Land O’ Lakes Feed
Land O’ Lakes Inc., Shoreview, MN
It would be great if the decision to add sugar to dairy cattle diets was a black and white issue. Unfortunately it is not a simple decision because the rumen is a complex ecosystem. This complex ecosystem will respond positively or negatively to the addition of sugar to dairy diets based upon the ruminal environment. The addition of sugars to dairy cattle diets has not always improved milk yield, ruminal microbial protein yields or milk components (Hristov and Ropp 2003; McCormick etal. 2001, Morales etal. 1989). In contrast, other trials have reported increased milk yield and milk fat percent or increased NDF digestibility (Broderick and Radloff, 2003, Broderick and Smith 2001, Varga etal. 2001, Oldick etal. 1997). The reported variation in response to sugar in dairy cattle diets can be explained by four processes that occur in the rumen. These processes are:
- A shift in the end products of sugar fermentation in the rumen based on bacterial growth rate and rumen pH.
- Not all sugars are used with the same efficiency by rumen bacteria for growth.
- Establishment of a viable population of anaerobic fungi in the rumen.
- Wasting of energy by rumen bacteria (energy spilling) when the supply of fermentable carbohydrates exceeds the needs for microbial growth.
Molasses-based liquid supplements and sugar are readily digestible sources of energy for dairy cattle. When added to dairy rations at 3 to 7% of the total ration dry matter, molasses-based liquid supplements and sugar may increase dry matter intake and fat-corrected milk yield. The mode of action appears to be through enhancing NDF digestibility, altering the ruminal microbial population and possibly providing an increased supply of nutrients for fat synthesis. Sugar or molasses, when fed at less than 7% of diet dry matter, can be used with the same efficiency as corn for milk production. Physical factors of the ration can influence responses to molasses or sugar. In rations with less than 19% ADF, and small particle size, use of sugar and molasses-based liquid supplements may not increase feed intake and milk production. Response to liquid supplements and sugar has been greater when the ration contains adequate amounts of rumen degradable amino acids and peptides. Research trials published since 1983 suggest that molasses and sugar do more than just increase ration palatability, they can play a greater role in dairy rations by altering ruminal microbial populations and possibly increasing microbial growth in the rumen of dairy cattle.
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