The effect of an exogenous fibrolytic enzyme on forage digestibility parameters

[摘要] ENGLISH ABSTRACT: The ruminant has the ability to utilize forages more efficiently than any otherproduction animal. The utilization of forage fibre is an important aspect of ruminantproduction systems, as this is the main source of energy available to the animal. Theavailability of high-fibre forage nutrients is, however, restricted by cell walldegradability, and since low quality forages contribute a great deal to ruminantproduction systems worldwide, the improvement of this degradation process is ofmajor economic importance.The use of exogenous fibre degrading enzymes has been proposed as a means ofenhancing this process, with positive results being obtained from in vitro studiesincorporating exogenous enzyme preparations. Positive in vivo results with regard toforage digestibility and other animal production parameters have consequently alsobeen obtained following the addition of exogenous fibre-degrading enzymepreparations to the ruminant diet.Two initial screening experiments were undertaken in order to identify fungal enzymepreparations that may have a positive effect on in vitro fibre degradability. The initialscreening employed an in vitro organic matter digestibility technique, and wassuccessful in identifying at least six enzyme preparations displaying enhanceddigestibility results that were statistically significant. A second in vitro gasproduction procedure was used to confirm results obtained from organic matter digestibility assays, as well as to increase screening capacity in order to evaluate newenzyme preparations more time-efficiently. Statistical analysis of results obtainedfrom the secondary screening identified various enzyme candidates producingpromising results. Only one of these, Abo 374, proved to be statistically superior tothe control and other enzyme preparations.A growth trial was subsequently conducted to assess the performance of this enzymein vivo. The trial involved individual feeding of 32 Dohne Merino ram lambs groupedaccording to weights into four groups consisting of 8 lambs each. Each grouprepresented a specific application level of enzyme to the wheat straw component of ahigh fibre diet, amounting to 10, 5, or 1 ml enzyme supematant/kg straw. Theenzyme was diluted with water at appropriate rates to obtain an application rate of300ml/kg straw. The fourth (control) group was treated with water at the sameapplication rate. The trial was conducted over a period of six weeks, during whichfeed intakes, weekly weight gains, as well as feed conversion efficiencies wererecorded. Results suggested significant weight gains in the high (10ml/kg) andmedium (5ml/kg) treatment groups, indicated by a P-value of 0.04. Similarly, feedconversion efficiencies were improved for above-mentioned groups (P=0.05), whilefeed intakes did not differ significantly between the four experimental groups.

[发布机构] Stellenbosch University