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Canadian Bovine Mastitis Research Network
 

All about Mastitis I Others

The Economic Impact of High SCC's  I  The Impact of Clinical Mastitis  I  The Impact of Culling at the Slaughter Plan
Significant Losses


Improving Udder Health
An Economic Gain

To the average dairy herd, mastitis is the costliest disease. But how can we put numbers on the losses caused by a high somatic cell count or a case of clinical mastitis?

To begin with, it should be pointed out that high somatic cell counts (SCC) and the frequency of clinical mastitis cases are fairly independent one from the other. The reason is quite simple: these two problems are usually caused by different bacteria, with different risk factors. Therefore, some herds may have a clinical mastitis problem without necessarily having high SCC issues, and vice versa. That being said, the two problems are not mutually exclusive and it is possible for a given herd to have a clinical mastitis problem and a high somatic cell count problem when the risk of infection from the pathogen bacteria responsible for both situations is high in the same herd.

The Economic Impact of High SCC’s
 
A few studies have examined the herd production decline. The potential production gain per lactation associated with the decrease of the SCC of a herd is presented in Table 1.
 
TABLE 1. PRODUCTION GAIN AS A FUNCTION OF THE DECREASE IN THE AVERAGE SCC OF THE HERD (IN KG OF MILK PER COW PER LACTATION)
 
Average SCC before (x1,000/ml)
Average SCC
after (x1,000/ml)
150
175
200
225
250
275
300
325
350
375
400
100
139
192
238
279
315
348
378
405
431
454
477
125
63
116
162
202
238
271
301
329
354
378
400
150
0
53
99
139
176
208
238
266
291
315
337
175
 
0
46
86
123
155
185
213
238
262
284
200
 
 
0
40
77
109
139
167
192
216
238
225
 
 
 
0
36
69
99
126
152
176
198
250
 
 
 
 
0
33
63
90
116
139
162
275
 
 
 
 
 
0
30
57
83
107
129
300
 
 
 
 
 
 
0
28
53
77
99
 
According to the figures, if the average SCC of a herd decreased from 300,000 to
150,000 SC/ml, its milk production would increase by 238 kg/cow. In the case of a herd of 100 cows, that would mean a $16,700 gain (100 cows * 238 l/cow * $0.70/l after marketing expenses).
 
However, certain variable costs must be taken into account in the production of this additional milk. To begin with, there are the marginal feed costs that would amount to about $0.12 per litre of additional milk produced per cow whose maintenance requirements have already been covered. Then, there would at the very least the interests paid to finance the extra quota required for the corresponding annual production increase, or approximately $10/hl, assuming a loan at 6% interest over 12 years. We now come to $22/hl of variable costs for the extra milk produced, bringing down the net impact of the production increase to $11,400 (100 cows * 238 l/cow * $0.48/l).
 
Another way of benefiting from the increased production per cow would be to reduce the number of cows in the herd, which would result in a decrease in variable costs.
 
The Impact of Clinical Mastitis
 
Clinical mastitis causes economic losses that are mainly due to declining production, milk withdrawal, increased mortality risk and finally, the cost of the treatment itself.
 
Declining production
During the clinical mastitis episode and in the following months, the production decline will be more or less severe. Although losses will be insignificant in mild cases (except for losses associated with high SCC’s), they can range between 375 to 1,000 kg per episode in moderate or severe cases of mastitis. The average loss, regardless of the severity of the infection, would be around 230 kg per mastitis episode.
 
The value of the average production decline would therefore be estimated at around $110 per case, taking into account the variable costs discussed earlier (230 l * $0.48/l).
 
Milk withdrawal
In addition to reduced production, you have to add the milk that must be discarded.
 
We can estimate that the milk from a mastitis infected cow must be discarded between 5 to 10 days, at a cost of around $60 to $120 per case, i.e. an average of $90 (20 l/day * 5 to 10 days * $60/hl). Here, the marginal feed costs are not deducted since the milk is indeed produced and the feed is served and consumed.
 
Mortality
In certain cases, mastitis can lead to death.
 
At present, the value of replacement stock is very high, at approximately $2,500 to $3,000 (let’s take an average cost of $2,750 per head). However, we should bear in mind that the dead cow has a lower value than the fresh heifer that will replace it.
 
In that case, the real cost of the death would be around $1,575, midway between the initial value and the final value if the cow was sold to a slaughter plant ($2,750 + $400)/2. The value of the dead cow depends, of course, on its potential, age, lactation status, breeding status, etc., but we can use this as a reference value. This cost is probably somewhat overestimated, since death is expected in cows that are older than the average.
 
Although the cost of a dead animal is high, mortality associated with mastitis is generally rare, less than one death per 50 mastitis cases (2%). Under such typical conditions, the average cost of mortality would therefore amount to approximately $30 per mastitis case (2% of $1,575).
 
The cost of treatment
The cost of treatment may be divided in four categories: intramammary antibiotics, systemic drugs (injectable antibiotics, fluids and anti-inflammatory drugs), veterinary fees (professional fees and visits) and labour.
 
These costs are summarized in Table 2. Overall, the average clinical case would have an associated treatment cost of $38, half of which would be labour costs while the rest would go for intramammary drugs, systemic drugs and professional fees. Of course, such costs can vary quite a bit depending on the circumstances, but it is a realistic estimated average.
 
TABLE 2. AVERAGE TREATMENT COSTS PER MASTITIS EPISODE
CLASS
DETAILED CALCULATION
AVERAGE $ PER MASTITIS CASE
Intramammary antibiotics
70% of mastitis cases * $10
7
Systemic antibiotics
15% of mastitis cases * $50
7.50
Veterinary fees
5% of mastitis cases * $90
4.50
Labour costs
- 85% of cases at 45 min. * $22/h
- 15% of cases at 1h30 min * $22/h
19
TOTAL PER MASTITIS CASE
 
38
 
Reproductive costs
Cows that suffered from clinical mastitis have a calving-conception interval of approximately 25 days more than cows that have not been infected, or 18 days per mastitis episode (assuming 1.4 mastitis episodes per infected cow). This effect on the number of days open can be estimated at around $77 per case (at $4.33/day open).
 
Summary of losses resulting from clinical mastitis
In Quebec, the total economic impact of clinical mastitis, excluding culling at the slaughter plant, would be $345 per case of clinical mastitis (see Table 3).
 
TABLE 3. SUMMARY OF AVERAGE COSTS PER CASE OF CLINICAL MASTITIS
CLASS
DETAILED CALCULATION
COST PER CLINICAL CASE ($)
Dairy production decline
230 l * $0.48/l
110
Breeding performance decline
18 days * $4.33/day
77
Milk withdrawal
5 to 10 days * 20 l/day * $0.60/l
90
Cost of treatment including labour
See Table 2
38
Mortality
 
63
TOTAL PER MASTITIS CASE
 
345
 
The estimated cost par clinical case reflects the typical distribution of clinical case severity among a herd, with only a minority of very severe cases. However, in a herd where the severity of the cases would be higher than the average, the economic impact of clinical mastitis could also be much higher. For a farm of 100 cows with 25 cases of clinical mastitis a year, that would mean losses amounting to $8,625, mortality included.
 
Just as for the SCC, it is not realistic to compare such losses with a situation where a herd would have no case of clinical mastitis at all. A more realistic scenario might be to shoot for a reduction from 25 to 15 clinical cases per 100 cows. Excluding culling, such an improvement in the rate of clinical mastitis for a herd of that size would amount to $3,450 (10 cases * $345/case). The profitability of that improvement in the rate of clinical mastitis would again depend on the investment required to achieve that goal.
 
The Impact of Culling at the Slaughter Plan
 
In order to figure out the economic impact of culling due to mastitis, it is necessary to consider that the average cow sold to the slaughter plant because of a udder health problem has a lower value than the average replacement heifer that will take its place because of its older age. The cost of replacing a cow culled as a result of mastitis will then amount to $1,175 (value at the time of culling minus the return value at the slaughter plant = $1,575 - $400).
 
In Quebec, about 16% of cull cows are attributed to mastitis or to a high SCC for a global culling rate of 34%, which means that about 5.5% of cows are eliminated every year because of a udder health problem.
 
Therefore, when compared with a perfect scenario, losses resulting from mastitis related culling would amount to an approximate average of $6,460 for a herd of 100 cows in Quebec (5.5% * 100 cows * $1,175/cull cow).
 
Lowering the number of cows sold to the slaughter plant because of a udder health by half would therefore represent a gain of about $3,200 to the owner of a herd of 100 cows.
 
Significant Losses
 
The economic losses associated with udder health are significant in Quebec’s herds.
  • With 25 episodes of clinical mastitis per 100 cows per year, the losses to clinical mastitis would amount to approximately $86 per cow in a Quebec herd, out of which about $50 could be recovered when comparing with the best performing herds (incidence below 10%).
  • The losses to high SCC’s are more difficult to measure but are also significant. If a herd with a SCC of 250,000 SC/ml (the Quebec average) lowered it to 100,000 SC/ml (the best herds), it could mean a gain of about $150 per cow.
  • Replacement costs associated with mastitis would amount to $64 per cow in a herd with a typical culling rate, out of which about $30 could be recovered.
We can therefore estimate that in a Quebec herd with an average udder health status, intramammary infections caused recoverable losses of $200 to $250 per cow per year, i.e. $2 to $3/hl.
 
How much is mastitis costing your business?

This article was published in Le producteur de lait québécois in November 2009 and was adapted from a conference presented at the Symposium des bovins laitiers, CRAAQ, 2009.
 
Written by Jérôme Carrier, consulting veterinarian, AMVPQ.





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