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Explanation of Feeding Trial Results

Milk production per cow is a major factor in determining dairy farm sustainability/profitability. The inclusion of non-fibrous carbohydrates (NFC) in the range of 35 to 42% of dietary dry matter is seen as a popular way to increase energy density and thus milk production. Balance of carbohydrates in the diet impacts milk production because it affects amount and ratios of ruminal volatile fatty acids produced, which in turn alters metabolism and partitioning of nutrients. A very compatible feedstock for grass diets is corn silage, which also increases energy density [GIS-33].

In the above studies, the higher the fiber in the forage, the more concentrate in the diet. This resulted in generally higher intakes and higher milk production. Higher concentrate feeding results in a shift toward propionic acid production by ruminal microbes. Propionic acid is used by the mammary gland to produce lactose, responsible for milk volume, which accounts for milk production of cows fed grass being as high as those fed a lower fiber alfalfa. Differences in DM intake and subsequent milk production can also be attributed in part to differences in fiber digestibility and indigestible residue, resulting from lignin differences, as well as to differences in NSC.