How to Read a DHI Record: Dairy Herd Improvement Basics for Juniors

Every month on thousands of dairy farms, a technician or a meter records how much milk each cow gave, takes a small sample and sends it to a lab. A few days later, the farm gets a report full of numbers. That is a Dairy Herd Improvement, or DHI, record, and it is one of the most useful management tools in the dairy business. For a junior exhibitor, learning to read one helps you understand your animal's production, back up your answers to judges and see how a good cow earns her keep.

This guide explains the main parts of a typical DHI report and how to use them. Report formats, abbreviations and the details of testing programs differ by region and provider, so ask your local DHI association or extension agent for explanations of your specific report. If you want to find dairy records workshops near you, agriculture.directory can help you find agriculture events in your area.

What DHI Is

Dairy herd improvement programs are cooperative systems that provide milk testing and record keeping services to dairy farms. Records are used for herd management, breeding decisions and genetic evaluations. National data is compiled and used by organizations such as the Council on Dairy Cattle Breeding at cdcb.us for genetic evaluation.

Test Day Basics

On a test day, each cow's milk is weighed or measured, and a sample is taken. The lab analyzes the sample for components and cell count. The report lists data for each cow, often with her identification, lactation number, days in milk and the test results. Cows are usually tested about once a month.

Key Columns on a Report

• Cow ID or name. Identifies the animal.
• Lactation number. How many times she has calved. First-lactation cows are often called first-calf heifers.
• Days in milk (DIM). Days since she last calved. Milk production typically rises to a peak a few weeks after calving, then declines.
• Milk. Pounds of milk produced on test day.
• Fat percent and protein percent. Components of milk that determine value in many milk pricing systems.
• Somatic cell count (SCC). A measure of white blood cells in milk, often expressed as cells per milliliter or on a linear score. Elevated counts suggest udder infection or inflammation. The National Mastitis Council at nmconline.org provides udder health information.
• Milk urea nitrogen (MUN). Sometimes reported, related to protein feeding.
• Projected or predicted production. Estimates of production over a whole lactation, such as 305-day milk.
• Reproductive information. Some reports include breeding dates, pregnancy status and due dates.

Lactation Summaries

At the end of a lactation, the record is summarized to give total milk, fat and protein for a standard period, often 305 days, along with the number of days in milk. Summaries allow comparisons between cows and between herds. Many show catalogs and pedigrees include lactation records of dams and grandams, such as milk, fat and protein totals and age at calving. Ask whether the numbers are on a 305-day basis and how many times a day the cow was milked.

Using the Numbers

• Spot problems early. A sudden drop in milk or a spike in cell count may signal illness.
• Compare cows. See which cows produce well and which do not.
• Evaluate feeding. Milk and component changes can reflect ration changes.
• Plan breeding. Choose sires and matings based on strengths and weaknesses.
• Make culling decisions. Persistent low production or high cell count may mean a cow does not pay her way.

Why It Matters in Your Project

If you have a milking Holstein, DHI data helps you track her performance and tell her story. If your heifer is from a herd with DHI records, the production records of her dam are a valuable piece of information. Judges and buyers often ask about the dam's production, and an exhibitor who can say something like "her dam made so many pounds of milk in a lactation and had good components" shows understanding. If your animal has no records, you can use your own milk weights.

Reading Responsibly

Production numbers depend on management, feeding, milking frequency, age and stage. Comparing a first-lactation heifer to a mature cow, or cows at different stages, can be misleading. Look at data in context, and ask experienced dairy people to help. University programs like University of Wisconsin Extension and University of Minnesota Extension dairy offer resources on interpreting records.

Starting Your Own Records

1. Record the date of calving and each day's milk if you milk by hand or with a meter.
2. Note feed, health events and breeding dates.
3. Look for patterns across months.
4. Use a notebook or spreadsheet.
5. Add notes to your record book.

Common Mistakes

• Looking at one test day only. Trends matter.
• Comparing cows at different stages. Adjust for days in milk.
• Ignoring cell count. It signals udder health.
• Treating records as a guarantee. They describe the past.
• Not keeping records. You cannot improve what you do not measure.

Farm.fm's page on a bulk tank alarm that calls the farmer at 2 a.m. is a humor piece about life with a dairy herd, and for another laugh, see farm.fm's humor piece on a Wisconsin dairy farmer who sells wholesale and buys retail.