Eficiencia predictiva de la digestibilidad enzimatica para estimar la digestibilidad in vivo de la materia organica de forrajes en diferentes estados de desarrollo.
1993
Alvarez G Maria Loreto
The objective of this research was to assess the predictive efficiency of tested enzymatic methods for estimating the organic matter (OM) in vivo digestibility (Do) of alfalfa, wheat and annual natural pasture from the onset of growth or annual regrowth until maturity. Either 20 or 24 samples of each crop were taken from material previously subjected to an in vivo digestibility trial. Additional determinations were enzymatic digestibility of OM (Do) utilizing two commercial enzymes (Rs and R10), in vitro digestibility according to Tilley and Terry (Di), total N content, OM, acid detergent lignin (Li), hemicellulose (He), neutral detergent fiber (NDF), acid detergent fiber (ADF), cellulose (Ce) and silica (Si). The results obtained were used to calculate step by step regression equations so as to obtain an equation predicting Do. When the determination coefficient (R2) was low, the outliers (points which were farthest from the curve) were eliminated and the R2 improvement level was analyzed. The results indicated that, in general, none of the methods proved satisfactory for alfalfa, the R2 values obtained not exceeding 0.40 (P>= 0.05). Neither the elimination of outliers nor the incorporation of more variables improved prediction. The most efficient equation was Do = 171.84 - 1.13 De - 1.57 Li R2 = 0.26 P0.03. For natural pastures, the predictive efficiency of the methods used was somewhat better, the best equation being Do = 69.76 - 0.60 FDN + 1.39 Ce R2 = 0.62 P = 0.01. For wheat, the enzymatic method proved a good prediction of Do, equations obtained being of type Do 11.84 + 0.94 DeRs R2 = 0.98 P<= 0.001. For both alfalfa and natural pasture, there exists a better prediction when the enzymatic method utilizes the R10 enzyme instead of the Rs enzyme. For the three forages studied, Do prediction with the enzymatic method is better than with the in vitro technique of Tilley and Terry.
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