Evaluation of low molecular weight fractions and crude enzyme preparation from a Trichoderma cellulase complex as a treatment for fibrous feeds

An experiment was conducted to evaluate effects of an enzyme filtrate or a crude enzyme preparation on in vitro disappearance of six common fibrous feeds being: alfalfa hay, brome grass hay, cottonseed hulls, soybean hulls, wheat bran and wheat straw. A commercial liquid feed grade enzyme product originating from a strain of Trichoderma reesei was used. To obtain filtrates, the crude enzyme preparation was filtered through membranes with molecular weight cutoffs of 5 and 10 kDa. Feeds were exposed to enzymes, filtrates, or a buffer, for 20 h. Filtrates and crude enzyme preparation were diluted in 12.5 mM sodium citrate buffer. In vitro fermentation followed treatment of the feeds for 24 and 48 h. Release of glucose and total monosaccharides was quantified following treatment of alfalfa hay and soybean hulls at 2 and 24 h, and release of phenolic monomers was measured at 24 h of incubation. For in vitro dry matter disappearance (IVDMD), treatment x time interactions occurred for alfalfa hay (P=0.01) and cottonseed hulls (P=0.04). Higher (P<0.01) IVDMD occurred at 48 h of incubation vs 24 h. The IVDMD of alfalfa hay and wheat bran was not affected by treatments. The crude enzyme preparation (CE) increased IVDMD compared to Ctrl for brome grass hay, cottonseed hulls, soybean hulls and wheat straw. Likewise, CE resulted in higher IVDMD than the 5 and 10 kDa treatments for the same feeds. Release of total monosaccharides from soybean hulls and alfalfa hay was higher (P<0.001) after 24 h than after 2 h of treatment. Although the 10 kDa treatment resulted in release of monosaccharides from soybean hulls, the greatest response was from CE after the 24 h treatment. Phenolics were released from alfalfa hay and wheat straw as a result of the treatments during a single 24 h incubation, with the biggest response from the 10 kDa and CE. When the enzyme complex from a commercial T. reesei enzyme product was partitioned by molecular weight and used as a treatment for brome grass hay, cottonseed hulls, soybean hulls and wheat straw, both the filtrates and the crude enzyme preparation increased IVDMD, with the crude enzyme preparation treatment causing the biggest IVDMD response. Release of monosaccharides and phenolics from the substrates also occurred as a result of the treatments. The addition of fungal enzymes or their subunits may prove a viable management opportunity to increase rumen digestibility of forages to enhance animal performance.