Energy Density in Dairy Diets

Energy density describes how much usable energy sits in each pound of feed dry matter. It becomes important when a cow cannot eat enough to meet her needs.

Key points

Energy density matters most when cow intake lags her needs.
Do not give up fiber to raise energy.
Better forage is the safest source of energy.
Intake, cow comfort and heat control come first.
Track body condition, manure and milk.

What energy density means

Energy density is the amount of energy per unit of dry feed. A dense diet gives the cow more energy per bite, which matters when her appetite cannot keep up with her milk output.

Energy comes from carbohydrates such as starch, sugar and digestible fiber, and from fat. Each source behaves differently in the rumen and in the cow.

A cow in a good energy balance holds her body condition within a sensible range, eats steadily, and produces milk without a long slide in weight.

Why it matters most in early lactation

Cows early in lactation produce more milk than they can fully feed with intake, so they draw on body fat. Some of that is normal. Too much, or a slow recovery, raises the risk of metabolic problems such as ketosis and fatty liver, and can affect fertility.

Early lactation diets are often higher in energy density, balanced carefully to keep the rumen healthy.

Prepare for this stage before calving. Cows that come out of the dry period well conditioned and eating well tend to handle the early weeks better, and the feeding plan for dry and close-up cows is covered in other guides on this site.

The trade-off with fiber

Raising energy density usually means adding more grain or fat and less forage. Forage supplies the fiber that keeps the rumen working. Too much energy and too little fiber raises the risk of rumen acidosis, with sorting, loose manure, lower butterfat and cows going off feed.

The aim is the highest energy density the rumen can handle, which differs from herd to herd and depends on forage quality, particle size and bunk management.

Bunk management helps here too. Consistent feeding times, frequent feed push-up and avoiding long periods of empty bunks all help the rumen stay steady.

Ways to raise energy density

Higher-quality forage is the best place to start, since digestible forage gives energy without risking the rumen. Cows can also eat more of it.

Other tools include carefully chosen grain and byproduct feeds, and fat supplements, which are covered in a separate guide. Each change needs the rest of the ration rebalanced.

Improve forage quality first
Adjust starch and sugar sources with your nutritionist
Consider fat supplements for specific groups
Check that fiber stays adequate
Keep the mix consistent

Intake comes first

Density only helps if cows eat. Fresh feed, clean bunks, enough bunk space, comfortable stalls and cool conditions all help intake. A dense ration offered to stressed cows is wasted.

Heat stress cuts appetite and raises the energy need at the same time, so plan for hot weather with your nutritionist and your cooling system.

Signs of too little or too much

Too little energy shows up as thin cows, slow rebreeding, falling milk and long periods of body condition loss. Too much shows up as acidosis signs, fat cows, and metabolic trouble around calving.

Track body condition on the 1-to-5 scale at set points in the lactation, along with milk, manure and cud chewing.

Ask your veterinarian about herd-level records for ketosis and displaced stomach, and review them with your nutritionist. Patterns in those records can show where energy feeding needs attention.

What to ask your nutritionist

Ask what energy density your groups need, where you can safely raise it, and what you should watch for after a change. Ask how forage quality changes the answer, and how to adjust in hot weather.

Report any off-feed cows, ketosis cases or digestive upset to your veterinarian promptly. Withdrawal times for any treated animals must be followed exactly as set by the label or the vet.

When to get help: Ask your nutritionist to set energy targets by group. Call your veterinarian for off-feed cows, suspected ketosis or digestive upset, and follow all milk and meat withdrawal times exactly.

Sources and further reading

Organization homepages are linked so you can search them for current guidance on this topic.

More in Nutrition, Feeding & Water

← Bypass Protein Explained for Dairy Farmers Fiber and Effective NDF in Dairy Rations →