**5. Alternatives to improve intake and digestibility of silages**

### **5.1. Use of biological additives**

The use of inoculants, especially lactic acid bacteria (LAB), is in an attempt to improve the efficiency of preserving the nutritional quality of the forage. In a review of experiments with inoculants, researchers found positive results for improving the feed intake, fed efficiency and milk production by about a third of the studies review; it is justifying the use of inoculants on silage also the effect on animal performance [34].

Some studies suggest a possible effect of LAB probiotics, although the mechanisms are unclear. Probiotics is a live microorganism in the food supplement that beneficially affects the host animal by improving intestinal balance [37]. One hypothesis is that specific strains of LAB interact with microorganisms of the rumen improving their function and animal performance [38–40]. Researchers found that LAB from silage inoculants could survive in rumen fluid for at least 96 hours, which would allow the probiotic activity [41].

Although the effects of LAB inoculant are not well studied, there may be still, the action of a type of bacteriocin that limits the bacterial activity, which can inhibit or harm the microorgan‐ ism in the rumen [39, 40]. Bacteriocins are biologically active proteins produced by LAB that are active against other bacteria, mainly grampositive bacteria as *Listeria monocytogenes* [42]*.* In an experiment, Amado et al. [42] observed that bacteriocin producing strain inhibits the activity of other undesirable microorganisms in silage.

Recent studies demonstrate that some heterofermentative bacteria [*Lactobacillus buchneri*, for example] produce ferulate‐esterase, enzyme that increases the degradation of the cell wall. This enzyme release considerable soluble carbohydrates for fermentation or for use by rumen bacteria [43].

An enzyme‐bacterial inoculant acts in two forms in silage: whereas bacterial inoculants improve fermentation profile and increase lactic acid bacteria population, enzyme inoculants act on the cell wall and the available higher quantity of soluble compounds, with improvement in silage digestibility [44].

Researchers study the effect of inoculants on silage, rumen function and digestibility. They found improvements in DM and NDF digestibility after 24 hours of incubation [38]. Others studies also found higher DM and NDF digestibility in inoculated corn silage than untreated silage [39].

Although there are some positive results, in the experiment realized by Fugita et al. [42], the addition of enzyme‐bacteria inoculants do not significantly influence nutrient intake, per‐ formance and carcass characteristics of feedlot finished crossbred bulls.

The use of microbial additives in sorghum silage resulted in positive responses to the hemi‐ cellulose content and value on *in vitro* DM digestibility. The lower hemicellulose content of the silage treated compared to control may result from the action of enzymes associated with bacteria, and the greater IVDMD found may reflect the enzymatic hydrolysis effect [45]. However, it has been reported that the effects of LAB inoculants on fiber degradation are not consistent [18] as LAB cannot use fiber as an energy source [46]. The hemicellulose degradation by LAB inoculation is inhibited in lower environmental temperature, requiring optimum temperature for its activity [47].

### **5.2. Use of chemical additive**

The exposure to air of silages affects the silage digestibility. The effects of air on silage can reduce the digestibility (**Table 5**). Sugarcane silage show lower digestibility than fresh sugarcane, and after 3, 6 and 9 days of exposure to air, sugarcane silage has reduced 7.20% of *in vitro* digestibility (IVD) and 2.7% true *in vitro* digestibility (TIVD). This reduction can be avoided or minimized by adequate ensiling management procedures and storage of silage, in

**IVD (%DM) TIVD (%DM)**

addition, to the use of additives.

112 Advances in Silage Production and Utilization

*Source:* Adapted from Balieiro Neto et al. [8].

**5.1. Use of biological additives**

**Table 5.** Effect of exposure to air on silage digestibility.

silage also the effect on animal performance [34].

at least 96 hours, which would allow the probiotic activity [41].

activity of other undesirable microorganisms in silage.

**Crop Digestibility**

Sugarcane 63.9 66.5 Sugarcane silage 59.7 62.1 Sugarcane silage (d3) 57.5 58.7 Sugarcane silage (d6) 54.5 58.3 Sugarcane silage (d9) 55.4 59.4

**5. Alternatives to improve intake and digestibility of silages**

The use of inoculants, especially lactic acid bacteria (LAB), is in an attempt to improve the efficiency of preserving the nutritional quality of the forage. In a review of experiments with inoculants, researchers found positive results for improving the feed intake, fed efficiency and milk production by about a third of the studies review; it is justifying the use of inoculants on

Some studies suggest a possible effect of LAB probiotics, although the mechanisms are unclear. Probiotics is a live microorganism in the food supplement that beneficially affects the host animal by improving intestinal balance [37]. One hypothesis is that specific strains of LAB interact with microorganisms of the rumen improving their function and animal performance [38–40]. Researchers found that LAB from silage inoculants could survive in rumen fluid for

Although the effects of LAB inoculant are not well studied, there may be still, the action of a type of bacteriocin that limits the bacterial activity, which can inhibit or harm the microorgan‐ ism in the rumen [39, 40]. Bacteriocins are biologically active proteins produced by LAB that are active against other bacteria, mainly grampositive bacteria as *Listeria monocytogenes* [42]*.* In an experiment, Amado et al. [42] observed that bacteriocin producing strain inhibits the Additives in silage can affect the DM intake and intervene in the nutritive value of silage, as digestibility of nutrients. Chemical additives are substances that act in the control of biochem‐ ical reactions of silage. The inhibitor additives function without distinction in all processes in the silage acting on undesirable microorganisms and fermentations, as the secondary proteol‐ ysis or aerobic growth. Among the main additives chemical inhibitors there are urea [48], propionic and formic acid.

Urea is an additive that contains between 42 and 45% of nitrogen [48], commonly used in fodder ammonization due to ease of application, not a pollutant, but as a source of non‐protein nitrogen, reduce the fibrous portion of forage (NDF), favor the partial solubilization of hemicelluloses, influence the increase in intake and digestibility of silage [49]. According to the classification McDonald et al. [4], urea is also a nutrient additive because it improves the nutritive value of silage.

Researchers showed the increase in the protein content of silage as result of high recovery of nitrogen applied and may reach up 77% recovery [50]. Nitrogen recovery is a positive feature of urea from both the nutritional and economical aspect. Urea also acts beneficially in the fibrous portion of the ensiled forage. Two main processes occurring in ammoniated forage mass with urea: ureolysis and ammoniolysis.

The inhibition of undesirable microorganisms in silage (able to realize proteolysis) reduced the adverse compound formation. The decrease in ammonia and butyric acid in TMR silage is

Intake and Digestibility of Silages http://dx.doi.org/10.5772/65280 115

Besides propionic acid, formic acid is an inhibitor of undesirable fermentation. Selwet [55] evaluated the effects of different levels of mixtures of formic and propionic acid on changes in the chemical composition and on aerobic stability of maize silages exposed to air during the

The results showed that the inclusion in maize silages of the propionic and formic acid mixture reduced undesirable microorganisms and positively influenced the changes in silage chemical composition. Silages treated with acids were characterized by higher dry matter, WSC and crude protein concentration, which could have been associated with the smaller losses of nutrients due the limitation of development of some groups of microor‐

Concentrations of acetic acid in additive silages were also decrease. The author concluded that this result is a favorable phenomenon because high concentration may limit feed intake by

In an experiment, Kung et al. [56] tested different mixtures of preserving agents such as acetic and propionic acid and ammonia on the intake and digestibility of lactating cows fed TMR silages. The TMR were composed of alfalfa silage (27%), corn silage (43%) and pelleted

There was no significant difference between the dry matter intake, daily milk yield, fat and milk protein in dairy cows fed on untreated TMR and TMR treated with chemical additive after exposure to air. Although this study found no difference between the performances of dairy cows, other tests reported that feed intake by sheep was negatively affected after silage

The use or not of a chemical or biological additive does not dispense the necessary care during the fermentative process of ensiling, because the quality of silage is directly related to species of plant, sol fertility, cultural tracts, ensiling point, compaction and sealing of silo, since only the additive does not match a considerable increase in silage quality produced

The ensiling process is complex and yields a variety of end‐products of fermentation. These products can influence directly and indirectly the intake and digestibility of silage. Some control mechanisms of this fermentation can be of use for improvement on intake and

exposure to air for 5 days, when compared with fresh corn silage [56].

desirable because these compounds may affect food intake in the ruminants.

process of feeding to animals.

concentrate (30%), and additives.

**6. Final considerations**

ganisms [55].

animals.

[48].

digestibility.

The ureolysis process is an enzymatic reaction that release ammonia through hydrolysis of urea. The ureolytic bacteria produces urease [an enzyme catalyst present in plants], that acts in the presence of moisture hydrolyzing the urea and producing two ammonia molecules [which acts directly on the cell wall of forage] and one carbon dioxide [48, 51].

From the urea hydrolysis occur chemical reaction ammoniolysis between the ammonia and the ester bonds existing between chains of hemicelluloses and between groups of carbohy‐ drates or carbohydrate molecules and lignin, resulting in formation of an amide [52]. The ammoniolysis cause lysis on bonds between the structural carbohydrates releasing and increasing the contact surface to the rumen microorganisms [53].

In addition, there is another important factor to consider, ammonia has a high affinity for water resulting in the formation of weak base, ammonium hydroxide [NH4OH]. The high affinity of ammonia to water promotes expansion and rupture of the cell wall components of tissues of forage treated with urea. Through specific studies using electron microscopy, change of cell wall can be seen [49].

Another chemical additive, propionic acid is used as antifungal agent able of preserve forage for much time. It inhibits undesirable microorganisms and improves the aerobic stability of silages [54].

In an experiment test, Chen et al. [54] evaluated the effects and propionic acid applied on the fermentation quality and aerobic stability of total mixed ration silage (TMR) prepared with whole‐plant corn in Tibet. They applied 0.4% propionic acid on a fresh matter basis of TMR, and found higher WSC concentration (88.92 g/kg DM) and decrease in butyric acid content (0.04 g/kg DM) in TMR after 45 days of ensiling, comparative to no additive TMR (WSC = 39.99 g/kg DM; butyric acid content = 0.19 g/kg DM). In aerobic stability assay, TMR silage with propionic acid showed low pH, higher WSC concentration and lower ammonia content than no additive TMR silage after 12 days of air exposure (**Table 6**).


**Table 6.** Chemical characteristics of total mixture ration silages (TMR) at opening silo and after exposure to air.

The inhibition of undesirable microorganisms in silage (able to realize proteolysis) reduced the adverse compound formation. The decrease in ammonia and butyric acid in TMR silage is desirable because these compounds may affect food intake in the ruminants.

Besides propionic acid, formic acid is an inhibitor of undesirable fermentation. Selwet [55] evaluated the effects of different levels of mixtures of formic and propionic acid on changes in the chemical composition and on aerobic stability of maize silages exposed to air during the process of feeding to animals.

The results showed that the inclusion in maize silages of the propionic and formic acid mixture reduced undesirable microorganisms and positively influenced the changes in silage chemical composition. Silages treated with acids were characterized by higher dry matter, WSC and crude protein concentration, which could have been associated with the smaller losses of nutrients due the limitation of development of some groups of microor‐ ganisms [55].

Concentrations of acetic acid in additive silages were also decrease. The author concluded that this result is a favorable phenomenon because high concentration may limit feed intake by animals.

In an experiment, Kung et al. [56] tested different mixtures of preserving agents such as acetic and propionic acid and ammonia on the intake and digestibility of lactating cows fed TMR silages. The TMR were composed of alfalfa silage (27%), corn silage (43%) and pelleted concentrate (30%), and additives.

There was no significant difference between the dry matter intake, daily milk yield, fat and milk protein in dairy cows fed on untreated TMR and TMR treated with chemical additive after exposure to air. Although this study found no difference between the performances of dairy cows, other tests reported that feed intake by sheep was negatively affected after silage exposure to air for 5 days, when compared with fresh corn silage [56].

The use or not of a chemical or biological additive does not dispense the necessary care during the fermentative process of ensiling, because the quality of silage is directly related to species of plant, sol fertility, cultural tracts, ensiling point, compaction and sealing of silo, since only the additive does not match a considerable increase in silage quality produced [48].
