CHANGES IN ESTIMATES OF SILAGE DRY MATTER INTAKE OR APPARENT DIGESTIBILITY AS AFFECTED BY METHODS OF DM DETERMINATION

Abstract

Apparent digestibility coefficients and voluntary dry matter (DM) intakes by sheep fed 11 silages, comprising 3 corn, 4 legume-grass and 4 corn-hay crop silage mixtures, were estimated when silage DM content was determined by (1) toluene distillation (TD), corrected for volatiles lost into the aqueous distillate, (2) uncorrected TD, (3) freeze-drying (FD), (4) oven-drying (OD) at 40 C and (5) OD at 65 C. Highest nutrient digestibility and DM intake (P < 0.05) data were obtained by the method of corrected TD. DM intake and DM digestibility were underestimated by 7.4 and 12.0%, respectively, when oven-drying at 65 C was compared to corrected TD (P < 0.01). Digestibility coefficients and DM intakes were similar between FD and OD at 40 C. These results suggest that in vivo expressions of silage nutritive value should be based upon corrected TD for silage DM content and that biochemical determinations can be conducted on silage that has been oven-dried at 40 C.