New evidence highlights how rumen performance, not just yield, is the key metric for dairy maize selection.
As dairy producers face mounting pressure to reduce input costs and improve environmental performance, it is key to reassess how maize silage is evaluated — shifting the focus from field output to rumen efficiency, with fibre digestibility emerging as the critical performance driver.
The message comes from Benoît Delord, animal nutrition product manager at Limagrain Field Seeds France, who argues that traditional measures of maize value — tonnes per hectare, starch percentage, or dry matter yield — are no longer sufficient benchmarks for a sector under pressure to do more with less.
“The first effect of fibre digestibility is on dry matter intake,” says Benoît. “The second is that you improve the energy content of each kilogramme of silage. So you have a double effect.”
A Dual Mechanism for Performance Gains
At the heart of the case for fibre digestibility is its impact on two interconnected processes in the rumen. Improved neutral detergent fibre digestibility (NDFD) reduces rumen fill constraints, enabling cows to consume greater quantities of forage dry matter. Simultaneously, it increases the extent of fibre degradation, driving higher production of volatile fatty acids — particularly acetate and propionate — which are the primary energy source for the dairy cow.
Research indicates that a 1% improvement in NDFD is associated with an increase in dry matter intake of approximately 0.15–0.25 kg per cow per day, alongside measurable gains in milk yield. Across high-yielding herds, these incremental improvements compound rapidly.
Where NDFD values move from 55% to 65%, the energy contribution from the fibre fraction can be equivalent to several kilogrammes of additional concentrate on an energy basis — a significant commercial consideration given current input costs.
Reducing Reliance on Purchased Feed
One of the most immediate practical implications of improved maize quality is its effect on concentrate use. Higher-quality forage allows producers to increase the forage proportion of the ration and reduce purchased concentrate inclusion — a shift that directly improves the economics of milk production.
“In reality, you don’t reduce feed — you change the balance,” says Benoît. “You increase the forage part and decrease the concentrate part.”
In practice, improvements in forage quality can reduce concentrate requirements by 1–3 kg per cow per day, depending on system intensity and baseline forage performance. In grass silage-based systems — where starch levels are typically below 5% — the substitution of high-quality maize silage containing 30–35% starch alongside digestible fibre can substantially reduce the need for bought-in energy. The result is both a reduction in feed costs and greater control over ration consistency.
Improving Feed Conversion and Reducing Methane
The efficiency gains extend beyond intake and energy supply. Improved fibre digestibility has a direct effect on the conversion of consumed nutrients into milk, reducing losses through methane production — which typically accounts for 6–10% of gross energy intake in ruminants.
Benoît Delord, Animal Nutrition Product Manager at Limagrain Field Seeds France
“Methane is a loss for the animal,” explains Benoît. “It’s carbon that is not used, but when you improve digestibility, you reduce this loss.”
From a biochemical perspective, improved fibre degradation shifts rumen fermentation towards propionate production at the expense of methane. European research indicates that improvements in forage digestibility can reduce methane intensity — measured as grams of methane per litre of milk — by up to 5–10%, depending on ration structure and baseline efficiency. Combined with higher milk output, the per-litre emissions benefit is amplified further.
Rumen Stability at Higher Inclusion Rates
As maize inclusion in dairy rations increases — often reaching 40–50% of forage dry matter in high-performing herds — the risk of sub-acute ruminal acidosis rises, particularly where total dietary starch exceeds 25–28% of dry matter. Improving the digestibility of the fibre fraction allows maize to contribute more to total energy supply without further increasing starch load, supporting rumen pH stability and cud chewing activity.
“It’s about producing more milk per cow, but under safe conditions,” says Benoît. “You need rumen comfort.”
The LGAN Response
These shifting priorities are reflected in Limagrain’s LGAN classification — a selection framework for maize hybrids evaluated specifically on feeding value, with fibre digestibility and overall energy availability as core criteria. LGAN varieties are assessed across eight parameters using a robust dataset combining official BSPB/NIAB trial data with five years of Limagrain data from 12 sites across the UK.
Across multiple European datasets, LGAN varieties have delivered improvements of 0.4–3 kg of milk per cow per day compared with standard comparators, frequently alongside reductions in concentrate use.
“First, you produce more biomass in the field. Then you improve the efficiency of converting that into milk,” says Benoît. “Fibre digestibility is key for that.”
Limagrain advises that variety selection should consider feed quality characteristics — particularly NDFD — alongside agronomic performance, and that ration formulation should reflect the full energy contribution of silage where forage quality allows.
