| Straw is a highly accessible,valuable and renewable resource in agricultural production.Scientific and effective microbial fermentation treatment can greatly improve the nutrients and palatability of straw.In this study,pig's cecum was used as the source of microorganisms and the bacterial strain was used to effectively decompose cellulose in the straw.The objective of the study was to provide the foundation for the development and utilization of straw resources and develop bacterial strain resources that are suitable for fermentation of straw diet for feeding pigs.Experiment 1: A cellulase-producing bacterial strain JY-1 was isolated from the content of pig cecum through CMC-Na Congo red culture medium and the detection results showed that its cellulase-producing activity was 0.32U/ml.It was identified as Bacillus velezensis with the molecular sequencing technique 16 SrDNA.Experiment 2: The enzymatic characteristics of CMC enzyme produced by bacterial strain JY-1 was studied and results showed that the pH value for optimum reaction was 5.5-6.0,and the optimum temperature was around 55?.At the pH value of 5.0-6.0 and the temperature of 30-40?,the enzyme could maintain a high activity.At the pH value of 3.0,it could maintain 79% of activity,with certain acid resistance.Experiment 3: A preliminary study was conducted on the optimum conditions for the JY-1 fermentation of corn straws and results showed that The optimal cellulaseproducing activity could be achieved when 1% of concentrate combination(the ratio of corn to bean pulp is 1:1)was added(P>0.05),the grinding particle size was 1-2mm(P < 0.05),the ratio of feed to water was 2%(P>0.05),the inoculation size was 2%(P>0.05),and the fermentation time should be at least 9 to 10 days.Compared with the period before fermentation,the NDF of the corn straws after fermentation dropped by 7.6%,with a significant difference(P<0.05).ADF dropped by 5.5%,with no significant difference(P>0.05).The CP content of corn straw after fermentation increased by 11.3%(P<0.05),indicating that this bacteria strain had a certain value in use.Experiment 4: The experiment aimed to explore the effect of the addition of fermented core straws in feed on the growth performance,nutrient digestibility of feed,blood VFA,and cecum microflora of piglets.In this experiment,24 healthy double hybrid piglets with a weight of 12.05 ± 0.32 kg were selected.Fermented core straws and corn straws were used to replace the equivalent amount of basic ration.The piglets were randomly divided into two groups with each consisting of 12 piglets,10% corn straw group and 10% fermented corn straw group.Each group had four repeating groups and each repeating group had three piglets.Experiment results showed:(1)Compared with the control group,for the fermented corn straw group,the average daily weight gain increased by 15.4%(P<0.05),the average daily food intake increased by 8.3%(P<0.05),and the ratio of feed to gain decreased by 4.7%(P>0.05).(2)For the 10% fermented corn straw group,its digestibility for CF,ADF,NDF and CP was higher than that of the control group(P<0.05)and there was no significant difference between the two groups in the digestibility for EE(P>0.05).(3)The content of acetic acid in the serum of 10% fermented corn straw group was higher than that of the control group(P<0.05)and there was no significant difference in the content of propionic acid and butyric acid(P>0.05).(4)The developmental form of small intestine in the 10% fermented corn straw group had no significant difference with that of the control group(P>0.05).(5)The microbial diversity at the cecum and the number of beneficial bacteria such as Prevotella and Lactobacillus increased in the 10% fermented corn straw group compared with that of the control group.The above experiment results show that this experiment isolates a cellulosedecomposing strain of Bacillus velezensis and the cellulose produced by it has a certain acid resistance.When it is used to ferment corn straws,it can reduce the content of cellulose in these corn straws and increase the content of crude protein.Compared with unfermented corn straws,when fermented corn straws with this strain are fed to pigs,it can enhance their productivity,increase the digestibility of feed,increase the content of acetic acid in the blood of piglets,do not have significant effects on the intestinal morphogenesis of piglets,and can improve the microflora of piglets to a certain extent. |
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