Everyone knows that you shouldn't overfeed dry cows. But new research from the University of Illinois helps to quantify some of the reasons why.

In an experiment, animals were assigned to one of three different prepartum energy intakes:

  • A high-energy diet that provided at least 150 percent of energy requirements during late gestation.
  • A restricted diet that provided 80 percent of energy requirements
  • A control diet that provided about 100 percent of energy requirements.

There were dramatic differences between the groups.

"Cows that were fed a ration too rich in energy during the dry period grossly over-consumed energy relative to their requirements," said Jim Drackley, animal scientist at the University of Illinois and one of the authors of the study.

After calving, these cows had greater serum NEFA and beta-hydroxybutyrate, the predominant ketone in cows. They also had greater fat accumulation in the liver postpartum, and a higher occurrence of displaced abomasum and treatment for subclinical ketosis compared with cows having controlled or restricted energy intake during the dry period.

"Overfeeding energy before calving was detrimental to transition-period adaptations and health," Drackley says. "This is important both for farms using two-group dry cow management, but also for farms using or considering using a single-group dry cow management system."