Research conducted at the University of Kentucky shows that increasing copper in the diet can help improve immune function and response in heifers challenged with E. coli.

In the study, researchers separated 23 pregnant Holstein heifers into two groups. The first group was fed a diet containing 6.5 parts per million (ppm) of copper and the other group was fed the same diet, plus an additional 20 ppm of copper sulfate was top-dressed on their feed. The copper levels contained in the control diet were about 35 percent less than the requirements listed in the 1989 NRC guidelines.

Liver and blood samples were taken at 60 and 21 days prepartum and three and 42 days postpartum to determine copper status. In addition, quarter milk samples were taken within three days of calving and then at seven, 14, 21 and 42 days after freshening to determine somatic cell count and bacteria counts. At day 34 of lactation, each heifer received a challenge dose of E. coli in one quarter.

Here’s what they found:

  • Liver samples revealed that heifers on the control diet were marginally deficient in copper.
  • Heifers receiving the supplemental copper had lower bacterial counts and lower somatic cell counts than unsupplemented heifers.
  • Supplemented heifers had lower peak temperatures than control animals. That means they were better able to limit bacteria growth and limit the severity of the infection.
  • Dry matter intake and milk production did not differ between the groups.
  • Copper supplementation appeared to decrease the severity of the E.coli infection while the duration of the infection remained the same.

The researchers concluded that the recommended dietary level of copper at 10 ppm seems adequate for growth and milk production, but not for optimal immune function and response.

The research was reported at the second International Symposium on Mastitis and Milk Quality.