Forcing dairy data to tell useful stories

Sports teams have taken old stats and reinterpreted them — and dairy farms can do the same

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Sports teams have seen a data revolution in which common statistics known for years have been reinterpreted into new metrics that have led to significant changes in how games are played.

The dairy sector should see the same sort of revolution, says Jeff Bewley, dairy analytics and innovation scientist with Holstein USA, an organization that has measured dairy statistics for years.

Why it matters: Dairy farmers harvest increasing amounts of data from their herds, but putting them to use can be challenging.

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“There’s a lot we can learn from other industries and bring into agriculture,” Bewley said.

James Harden is a basketball star for the Houston Rockets. An analysis of data showed that the three-point shot is the most efficient way to rack up points on the basketball court. Harden’s advantage is that he’s an expert at drawing fouls as he’s shooting three pointers. As an excellent shooter, he’ll take as many free throws as he can get.

In similar fashion, data can unearth the “silent stars” in a herd. “They are really the cows we want more of,” says Bewley.

Danny Green, another basketball player, isn’t a top scorer, the metric by which the best basketball players are measured. However, he’s won three NBA championships, including one in 2019 with the Toronto Raptors.

“When Danny Green is on the floor the more likely a team is to win a game,” says Bewley. Player efficiency ratings tell an overall story and there are such metrics available for dairy farms that tell the story of cow and financial health.

Bewley outlined some of his favourite metrics that can tell valuable stories on dairy farms at the recent virtual Ruminant Feed Industry Day put on by the Ontario Ministry of Agriculture, Food and Rural Affairs and the Ontario AgriBusiness Association. He emphasized that most of these calculations can be completed using data that farmers already collect. He also advised slowing down and making sure that the data is complete and useful to a particular herd’s situation.

“Data can lie to us if we don’t know what’s going on on the farm,” he said.

Overall dairy finances:

  • Money-corrected milk is a calculation that considers revenue and the impact of how farmers are paid for their milk, especially fat and protein levels.
  • Retention pay off looks at the value of a cow’s future net revenues compared to a potential replacement.
  • Longevity-corrected milk is another calculation that shows the value of older cows by looking at their long term production by attributing 30 per cent to a first lactation, 20 per cent to the second and 50 per cent to a third lactation.
  • Summer to winter ratio: Some cows and farms have greater variation than others when it comes to summer versus winter production. The closer the ratio is to zero, the less there is variation by season. An American project showed that in every region of the country, there is 10 per cent variation among dairy farms based on seasons and heat stress.

Profit measures

At a farm operations levels, key performance indicators tell the story about operations.

  • Week four and week eight milk: Peak milk is a common measure on dairy farms, but looking at week four and week eight tells more about cow health.
  • Per cent of cows at less than breakeven milk yield: This measure identifies when cows aren’t helping a farm make a profit.
  • First lactation week eight production as a per cent of mature milk yield.
  • Milk per day since 22 months of age: This metric shows how efficient a cow has been overall and takes into account reproduction and dry period length.


There are several important key performance indicators around reproduction including:

  • Pregnancy rate.
  • Conception rate breakdown.
  • Days to first service: This shows how quickly cows are first bred on average.
  • Per cent pregnant by 150 days in milk.
  • “Per cent service intervals greater than 36 days: This shows how well cows are doing after first service,” says Bewley. “I see a lot of herds who do a really nice job of first service, but struggle with subsequent services.”
  • Per cent reproduction culls. Bewley says this is often a hidden number on a farm.

Milk quality

There are many ways to measure udder health, mastitis and milk quality including:

  • Bulk tank somatic cell count (SCC).
  • New infection rate: This is a leading indicator, whereas Bewley says SCC is a lagging indicator.
  • Per cent cows with subclinical mastitis.
  • Per cent clinical cases. “More people should record clinical mastitis to do the culture work behind that,” says Bewley. “You can have high SCC with low clinical indices or vice versa.”
  • Mastitis cull rate: Many herds do a great job of controlling SCC, but they do it by aggressive culling, which “isn’t always the most economical way to get to a low SCC rate.”

Overall health

Understanding where and why animals leave the herd is another area to measure.

  • Per cent of culls in first 60 days in milk: These culls are “very very expensive”, says Bewley.
  • Death rate.
  • Heifer survival rate: What percentage of heifers make it into the milking herd?
  • Fresh cow disease incidence: Are the cows getting off to a good start?

The large number of potential metrics can be overwhelming. Bewley recommends choosing ones that have most impact on the herd and start with those.

About the author


John Greig

John Greig has spent his career in agriculture journalism and communications. He lives on a farm near Ailsa Craig, Ontario. Contact John at [email protected] or follow him on Twitter @jgreig



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