Effect of fibrolytic enzymes on the nutritive value of tropical forages and performance of beef steer

Three experiments were conducted to evaluate the effect of applying fibrolytic enzymes to tropical forages on their nutritive value. An additional study investigated the effects of enzyme application on beef cattle performance. Experiment 1 determined the effects of using Depol 740L (D740) on the digestibility of three tropical forages. The enzyme was applied to 12-wk regrowths of Pensacola bahiagrass (BAH; Paspalum notatum ), Coastal bermudagrass (C-B; Cynodon dactylon) and Tifton 85 bermudagrass (T-B; Cynodon sp.) at rates of 0, 0.5, 1, 2, and 3 g/100g DM. The enzyme enhanced the chemical composition, in vitro dry matter digestibility (IVDMD), in vitro neutral detergent fiber digestibility (IVNDFD) and in situ degradability of the three hays, particularly the bahiagrass. Experiment 2 examined the effect of applying Depol 670L (D670) on the same forages as in Exp. 1. Enzyme D670 enhanced the initial phase of digestion of C-B and BAH, and slightly (2-4%) increased the extent of digestion of BAH and T-B. Experiment 3 evaluated the effects of the method of applying a commercial fibrolytic enzyme, Biocellulase A20 (A20), or ammonia to bermudagrass hay on the feed intake, digestion kinetics and growth performance of fifty Angus-Brangus steers. Five-week fall regrowth of bermudagrass was harvested and treated with either anhydrous ammonia (3 g/100g DM) or A20. The A20 was applied at the manufacturers recommended rate of 15 g/ton of hay immediately after harvesting (Ec), immediately before baling (Eb) or immediately before feeding (Ef). The hays were supplemented with cottonseed meal and soy hulls at 1% of bodyweight and fed to steers for 84 d. Ammonia and Ec treatment increased overall dry matter intake (DMI) but did not increase the DMI as a percent of BW, whereas Ec also increased neutral detergent fiber (NDF) intake, but none of the treatments increased the growth performance of the steers.;These experiments suggest that certain fibrolytic enzymes can improve the nutritive value of mature tropical hays but the response depends on forage species. An enzyme preparation was also found to be as effective as ammonia at increasing the quality of 5-wk regrowth of bermudagrass hay.