by Katie Navarra

Immature heifers leave a long shadow over a herd that cannot be remedied. Early calving may get milk faster, but over time total volume is comprised. During the Dairy Calf & Heifer Association (DCHA) Virtual Conference in April, Gavin Staley, technical services specialist, Diamond V, shared his evaluation of DairyComp305 production records, which sheds insight into the significant impact of heifer immaturity on whole herd production.

“The first lactation milk production sets a ‘ceiling’ for the whole herd,” Staley said. “The herd cannot outperform the production level set by the first lactation.”

Staley defines heifer maturity as the point at which an animal has the frame and weight that allows her to express her full potential milk production. Traditionally, age has been the driving factor in breeding decisions, but weight and maturity are proving to be more influential.

Through the observation of calving weights and milk production at 174 dairies, Staley found that across all herds these factors were the same:

  • At five weeks of lactation the difference between first lactation and second lactation is 30 pounds in Holsteins
  • At five weeks of lactation the difference between second lactation and third lactation is eight – 10 pounds in Holsteins

This difference appears to be independent of the level of production or milking frequency.

Weight at calving impacts far more than the first lactation milk production. It predicts the average annual milk for the entire herd. DCHA has set a standard for producers to strive for, suggesting that heifers should be at 85% of mature body weight post-calving and close-up heifers should be at 95% of mature body weight.

“Most people aren’t weighing their animals and making a guess without background information,” he said. “Monitoring performance based on weight becomes visual and is motivating.”

If an animal does not reach the required level of maturity before calving, she will reach it during lactation, but at the expense of production. The pre-calving maturity deficit is “paid back” in lactation. For every missing pound of body weight at calving, the animal’s daily growth rate is seven times slower than it was before calving, and underweight heifers produce seven less pounds of milk, according to Staley.

Multiply seven pounds of lost milk across the entire herd and that is a costly loss in daily volume. But milk production isn’t the only sacrifice when immature heifers calve. Younger animals have higher stillbirth rates and that can bring additional complications from disease and the animal may need to be culled from the herd.

“Mastitis is damaging metabolically because it uses a lot of protein and glucose to fight infection,” he said. “When the animal should be peaking, she is instead fighting for her life.”

Staley said there is a belief that heifers can be raised cheaply, but he cautions against shortcuts with this group of cattle. These young animals set the annual average for the whole herd.

“A profound disconnect between growth rate (ADG) and AGEFR has occurred on many dairies,” he said. “The solution is managing and monitoring for maturity that takes frame and weight into consideration.”

Tracking heifer weights is the best place to start to make changes. Weight tapes are fairly accurate in determining an animal’s weight by measuring its girth. Increasingly, farms are placing scales in alleyways to capture data as the animals pass through.

Penn State Extension offers breed specific growth charts and a customizable spreadsheet free of charge at

What data do you need? Staley offered a heifer maturity checklist that highlights the data farmers should strive to gather:

  • The mature body weight of third and fourth lactation cows at 80 and 120 days in milk
  • Weigh heifers as they freshen and several times throughout the year
  • Calculate the weight differences between the desired and actual weights
  • Evaluate the average daily growth rate of the farm’s raising system to see if it is delivering as expected
  • Set heifer health and growth goals for all stages from colostrum to calving

“It’s difficult to make decisions to breed at an arbitrary age without back up data on the animal’s frame and weight,” he said. “There is ample evidence that looking at weight and frame as much as age significantly impacts the herd average.”