Publication Date
1989
Description
In vivo organic matter digestibility (OMd) of forage is very variable. That of standing forage varies, depending on species, growth cycle number and more especially stage of development or forage age, between 49 and 86 p. 100 according to the 1 719 samples of grasses, legumes and permanent pastures studied on sheep in our Laboratory (Demarquilly and Andrieu, 1987). Variation may also be caused by conservation method, particularly hay-making. Since net energy value depends closely on OMd, a good knowledge of the latter is indispensable in the preparation of animal diets. It is also important in the choice of crop species and of the optimum harvest stage. However, OMd measurements on animals are long and expensive and therefore laboratory predicting methods are of great interest. Predicting precision can be considered as sufficient (RSD, residual standard deviation, generally between 2 and 3 points) from forage age, harvest conditions or chemical composition (ash, crude protein, crude fibre), but only when regression equations specific for each species and for each growth cycle are used (Andrieu et al., 1981). These equations cannot therefore be used to predict OMd of forages not studied in vivo, such as complex mixtures of gramineae, grass-legume associations and permanent pastures with flora different from that in our studies. Other laboratory methods are therefore necessary. Of these, biological methods (in sacco or in vitro digestibility) are the most precise (Demarquilly and Jarrige, 1981) but cannot be used in routine laboratories since they require maintenance of fistulated animal. It is possible to eliminate this requirement by using cellulolytic enzymes (cellulase). This paper compares two enzymatic methods for predicting forage digestibility : one with pepsin-cellulase, generally used for forage, and a second method for concentrate feeds, by-products and feed mixtures.
Citation
Aufrere, Jocelyne and Demarquilly, C, "Predicting Organic Matter Digestibility of Forage by Two Pepsin-Cellulase Methods" (2025). IGC Proceedings (1989-2023). 61.
https://uknowledge.uky.edu/igc/1989/session7/61
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Predicting Organic Matter Digestibility of Forage by Two Pepsin-Cellulase Methods
In vivo organic matter digestibility (OMd) of forage is very variable. That of standing forage varies, depending on species, growth cycle number and more especially stage of development or forage age, between 49 and 86 p. 100 according to the 1 719 samples of grasses, legumes and permanent pastures studied on sheep in our Laboratory (Demarquilly and Andrieu, 1987). Variation may also be caused by conservation method, particularly hay-making. Since net energy value depends closely on OMd, a good knowledge of the latter is indispensable in the preparation of animal diets. It is also important in the choice of crop species and of the optimum harvest stage. However, OMd measurements on animals are long and expensive and therefore laboratory predicting methods are of great interest. Predicting precision can be considered as sufficient (RSD, residual standard deviation, generally between 2 and 3 points) from forage age, harvest conditions or chemical composition (ash, crude protein, crude fibre), but only when regression equations specific for each species and for each growth cycle are used (Andrieu et al., 1981). These equations cannot therefore be used to predict OMd of forages not studied in vivo, such as complex mixtures of gramineae, grass-legume associations and permanent pastures with flora different from that in our studies. Other laboratory methods are therefore necessary. Of these, biological methods (in sacco or in vitro digestibility) are the most precise (Demarquilly and Jarrige, 1981) but cannot be used in routine laboratories since they require maintenance of fistulated animal. It is possible to eliminate this requirement by using cellulolytic enzymes (cellulase). This paper compares two enzymatic methods for predicting forage digestibility : one with pepsin-cellulase, generally used for forage, and a second method for concentrate feeds, by-products and feed mixtures.
