Evaluation of Laboratory Methods for Determining Quality of Corn and Sorghum Silages: II. Chemical Methods for Predicting In Vivo Digestibility1
- G. C. Marten2,
- R. D. Goodrich3,
- A. R. Schmid4,
- J. C. Meiske3,
- R. M. Jordan3 and
- J. G. Linn5
Numerous chemical procedures have been suggested for predicting feeding quality of perennial forages but none have been adequately tested for their ability to predict quality of silages of corn (Zea mays L.) and sorghum [Sorghum bicolor (L.) Moench, S. sudanense (Piper) Stapf, and their hybrid]. The objective of this phase of a comprehensive study was to determine the value of 20 of these chemical procedures for predicting in vivo digestibility of corn and sorghum silages.
We determined in vivo digestible dry matter (DDM) of 51 silages (17 in each of 3 years) in conventional sheep feeding trials.
Acid detergent fiber (ADF) was the best chemical predictor of in vivo DDM for both corn and sorghum silages. ADF concentration accounted for 80% of the variation in digestibility of sorghum silages and 61% of the variation in digestibility of corn silages. More than half of the variation in digestibility of these silages was also accounted for by calculated cellulose and by crude fiber (CF) concentration. Permanganate lignin accounted for 74% of the variation in digestibility of sorghum silages but only 23% of the variation in corn silage digestibility. Inclusion of crude protein concentration did not improve the digestibility prediction potential of ADF, CF, or the other chemical methods.
The Van Soest summative equation, acid detergent lignin (ADL), ADL/ADF, dry matter solubility in 1 NH2SO4, and solubility in acid pepsin all failed to provide satisfactory estimates of corn or sorghum silage digestibility.
None of the chemical methods equaled our modified Tilley and Terry in vitro DDM as a predictor of in vivo DDM of corn or sorghum silages. However, ADF accounted for only 4% less of the variation in digestibility of sorghum silages and 9% less of the variation in digestibility of corn silages than did in vitro DDM. The relatively low cost of ADF analysis makes it a useful procedure for testing silages that are intended as feeds for ruminants.
We present simple regression equations for prediction of in vivo DDM of corn and sorghum silages from their concentrations of several chemical entities.Please view the pdf by using the Full Text (PDF) link under 'View' to the left.
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