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Fibre digestibility plays a pivotal role in dairy cow nutrition, directly influencing dry matter intake (DMI), rumen health and milk production. In Canada, where forage-based diets are the norm, maximizing fibre utilization is essential for both herd performance and farm profitability. The drought of 2025 intensified challenges in forage quality, particularly in Ontario and Quebec, prompting producers to explore innovative nutritional strategies.
Understanding fibre digestibility
Fibre in dairy nutrition is typically measured as neutral detergent fibre (NDF), encompassing cellulose, hemicellulose and lignin. However, not all NDF is digestible. Advanced metrics such as undigested NDF at 240 hours (uNDF240) and physically effective NDF (peNDF) offer deeper insights into how fibre behaves in the rumen and its influence on intake and milk yield.
Modern nutritional models divide fibre into three pools – indigestible, fast-fermenting and slow-fermenting – to better predict cow performance. Forages with high uNDF240 can restrict intake and reduce milk output, especially when chopped too coarsely. In contrast, finely chopped forages with low uNDF240 can enhance intake and overall performance.
Impact of drought on forage quality
The drought of 2025 had a significant impact on forage crops across Canada, with regions in Ontario and Quebec experiencing some of the most severe conditions. In southern areas of both provinces, precipitation levels dropped to less than 60% of the seasonal average, and in some locations, rainfall fell below 40%. These extreme conditions led to poor regrowth of haylage and increased lignification in plant cell walls. In contrast, a noticeable decline in starch and sugar concentrations will most likely be observed across most silages harvested under drought conditions.
As the drought persisted into the latter part of the growing season, concerns extended beyond nutritional value to feed safety. Elevated nitrate levels – often a consequence of drought stress – became a potential risk, posing challenges not only to forage quality but also to the health and safety of dairy herds consuming the harvested feed.
How can we improve fibre digestibility?
During periods of poor forage quality – such as the drought conditions experienced in 2025 – dairy cows often struggle to extract sufficient energy from their diets. Strategic use of feed additives can help address this challenge by enhancing fibre digestion and supporting overall cow performance.
One such additive is dried Aspergillus oryzae fermentation concentrate (AOFC). Derived from the natural fermentation of the fungus Aspergillus oryzae, AOFC is a concentrated source of enzymes and microbial stimulants that promote the activity of fibre-digesting bacteria in the rumen.
AOFC works by stimulating the growth of cellulolytic microbes, accelerating the breakdown of fibre into volatile fatty acids (VFAs) – critical energy sources for milk production – and improving both feed intake and milkfat content. Research has shown that incorporating fermented fungal products into dairy rations can lead to measurable increases in DMI and fat-corrected milk yield. These benefits have been observed across a variety of forage types and feeding systems.
In particular, AOFC has demonstrated the ability to improve fibre digestibility by up to 28% in forages such as alfalfa. Under the challenging conditions of this year’s growing season, incorporating fibre-enhancing additives like AOFC offers producers a practical way to stretch limited feed resources and maintain herd performance despite compromised forage quality.
Complementary strategies to enhance fibre digestibility
In addition to AOFC, several other tools and techniques can help improve fibre utilization. Silage inoculants like Lactobacillus buchneri and fibrolytic enzymes, whether added during ensiling or feeding, can boost NDF digestibility by up to 30%. These additives enhance fermentation and fibre breakdown, particularly in drought-stressed forages.
Managing particle size is also crucial. Adjusting forage chop length based on uNDF240 and peNDF metrics can optimize rumen fill and fermentation. Finer chopping of high-uNDF240 forages increases DMI, while overly fine chopping of low-uNDF240 forages may reduce rumination.
Incorporating alternative soluble fibre sources such as beet pulp and soyhulls can support milkfat synthesis. These byproducts ferment rapidly and can replace starch in the diet, helping to reduce insulin spikes and prevent mid-lactation overconditioning.
Financial impact of fibre digestibility
Improving fibre digestibility delivers substantial economic advantages for dairy operations. Since fibre is the least energy-dense component of the total mixed ration, enhancing its digestibility unlocks more usable energy, resulting in higher energy-corrected milk yields, improved feed conversion efficiency and reduced feed costs per litre of milk.
Better fibre utilization also decreases dependence on costly grain-based concentrates, helping to lower overall ration expenses and improve profit margins. This is especially critical during drought conditions, when concentrate prices tend to spike and when additional sources of rumen-digestible starch are needed to compensate for reduced starch levels in drought-stressed corn silage.
Moreover, enhanced fibre digestion supports rumen health by reducing the risk of metabolic disorders such as acidosis and displaced abomasum. Healthier cows enjoy longer, more productive lifespans – further strengthening herd economics.
Conclusion
Fibre digestibility is more than a nutritional metric – it’s a strategic tool for dairy farm success. In drought years like 2025, producers faced significant challenges in forage quality and availability. Integrating feed additives that support fibre digestibility into feeding programs, alongside silage inoculants, precision forage analysis and soluble fibre sources, offers a strong approach to enhance rumen function, improve feed efficiency and protect profitability.
