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

The in sacco protein and protein-free dry matter rumen degradability of thr ee feeds, concentrate, alfalfa hay and maize silage, was determined simulta neously in three animal species: four Mediterranean buffalo (Bubalus bubali s) bulls, four Friesian hulls and four Delle Langhe rams, which received fo ur 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 t hree 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 differenc es were found among the three species with regard to crude protein and prot ein-free dry matter rumen degradability for the three feeds, with the excep tion 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). Th e effective rumen degradability has also been calculated utilizing the theo retical 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 sp ecies was not affected by the use of experimental or theoretical k(1) for b oth effective crude protein rumen degradability of utilized forages and eff ective protein-free dry matter rumen degradability of maize silage. Two cor relations were considered: between degradation rate constant "c" and passag e rate constant "k(1)" of solid or fluid values as well as between the degr adable fraction degraded per unit of time "(b/100)"c" and passage rate cons tant "k(1)" of solid and fluid values. The largest number of significant va lues for crude protein was recorded in sheep and buffalo while largest numb ers were recorded in cattle for protein-free dry matter. (C) 2000 Elsevier Science B.V. All rights reserved.