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While foregut fermentation is generally considered more efficient, and monogastric animals cannot digest cellulose as efficiently as ruminants, [5] hindgut fermentation allows animals to consume small amounts of low-quality forage all day long and thus survive in conditions where ruminants might not be able to obtain nutrition adequate for their needs.
Tannins can be toxic to ruminants, in that they precipitate proteins, making them unavailable for digestion, and they inhibit the absorption of nutrients by reducing the populations of proteolytic rumen bacteria. [36] [37] Very high levels of tannin intake can produce toxicity that can even cause death. [38]
Ribbon representation of the Streptomyces lividans β-1,4-endoglucanase catalytic domain - an example from the family 12 glycoside hydrolases [1]. Cellulase (EC 3.2.1.4; systematic name 4-β-D-glucan 4-glucanohydrolase) is any of several enzymes produced chiefly by fungi, bacteria, and protozoans that catalyze cellulolysis, the decomposition of cellulose and of some related polysaccharides:
The reticulorumen thus hosts a microbial fermentation which yields products (mainly volatile fatty acids and microbial protein), which the ruminant is able to digest and absorb. This allows the animals to extract nutritional value from cellulose which is usually undigested.
Ruminants can extract food energy from the respiration of cellulose because of bacteria in their rumens that decompose it into digestible carbohydrates. Other minor components of the human diet that contribute to its energy content are organic acids such as citric and tartaric , and polyols such as glycerol , xylitol , inositol , and sorbitol .
Most animals, however, do not produce cellulase; the enzyme needed to digest cellulose. However, some animals and species have developed symbiotic relationships with cellulase-producing bacteria (see termites and metamonads.) This allows termites to use the energy-dense cellulose carbohydrate. [1]
A large percentage of herbivores also have mutualistic gut flora made up of bacteria and protozoans that help to degrade the cellulose in plants, [1] whose heavily cross-linking polymer structure makes it far more difficult to digest than the protein- and fat-rich animal tissues that carnivores eat. [2]
Fiber can be either soluble (pectins and gums) or insoluble (cellulose, hemicellulose and lignocellulose). [13] A simple gastrointestinal tract is not capable of extracting enough nutrients for these animals. One strategy to get the needed nutrition is used by ruminants (e.g., cows). They chew the cud in order to process their food a second ...