By Tessa Kelly, Lab Manager, The Dairy Authority
The lab says you need to collect an aseptic milk sample. But what exactly does that mean?
By definition, an aseptic sample is one that has been collected following specific steps that ensure that no bacterial contamination occurs during collection. When collecting a milk sample, it is important to understand that bacteria is present on the skin of the cow, the hands of the person collecting the sample, and in the environment.
That’s why specific steps must be taken to prevent unintended bacterial contamination of the milk sample. Besides, if you are going to spend the money to test a milk sample to find out what bacteria is causing mastitis you want to make sure the right culprit is identified so the appropriate treatment can be used.
So how do you collect an aseptic milk sample? It’s really not difficult. Just follow these steps:
1. Collect supplies. You will need sterile plastic flip-top tubes, a waterproof permanent marker to label samples, 70% alcohol (ethyl or isopropyl), cotton balls or gauze soaked in 70% alcohol (or individually packed alcohol swabs), a cooler with ice for storing samples, disinfectant for cleaning teats, paper towels or individual cloth towels, and disposable gloves. Milk samples should be collected before milking the cow, or at least 4 hours after the last milking.
2. Label tubes. Plastic tubes with flip-top lids that snap shut work best for collecting milk samples. Label the tube with the date, farm name, cow identifier, and quarter before collecting the sample. Use a waterproof marker to write on stick-on labels or to write directly onto the vial. When writing on the vial, make sure the vial is completely dry before writing to prevent smearing, or better yet, write on the vial before collecting the sample.
3. Glove up. Wash your hands and put on new disposable gloves.
4. Udder prep. Use a clean, dry towel to brush off any dirt or manure from teats and the udder. Dip teats with the disinfectant teat dip used for udder prep in the parlor. Leave on for 30 seconds. Dry the teat(s) with a paper towel or single use towel. Make sure the teat is free of dip. Any residual dip may kill the bacteria you are trying to identify.
5. Scrub teat ends with alcohol-soaked gauze pads or cotton balls. Use one for each teat. Scrub until each teat end looks clean. Use multiple gauze pads or cotton balls if necessary. If you will be sampling more than one quarter, start scrubbing the teats that are furthest away, then clean those nearest to you.
6. Discard three to four streams of milk. This helps minimize the risk of contamination of the sample from bacteria in the teat canal.
7. Sampling order. When collecting samples from more than one quarter, follow reverse order from the scrubbing procedure. In other words, collect milk samples from the teats closest to you, then move to those furthest away. Sample each quarter individually.
8. Collect the sample. When you are ready to collect the sample, flip open the lid of the sample vial, then hold at about a 45-degree angle. Direct the milk stream into the vial without touching the vial or lid. Collect about 2 to 3 streams of milk (about 2 mL or 1/2 full). Close vial lid and make sure it snaps shut for an airtight seal. Do not overfill.
9. Cool immediately. Place milk samples in a cooler with ice. If samples will be shipped to a lab for testing, follow the lab’s directions regarding whether samples should be kept cold or can be frozen. The TDA Milk Lab recommends the following: (a) When testing to determine somatic cell count, protein or fat content keep samples cold. (b) When testing to identify bacteria, mycoplasma, or run a standard plate count or coliform count samples can be shipped cold or frozen.
10. Shipping. When shipping milk samples to a lab it is best to send overnight, or 2-day by UPS or FedEx. Pack samples tightly so they cannot move around. This helps prevent spills and breakage. Include ice packs to keep cold. Fill out the lab’s sample submission form with instructions on what testing you want done. Be sure to put the instructions in the box!
If you have any additional questions, or would like to learn more about the testing services at The Dairy Authority Lab, please contact us at info@dairymd.com or read the blog “All of Your Milk Lab Needs in One Place.”
Additional resources
Collecting an aseptic milk sample:
To view or download a pdf poster on How to Collect a Milk Sample that you can display in your milking center from The Dairy Authority click here.
