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Dietary Sugars for Optimizing Rumen Function and Dairy Cow Performance

M.B. de Ondarza , S.M. Emanuele , and C.J. Sniffen
Paradox Nutrition, LLC, West Chazy, NY
Phileo-Lesaffre Animal Care, Milwaukee, WI
Fencrest LLC, Holderness, NH


Typical US lactating dairy rations without supplemental sugars contain about 1.5 to 3% sugar. The use of more fermented forages and processed feeds has resulted in the removal of many sugars that would otherwise naturally be in the dairy cow diet. Sugars are water-soluble and include monosaccharides (glucose and fructose) as well as disaccharides (sucrose and lactose). Adding supplemental dietary sugar often reduces rumen ammonia, suggesting that rapidly digestible sugars help the rumen microbes capture and use nitrogen. Fiber digestion, microbial protein synthesis, energy absorption and rumen pH can increase with additional dietary sugars when balanced appropriately with dietary starch to positively impact dairy cow performance. Dietary factors such as physically effective fiber, level of starch, starch digestion rate, degradable proteins, and unsaturated fatty acids may affect cow response to supplemental sugars. Level of milk production and DIM may also influence responses to added dietary sugars.

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Practical Applications

Consider supplementing sugar in lactating dairy diets to achieve 6 to 8% diet sugar for optimum rumen function and performance. Generally, 0.7 to 1.0 kg/cow/d of supplemental sugar would be needed to achieve 6 to 8% total sugar in typical US diets. Higher producing cows would be expected to have more positive responses to added dietary sugar. Liquid sugar sources have the added benefit of reducing TMR sorting.

Recognize the interactions between sugar, starch, soluble fiber, and rumen degradable protein. Research and field experience suggest the following optimal nutrient ranges (%DM): starch at 22 to 27%, soluble fiber at 6 to 8%, and RDP at 10 to 11%. Further, consider the impact of starch and protein degradation rates on responses to supplemental sugars. Sugars would be expected to have a more positive effect with a diet containing a lower percentage of rapidly digestible starch. Consider increasing soluble protein, using milk urea nitrogen (MUN) levels as a guide.

Future research to characterize and understand the effects of dietary sugars by type (glucose, sucrose, fructose, lactose, etc.) as well as to define multiple starch pools based on digestion rate and understand their impact on dietary sugar optimization would be helpful.