DEGRADABILITY CHARACTERISTICS OF DRY-MATTER AND CRUDE PROTEIN OF FORAGES IN RUMINANTS

Twelve corn silages, 22 grass silages and 14 grass hays, obtained from various farms located in the lower Eraser Valley region of British Co lumbia, and 16 alfalfa hays, grown primarily in the Columbia basin of central Washington State, were evaluated using both the rumen and the mobile nylon bag in situ techniques, Nylon bags containing each forage were incubated in duplicate for 0, 2, 4, 8, 12, 24, 48, 72, or 96 h i n two of six non-lactating Holstein cows fitted with rumen and duodena l cannulae, All forage types were evaluated in terms of the following dry matter (DM) and crude protein (CP) digestion characteristics: solu ble fraction A, degradable fraction B, degradation rate, lag phase, an d effective degradability, The mobile nylon bag technique was used to determine intestinal disappearance of DM and CP from the forages follo wing pre-incubation in the rumen for 12 h, Significant (P < 0.05) diff erences in degradation characteristics occurred within all forages wit h regard to the soluble and potentially degradable DM and CP fractions , Soluble CP content in the rumen varied from 44.08 to 75.37% and from 18.74 to 65.38% in the corn and grass silages, respectively, and from 48.27 to 75.43% and from 30.13 to 65.95% in the alfalfa and grass hay s, respectively, Significant differences within each forage type were also observed for the degradable CP in fraction B: 10.89 to 45.28% for corn silage, 20.72 to 82.77% for grass silage, 16.67 to 44.88% for gr ass hay and 25.44 to 62.93% for alfalfa hays, Significant differences (P > 0.05) were observed in fractional rates of ruminal DM degradation of the grass hays and corn silages. Significant differences did exist in the fractional rates of ruminal CP degradation within ail forage t ypes with the exception of alfalfa hays, Effective degradabilities of DM and CP were also significantly different between samples of a parti cular forage type. The mobile nylon bag data indicated that approximat ely 20% of the original CP in the grass silage, grass hay and alfalfa hay samples disappeared in the intestine and that there was significan t variation between individual samples. On average, in the corn silage samples more than 10% of the original nitrogenous material disappeare d in the intestine. The results presented in this study clearly demons trate that the use of tabulated values for describing individual batch es of forages in terms of their degradability characteristics is inacc urate since they may not reflect the particular forage being used in t he ration and thus may lead to errors in diet formulation.