Protein and protein-free dry matter rumen degradability in buffalo, cattle and sheep fed diets with different forage to concentrate ratios

The in sacco protein and protein-free dry matter rumen degradability of three feeds, concentrate, alfalfa hay and maize silage, was determined simultaneously in three animal species: four Mediterranean buffalo (Bubalus bubalis) bulls, four Friesian hulls and four Delle Langhe rams, which received four diets differing in forage:concentrate ratio (1 = 87.5:12.5; 2 = 75.0:25.0; 3 = 62.5:37.5; 4 = 50.0:50.0) at the level of 50 g DM/kg(0.75) per day. The three feeds, which composed the four diets, were incubated in the rumen for 0, 2, 4, 8, 24, 48 and 72 (120 only for hay) hours. The solids passage rate values k(1), utilized to compute the effective degradability of the three feeds, were: 2.80, 2.42, 2.39 and 2.24 g/100 g h(-1) for buffalo; 3.57, 2.82, 2.86 and 2.67 g/100 g h(-1) for cattle; 3.07, 2.88, 2.84 and 2.57 g/100 g h(-1) for sheep, obtained with the four diets. Significant differences were found among the three species with regard to crude protein and protein-free dry matter rumen degradability for the three feeds, with the exception of alfalfa hay for the last parameter. The lowest values were recorded in cattle and sheep compared to buffalo (crude protein rumen degradability: 58.8 and 62.8 vs. 64.8 g/100 g concentrate, 57.0 and 56.4 vs. 62.7 g/100 g hay, 58.7 and 60.7 vs. 68.6 g/100 g maize silage; protein-free dry matter rumen degradability: 64.1 and 69.0 vs. 70.0 g/100 g concentrate, 48.2 and 48.5 vs. 49.2 g/100 g hay; 56.0 and 58.6 vs. 64.8 g/100 g maize silage). The effective rumen degradability has also been calculated utilizing the theoretical passage rate constants (k(t) = 3 g/100 g h(-1) for forages and k(1) = 6 g/100 g h(-1) for concentrate); the estimation of differences among species was not affected by the use of experimental or theoretical k(1) for both effective crude protein rumen degradability of utilized forages and effective protein-free dry matter rumen degradability of maize silage. Two correlations were considered: between degradation rate constant "c" and passage rate constant "k(1)" of solid or fluid values as well as between the degradable fraction degraded per unit of time "(b/100)"c" and passage rate constant "k(1)" of solid and fluid values. The largest number of significant values for crude protein was recorded in sheep and buffalo while largest numbers were recorded in cattle for protein-free dry matter. (C) 2000 Elsevier Science B.V. All rights reserved.