Agronomic Factors in Evaluating Forage Crops I. Predicting Quality Measures of Crude Protein and Digestibility from Crop Leafiness

Abstract

Stage‐to‐stage changes in leaf percentage, crude protein concentration and in vitro true disgestibility of alfalfa herbage materials of the same age and common harvest dates across there different growing season were determined. Leafiness decreased with advancing crop maturity. Herbage leaf content was closely associated with the total herbage C P and IVTD. When leaf percentage was regressed on quality measures of C P and IVTD, the regression analysis provided highly significant linear relationship for CP(r2= 0.823), IVTD (r2= 0.854) for alfalfa crop diverse in stand and canopy ages, stages of maturity and across locations and seasons of the year. These relationships indicated practical applicability of the use of crop leafiness for predicting the herbage quality.

Agronomic Factors in Evaluating Forage Crops II. Predicting Fiber Components (NDF, ADF, ADL) from Crop Leafiness

“…Combined data setts of 1980 and 1981 did not significantly affect both the coefficients of determination and the maximum REMS of 2.7 for NDF, 1.9 for ADF and .8 for ADL. These were comparable with the predictive capability of the mean stage (MSW), system of KALU and FICK . (1983) where the max-imum REMS were 2.2 for NDF, 2.4 for ADF, and .8 for lignin (Table 3) when the data from the two years were similarly combmed.…”

“…The mean stage by weight (MSW) System of KALU and FICK (19S1, 1983) has been tested to be a robust procedure for predicting quality components of CP, IVTD, NDF, ADF, and ADL. Predictive equations for these have been provided elsewhere by KALU and FICK (1983) and KALU et al (1988). For fiber components, MSW accounted for 95 %, 90 %, and 84 % of the variability in alfalfa NDF, ADF, and ADL respectively (KALU and FICK 1983).…”

“…The experimental design, and the sampling procedure of sequential harvesting for obtaining stands of different ages and stages of maturity at common harvest dates were the same as those described by KALU andFICK (1981, 1983). The numerical stage classification system of KALU and FlCK (1981) was used for separating the herbage materials into morphological stage categories designated as the stage numbers.…”

“…Such an understanding would facilitate good predictive estimates to be made of nutritional quality. For the alfalfa (Medicago sativa L.) crop, the prediction of quality measures of crude protein (CP), digestibility, and fiber components (Neutral detergent fiber, NDF; Acid detergent fiber, ADF; and Acid detergent Lignin, ADL) have been developed from morphological characters of the crop and from weather data (KALU and FiCK 1981, KALU 1982, KuHBAUCH 1983, FICK and ONSTAD 1983, 1988, FICK 1984, KALU et al 1988). The ap-proaches considered the known effects of environmental variables on growth, development and maturity of the crop especially the alterations in morphological characters and chemical composition.…”

“…From the available reports, most affected are crude protein, digestibility and fiber components. For example, high concentration of CP and in vitro true digestibility (IVTD) and low fiber were associated with enrichment by high leaf proportions of the total herbage of low mean stage values while poor quality was associated with loss of leaves on old materials with high mean stage values (KALU andFICK 1983, KALU et al 1988). The significance of leaf percentage in a total herbage could be seen from the magnitude of leaf loss as maturity progresses.…”