Rations for today’s lactating dairy cows contain a lot of fermented forages and processed feeds. Unless supplemental sugar is fed, the ration only contains about 1.5 to 3% sugar. That’s because a lot of the natural sugars found in feeds have been removed during processing or by fermentation. But does the lactating cow need more sugar in the diet?
The answer is yes, says Mary Beth de Ondarza, Paradox Nutrition, West Chazy, N.Y. The question is how much. Sugar plays a role in microbial protein synthesis, rumen pH, milk fat percentage and fiber digestion. In a study using 21 scientific papers with 85 observation data sets, researchers examined the impact of dietary sugar on lactating cow responses (de Ondarza et al., 2017). To be included in the analysis, individual feed ingredients had to be specified so that sugar, starch and soluble fiber content of the diet could be estimated. The data sets selected were representative of rations typically fed on commercial dairy farms in the United States.
Results showed that additional dietary sugar increased milk yield, 3.5% fat-corrected milk and milk true protein. The response was even greater in cows producing 73 lbs milk/day or more. Additional dietary sugar also impacted the concentration of volatile fatty acids in the rumen. It did not impact dry matter intake or feed efficiency.
Researchers also sought to identify the optimal levels of starch, soluble fiber and rumen degradable protein that should be fed with added sugar. Based on research and field experience, de Ondarza suggests the following nutrient ranges for lactating dairy cows: Sugar 6 to 8% of diet DM, starch 22 to 27% DM, soluble fiber 6 to 8% DM and rumen degradable protein 10 to 11% DM.
To learn more on this topic, please see “Dietary Sugars for Optimizing Rumen Function and Dairy Cow Performance,” Mary Beth de Ondarza, Cornell Nutrition Conference 2020.