PREDICTION OF THE DIGESTIBLE CRUDE PROTEIN AND PROTEIN DIGESTIBILITY OF FEED INGREDIENTS FOR RABBITS FROM CHEMICAL-ANALYSIS

Ninety-five data of individual feedstuffs, for which information on ch emical analyses and crude protein digestibility (CPD) was available, w ere subject to sequential multiple linear regression analysis employin g CPD and digestible crude protein (DCP) as dependent variables and ch emical analysis as independent variables. The feedstuffs were classed separately into dry forages (n = 26), cereals and cereal by-products ( n = 29), protein concentrates (n = 18) and by-products (n = 22) groups . The procedure followed in each of the groups was to utilize: (1) the feedstuffs in which the Van Soest fiber and the Weende analysis were simultaneously available, and (2) all feedstuffs with data of the vari ables selected in the first step. The CP content was the best single p redictor of the DCP content of feeds, the best equation in terms of R- 2 was obtained in the total group: DCP (g kg(-1)) = -34.67 + 0.876 x C P (g kg(-1)), R-2 = 0.948, RSD = 7.36, n = 93. The addition of the ash content to sequential analysis improved the accuracy of DCP predictio n, increasing the R-2 up to 0.960. Acid detergent fiber was the second independent variable selected in the cereals and by-products groups, the R-2 Obtained was, respectively, higher (0.969) and lower (0.895) t han that of general equation. The correlations among the independent v ariables employed and CPD were low. Only when in the total group the n itrogen linked to acid detergent fiber (N-ADF) measurement was include d as independent variable (n = 11) a high R-2 (0.905) was obtained. Th e N-ADF content that included the heat-damaged protein and the nitroge n associated with lignin could be adequate to estimate the indigestibl e protein content of feeds. However, more data points would be necessa ry to confirm its accuracy, taking into account the non-uniformity in the distribution of current data. (C) 1998 Elsevier Science B.V.