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Comparison of methods to describe the kinetics of digestion and passage of fibre in sheep
Author(s) -
Aitchison Elisabeth,
Gill Margaret,
France James,
Dhanoa Mewa S.
Publication year - 1986
Publication title -
journal of the science of food and agriculture
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.782
H-Index - 142
eISSN - 1097-0010
pISSN - 0022-5142
DOI - 10.1002/jsfa.2740371103
Subject(s) - digestion (alchemy) , rumen , hay , kinetics , chemistry , zoology , mordant , chromatography , food science , biology , organic chemistry , physics , quantum mechanics , dyeing , fermentation
A mathematical model is described which was developed with the objective of analysing and interpreting data from rumen‐emptying studies to estimate rates of digestion ( k d ) and passage ( k p ) in sheep offered hay once daily. It assumed that first‐order kinetics applied to digestion in and passage from the rumen within a 24 h feeding cycle. The model predictions of k d and k p were compared with rates of digestion estimated by incubation of the hays in dacron bags and rates of passage determined using chromium‐mordanted hay, in the same experiments. The predictions for rates of passage determined over the period 5–15 h postfeeding were lower than those determined from the chromium‐mordant data and the simulations indicated that the fractional rate of passage during feeding was higher than that recorded in the postfeeding period. This suggests either that more than one fractional rate constant applies within a 24 h period, or that first‐order kinetics do not apply. The estimates for k d were considerably higher than those determined in dacron bags. Evaluation of the ability of the combined dacron bag and mordant techniques to estimate extent of digestion by comparison with in‐vivo digestibility values indicated that the extent of digestion was underestimated. The predictions obtained from the rumen‐emptying data were much closer to the in‐vivo values.