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The validity of in vitro techniques using rumen fluid or cellulase for predicting changes in the dry matter digestibility of grasses caused by fertilizer calcium, sulphur, phosphorus and nitrogen
Author(s) -
REES M. C.,
MINSON D. J.
Publication year - 1979
Publication title -
grass and forage science
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.716
H-Index - 56
eISSN - 1365-2494
pISSN - 0142-5242
DOI - 10.1111/j.1365-2494.1979.tb01443.x
Subject(s) - fertilizer , dry matter , rumen , phosphorus , cellulase , agronomy , nitrogen , zoology , chemistry , in vivo , sulfur , calcium , pepsin , biochemistry , biology , cellulose , microbiology and biotechnology , enzyme , fermentation , organic chemistry
Sixty‐four samples were used to measure the accuracy of in vitro techniques using rumen fluid‐pepsin or pepsin‐cellulase for predicting digestibility of grasses grown with different levels of fertilizer calcium(Ca), sulphur(S), phosphorus (P) and nitrogen (N). In each case, fertilizers changed in vivo dry matter digestibility (DMD) and the in vitro techniques accurately predicted the changes in in vivo DMD caused by fertilizer Ca, P and N. The in vitro techniques gave biased estimates of in vivo DMD in studies with fertilizer S. This bias was caused by a decrease in the digestive efficiency of the sheep when fed the unfertilized feed. It was concluded that biased estimates of DMD may be associated with low fertilizer levels and these cannot be eliminated by improving the in vitro techniques and would also apply to estimates of DMD based on chemical analysis of the feed.