Foraging bacterial

Vetter, Y. A., Deming, J. W., Jumars, P. A. and Krieger-Brockett, B. B. (1998). A predictive model of bacterial foraging by means of freely released extracellular enzymes, Microb. Ecol., 36, 75-92. 

Dairy cattle are raised for their milk, which is a nutritious fluid rich in sugar, protein, and fat. Dairy cattle are usually kept under relatively confined conditions, although when the weather is suitable they are usually allowed to forage in local pastures. Cow milk can be drunk directly by humans (after pasteurization to kill bacterial pathogens that may be present), or used to manufacture butter, cream, cheese, or other foods. When their milk production starts to decline significantly as they age, dairy cows are typically slaughtered for their meat. 

In the first place, plant cell walls of forages can be readily prepared by peptic and amylitic digestion of coarse-milled tissue (65) (20 mesh) or by neutral-detergent extraction of plant tissue (61), conditions which do not cause any removal of lignin. These observations also support the conclusion that a lignin-free fraction exists. Furthermore, ruminant feces appear to be composed of undigested plant cell walls in a fine state of division (50-70 mesh), plus much metabolic and bacterial matter (31,... 

Saponins are present in many pasture plants (Bondi et al., 1973). Appreciable quantities accumulate in some, especially in certain forage legumes. These compounds are probably involved in the condition known as ruminant bloat. By altering the surface tension of the ruminal contents, saponins cause gas formed in the rumen by anaerobic bacterial fermentation to be entrapped as a froth. When fed to cattle, saponins elicit characteristic symptoms of bloat. In mono-gastric animals, saponins are responsible for reduced growth rate and decrease in food consumption. Poultry are particularly sensitive to alfalfa that contains saponins. Swine are less sensitive (Applebaum and Birk, 1979). 

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