6 



The inorganic mineral sources are those which are not 



bound to organic molecules, but to other inorganic elements 



(e.g. sulfur, chloride, carbonate, oxide or the metal form 



itself) . 



Trace Mineral Bioavailability 



Total concentration of a particular element in feed does 

 not reflect the actual amount that will be absorbed by the 

 animal . The reason is that frequently only a portion of that 

 element will solubilize and then only a portion of that will 

 be actually absorbed by the animal. Fox et al . (1981) defined 

 bioavailability as a quantitative measure of the utilization 

 of a nutrient under specified conditions necessary to support 

 the organism's normal structure and physiological process. It 

 is important to realize that just because an element is 

 absorbed does not necessarily indicate that it will be 

 utilized by the animal. The substance may not be metabolized 

 for body function and may be excreted immediately (Bender, 

 1989). O'Dell (1985), therefore, offers a simplified 

 definition of bioavailability which is the proportion of a 

 nutrient in a feedstuff that can be absorbed and utilized. 



Bioavailability of a compound implies the availability of 

 that compound to some organism for body use (Miller, 1980) . 

 In trace elements, therefore, bioavailability refers to the 

 portion which can be utilized by the animal to fulfill the 

 functions for which the element is needed (Miller, 1980) . 



