As cows transition from pasture to indoor housing, winter milk production presents unique nutritional challenges for dairy farmers.

Maintaining yield, milk quality, and cow health requires a carefully balanced diet tailored to seasonal conditions.

Tony Brennan, Tirlán Milk Solids Growth Specialist, explained: “Winter feeding is all about consistency.

“If we get the diet right, we protect fertility, drive milk solids, and avoid costly health issues down the line.”

The four key dietary requirements are: energy; protein; fibre; and minerals; with energy often being the most limiting factor.

Underfeeding energy can lead to reduced production, poor fertility, and issues like lameness.

Energy needs are measured in feed units for lactation (UFLs). A housed cow requires approximately 6 UFLs for maintenance, plus 0.45 UFLs/L of milk produced.

See the table below for examples:

Silage is the cornerstone of winter feeding. Ideal silage should have:

Dry Matter (DM): 25-30%
DMD (Dry Matter Digestibility): >74%

“Every 5-point drop in DMD can mean an extra 1-1.5kg of concentrate per cow per day,” Tony explains.

“That’s why silage testing is non-negotiable - it’s the foundation of a balanced diet.”

Concentrate levels depend on forage quality and cow genetics.

A typical range is 6-13kg per cow per day, depending on silage quality, and the genetic potential of the herd.

*assuming 13kg DMI

Maintaining cow Body Condition Score (BCS) during winter is essential for sustaining milk yield and reproductive performance.

However, visual signs of condition loss can be subtle and often go unnoticed until significant damage has occurred.

Tony said: “One of the most effective early indicators of underfeeding is the butterfat to protein ratio in milk.

The ratio is calculated by dividing the butterfat percentage by the protein percentage. For example, if butterfat is 4.2% and protein is 3.3%, the resulting ratio is 1.27.

Tony explained: “When the ratio exceeds 1.4, it typically indicates cows are not receiving adequate energy in their diet.

"This can lead to reduced milk output, poor fertility, and compromised overall health.”

Aim for 15.5–17% crude protein in the overall diet.

Forages like maize silage which are lower in crude protein compared to grass silage and require higher-protein concentrates to balance the ration.

“Winter diets often lack key minerals like magnesium, calcium, phosphorus, and trace elements such as copper, selenium, and iodine,” Tony said.

“Mineral deficiencies don’t always show up immediately, but they’re frequently the root cause of poor fertility and immune issues.

"A tailored mineral mix is essential.”

Cows can drink in excess of 100L of water per day. Clean, accessible water boosts feed intake and milk yield.

Housing should be:

Dry and well-ventilated;
Comfortable with adequate feed space.

“Feed space is often overlooked,” Tony noted.

Balancing winter diets is a proactive, data-driven process.

By focusing on forage quality, concentrate use, mineral supplementation, and cow comfort, farmers can maintain high yields and healthy herds.

“Nutrition is an investment, not a cost,” Tony said.

“Get it right, and you’ll see the return in productivity, fertility, and herd longevity.”