M.A.Kossaibati & R.J. Esslemont

DAISY Research, Department of Agriculture, The University of Reading, Reading, Berkshire, RG6 6AT

Abstract for MDC Meeting on Mastitis, Honiley Court, Warwick. March 7^th 2000

There is a shortage of accurate statistics on the prevalence, rate and type of mastitis. There are around 40 cow cases (equivalent to 43 quarter cases) of clinical mastitis per 100 cows (based on a DAISY survey reported by Kossaibati, Hovi and Esslemont in 1998). It is estimated that 90% of these are mild (being treated by the farmer), 9.8% severe (requiring a visit from the veterinarian) and only 0.2% are fatal. It is assumed that mild cases result in 5% reduction in lactation yield, while severe cases are associated with a yield loss of 15%. The costs of clinical mastitis depend on milk price (17p/litre), feed costs (4p/litre), amount of discarded milk due to treatment (117 litres for mild and 138 litres for severe cases respectively), costs of the vet’s time dealing with severe cases (£16 turnout fee and £75 per hour of routine work), cost of drugs (typically 3.5 tubes at £2.30 per tube, plus £50 for a severe case and £70 for a fatal case), the cost of the herdsman’s time (£6/hour: 10 minutes for a mild case, 30 minutes for a severe case, and 60 minutes for a fatal case).

It is also assumed that, on average, 10% of cows with mild mastitis are culled. In severe cases the risk of culling is assumed to be at least 20%. A cull cow is assumed to cost £420 per cull, and the cost of a fatality is £1251. Prices of all items involved are based on February 2000 values.

The costs of clinical mastitis are considered in two categories: direct costs which are normally easy to quantify (e.g. costs of treatments, herdsman's time, veterinarian's time and discarded milk) and indirect costs which can be highly variable (e.g. costs of reduced yield, increased culling and any fatality due to mastitis).

The direct cost of a mild case adds up to £28.9, and the total cost per case (including the costs of lost yield and increased culling) is £113.2. The total cost per affected cow (which has an average of 1.5 cases: 1.2 initial cases and 0.3 repeat cases per year) is £144.5. For a severe case of clinical mastitis the direct cost is £122 per cow case, while the total cost per case is £332.7. The total cost of severe mastitis per affected cow per year is calculated at £435.8. The total cost of losing a fatal case of mastitis is about £1251 for the loss of the cow and £167 for the veterinarian’s intervention, making a total loss of £1418.

Based on the given proportions of mild, severe and fatal cases the weighted average direct cost of a single cow case of clinical mastitis is £38.3, while the total cost per single case is calculated at £137.3. Total cost per affected cow per year is £175.6. Based on the incidence of clinical mastitis found in the DAISY survey, the calculated annual cost of clinical mastitis for an average 100-cow herd is £4389 (of which the direct cost is 35%). The total cost for a herd within the worst 25% is calculated at £6715. However, actual losses could be much higher depending on culling rate.

Assuming that the mean of the top 25% of herds is the target incidence to aim for (21.7 cow cases per 100 cows), the typical herd in the UK with 40 cow cases per year is losing £1892 (about £19 per cow). On the same basis, a dairy herd in the worst 25% is losing £4218 (over £42 per cow in the herd). Details of the calculations are shown in the given example of costing clinical mastitis at herd level (see attached table). The standard achieved by the top 25% of herds may not be good enough to be used as a target in which case the disease should be seen as even more expensive. One suspects that more cows than are estimated here would be culled for mastitis if there were scope (i.e. if a lot of cows were not already being culled for infertility).

The effect on the herd of keeping chronically infected animals into further lactations causing fresh and repeat cases in other cows also needs adding to the equation, as do the costs of having cows with high somatic cell counts. As it is, with a potential loss per cow of £19 (for the average herd when compared with top herds), and with 2.2m cows in the national herd, the cost of clinical mastitis in the UK is calculated at £41.8m. However, it should be emphasised that the above costs do not include the cost of sub-clinical mastitis (extra culling for high somatic cell count, further reduction in yield, etc), and therefore the actual total losses associated with mastitis can be much higher.

For more accurate models of costing mastitis, more information is needed on the types and severity of clinical cases of mastitis, their particular effects on the performance of the cow and the herd as a whole. Trends and patterns of the disease need monitoring properly.

Kossaibati, M.A., Hovi, M. and Esslemont, R.J. (1998). Incidence of clinical mastitis in dairy herds in England. The Veterinary Record, 143, 649-653.