Fructose and sorbitol are also common dietary carbohydrates that may be malabsorbed. Fructose-containing foods include honey, fruits, fruit juices, and many commercially available fruit-flavored and/or carbonated beverages. The fruits highest in fructose include apples (5 g/100 g of apple) and pears (5 to /100 g of pear). The fructose contents of apple and pear juice are comparable (6 g/100 mL of juice). Excessive intake of these products may lead to abdominal pain in susceptible individuals and should be discouraged. Sorbitol is a polyalcohol sugar commonly found in “sugar-free” gums and confections. It is poorly absorbed by the small intestinal mucosa and has been shown to cause chronic abdominal pain in children. 42
Ammonia is used as a nitrogen source for microbial growth and VFAs absorbed from the rumen are a key energy source for the cow. Increasing the rumen-available energy content of the diet in the form of sugar and starch stimulates papillae growth, improving VFA absorption. While rumen fermentation allows good use to be made of fibrous feeds that could not otherwise be digested, it does mean only around 70-85% of the energy in the feed is available to the animal - 6-15% commonly being lost as gases (mainly methane) and 6-7% as heat.