Hua Jin-ling, Wang Li-ke, and Dai Si-fa

College of Animal Science, Anhui Science and Technology University, Fengyang 233100, Anhui, China

Introduction

Previously Fermented Juice (PFJ) is a new type of silage additive. In addition to having the effects of preparation and lactic acid bacteria similar outside,there are the following advantages of the PFJ: ① the PFJ production process is simple and economic, the operation will be environmentally friendly. And it can avoid acid corrosion to instruments and machinery in the process of silage produced; ② the lactic acid bacteria in the PFJ are natural lactic acid bacteria,which have many kinds and large quantity, and been adapted to environment. Therefore, as a kind of silage additives, it can demonstrate a higher stability of fermentation, which improve silage fermentation quality and better to improve the fermentation quality of silage (Ohshimaet al., 1997). The objective of the present study was to investigate the effect of diluted the PFJ (dPFJ) on the fermentation quality of rice straw silage, which was supposed to contain a number of species of domestic LAB, as a silage additive using rice straw silage.

Materials and Methods

Rice straw and additives

Rice straw was obtained from Tangchi in Anhui Province, the rice straw was harvested at full-ripening stage while the stems had high moisture content(60%-75%) and were still green.

Additives: 50 g of growth alfalfa was harvested by hand at the vegetative stage, macerated with 250 mL of a 2 g · l00 mL-1glucose solution and filtered through double cheese cloth (PFJ). One of the PFJ solution was prepared by making up 5 mL to 100 mL with 2 g · l00 mL-1glucose solution (dPFJ). They were preserved anaerobically for 2 days at 30℃. After fermentation both the PFJ and the dPFJ solutions were diluted 5 mL to 100 mL with 2 g · l00 mL-1glucose solution (the PFJ20 and the dPFJ20), respectively.These treatments were also preserved anaerobically for 2 days at 30℃. All the treatments consisted of the three replicates (Ohshimaet al., 1997) .

Ensiling

Rice straw was ensiled whole to a theoretical length of 6-cm using a rice harvester. Whole rice straw was treated with five different additives. i) No additive, ii)PFJ, iii) dPFJ, iv) PFJ20, v) dPFJ20. Additives were dissolved in deionized water and sprayed uniformly on the rice straw constantly and thoroughly.Approximately 5 kg of rice straw was then packed and sealed in plastic bags and stored at ambient temperature (20 to 25℃) in an enclosed barn for 45 days. All the treatments consisted of three replicate silos. After completion of ensiling time, silos were opened; the RS silages were randomly sampled by drawing vertical cores from three different positions,and then mixed thoroughly to get a composite sample.Samples were stored on ice until taken back to the laboratory for chemical analyses.

Laboratory analyses

Silage samples were analyzed for DM, CP (AOAC,1997), NDF and ADF (Van Soestet al., 1991).

According to the method of Nishino and Uchida(1999), 20 g silage sample was homogenized with 180 mL of distilled water and stored overnight at 4℃ in a refrigerator. Then the mixture was filtered through Whatman 54 filter paper and the filtrate was used for pH, ammonia-N, lactic acid and the VFA determination. The pH was directly measured by pH meter(Thermo Orion, USA). The NH3-N concentration was measured by ammonia-sensing electrode (Expandable Ion Analyzer EA940, Orion, USA). Lactic acid concentration was analyzed using high performance liquid chromatography (Waters 600E, USA). Samples for the VFA analysis were prepared as described by Li and Meng (2006), and the VFA concentrations were determined using gas chromatography (GC-2010,Shimadzu, Japan) with a 30 m the FFAP capillary column (0.25 mm i.d. and 0.30 μm film thickness).Each analysis was performed in triplicate.

Statistical analyses

Data was subjected to statistical analysis using the general linear model (GLM) procedure of the SAS(1999) for a completely randomized design to test the main effects of the PFJ addition on nutritive value of ensiled rice straw. Significance was declared atp＜0.05 unless otherwise noted.

Results

Fermentation quality of rice straw silage

The data on silage fermentation quality of different PFJ additions in rice straw silage is shown in Table 1.

Table 1Effects of different PFJ additions on fermentation quality of rice straw silages

The results demonstrated that pH differed between the control and the PFJ treatments (p＜0.05), while pH did not differ between the PFJ and the dPFJ (p＞0.05) ,and the same results were obtained between the PFJ20 and the dPFJ20. At the same time, the addition of the PFJ significantly decreased NH3-N concentration(p＜0.05), the lower NH3-N attained in the dPFJ might be attributable to the higher content of lactic acid bacteria. Concentration of lactic acid of the PFJ treatments was higher significantly than that of the control (p＜0.05), and level of lactic acid in the PFJ group was the highest among the PFJ groups (p＜0.05).Concentration of acetic acid of the control was significantly higher than that of others (p＜0.05). Level of butyric acid did not significantly differ among treatments. L : A value of the PFJ and the dPFJ was higher significantly than that of others (p＜0.05).

Chemical composition of rice straw silage

The effects of different PFJ additions on chemical composition of rice straw silage are shown in Table 2. The PFJ addition affected chemical composition of silage including CP, NDF, ADF and DM losses, with a significant interaction on CP and DM losses (Table 2;p＜0.05).Concentration of DM, NDF and ADF did not differ among treatments. Level of CP in the PFJ was signifi-cantly higher than that of the control, PFJ20, and dPFJ20 groups (p＜0.05); however, CP in the PFJ did not differ from the dPFJ (p＞0.05). DM loss of the dPFJ20 was significantly higher than that of others (p＜0.05).

Table 2Effects of PFJ on chemical composition and DM loss of rice straw silages

Discussion

pH and ammonia nitrogen

The pH is often considered as one of the crucial factors in evaluating the fermentation quality of silage (Muck,1988). The PFJ addition in rice straw dramatically decreased pH, and pH fell below 4.0. The PFJ addition provided slightly abundant lactic acid bacteria for the fermentation of rice straw. The close correlation between additives and fermentation quality of alfalfa silage could partly explain the pH changes in this study (Ohshimaet al., 1997). The results showed that pH declined as the inclusion the PFJ suggesting the higher the inclusion level of lactic acid bacteria in the PFJ, the better the quality of rice straw silage.

Addition of the PFJ significantly decreased NH3-N concentration, which was consistent with the findings of McDonaldet al(1991). Addition of the PFJ resulted in a similar improvement in silage quality as the addition of the LAB in improving silage quality(Kunget al., 2003; Schmidtet al., 2009). Inoculating grass silage with homolactic inoculants of the LAB lowered NH3-N content, which was attributed to the fact that pH declined to a lower level faster, resulting in inhibition of proteolytic bacteria (Jatkauskas and Vrotniakiene, 2004; Whiter and Kung, 2001).

Organic acids

The concentration of lactic acid was significantly higher in the dPFJ than that in others (p＜0.05). This phenomenon might be easily explained by the fact that the addition of the PFJ tended to increase the lactic acid bacteria populations. The ratio of lactic acid to acetic acid is a good indicator of the type of fermentation which the silage has undergone.A ratio of at least 2 : 1 indicated strong homolactic fermentation, suggesting homolactic acid bacteriumP. pentousaceuswas the predominant bacterium during ensiling which was supported by our findings. The PFJ and the dPFJ addition significantly increased lactic acid concentration in rice straw silage. Acetic acid has been considered as a good antifungal component in naturally fermented silages and shown to improve the aerobic stability (Danneret al., 2003), due to its capacity to inhibit yeast and mold growth (Moon,1983). Despite the yeast and mold numbers not being measured in the present experiment, higher acetic acid concentration in the PFJ and the dPFJ addition rice straw silages indicated that these rice straw silages had less potential for better aerobic stability of silages.

During the ensiling period, acetic and lactic acids were fermentation end-products which improved silage quality (Gaoet al., 2005), while butyric acid often deteriorated silage quality (McDonaldet al.,1991). The low concentration of butyric acid has been identified as one of the factors that inhibited the growth of fungi (Muck, 1988). The relatively low content of butyric acid in the PFJ and the dPFJ addition rice straw silage was an indicator of good fermentation quality and stability observed in the present study.

Chemical composition and DM losses

The PFJ rice straw silage had significantly lower the DM losses than the control and the dPFJ20. While there were no statistical differences in the DM content between the silages. Oude Elfericket al. (1999a)reported that extra the DM loss would result from CO2emission, which was formed during the conversion of lactic acid to acetic acid and 1, 2-propanediol.Therefore, the DM loss could be considered as a good reflection of the metabolism of lactic acid byL. buchneriduring the fermentation processes. The DM loss data in our research implied that inoculation with the PFJ might significantly reduce the activity ofL. buchneri. However, previous studies had shown that increasing inoculation level ofL. buchneriin maize silage resulted in extra DM losses (Driehuiset al., 1999a). This was presumably due to the different ensiled materials used in these experiments. As mentioned earlier, homolactic acid addition caused a rapid fall in pH and reduced the NH3-N content.Surprisingly, the CP content of rice straw silages linearly decreased with the dilute of the PFJ addition.This contradiction could be partly explained by content of lactic acid bacteria in the PFJ additive; however,the exact reason need more research. The NDF and the ADF contents were not in fluenced by the addition of the PFJ additive.

Conclusions

Inoculating rice with PFJ additive could significantly improve the silage quality. The PFJ and dPFJ rice straw silages had better fermentative quality than others.

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