The researchers also noticed that cows fed the CE diet showed less prepartum versus postpartum variation in how much they ate. By contrast, the cows fed the high energy diet were eating more than they needed before calving.
“Cows and ruminants cannot export well from the liver,” said Cardoso. “Any time a large amount of fat is going to the liver, that’s going to cause a lot of problems. They are going to have lower levels of glucose and ketone bodies will form. Feed intake will start to drop, and the cow will start feeling ill.”
In a follow-up study that has not yet been published, the researchers tried to strategies to make the cows eat less. One was to give them just 80 percent of what they needed; the other was to increase fiber in the day so the diet would be lower in energy and the cows could eat more. They had similar results for the two strategies.
There are indications that a CE diet has other benefits. It may help food to remain longer in the rumen, which is beneficial to the cow if she is stressed.
In short, Cardoso advised, just give the cow what she needs and she will perform better metabolically and reproductively.
“There is money associated with this,” he said. “Any disease costs money.”
But long intervals between calvings also costs money. “In the dairy business, we’d like the cow to calve once a year and the calving interval to be around 12 to 13 months. Because to give milk, she needs to calve, so we want her pregnant as soon as possible,” Cardoso explained.
He added that research has shown that every day after 90 days in milk that the cow does not get pregnant represents a cost of 2 to 3 dollars.
“Prepartum Dietary Energy and Reproduction” by F.C. Cardoso, S.J. LeBlanc, M.R. Murphy, and J.K. Drackley, has recently been published in Journal of Dairy Science and is available at http://www.journalofdairyscience.org/article/S0022-0302%2813%2900465-7/abstract.