Benchmarking Your Bulk Tank: What "Good" Looks Like for Holstein Herds

The bulk tank report is the one piece of paper every dairy gets on a regular schedule, and it is often read for only one number. Somatic cell count (SCC) matters, but the bacteria counts next to it tell you whether trouble is coming from the udder, the milking routine, the equipment or the cooling system. Ohio State University Extension published a clear set of targets in its Key Mastitis Control Points for Best Milk Quality article. This article walks through them and what to do when a number drifts. Nothing here is specific to Holsteins biologically, but Holstein herds are usually high-volume, so small percentage problems turn into big dollar problems.

The benchmarks at a glance

Test	Target	Warning
Somatic cell count	Under 200,000 cells/mL is low risk	200,000 to 400,000 medium; over 400,000 high
Standard plate count (SPC)	Under 5,000 cfu/mL	Over 10,000 signals a problem; federal Grade A limit is 100,000
Preliminary incubation count (PIC)	Under 10,000 cfu/mL ideal; up to 20,000 acceptable	Over 50,000 points to cleaning or pre-milking problems
Laboratory pasteurized count (LPC)	Under 100 cfu/mL	Over 200 is high
Coliform count	Under 10 cfu/mL	Over 50 suggests manure or soil on teats; over 100 points to poor milking practices, dirty equipment or contaminated water

Those values come from the Ohio State article. Your plant, cooperative or state regulations may set stricter limits or pay premiums at different cut points, so check your milk contract as well.

Reading each number

Somatic cell count: the udder

SCC reflects inflammation in the udder. The Ohio State article says individual uninfected quarters should be under 100,000 cells per milliliter, and milk at 200,000 or more suggests inflammation from infection or recovery. A rising bulk tank SCC means more infected cows, or infected cows contributing more. Our guide to SCC and the 750,000 line explains the regulatory side, and the SCC reduction protocol shows how to respond.

Standard plate count: the whole system

SPC is a general measure of bacteria in the milk. A high SPC can come from mastitis organisms, dirty equipment, poor cooling or a combination, so it is a prompt to look at the other tests. A low SPC alongside a high SCC points toward the udder rather than the equipment.

Preliminary incubation count: prep and cleaning

PIC is often used as a clue about equipment cleaning and cow prep. Ohio State says counts over 50,000 point to cleaning or pre-milking problems. Think wash cycle, water temperature, detergent, rinse and the state of liners and hoses, as well as dirty teats at unit attachment.

Laboratory pasteurized count: the heat-tolerant bugs

LPC counts organisms that survive laboratory pasteurization. Ohio State says over 200 is high and often points to sanitizing or cooling-system issues. Aged or worn rubber, milk residues in hard-to-clean places and an underperforming cooling system are common suspects, though a technician should confirm.

Coliforms: manure, soil and water

Coliform counts tell you about environmental contamination. Over 50 suggests manure or soil on teats, and over 100 suggests poor practices, dirty equipment, contaminated water or coliform mastitis, according to the same source. Look at bedding, stall cleanliness, teat prep and your rinse water.

How to use the numbers together

1. High SCC, low bacteria counts: focus on udder health and contagious organisms. University of Minnesota Extension recommends culturing recent clinical cases and using multiple bulk tank cultures before ruling out contagious pathogens (see its mastitis problem-solving guide).
2. High PIC or LPC, normal SCC: start with the wash system, rubber parts and cooling equipment.
3. High coliforms: check bedding, teat prep and water supply.
4. Everything high: start with the basics and call your milk quality team, then work through them one by one.

Herd-level benchmarks that go with the tank

The Minnesota guide offers two herd-level monitors that pair well with tank reports: under 5 clinical cases per 100 milking cows per month as a good goal (1 to 2 is excellent), and a new infection rate under 8 percent per month. Tracking them monthly lets you catch a trend before the tank report does. Since the tank is an average of all cows, a single heavily infected cow can move it, so combine tank data with individual DHI records; see how to read a DHI record.

A routine for the paperwork

File every report. Plot SCC, SPC, PIC, LPC and coliforms on one sheet, month by month, and add notes for changes in crew, equipment service, weather, forage, bedding or cow groups. Ask your plant or lab for the raw test dates, since a single day's spike has different causes than a slow drift. Before drawing conclusions, ask your vet, equipment dealer and milk plant fieldman to review the pattern with you.

What good looks like

Good is a short, boring report: SCC well under 200,000, plate counts in the low thousands, coliforms near zero, and no surprises month to month. Good also means you can say why. Our companion piece on a consistent milking routine explains the habits behind it. For industry news see farm.fm's dairy section, and for lab and extension contacts use the Agriculture Directory. This site is independent and not affiliated with any breed association.