U.S. milk producers saw no change in average somatic cell counts (SCC) based on an annual summary of Dairy Herd Improvement (DHI) test-day results.
Nationally, the average 2024 DHI test-day herd SCC was 181,000 cells per milliliter, unchanged from 2023, according to a summary report from the Council of Dairy Cattle Breeding (CDCB) and compared to previous reports from CDCB and the USDA’s Animal Improvement Programs Laboratory.
SCC test-day data comes from herds on any DHI test plan (including owner-sampler recording). Reflecting an ongoing trend, herds and test-day totals are down from the previous year: The 2024 results included 8,250 herds and approximately 3.7 million cows.
Individual state data
Tables featured here include state data for herd test days, average number of cows per herd, average daily milk yield, butterfat and protein percentages, and average SCC. It also breaks out two categories of SCC levels: the percent of days over 750,000 cells per milliliter, the current federal limit for bulk tank SCC for Grade A producers; and the percent of test days over 400,000 cells per milliliter, the current maximum level for milk used to produce dairy products for export.
Herd test days higher than the federal limit may overestimate the percentage of herds shipping milk exceeding that limit because milk from cows treated for mastitis is excluded from the bulk tank, even though it is included in DHI test data.
A few states have lower SCC limits compared to federal requirements: California – 600,000 cells per milliliter, Oregon – 500,000 cells per milliliter, and Idaho and Washington – 400,000 cells per milliliter.
Four (Central, Mideast, Southwest and Upper Midwest) of the current 11 Federal Milk Marketing Orders (FMMOs) adjust milk payments to producers based on the SCC in raw milk. Price adjustments are made on a per hundredweight basis for every 1,000 cells per milliliter variation from 350,000 cells per milliliter. Positive payments are made for SCCs below that level and negative adjustments occur for milk with higher counts. The magnitude of the SCC adjustment varies monthly based on the wholesale price of cheese.
State variations
Variation in SCC among states remains large in part, but not necessarily all, due to climatic conditions (temperature and humidity). Average annual SCC in 20 states was at or less than the national average, led by North Dakota and Michigan. Arkansas, Oklahoma and Tennessee averaged more than 300,000 cells per milliliter.
DHI data showed 29 states improved annual average SCC in 2024, with 14 states improving by 10,000 cells per milliliter or more. Largest improvements were in Alabama, Georgia, North Dakota, Nebraska and Colorado. Year-over-year annual average SCC increased in 16 states, rising by 25,000 cells per milliliter or more in Arkansas, Louisiana and Virginia.
Herd sizes compared
Cow numbers in DHI herds increased by about 11 in 2024 to 299. Based on herd size, year-over-year changes in SCC levels were mixed. DHI herds greater than 4,000 had the largest increase in SCC compared to a year earlier. Also posting small increases were herds with 100-149 cows and 150-199 cows. Those lowering average SCC levels from the year before were herd categories with less than 50 to 99 cows and categories with 200 to 3,999 cows.
Monthly breakouts
U.S. average SCC levels were also mixed compared to the same month a year earlier, increasing in March, May-July and November-December, holding steady in August, and declining in January-February, April and September-October.
Milk, fat and protein data
Test-day average milk yield rose a little to 83.1 pounds, with fat percentage up 0.09% to 4.24%, and protein percentage up 0.03% to 3.29%. The milk with the highest component percentages was produced in November and December; lowest component percentages were produced in June through August.
