Does intramammary treatment of heifers pre-calving increase subsequent milk production?

Research shows the outcome of this practice on milk yield is inconsistent, and so it needs to be considered on an individual herd basis, says Pam Ruegg, veterinarian and extension milk-quality specialist at the University of Wisconsin.

“If (heifers) develop subclinical infection, it may result in damage to developing secretory tissue,” Ruegg says. “If you have less secretory cells, you’d expect there should be less milk.”

However, if you look at the cumulative research, the impact of heifer mastitis on long term milk yield is really quite variable.

“In some herds, it appears that heifer mastitis reduces yield really dramatically, maybe up to 1,200 pounds per lactation,” Ruegg said during a presentation in April at the 2011 Dairy Calf & Heifer Conference. “In other herds, it’s very difficult to document an effect.”

On one farm, Ruegg and colleagues collected quarter milk samples from 113 heifers in the first week post-calving. They looked at bacteria levels, somatic cell count and milk yield during the first five weeks post-calving.

Those heifers whose samples showed evidence of coagulase-negative Staph (CNS) in at least one quarter had reduced milk production. In fact, there was almost a 10-pound loss in daily milk yield at five weeks post-calving.

In this particular herd, treating heifers before they calve could have a significant impact on milk yield, Ruegg says.

Gold Standards, established by the Dairy Calf & Heifer Association and available at, state that treatment rates for mastitis and other non-respiratory conditions should not exceed 4 percent for Holstein heifers six to 12 months of age and 2 percent for heifers 12 months of age to freshening.