| In developing countries,there was an increase of requirement for meat and dairy products.It is very important to provide stable and nutritional feed for animals.Sweet sorghum(Sorghum bicolor),king grass(Pennisetum purpuphoides),and elephant grass(Pennisetum purpureum)were planted in many subtropical and tropical countries,which are deemed as the good resources for the animal production.However,they are characterized as low water-soluble carbohydrate(WSC),high moisture content or buffering capacity.It is difficult to use them to make good silage.In recent years,one of the effective approaches to improve the fermentation quality of silage is inoculated lactic acid bacteria(LAB)additive.However,some commercial LAB additives don't have good performance in improving fermentation quality of silage because of the poor adaptation in subtropical and tropical countries.Generally,some epiphytic LAB on tropical grass had the good adaptation.Therefore,it is very important and worthy to isolate and utilize this kind of LAB for making silage in subtropical and tropical countries.In the present study,the physiological and biochemical characteristics of the isolated LAB from king grass,the effects of the isolated LAB and commercial LAB additives on improving fermentation quality of sweet sorghum,elephant grass,and king grass,and the rabbit performance on isolated LAB treated silages were analyzed as follows.1.Characteristics and molecular identification of LAB isolated from king grassSeventy six LAB strains were isolated and temperature-tolerance test.Only five strains were selected for further physiological and morphological tests and 16S rRNA identification.The results were as follows.All five strains grew well at pH 3.5,4.0,4.5,5.0,6.5,7.5 and 8.0,temperature 35?,40?,45? and 50?,and endure NaCl concentrations 3.0%,6.5%and 9.5%.One strain was identified as Lactobacillus plantarum HDASK,the others were identified as Pediococcus acidilactici SK3907,SK2A32,SK3A42 and ASKDD,respectively.Therefore,three strains,L.plantarum HDASK,P.acidilactici SK3907 and P.acidilactici ASKDD,were considered as potential inoculants for making silage in following tests.2.Effect of the isolated LAB on the fermentation quality of sweet sorghum silageSweet sorghum silage was treated without(SKC,the control)or with three isolated strains(SKA,L.plantarum HDASK;SKB,P.acidilactici SK3907;SKD,P.acidilactici ASKDD)and one commercial additive(SKP,commercial L.plantarum additives).After ensiling for 1,3,5,7,14,30,60 and 90 days at room temperature in experimental silos,silages were sampled for testing.The results were as follows.Compared with the control on all ensiling days,LAB treatments significantly decreased the pH,number of aerobic bacteria(AB)and yeasts,contents of acetic acid(AA),ammonia-nitrogen(NH3-N),butyric acid(BA),ethanol and propionic acid(PA)(P<0.05),significantly increased lactic acid(LA)and LAB(P<0.05),indicated by improving fermentation quality.SKD had the lowest pH,the highest contents of LA and WSC among the LAB treatments(P<0.05).It was concluded that P.acidilactici ASKDD could better improve the fermentation quality of sweet sorghum silage than commercial LAB additive.3.Effect of the isolated LAB on the fermentation quality of elephant grassElephant grass silage was treated without(EKC,the control)or with three isolated strains(EKA,L.plantarum HDASK;EKB,P.acidilactici SK3907;EKD,P.acidilactici ASKDD)and one commercial additive(EKP,commercial L.plantarum additives).After ensiling for 35 5,7,14 and 30 days at room temperature in experimental silos,silages were sampled for testing.The results were as follows.Compared to control silage,LAB treatments significantly reduced the pH,contents of AA and ethanol(P<0.05),and significantly increased LA content at each ensiling day,indicated by improving fermentation quality.In addition,compared with the control silage,LAB treatments significantly reduced NH3-N content after ensiling for 14 and 30 days(P<0.05).Compared with EKP,EKA,EKB and EKD had lower pH and higher LA content(P<0.05).It was concluded that L.plantarum HD ASK,P.acidilactici SK3907 and P.acidilactici ASKDD could better improve the fermentation quality of elephant grass silage than commercial LAB additive.4.Effect of the isolated LAB on the fermentation quality of king grassKing grass silage was treated without(SKC,the control)or with two isolated strains(SKA,L.plantarum HDASK;SKI,L.paraplantarum SKI)and one commercial additive(SKP,commercial L.plantarum additives).Strain SKI is an isolated LAB,which was isolated by other members in our lab.After ensiling for 1,3,5,7,14,30,60 and 90 days at room temperature in experimental silos,silages were sampled for testing.The results were as follows.Compared to control silage,LAB treatments significantly reduced the pH,contents of AA and BA(P<0.05),and significantly increased LA content after ensiling for 90 days,indicated by improving fermentation quality.There was no difference in pH,contents of LA,BA,and NH3-N among SKA,SKI and SKP(P>0.05).It was concluded that the L.plantarum HDASK,L.paraplantarum SKI,and commercial LAB additive had same effects on improving fermentation quality of king grass silage.5.Effect of the isolated LAB treated king grass silage on the performance of rabbitKing grass was ensiled without(Control)or with L.paraplantarum SKI(SKI),P.acidilactici ASKDD(DD),and L paraplantarum SKI+P.acidilactici ASKDD(SKI+DD)for 30 days.A total of 72 male rabbits(6 weeks)of similar weight and appearance were housed in groups in metallic cages in a completely randomized design.After feeding LAB treated king grass silages for 42 days,productive traits and blood biochemistry of rabbit were sampled to test.The results were as follows.Compared with the control,LAB treatments did not influence the daily feed intake,body weight gain and feed convention ratio(P>0.05),decreased concentrations of copper and manganese(P<0.05),and increased zinc concentration in the blood(P<0.05).Compared with the other treatments and the control,DD increased concentrations of triglyceride(2.94 U/L)and alanine aminotransferase(0.92 mmol/L)(P<0.05).Compared with other treatments and the control,SKI increased the concentrations of superoxide dismutase(658.01 nmol/ml),phosphorous(5.1 mg/kg)and magnesium(2.43 mg/kg)(P<0.05),Therefore,the L.paraplantarum SKI,P.acidilactici ASKDD,and their combination had the same positive performances in improving antioxidant defense system.In conclusion,compared with the control,three isolated LAB strains,L.plantarum HDASK,P.acidilactici SK3907 and P.acidilactici ASKDD improved fermentation quality of sweet sorghum,elephant grass,and king grass silage.Compared with commercial LAB additive,these three isolated LAB strains had same or better performance in improving fermentation quality of sweet sorghum,elephant grass,and king grass.The P.acidilactici ASKDD had the same positive performances with L.paraplantarum SKI in improving antioxidant defense system of rabbits.P.acidilactici ASKDD had a potential value of applying in making good silage and improving the ability of animal antioxidant defense. |
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