Why Digestibility Matters More Than Bulk in Pasture

27 Oct

As pasture farmers, it’s easy to look across a tall, lush paddock and feel a sense of pride. A lot of green, a lot of bulk — surely that means happy, well-fed animals, right? Often, it’s a miracle. While quantity matters, pasture digestibility — not just bulk — is what truly drives animal performance, feed conversion efficiency, and your bottom line. Think of it like fuel quality: you wouldn’t fill your vehicle with a low-grade, cheap fuel just because it’s abundant. You’d choose the fuel that lets your engine run efficiently and deliver more km per $$ spent. The same applies to your livestock — it’s not how much they eat that counts, but how well they can digest and use it.

The Hidden Cost of Indigestible Bulk

When forage becomes less digestible, animals extract less nutrition per mouthful. This isn’t just inefficient — it’s expensive.

Reduced Intake: Animals can only eat so much per day. When the pasture is low in digestibility, their rumen fills quickly with tough, fibrous material that takes longer to break down. This “gut fill” triggers a feeling of fullness, even though the animal hasn’t absorbed enough energy or protein.
Lower Production: Low-digestibility forage means animals are expending energy to chew, ruminate, and ferment poor-quality feed, with little return. The result is slower liveweight gains, reduced milk production, and poorer reproductive performance.
Wasted Pasture Potential: Tall, stemmy grass might look impressive, but much of it ends up trampled or underutilized. If animals can’t efficiently convert it into meat or milk, you’re not truly harvesting that feed.

What Makes Forage Digestible?

Genetics, plant structure, and stage of growth determine digestibility. Young, leafy pasture has thin cell walls and is rich in sugars, proteins, and lipids — all of which are easily broken down by rumen microbes. As plants mature, their cell walls thicken and become reinforced with lignin, an indigestible compound that resists microbial breakdown. There are varieties bred to have thinner cell walls in view of increasing digestibility like Stride and Algira. More on these HERE https://www.vernado.co.nz/perennial-ryegrass-tetraploid

The Difference Between Bulk and Feed Value

It’s not just how much pasture you grow — it’s what’s inside it that counts. A paddock full of long, rank grass looks productive but often has low metabolizable energy (ME) and crude protein. By focusing on feed value over feed volume, you’re optimizing both animal production and pasture utilization.

Why Digestibility Drives Performance

High-digestibility pasture delivers a cascade of benefits:

✔ Higher Dry Matter Intake (DMI)

✔ Better Feed Conversion Efficiency

✔ Improved Milk Solids and Liveweight Gains

✔ Faster Recovery and Regrowth

Even a small lift in digestibility can deliver a large improvement in output and profitability — often more than any fertiliser or supplement alone.

Managing for Digestibility – Whether Grazed or Cut

Graze or Cut at the Right Leaf Stage: For ryegrass, the sweet spot is around the 2.5–3 leaf stage.
Avoid Reproductive Growth: Once seedheads start to form, digestibility drops.
Rotate Frequently: Shorter grazing intervals maintain quality.
Balance Fertility and Species: Choose modern, high-ME ryegrass and clovers bred for digestibility and persistence.

The Soil Health Connection: Fueling Digestibility from the Ground Up

Healthy, biologically active soils feed the plant–animal cycle.

Enhanced Nutrient Uptake: Active soil microbes and mycorrhizal fungi boost plant nutrition.
Optimal Plant Metabolism: Trace elements like zinc, manganese, and boron improve energy and protein synthesis.
Better Soil Structure: Healthy soil reduces plant stress, lowering lignin formation.
Balanced Growth: Plants stay leafy and digestible longer.

The Gut–Soil Axis:

The link between soil biology and rumen microbes forms a powerful feedback loop — better soil builds better forage, which builds better animals.

Digestibility and the Economics of Conserved Forage (Hay & Silage)

When it comes to hay and silage, ME is king.

High-Quality Silage: Made from young, leafy forage with high ME.
Lower Supplement Needs: High-ME feed reduces purchased inputs.
Faster Growth: Supports steady performance year-round.
Minimized Waste: Digestible forage is eaten completely.

Harvest for quality, not just quantity — cut earlier to capture energy and protein before lignin builds.

Not All Ryegrass Is Created Equal

Two paddocks can look the same, but yield very different results:

Variety A: 5,000 kg/ha → 850 kg DM/ha available energy
Variety B: 7,500 kg/ha → 650 kg DM/ha available energy

It’s usable energy — not tons — that counts.

Why Digestibility Outweighs Yield

Cell Wall Structure: Lignin locks up nutrients.
Faster Rumen Turnover: More digestible feed = more intake.
Energy–Protein Synchrony: Efficient conversion into milk and muscle.

Benefits of Highly Digestible Ryegrass

✔ Higher milk and meat yield

✔ Improved rumen health

✔ Lower methane emissions

✔ Enhanced nutrient efficiency

✔ Better silage quality

The Takeaway for Farmers

It’s not about growing more grass — it’s about growing the right grass.

Ask yourself:

How digestible is my pasture? Take some herb tests?
What proportion of my yield is usable energy (ME)?
Am I managing nutrients, grazing, and cutting to keep it leafy?

Bulk might look impressive from the gate, but digestibility pays the bills — and builds a more resilient, profitable farm.