**6. Conclusion**

NDFD. Moreover, they found that the inoculation of four corn silage hybrids with a combination of *L. buchneri* and *L. paracasei tolerans* enhanced NDFD by 7% [112, 113]. Several studies have confirmed that esterase enzymes can complement the effects of cellulose and hemicellulase enzymes on plant cell walls, thereby increasing DM or fiber digestibility [114]. Conversely, some studies have reported no effect from adding ferulic acid esterase-producing inoculant on fiber digestibility of silage [115]. Kang et al. reported an enhancement in fiber digestibility when corn hybrids were treated by a third-generation inoculant [116]. The author suggested these effects to the properties of the forage to which they are applied. Other studies have reported improvements in digestibility and steers performance fed barley silage treated with

There is increasing interest in using exogenous enzymes as a cost-effective method for improving animal productivity. The main enzyme products marketed for livestock are derived mainly from only four bacterial (*Bacillus subtilis*, *L. acidophilus*, *L. plantarum*, and *Streptococcus faecium*) and three fungal (*A. oryzae*, *T. reesei*, and *Saccharomyces cerevisiae*) species. Other fungal species, including *Humicola insolens* and *Thermomyces lanuginosus*, are being marketed to a lesser extent [119]. Several studies have confirmed that the addition of enzymes to feeds can

DMI (kg/day) 7.13 7.05 0.40 Average daily gain (kg) 1.43 1.41 0.70 Gain: feed DM ratio 0.20 0.20 0.65

DMI (kg/day) 7.6 7.1 0.02 Average daily gain (kg) 1.29 1.31 065 Gain: feed DM ratio 0.17 0.19 0.02

**Table 5.** Effects of silage inoculants on feedlot steers performance fed whole-crop barley silage diets inoculated or

Exogenous feed enzymes with fibrolytic activities have been reported to enhance fiber digestion in the rumen [121, 122]. Most of the commercial products that have been investigated in dairy cows have had cellulases and xylanases activates, with proteases and amylases being tested in a minor number of studies. **Table 5** showed some studies that have been performed in dairy cows fed TMR supplemented with enzymes that were characterized by cellulase and/ or xylanase activities. It appeared that the preparations of the current enzyme do not introduce novel enzyme activity into the rumen as they finally increase only the rate and not the extent of digestion of the cell wall [123, 124]. Beauchemin et al. reported that DMI would increase by

*Uninoculated Inoculated P-value*

a third-generation inoculant (**Table 2**) [117, 118].

136 Advances in Silage Production and Utilization

**5.5. Using enzymes to enhance fiber utilization**

increase DMI and fiber digestibility [120].

uninoculated using first and third generation.

*First generation*

*Third generation*

Silage contains a high content of neutral detergent fiber. Even under optimum conditions, NDF digestibility in the rumen is frequently less than 50%. Improving ruminal fiber degradability could allow cattle to consume more feed and hence increase milk yield. Selecting forage with higher NDFD could be a practical approach to increasing digestible carbohydrate and feed intake in dairy cattle. Ferulic acid-producing bacteria that are targeted at breaking the bonds between ferulic acid and hemicellulose could be the key to increasing fiber digestibility in ruminants. Addition of enzymes to feeds would increase NDFD. However, responses to feed enzymes are expected to be greatest in situations where digestible energy is the first limiting nutrient in the diet.

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