Feed & Additive Magazine Issue 25 February 2023

ISSUE FOCUS 26 FEED & ADDITIVE MAGAZINE February 2023 Ruminants have the unique ability to release energy from plant fiber thanks to the fermentative activity of the rumen. The fiber components, and the subsequent production of volatile fatty acids (VFAs), provide the majority of the energy for the ruminant. Better understanding of how fiber is degraded in the rumen helps identify the levers that can help make sure fiber is no longer an untapped energy source. TURNING FIBER INTO MILK Fiber is slowly degraded in the rumen due to its physical structure and the lignin cross-linking that holds the fiber intact. Fiber degradation in the rumen is influenced by: • The anatomy of the fiber (pectin, hemicellulose and cellulose concentration), which is related to species • Lignin content and structure (maturity, species, stressors, etc.) • Particle size • Passage rate (highly influenced by particle size, uNDF, DMI) and its impact on rumen dynamics • Cud-chewing and ruminal contractions • Rumen microbial population (microbiome) influenced by several factors (diet, environment) The ruminant reduces the particle size of the forage through the eating process via initial mastication (chewing). These particles are swallowed and float to the top of the rumen mass. The particles are then regurgitated and rechewed (cud-chewing) to increase moisture content and surface area of the material as well as to abrade the fibrous portion. After initial mechanical abrasion of fiber through mastication, the feed is then exposed to the diverse population of microorganisms in the rumen. The first step in fiber degradation is the colonization in the rumen of the particle of fiber by fungi and bacteria. Fibrolytic microbiota are very sensitive to oxygen. Strict anaerobic conditions (measured though reTURNING FIBER INTO MILK: THE ROLE OF THE RUMEN ENGINE Aurélien Piron Ruminant Technical Manager Lallemand Animal Nutrition - France Key role of the rumen in digestion • A huge fermenter (up to 200 L) with unique digestive capacity • Over 100 billion microbes/mL of rumen fluid • A complex ecosystem: anaerobic bacteria, ciliate protozoa, fungi, archaea • Up top 70% of the feed is digested in the rumen

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