It’s simple to see how well cows produce milk by monitoring milk weights and tracking milk component percentages. But knowing and tracking these figures can be misleading when it comes to determining how well a dairy is actually performing. That’s because these values do not allow you to compare productivity between days, months or cows on a level playing field due to the three moving parts (volume, fat and protein).

Michael neil
Nutritional Consultant / Progressive Dairy Solutions
Michael received both DVM and MBA degrees from Purdue University and has over 30 years of industr...

Milk weights and component percentages individually do not accurately allow you to assess efficiency, profitability or how to make economically based purchases or management decisions that impact milk and component production.

To improve decision-making, energy-corrected milk (ECM) was developed to put all cows on an equal basis for comparative purposes over time. ECM determines the amount of milk produced and adjusted to 3.5 percent fat and 3.2 percent protein.

For example, dairy producer Joe Smith wants to know more about how his 500 cows are producing milk on a monthly basis. He knows that last month, his cows produced 85 pounds of milk, 3.7 percent butterfat (3.145 pounds) and 3.1 percent protein (2.635 pounds). This month, the values are slightly different.

Instead of simply noting that butterfat percentage went up or down while milk weights went up or down, calculating ECM helps Joe equalize the two months’ production values so that he can evaluate performance in light of any changes in feeding, management or cow environment that occurred during that time frame.


This knowledge helps determine how cows are performing and allows him to make more informed management decisions.

equation for energy correct milk

Energy-corrected milk (ECM) determines the amount of energy in the milk based upon milk, fat and protein and adjusted to 3.5 percent fat and 3.2 percent protein.

In Joe’s case, the equation for last month’s production looks like this:

(0.327 x 85) + (12.95 x 3.145) + (7.2 x 2.635) = ECM or 27.795 + 40.727 + 18.972 = 87.494

To compare to this month’s values of 90 pounds of milk, 3.3 percent butterfat (2.97 pounds) and 3.1 percent protein (2.79 pounds), simply calculate ECM for those production results.

29.43 + 38.46 + 20.88 = 88.71

Without calculating ECM, Joe might have been misled that his production rose by 5 pounds of milk (85 versus 90), because the reality is that he only increased milk production by 1.2 pounds.

This figure can be calculated on a whole-herd basis or for groups of cows to help determine the economic impact of nutritional changes, for example, on productivity. It should be tracked consistently over time to give an accurate indication of cow and herd performance.

This matters because:

• Milk fat concentration is the most sensitive to dietary changes and can vary over a range of nearly 3 percentage units.

• Dietary changes can result in milk protein concentration changing approximately 0.6 percentage units.

Knowing ECM values over time helps Joe evaluate feed ingredient responses, as well as optimize management strategies that improve ECM like cow environment, cow comfort, genetics, transition cow health and implementing new ration strategies.

Now, if Joe also knows the dry matter intake of each group or for the herd, he can simply take this ECM value and divide by the feed intake to determine the efficiency of feed conversion to milk.

As Joe makes diet changes or as milk components vary with the weather, season or forage quality, he can track his herd’s productivity and efficiency with greater precision.

Using the above example, if the dry matter intake stayed the same or decreased a bit to get that additional 1.2 pounds of milk, feed efficiency increased – and Joe may be better off financially as a result. The increase in ECM production also indicates that either ration digestibility or nutrient balance has improved.

If Joe had introduced a heat abatement program in the summer or reduced overcrowding, the increase in feed efficiency might be a reflection of that as well, and Joe can now evaluate his decision.

Keep in mind that dairies are paid for component yield, not component percentage, so evaluate nutrition programs and solutions that impact pounds of ECM production. That is what improves efficiency, and ultimately, a dairy’s profitability.

Neil Michael received both DVM and MBA degrees from Purdue University and has over 30 years of industry experience including veterinary practice, dairy management, reproduction and nutritional consulting.