ROLE OF BIOLOGICAL ADDITIVES IN SILAGE PRODUCTION FOR IMPROVING FORAGE NUTRIENTS CONSERVATION AND DIGESTIBILITY FOR RUMINANTS NUTRITION

The general aim of this thesis was to study the effect of lactobacillus inoculants and exogenous fibrolityc enzymes on ensiled forages. The thesis includes the results of three experiments. The first experiment investigated the effects of a microbial inoculum containing homofermentative lactobacillus (hoLAB) ( a strain of Pediococcus pentosaceus and a strain of Lactobacillus plantarum) as maize silage additive, alone (L) or in combination with a pool of fibrolityc enzymes (LE) in comparison with untreated silage (C) on fermentative profile at 2, 5, 40 and 110 days of ensiling, dry matter (DM) losses at the same time points, and multiple points in vitro Gas Production (GP) after 110 days of ensiling. Results evidenced that, the hoLAB inoculant and hoLAB+ enzymes treatments determined a significant effects relative to a shifting of silage fermentation: reduced pH, increased lactic acid concentration and decreased ethanol production; dry matter recovery was also positively affected by the treatments. hoLAB inoculum is also able to affect the rumen fermentability of the silage increasing the potential GP and the fractional rate of gas production during in vitro test. The addition of fibrolytic enzymes to hoLAB inoculant seems instead to inhibit this capacity to increase GP. The second study was performed relative to whole crop cereals silages: in a first part of this study we determined fermentative profile, DM losses, chemical composition, in vitro dry matter digestibility (DMD) and neutral detergent fibre digestibility (NDFD) and in vitro GP of whole crop silages made from wheat (var. Artico and var. Sollario) , triticale (var. Magistral) and wheat–barley-triticale mixture (WesternTM) harvested at two different maturity stages (Early vs Late). In the second part the aim was relative to determine the effects, on the same parameters of the first part, of the addition at ensiling of an inoculum of lactobacillus and fibrolitic enzymes mixture on a selected wheat ( var. Artico) harvested at two different maturity stage in comparison with the untreated silage (C). All forages resulted well preserved. Neutral Detergent Fibre (NDF) content was influenced by maturity stage and crop. NDFD was reduced with increasing of maturity stage (50.5 vs 45.0%, P<0.001). Gas production (GP) at 8 h of incubation was positively influenced by maturity stage (P<0.001), showing a linear relationship with starch content. Inoculum addition reduces dry matter losses during the ensiling period, and seems to slightly reduce the fibre fractions. The significantly higher GP value at 8 h at early stage suggests a release of carbohydrates from fibre fraction to a fraction with higher degradability. From this point of view further investigations would be desirable in order to better clarify the action of the inoculum of lactobacilli and fibrolytic enzymes on the fibre components of the ensiled crop. The third experiment was conducted to investigate the effect of a lactobacillus inoculum (containing a blend of Lactobacillus plantarum , Pediococcus pentosaceus and Lactobacillus brevis) or, two different pool of exogenous fibrolityc enzymes (conteining different concentration of ß-glucanase, Cellulase, Mannanase e Xylanase), alone or in combination, on fermentation characteristics, in situ NDF degradability and in vitro OM Gas production of two maize stove silage harvested at different stage of maturity. The corn plants without cobs were harvested at two different stages of physiological maturity (dought and advanced dought) in order to test the action of the treatments on two fibrous matrices with a supposed diversity of fiber degradation due to the different degree of lignification (High vs. Low). The ensiling of two different fibrous matrices has been done in 2 liters microsilos from, which were then stored at controlled temperature for 110 days. The primary effect of all the treatments was in modifying the fermentative profile of the silages after 110 days of incubation, specially increasing the lactic acid concentration and reducing the ethanol production . In addition, in vitro ruminal fermentation indicated that LAB have a potential for increasing gas production, whereas this is not the case of enzymes treatments. The combination of LAB and enzymes resulted in an higher GP than control only for the highest dosage of enzymes, but without any benefit compare to LAB treatment. Results suggest that microbial inoculants can consistently improve fermentation profile and positively alter ruminal in vitro fermentation and thus potentially improve animal performance. Enzymes, alone seems to have an effect just on the fermentative process during the ensiling period, whereas the combination of LAB and enzymes need to be further investigated in order to explore better the interactions between the two additives.