Total digestible nutrients

Table I. Relative Values of Feeds Expressed on a Total Digestible Nutrient (TDN) and Net Energy Basis (NE)a...

Source NRC (National Research Council). 1988a. Nutrient Requirements of Dairy Cattle. National Academy Press. Washington, D.C. Total digestible nutrients. 

TDN (total digestible nutrients) A term widely used in animal nutrition that indicates the energy value of feeds. TDN = % digestible protein + % digestible nitrogen-free extract (carbohydrates) -i- % digestible fiber + (% digestible fat x 2.25). 

Weiss, W.P., H.R. Conrad and N.R. St. Pierre, 1992. Atheoretically-based model for predicting total digestible nutrient values of forages and concentrates. Anim. Peed Sci. Technol. 39, 95-110. 

FAHEY G c Jr (2002a) Supplemental fructooligosaccharides andmannanoUgosaccharides influence immune function, ileal and total tract nutrient digestibilities, microbial populations and concentrations of protein catabolites in the large bowel of dogs. J Nutr 132 980-9. 

Houdijk, J.G.M., Bosch, M.W., Tamminga, S., Verstegen, M.W.A., Berenpas, E.B., and Knoop, H., Apparent ileal and total-tract nutrient digestion by pigs as affected by dietary nondigestible oligosaccharides, J. Anim. Sci., 77, 148-158, 1999. 

Haydon KD and West JW (1990) Effect of dietary electrolyte balance on nutrient digestibility determined at the end of the small intestine and over the total digestive tract in growing pigs. J Anim Sci 68 2400-2406. 

Clapper, G.M. C.M. Grieshop N.R. Merchen J.C. Russet J.L. Brent, Jr G.C. Fahey, Jr. Ileal and total tract nutrient digestibilities and fecal characteristics of dogs as affected by soybean protein inclusion in dry, extruded diets./. Anim. Sci. 2001, 79, 1523-1532. 

Smiricky-Tjardes, M.R. C.M. Grieshop E.A. Flickinger L.L. Bauer G.C. Fahey, Jr. Dietary galactooligosaccharides affect ileal and total-tract nutrient digestibility, ileal and fecal bacterial concentrations, and ileal fermentative characteristics of growing pigs. /. Anim. Sci. 2003b, 81, 2535-2545. 

Tabk I. Microbial ecology and apparent total tract nutrient digestibility ofpigs fed different dietary markers for 38 d. 

Cobalt is one of twenty-seven known elements essential to humans (28) (see Mineral NUTRIENTS). It is an integral part of the cyanocobalamin [68-19-9] molecule, ie, vitamin B 2> only documented biochemically active cobalt component in humans (29,30) (see Vitamins, VITAMIN Vitamin B 2 is not synthesized by animals or higher plants, rather the primary source is bacterial flora in the digestive system of sheep and cattle (8). Except for humans, nonmminants do not appear to requite cobalt. Humans have between 2 and 5 mg of vitamin B22, and deficiency results in the development of pernicious anemia. The wasting disease in sheep and cattle is known as bush sickness in New Zealand, salt sickness in Florida, pine sickness in Scotland, and coast disease in AustraUa. These are essentially the same symptomatically, and are caused by cobalt deficiency. Symptoms include initial lack of appetite followed by scaliness of skin, lack of coordination, loss of flesh, pale mucous membranes, and retarded growth. The total laboratory synthesis of vitamin B 2 was completed in 65—70 steps over a period of eleven years (31). The complex stmcture was reported by Dorothy Crowfoot-Hodgkin in 1961 (32) for which she was awarded a Nobel prize in 1964. 

Basal metabolism is the rate of total heat production ol an individual who is awake but in complete mental and physical repose, at comfortable temperature and without having had food for at least 12 hours. See also Basal Metabolism, Under these conditions, oxidation of stored nutrients provides the sole source of energy expended and Ileal is measurable hy calorimetry. See also Digestion. 

A high proportion of the phosphorus present in feedstuff s may be in the form of phytate, which is poorly digested by birds because they lack the requisite enzyme in the gut. Consequently, the content of non-phytate phosphorus in feed ingredients is used in formulating poultry diets to ensure the required level of phosphorus, rather than the total phosphorus content. It is now becoming a common practice for a microbial phytase to be added to conventional poultry diets. This achieves a greater release of the bound phosphorus in the gut and a reduced amount to be excreted in the manure and into the environment. Use of microbial phytase may also improve digestion of other nutrients in the diet, associated with breakdown of the phytate complex. 

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