ChileanJAR

A previous papel (Chapter 1) examined the faetors affeeting the voluntary consumptíon ai sllage. The present knowledge on the two other components of nutriuve value (digestion and efficiency of utilization) is reviewed here, particularly comparíng silage with the original forage fed fresh or conserved as hay or by artilficíal dehydration.
The dígestibility of ensiled forages depends mainly on the digestibility of the original crop. The process of forage fermentation during ensiling may significantly influence the digestibility of the ensiled material. This effeet will depend on the characteristies of the fermentation process. Digestibility of the dry matter of silage is often reduced, although the magnitude of this effect is variable.
The effect of wilting the forage and the use of additives prior to ensiling upon digestibility of ensilage is not clear and more information is needed to clarify this point.
The utilization of energy is a complex process, with several diet and animal factors playing an important role. Information on the efficiency of utilizatian of energy obtained from calorimetric studies or by the comparative slanghter teehnique is limited. Different laboratories have often studied only one or two of the variables involved in the utilization of digestible and metabolizable energy of silage for maintenance and productive purposes, and the results obtained have been variable. From these rectrieted data it is not possible to obtain a complete understanding of the factors which have given rise to the variable results in published experiments. The nature of rumen fermentation appears not to differ markedly for animals fed silage, fresh forage or hay, and this factor will probably play a less important role on differences in effieiency of utilization of metabolizable energy between types of forage. Differences in mastication activity between these types of feed allows speculation on a possible negative influence by this concept upon the effi