EFFECTS OF DIFFERENT DRY MATTER DETERMINATION METHODS ON CHEMICAL COMPOSITION AND IN VITRO DIGESTIBILITY OF SILAGES

Abstract

Dry matter (DM) contents of 13 silages, comprised of 5 corn, 4 legume–grass, and 4 corn–hay crop silage mixtures, were determined by (1) toluene distillation (TD), corrected for volatiles lost into the aqueous distillate; (2) TD, uncorrected; (3) freeze-drying (FD); (4) oven-drying (OD) at 40 C; (5) OD at 65 C; and (6) moisture-tester at 100 C. Corrected TD showed significantly higher (P < 0.01) DM levels compared with other methods. Up to 12.8% loss of DM resulted from heat-drying, depending on the method and the sample. Dried-ground silages were analyzed for nutrient composition. No significant changes in cell-wall constituents or organic matter contents were observed. Silages that were FD were highest in cellulose content (P < 0.05), whereas both FD and OD at 40 C resulted in significant increases in gross energy (P < 0.05) and crude protein (P < 0.01) content compared with other methods. FD or OD at 40 C resulted in the highest dry matter solubility and in vitro digestibility of cellulose, dry matter, and organic matter (P < 0.05). The lowest values for these analyses were obtained with silages heat-dried at 65 and 100 C. Results of these studies suggest that corrected TD should be used for determination of silage DM content and that in vitro analyses or other biochemical determinations should be conducted on silage samples that have been freeze-dried or oven-dried at 40 C.