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Ruminant Division, Department of Animal Science University of Illinois, Urbana 61801
ABSTRACT
Incomplete extraction of certain haylages during assay of ß-carotene by the usual methods results in an apparent greater excretion than intake in cattle. Such haylage was incubated in an in vitro digestion system corresponding to bovine in vivo conditions. A doubling in extractable ß-carotene could be measured with the major increase occurring as a result of the rumen and pepsin-HCl incubations. This increase was due primarily to a pH-water effect on the haylage, with a pH 7.0 presoak increasing the rate of acid release of ß-carotene. Since various proteolytic enzymes did not enhance the rate or amount of release of ß-carotene, protein was not considered to be the primary binder. However, protein integrity or the presence of taurocholic acid was necessary to retard the destruction of pigment during incubations.
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