Is your dairy losing money because of subclinical mastitis? Most of my customers look puzzled when I ask them this question because unless they’re seeing physical mastitis symptoms – abnormal milk, udder swelling, fevers – it doesn’t exist.
Producers and veterinarians are trained to look for physical evidence when it comes to identifying diseases in cows. After all, we can’t manage a problem if we don’t see it. But evidence of subclinical mastitis isn’t completely untraceable. An individual SCC in excess of 200,000 cells per milliliter (mL) in a cow may indicate a subclinical mastitis infection. You can spot this problem in:
- Monthly individual cow somatic cell count (SCC) test reports
- Bulk tank reports
Even if you are paying attention to individual cow SCCs, are you giving the situation enough attention? Do you know how much SCC can impact potential profit on your dairy?
Look at net farm income (profit)
Zoetis teamed up with AgStar Financial Services to identify dairy production measures that correlate with the financial health of dairies.
After analyzing nine years of herd data (collected from 367 year-end financial and production record summaries from 2014 through 2016), results showed six factors account for 85 percent of the net farm income (profit): SCC, energy-corrected milk per cow, death losses, net herd replacement costs, pregnancy losses and heifer survival. Based on the study, the biggest profitability driver was SCC.
The analysis showed that management of SCC, especially in herds with more than 500 cows, had little to do with revenue generation associated with milk quality bonuses. For profitability, SCC shouldn’t be managed to obtain milk quality premiums, but to manage the dramatic negative effects of clinical and nonclinical mastitis.
Looking at the top one-third of most profitable herds based on SCC with an average bulk tank SCC of 196,000 cells per mL compared with the bottom one-third with an average bulk tank SCC of 239,000 cells per mL, the negative impact of milk quality is evident.
The high herds averaged 91 pounds of milk per cow per day of energy-corrected milk (ECM) versus 72 pounds of milk per cow per day for the low-end herds. Because of milk quality impact on reproductive performance, milk production, death loss and veterinary costs, this resulted in a difference in profit of $1.14 per hundredweight (cwt) of ECM, or approximately $115,000 per year, between the highest one-third and lowest one-third of farms.
Look at reproduction
Let’s zoom in on how SCC can impact reproductive performance. If you aren’t sorting cows that have mastitis, you might miss the impact it is having on their reproductive performance. Data from a study presented at the 2016 National Mastitis Council annual meeting shows that cows with first-test SCC scores above 200,000 take 17 additional days to become pregnant as compared with cows with less than 200,000 at first test.
Even more, cows with SCC scores greater than 4.5 (300,000) before breeding were twice as likely to lose their embryo by days 35 to 41, compared with cows with linear scores of less than 4.5.
Look at milk production
It’s no big secret that milk production per cow is an important variable in determining profitability on dairies. If a cow has mastitis, she could be milking at about 65 to 70 percent of her normal production potential. You might not see the impact on bulk tank SCC immediately, but when you think about a 30 to 35 percent drop in milk production per day, this can escalate quickly.
In fact, data shows that the economic impact from first-test SCC scores above 200,000 cells per mL can cost producers more than 1,500 pounds of lost milk for that lactation. Put into dollars, that’s $285 in lost milk yield per cow (based on $18 per cwt). Looking at the bulk tank, for every 100,000 increase in bulk tank SCC, you can expect to see milk yield drop 5.2 pounds.
Look at additional culls
When cows have high SCC (greater than 200,000 cells per mL), there’s a 2.5 times greater likelihood that the infected animal will develop a case of clinical mastitis by 60 days in milk. This means your culling rate could be three times greater in the first 60 days of lactation compared with first-test SCCs lower than 200,000 cells per mL.
It’s important to realize the cost of net herd replacement is not just the difference between replacement heifer costs and the value of a cull cow. You must consider the productivity potential of the animal being removed compared with its replacement.
Second-lactation cows produce 15 percent more milk than first-lactation cows, and third-lactation cows produce 10 percent more milk than second-lactation cows. This means that replacing an older cow with a first-lactation cow represents a significant loss in current productivity and cash flow.
Look at the cost to cure
When a cow develops clinical mastitis, it’s not just the cost of the treatment. It also is the number of days milk and meat are withheld. Are you keeping track of whether or not the treatment worked? If you didn’t reach a bacterial cure, you’ll also have to factor in relapses and costs of re-treatments.
If you’re re-treating, are you following label directions for proper treatment dosage and milk and meat withhold times? And are you keeping treatment records to track dosage and milk discard times? Any misstep with re-treatment can put you at risk for a residue violation.
Look at overall health
Profitability is driven by cows that are healthy, reproductively sound and genetically capable of achieving their potential of living long enough to produce more milk during the prime of their careers. Excellent animal husbandry skills, influenced by a qualified, invested workforce, go hand in hand with improved animal health and productivity.
What areas of opportunity can you give more attention to help achieve healthier cows and more efficient production? Are you giving SCC enough attention? Work with your veterinarian to help properly manage and identify high-SCC cows in your herd. 
References omitted but are available upon request. Click here to email an editor.
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Greg Edwards DVM
- Managing Veterinarian Dairy Technical Services
- Zoetis
- Email Greg Edwards DVM
