There’s nothing quite like the sight of dairy cows heading back out to grass after a long winter indoors. Turnout signals a shift towards lower feed costs, improved cow comfort, and the start of a new grazing season.

Kathryn Thompson :: Wednesday 4th March 2026 :: Latest Blog Posts

Spring Transition for Dairy Cattle: Safely Introducing Fresh Grass After Winter Housing

There's nothing quite like the sight of dairy cows heading back out to grass after a long winter indoors. Turnout signals a shift towards lower feed costs, improved cow comfort, and the start of a new grazing season.

But while spring grass brings opportunity, it also brings risk.

A sudden move from a controlled winter ration to lush, fast-growing pasture can unsettle the rumen, reduce milk solids, and knock performance just when margins matter most. Careful management during this transition period protects milk yield, fertility and overall herd health.

Here's how to introduce fresh forage safely and set your dairy herd up for a productive grazing season.

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Why Spring Grass Presents a Nutritional Challenge

Early spring grass is very different from winter silage. Fresh pasture typically contains:

  • High levels of rapidly fermentable sugars
  • High crude protein
  • Low structural fibre
  • High moisture content

This combination drives rapid rumen fermentation. While that can support milk yield, it also increases the risk of sub-acute ruminal acidosis (SARA) if not properly managed.

When cows move abruptly from a fibre-based total mixed ration (TMR) to highly digestible grass, rumen microbes need time to adapt. Without that adjustment period, you may see:

  • Loose dung
  • Reduced cud chewing
  • Milk fat depression
  • Variable intakes
  • Reduced feed efficiency

According to AHDB guidance on rumen health, maintaining effective fibre and managing rapid diet change are key to reducing SARA risk in dairy herds (AHDB Dairy – Feeding for a Healthy Rumen:https://ahdb.org.uk).

Prepare the Herd Before Turnout

A successful spring transition starts before the gates are opened.In the final weeks before turnout:

  • Avoid abrupt changes in concentrate levels.
  • Maintain adequate effective fibre to support rumination.
  • If possible, begin exposing cows to small amounts of fresh grass.

This allows rumen microbes to begin adapting to higher sugar levels.

Ideally, cows should be around BCS 2.75–3.0 at turnout. Over-conditioned cows are more prone to metabolic issues, while thin cows may struggle to maintain yield when intakes fluctuate during early grazing.

Spring is not the time to correct major condition issues, planning earlier in the winter pays dividends now.

Introduce Fresh Grass Gradually

One of the most common mistakes at turnout is allowing cows unrestricted access to lush pasture straight away. A phased approach reduces digestive upset and supports consistent milk output.

Step-by-Step Turnout Strategy

Days 1–3:

  • Turn cows out for 2–3 hours per day after morning milking.
  • Ensure they are not excessively hungry before grazing.

Days 4–10:

  • Gradually increase grazing time.
  • Continue feeding silage indoors to maintain fibre intake.

After 10–14 days:

  • Move towards full-time grazing if ground and grass conditions allow.

Avoid turning cows out onto very immature, high-sugar swards first thing in the morning, particularly after a frost followed by sunshine, when sugar levels are elevated.

The Importance of Buffer Feeding at Grass

Even once cows are grazing for longer periods, removing conserved forage too quickly can destabilise rumen function.

Buffer feeding with silage during early turnout:

  • Maintains effective fibre levels
  • Stabilises rumen pH
  • Reduces milk fat depression
  • Helps maintain consistent dry matter intake

This is especially important for high-yielding cows, who are less able to tolerate fluctuations in energy supply.

A well-balanced complementary feed can also help match the energy-to-protein ratio of spring grass, improving nitrogen utilisation and reducing waste.

Managing Concentrates During the Transition

Spring grass is often high in crude protein, sometimes exceeding 20%, but energy supply must be synchronised with that protein for efficient microbial protein production in the rumen. Simply cutting concentrates because "the cows are at grass" can backfire.

Key Considerations:

  • Avoid sudden reductions in starch supply.
  • Adjust concentrate feeding in line with milk yield and grass intake.
  • Monitor milk constituents closely.

A drop in butterfat percentage is often the first indicator that rumen balance is compromised. Regular milk recording and ration reviews during this period provide valuable early warning signs.

Preventing Common Spring Problems

Sub-Acute Ruminal Acidosis (SARA)

Watch for:

  • Loose, bubbly dung
  • Undigested fibre in faeces
  • Reduced cud chewing
  • Milk fat depression

Maintaining fibre intake and avoiding abrupt dietary change remain the most effective preventative measures.

Grass Tetany (Hypomagnesaemia)

Early spring grass can be low in magnesium and high in potassium and nitrogen, which interferes with magnesium absorption.

According to the Agriculture and Horticulture Development Board (AHDB), magnesium supplementation is essential during high-risk periods in early grazing (AHDB – Managing Grass Tetany:https://ahdb.org.uk).

Consider:

  • Magnesium supplementation in concentrates
  • Mineral buckets in fields
  • Ensuring consistent daily intake

Grass tetany often strikes without warning, so prevention is critical.

Fertility Impacts

Nutritional stress, fluctuating energy intake and imbalanced protein can all affect reproductive performance.

Maintaining steady intakes and avoiding sudden body condition loss during early grazing supports:

  • Stronger heats
  • Better conception rates
  • Improved embryo survival

For spring-calving herds in particular, this period is pivotal.

Monitor, Measure and Respond

Close observation during the first few weeks of grazing makes all the difference. Keep an eye on:

  • Dung consistency
  • Cud chewing activity
  • Milk yield and constituents
  • Cow behaviour
  • Body condition

If performance dips, act early rather than waiting for issues to escalate. Spring grass quality can change rapidly depending on weather, so flexibility in ration planning is essential.

Setting Your Herd Up for a Productive Grazing Season

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With careful planning, gradual introduction, and balanced supplementation, dairy herds can maintain milk yield, protect milk solids, and transition smoothly from winter housing to full grazing.

Every herd is different. Soil type, grass quality, calving pattern and yield level all influence nutritional requirements. That's why tailored advice matters.

At BW Feeds, we work alongside UK dairy farmers to design practical, cost-effective feeding strategies that support rumen health, milk performance and long-term herd productivity.

If you'd like support reviewing your spring ration or preparing for turnout, speak to our team today. A well-managed transition now sets the tone for the entire grazing season.