Feeding controlled-energy diets prior to calving can help increase feed efficiency and profitability, said Dr. Phil Cardoso, assistant professor, dairy researcher and extension at the University of Illinois. Cardoso was one of the presenters at the Four-State Dairy Nutrition and Management Conference held June 11 and 12 in Dubuque, Iowa.

There has been a lot of discussion in recent years about high-energy (HE; approximately 0.72 Mcal per pound dry matter) and controlled-energy (CE; approximately 0.59 Mcal per pound dry matter) diets in prefresh cows. Cows on a CE diet are more efficient and more profitable than those on an HE diet for several reasons, Cardoso said, including:

• Similar milk production compared to HE diets
• Lower disease and disorders incidence, including fewer displaced abomasums and clinical ketosis
• Less decline of dry matter intake (DMI) prepartum
• Improved DMI postpartum
• Reduced days to pregnancy
• Reduced body conditioning score (BCS) loss during the first six weeks of lactation

Keeping cows healthy during transition through diet is important because cows are more affected by metabolic disorders and infectious disease during this time, he said. “Metabolic disorders during early lactation are linked to energy intake during the dry period.”

Cows that received CE diets during the last three weeks before calving averaged 10 days less to pregnancy than cows that consumed HE diets. This may be attributed in part to increased net energy intake in the first four weeks postpartum for cows that received CE diets in the prefresh period, and lower incidence of diseases before and after calving.

In addition, lower BCS loss in the first six weeks after calving and slightly greater glucose concentrations at week three may have contributed to improved reproductive performance, he said. Energy-limited cows also had lower liver triglyceride concentrations two weeks before calving, which may also be what leads to fewer days to conception.

“A strategy of CE prepartum may have a favorable impact on both health and reproductive performance. Research evaluating the effect of CE diets prepartum on more specific reproduction variables, such as progesterone concentrations, ovarian function, time to first ovulation and embryonic death, is needed,” said Cardoso.

Cardoso said BCS is a good way to monitor what is going on with a transition cow. He noted a cow with a high BCS typically loses weight as she joins the milking herd, while a cow with a low BCS actually increases. “At 15 weeks, they are both typically at the same weight,” he said.

Cows that calved with a low BCS generally ate more and made more milk, but Cardoso quickly noted that dairy producers should not get the message to have cows too thin when calving.

Cows that are too thin are typically more difficult to breed than those at a healthy weight, and they also have a higher rate of lameness associated with sores in their hooves because they don’t have the proper fatty tissue for cushion.

He recommends a BCS of about 2.75 to 3 at the time of calving (recommendations in the past called for a body score of 3.5). The level of starch and protein in a fresh cow’s diet should be adjusted based on her BCS.

The BCS is determined mainly by the amount of fat covering the rump and tailhead. Producers who are not familiar with how to score can talk with their veterinarian, dairy supervisor or a neighboring producer to learn more. Routine body condition scoring can help detect potential health problems before they negatively affect milk production.

He said the goal for dry cows should be to “give her what she needs, not more, not less.”

Solving problems with transition efficiency can be as simple as monitoring input, output and BCS, he said.

He urges the weighing of refusals from dry cows so producers know how much the cows are actually consuming. He also encourages the measuring of dry matter in forages.

“Dry cows will easily consume more energy than required,” he said. “Dry cows given feed freely will consume up to 156 percent more than they need.”

Cardoso and his colleagues conducted a study assessing CE intake during the dry period and the effects on cow performance and blood metabolites during the transition period and if cows fed HE diets develop insulin resistance.

They found that even “modest overfeeding during a normal dry period could lead to a greater than 75 percent increase in visceral adipose (fatty) tissues that drain directly to the liver (the ‘bad fat’ deposits in humans).”

Fatty livers are associated with an increased risk of ketosis.

They also concluded that insulin sensitivity increased in cows fed a CE diet or a restricted-energy diet; a high-energy diet seems to be a model for insulin resistance in dairy cows (similar to diabetes type 2 in humans) around the time of calving.

“This can mean that even though the cow is doing the ‘hard job’ of consuming nutrients/feed at a cellular level, glucose uptake by the cell is not happening, and therefore the energetic status of the cow is still in deficit. Insulin-resistant cows are more prone to have an extreme negative energy balance (NEB) where output is greater than their input of nutrients.”

Cardoso and his colleagues define a CE diet as a high-fiber diet (always available to the cows) which meets 100 percent of the National Research Council’s nutritional requirements.

Cardoso makes the following dietary recommendations for dairy producers and nutritionists wanting to create a controlled-energy diet for their prefresh cows:

• Net energy for lactation (NEL): Control energy intake at 14 to 16 Mcal daily (approximately 0.59 Mcal per pound dry matter) for mature cows
• Crude protein (CP): 12 to 14 percent of dry matter
• Metabolizable protein (MP): greater than 1,000 grams per day
• Neutral-detergent fiber (NDF) from forage: approximately 0.7 to 0.8 percent of bodyweight, or 10 to 11 pounds per head daily
• Minerals and vitamins: Follow guidelines but target for at least 0.4 percent of dry matter of magnesium. PD

Kelli Kaderly-Boylen is a freelance writer based in Waterville, Iowa.