Purpose: Unground in situ may better estimate in vivo differences in corn silage than in situ or in vitro of ground samples due to destruction of natural physical barriers which repel microbial attack while grinding samples through a 1- or 2-mm screen.
 

Materials and Methods:
 

Weigh 80 g subsample of undried, unground substrates directly into the 25 by 30 cm (Ankom) nylon bags.
 

Dry subsample of the original silage at 55^o C for 72 h, grind to pass through a 1-mm screen, and analyze for dry matter.
 

Feed heifers once daily a diet consisting of 60% corn silage and 40% alfalfa on a DM basis. Incubate samples in quadruplicate in at least 2 heifers.
 

Remove bags after each of 24 h of ruminal incubation and. Rinse twice with machine washer (Cherney et al., 1990) and dry at 55^o C for 72 h. Weigh to determine DM disappearance.
 

Grind residue from combined bags from each sample to pass a 1-mm screen and analyze for starch, NDF and ADF.
 

Reference:
 

Cherney, D.J.R., J.A. Patterson, and R.P. Lemenager. 1990. Influence of in situ bag rinsing technique on determination of dry matter disappearance. J Dairy Sci 73:391-397.