Following are three graphs depicting data from Carl Hunt concerning the effect of grinding on in situ digestibility of corn silage. The data are for hybrids harvested at two stages of maturity (dent and black layer) with five different processing treatments prior to in situ determinations (undried-unground, dried-unground, dried-4ml grind, dried-3ml grind and dried-2ml grind). The digestion was for 24 hours with the procedure as described in "Unground In Situ Analysis" except that samples were hand washed after the digestion.

 Dry matter disappearance showed the trend observed in vivo only for unground samples.
 

Fiber digestibility was the opposite trend for ground and unground samples. Digestibility increased with sample maturity with grinding.
 

Starch disappearance was significantly lower for more mature samples when analyzed unground while only small differences were observed in ground samples.

These results are from one study and need to be repeated, but if verified, indicate problems with data from ground-sample digestion determinations for corn silage. It appears that the unground, in situ produces responses more similar to those observed in vivo. Of particular concern is the difference in fiber digestibility between ground and unground samples.