| In the previous study,a yeast ZR1(Pseudozyma aphidis strain)with phytase producing ability was screened and separated from the intestines of bullfrog(Rana(Lithobates)catesbeiana).On the basis of this experiment,we studied the fermentation characteristics of ZR1,then used this strain to ferment the soybean meal,and investigated the optimum fermentation conditions for phytate phosphorus'degradation.Next stage we conducted a feeding trial to investigate the effects of fish meal(FM)and soybean meal(SM)replaced by fermented soybean meal(FSM),which fermented by ZR1,on growth performance,serum biochemical index,nutrient digestibility,digestive enzyme activity and intestinal structure of bullfrog.The main results are as follows:1.Study on growth characteristics and phytase production characteristics of ZR1.The results showed that ZR1 was a facultative anaerobes,but under the aerobic condition,it showed stronger phytase activity.The optimum growth temperature was 33?.After 13 hours of culture,ZR1 reached mid exponential growth phase.The maximum tolerance temperature was45?.The pH tolerance range was pH 4~8.The protease activity and lipase activity of the ZR1fermented seed liquid were 39.71 U/dL and 10.34 U/dL respectively.2.Degradation of phytic acid phosphorus by fermentation of soybean meal using ZR1.Fermentation test set of 3 factors and 3 levels in each factor,the 3 factors included the inoculation amount(1×10~6 CFU/m L,5×10~6 CFU/mL,1×10~7 CFU/mL),the ratio of material to water(1:0.6,1:0.8,1:1)and the fermentation period(24h,48h,72h),to investigate the degradation of phytic acid phosphorus in fermented soybean meal under different fermentation conditions.The results showed that the optimum fermentation conditions about inoculated amount was 1×10~7 CFU/mL,the ratio of feed to water was 1:0.8,and the fermentation time was48h.Under the optimum fermentation conditions,the degradation rate of phytate phosphorous was 41.68%.The SDS-PAGE results of soybean glycinin and?-Conglycinin in fermented soybean meal showed that soybean meal fermented by ZR1 could completely degrade?-Conglycinin and acid group of soybean glycinin,80.56%basic group of soybean glycinin.The crude protein,crude lipid and total amino acid increased 4.71%,0.17%and 3.1%after fermentation,respectively.3.Effects of yeast ZR1 fermented soybean meal on growth,digestion,body composition and serum biochemical parameters in bullfrog.Four isonitrogenous and isolipid diets,included FM group(including 20%fish meal and25%soybean meal),SM group(including 55%soybean meal),SM+FSM(including 25%soybean meal and 27.5%fermented soybean meal)and FSM group(including 50%fermented soybean meal),were formulated to investigate the effects of fish meal replacement and soybean meal replacement by fermented soybean meal with on growth,digestion,body composition and serum biochemical parameters of bullfrog.The initial body weight(IBW)of the bullfrog was(35.23±0.03 g),and each group had 4 repeats,each of which was repeated with 12 bullfrogs,feeding twice a day,and the experiment period was 8 weeks.The results showed that the maximum value of final body weight(FBW),feed rate(FR),weight gain rate(WGR),specific growth rate(SGR)and protein efficiency ratio(PER)were all in FM group(P<0.05),and there was no significant difference in the rest of the other groups.There was no significant difference in hepatosomatic index(HSI)and hind leg index(HLI)between all groups(P>0.05).The apparent digestibility coefficients(ADC)of dry matter in SM group was significantly higher than that in group FM and FSM(P<0.05),but there was no significant difference from SM+FSM group(P>0.05),and it showed a trend of decreasing as the proportion of fermented soybean meal instead of soybean meal increased.The ADC of crude protein in FM was significantly higher than that in other groups,and it showed a significant decrease in the proportion of fermented soybean meal instead of soybean meal(P<0.05).The maximum value of ADC of calcium and phosphorus was both found in group FM,while the minimum value was found in group SM,it showed a significant increase in the proportion of fermented soybean meal instead of soybean meal(P<0.05).The maximum moisture was found in group SM,with the lowest value in group FM(P<0.05),it showed a trend of decreasing as the proportion of fermented soybean meal instead of soybean meal increased.The body crude protein in group FM and SM were significantly higher than those in group SM+FSM and FSM(P<0.05).There was no significant difference in body crude lipid and crude ash between the four groups(P>0.05),however,they all showed a trend of increasing with the increase of the proportion of fermented soybean meal instead of soybean meal.Blood ammonia and blood urea nitrogen in group SM+FSM and group FSM were lower than those in group FM and SM,and group FSM was significantly lower than group FM and SM(P<0.05).4.Effects of yeast ZR1 fermented soybean meal on digestive enzymes and intestinal structure of bullfrog intestine.The lowest value of protease activity in the intestine was found in group SM(P<0.05).There was no significant difference between the other groups.The highest value of amylase activity was found in group SM(P<0.05),and there was no significant difference between the other groups.The lowest value of lipase activity appeared in the SM group,the highest value appeared in group FM(P<0.05),and it showed a significant increase in the proportion of soybean meal instead of soybean meal.The intestinal villus in group SM was short and sparse with goblet cell decreased,and damages were observed at the end of the intestinal villus.The intestinal villus in group SM+FSM and FSM were long and dense with goblet cell increased,and there were no damages observed at the end of the intestinal villus,the health of the intestines was improved. |
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