Nutrition and feeding aspects of the utilization of processed lignocellulosic waste materials by animals

Abstract

Lignocellulosic wastes are a major underutilized resource. To convert them into useful feeds, processing in some form is usually required to enhance the rate and/or extent of digestion and to increase daily intake.

Mechanical processing, such as grinding and pelleting, usually increases daily intake but decreases digestibility of the dry matter. The response to mechanical processing are generally greater with low-than with high-quality forages and with smaller, younger animals than with larger, older ones. This is attributed to the greater degree of comminution necessary before the residue will pass from the reticulo-rumen of the smaller animals. However, improved protein status of animals fed mechanically processed wastes may contribute to the higher daily intakes because more dietary protein escapes rumen fermentation.

Chemical processing is necessary to produce useful feed from some highly-lignified wastes. NaOH and NH₃ have been the most extensively investigated chemicals and both are used commercially for improving the nutritive value of low-quality forages. NaOH treatment often shows a greater increase in digestibility when evaluated byin vitro procedures than when evaluated in vivo, particularly at higher levels (over 5%) added NaOH. This is probably due to physiological effects of the high level of Na, as diluting the treated material with other feed often improves the apparent digestibility. Variations in the composition of the starting material and in treatment conditions, especially with NH₃, can affect the results from chemical treatment. Adequate supplementation with protein, minerals and vitamins are required for optimum levels of production from animals fed chemically treated lignocellulosic wastes.

Considerable research is underway to find practical ways of using microbial processes to improve the nutritive value of lignocellulosic wastes. While several approaches are promising, none has yet reached widescale commercial application.

Most of the research on processing lignocellulosic wastes has been done with straws, stover and low-quality forages and to a lesser extent with forest industry wastes. Other wastes exist in all parts of the world which could be improved in nutritive value by processing. The development of practical procedures for treatment could greatly increase the world supply of food from animals.