I saw another COVID survivor wheeled out of the Hospital with happy claims of success. It made me wonder, what is a successful treatment in the dairy industry? How do we discuss a cure rate? It is an important discussion because labor and treatment costs in the hospital are not trivial.
The following contains a case study to allow for an important discussion. The topic may seem complex, but here is a summary of what I will talk about:
- When a cow is added to the hospital pen, what is the cause of other performance factors besides the infection?
- When looking at the immediate results after hospitalization, why is a long-term perspective important?
- I’ll then review an actual case study on mastitis.
- Finally, why is it important to define both when to treat an infection and how to measure the results of a treatment (or non-treatment)?
Performance Factors
Some cows make it out of the hospital only to leave the herd because of other complications. Commonly, these are not getting bred or are too low in milk. These results are common because mastitis usually occurs just prior to peak milk and just when the animal is getting bred. Because of that, they are sometimes left out of the systematic reproduction program and on top of that, the ration they are given is usually not formulated for milk production.
A Long-Term Perspective
Here are some examples using DHI-Plus Rx tools. I will compare the animals treated for Mastitis that are left in the herd after completing the withdrawal period. Study the tables below and look at what happens over time.
Herd One: 1585 Cases in One Year
| Days After Withdrawal | Still in the Herd | Sold | Died |
| 14 | 95% | 4% | 1% |
| 28 | 92% | 9% | 1% |
| 60 | 85% | 14% | 2% |
| 150 | 70% | 26% | 3% |
| 210 | 54% | 42% | 4% |
Herd Two: 2181 Cases in One Year
| Days After Withdrawal | Still in the Herd | Sold | Died |
| 14 | 91% | 7% | 2% |
| 28 | 87% | 12% | 2% |
| 60 | 80% | 18% | 2% |
| 150 | 68% | 28% | 4% |
| 210 | 62% | 33% | 4% |
As you can see, time does make a difference. If we only look at what happened just after getting out of the hospital, I would say Herd One had the most treatment success. However, over time Herd Two was more successful because they did the better job of keeping the Hospital cows in the herd.
The Case Study
When measuring treatment success it is important to define what that looks like. From my perspective, another tool used to determine successful treatment is a drop in Somatic Cell Count (SCC). I find however, looking at quarter samples individually is the most valuable. For the following example, I have used an advanced animal diagnostic machine which gives both somatic cell count by quarter and a white blood cell differential.
Cow 3280 was diagnosed with mastitis in the left rear quarter with the following organisms.
| LR | 3/20/2020 | Enterococcus sp. (including faecalis and faecium) (27.5 Ct) |
| LR | 3/20/2020 | Staphylococcus sp. (33.3 Ct) |
| LR | 3/20/2020 | Str. uberis (36.4 Ct) |
She was treated for the Enterococcus sp.
She also had a case of mastitis in the Right Front.
| RF | 3/20/2020 | S. marcescens (39.2 Ct) |
Here are the SCC and white blood cell differential results:
Q Scout 3/4/2020
| 3280 | 3/4/20 | LF | Negative | 52 | 28 | 53.2% | <10 | 15.2% | 16 | 31.6% |
| 3280 | 3/4/20 | LR | Positive | 359 | 209 | 58.2% | 48 | 13.4% | 102 | 28.4% |
| 3280 | 3/4/20 | RR | Disabled | N/A | N/A | N/A | N/A | N/A | N/A | N/A |
| 3280 | 3/4/20 | RF | Positive | 389 | 219 | 56.5% | 73 | 18.7% | 97 | 24.8% |
Q Scout taken 3/11/2020
| 3280 | 3/11/20 | LF | Negative | 37 | 13 | 33.9% | <10 | 7.1% | 22 | 58.9% |
| 3280 | 3/11/20 | LR | Positive | 459 | 304 | 66.2% | 35 | 7.6% | 120 | 26.1% |
| 3280 | 3/11/20 | RR | Disabled | N/A | N/A | N/A | N/A | N/A | N/A | N/A |
| 3280 | 3/11/20 | RF | Negative | 323 | 173 | 53.8% | 32 | 9.8% | 117 | 36.4% |
Q Scout taken 3/30/2020
| 3280 | 3/30/20 | LF | Negative | 38 | 18 | 46.4% | 12 | 30.4% | <10 | 23.2% |
| 3280 | 3/30/20 | LR | Positive | 1273 | 844 | 66.3% | 264 | 20.8% | 165 | 12.9% |
| 3280 | 3/30/20 | RR | Disabled | N/A | N/A | N/A | N/A | N/A | N/A | N/A |
| 3280 | 3/30/20 | RF | Positive | 685 | 408 | 59.6% | 146 | 21.2% | 131 | 19.2% |
Q Scout taken 4/6/2020
| 3280 | 4/6/20 | LF | Negative | 24 | <10 | 38.9% | <10 | 22.2% | <10 | 38.9% |
| 3280 | 4/6/20 | LR | Positive | 837 | 466 | 55.6% | 127 | 15.2% | 244 | 29.2% |
| 3280 | 4/6/20 | RR | Disabled | N/A | N/A | N/A | N/A | N/A | N/A | N/A |
| 3280 | 4/6/20 | RF | Negative | 161 | 75 | 46.5% | 26 | 16.2% | 60 | 37.8% |
Q Scout taken 4/24/2020
| 3280 | 4/24/20 | LF | Negative | 29 | 13 | 43.2% | <10 | 9.1% | 14 | 47.7% |
| 3280 | 4/24/20 | LR | Positive | 971 | 616 | 63.4% | 80 | 8.2% | 275 | 28.3% |
| 3280 | 4/24/20 | RR | Disabled | N/A | N/A | N/A | N/A | N/A | N/A | N/A |
| 3280 | 4/24/20 | RF | Negative | 313 | 170 | 54.1% | 36 | 11.5% | 108 | 34.4% |
Q Scout taken 5/14/2020
| 3280 | 5/14/20 | LF | Positive | 4983 | 3822 | 76.7% | 621 | 12.5% | 540 | 10.8% |
| 3280 | 5/14/20 | LR | Positive | 2159 | 1163 | 53.9% | 312 | 14.4% | 684 | 31.7% |
| 3280 | 5/14/20 | RR | Disabled | N/A | N/A | N/A | N/A | N/A | N/A | N/A |
| 3280 | 5/14/20 | RF | Positive | 526 | 250 | 47.6% | 104 | 19.8% | 171 | 32.6% |
Taken 5/20/2020
| 3280 | 5/20/20 | LF | Positive | 15595 | >10000 | 86.1% | 1085 | 7% | 1089 | 7% |
| 3280 | 5/20/20 | LR | Positive | 3144 | 1998 | 63.5% | 525 | 16.7% | 621 | 19.8% |
| 3280 | 5/20/20 | RR | Disabled | N/A | N/A | N/A | N/A | N/A | N/A | N/A |
| 3280 | 5/20/20 | RF | Negative | 278 | 159 | 57.2% | 49 | 17.8% | 69 | 24.9% |
There is a lot going on with this cow. To start she is a three teated animal and because of everything going on she may very well be a two teated animal. The question should be do we even want a two teated cow? Do we even want to treat her?
After the initial questions, let’s follow the mastitis in the RF teat throughout this process. This is fascinating to me because nobody except a veterinarian will usually look at long-term results. So keep in mind that she was treated for the Enterococcus sp. in her LR teat and that 40% of mastitis cases resolve themselves.
It also helps to know that the first number is the total SCC. The second going left to right is Neutrophils. These white blood cells are the ones that attack the bacteria and are present in acute infections. The next number is Lymphocytes. These white blood cells trigger antibodies in an infection. Finally, the last group is Macrophages. These cells are present in high numbers during the clean-up of phase of an infection.
On March 3rd the total somatic cell count is 389,000 in the right front quarter. The industry would say she had a subacute infection. Notice the Neutrophils are the highest portion of the cell count. A week later, she is considered cured because her Neutrophils are dropping and her Macrophages are on the rise. This would be a clean-up phase.
Forward to March 30 and she is infected again. Total SCC in the quarter is over 685,000 and the Neutrophils are over 55% and the Macrophages are under 20%. On April 6 she is cured again with the total cell count of 161,000, Neutrophils under 55%, and Macrophages over 20%. She again fights an infection on May 14 which is cured by May 20. This to me proves that animals do fight and cure mastitis on their own. However, when the subclinical infection happens over and over again, you have to look at underlying problems such as teat structure or the immune function of the animal.
Measuring Success
Here I want to point out that the vast majority of animals that are treated with antibiotics are already in the clean-up phase—which is when they are already going to self-heal. My overall perspective for measuring when a mastitis case is cured is when I see the Neutrophils drop and the Macrophages rise in a clean up the debris stage. I would note the clean-up stage is when visible garget is seen in the milk. This is the aftermath of the battle not the battle itself.
If you are interested to see an actual infection, take a look at the left front quarter from April 24 through May 20.
Once again this is a great discussion to have with your veterinarian. Define success, otherwise you won’t know when you are improving or if an animal should be treated at all!