall BSCC in a herd. These cows also act as a source of infection for the rest of the herd.

Specific bacteriology and investigation of recurrent cases is indicated.

Tubes used per cow per year

• Calculated using the number of cows in the herd and the tubes used in a year
• The number of tubes used can be established from the practice records for product supplied to that farmer
• The medicines record book on farm should perhaps be the most accurate record to use

Areas to consider:

Is a high level due to a high number of cases or a high number of tubes needed to treat each case?

Does the number of tubes match the number of cases reported and the number of tubes used per case? Discrepancies suggest records could be improved!

Tubes used per case

• The number of tubes used per case is frequently higher than that recommended by the manufacturer
• A calculation based on tubes per cow per year and number of cases can confirm the accuracy of the farm records

Areas to consider:

If high, then treatment regimes should be reviewed, selection of tube considered and response to treatment considered.

Bacteriology results can assist with this process.

Dry cow mastitis (%)

• The number of cases of mastitis in non-lactating cows expressed as a percentage of the number of cows in the herd
• Clinical cases of mastitis in the dry period can be a major loss

Areas to consider:

• Is dry cow therapy (DCT) used on all cows?
• Is the same therapy used on all cows?
• Do all cows have the same length of dry period?
• How is the choice of DCT made?
• Are bacteriology results used to assist in the decision making for DCT?
• Are high SCC cows considered individually and treated differently?
• Are recurrent cases considered individually and treated differently?

Further reading

Blowey, R. (1986) An assessment of the economic benefits of a mastitis control scheme. Vet Rec 119: 551-553

Philpot, W. N. (1984) Veterinary Clinics of North America Food Animal Practice, 6

Blowey & Edmonson (1995) Mastitis control in dairy herds. Farming Press 1995. ISBN 0 8523 6314-1

To order a copy of the Intervet mastitis book, please e-mail support.uk@intervet.com