| In this paper,the effects of different proportions of cumin straw instead of wheat straw on the growth and development,digestibility,plasma index,meat performance,rumen microorganisms and gastrointestinal development of lambs were studied.The aim was to provide basic data for evaluating the feeding value of cumin straw in herbivorous ruminants,provide scientific basis for the effective development and utilization of cumin straw,and help alleviate the shortage of local roughage resources.Part I: Analysis of nutrient composition,in vitro fermentation parameters and active substance composition of cumin straw.The cumin straws in Aksu,Hami and Korla were collected to determine and analyze the conventional nutrients.The active substances in cumin straw were extracted by n-hexane and petroleum ether,and detected by gas chromatography-mass spectrometry.The rumen fermentation characteristics of cumin straw and wheat straw in Aksu area were determined by in vitro method.The results showed that The results showed that the contents of CP in cumin straw were significantly higher than those in wheat straw(P<0.05),and the contents of ASH,NDF and ADF were significantly lower than those in wheat straw(P<0.05).In vitro fermentation experiments showed that the p H value of cumin straw was significantly lower than that of wheat straw(P<0.05),there was no significant difference in dry matter disappearance rate(P>0.05),and the total gas production and ammonia nitrogen concentration were significantly higher than those of wheat straw(P<0.05).The contents of total volatile acid,acetic acid,propionic acid,butyric acid,isobutyric acid,isovaleric acid and valeric acid in cumin straw were significantly higher than those in wheat straw(P<0.05).The cumin characteristic active ingredients such as cumin aldehyde and cumin alcohol were detected in cumin straw.Part II: Effects of replacing wheat straw with cumin straw on production performance,rumen microbial composition and gastrointestinal morphology of lambs.Twenty-seven healthy hybrid Karakul ram lambs with medium body condition and similar body weight(18.42 kg ± 1.74kg)were selected for feeding test and digestion test.The experimental animals were randomly divided into 3 groups control group(wheat straw),cumin straw replacement 30 % wheat straw group(cumin straw accounted for 12 % in the diet,CS1group)and cumin straw replacement 60 % wheat straw group(cumin straw accounted for 24 % in the diet,CS2 group).Each group of 9,single column feeding.The pre-test period was 15 days and the test period was 60 days.The growth performance indexes were measured regularly.Blood samples were collected before morning feeding on the 60 th day of the trial period.At the end of the trial,the longissimus dorsi and gastrointestinal tissues were slaughtered,and rumen fluid was collected to detect the effects on plasma biochemical indexes,meat quality,rumen microbial composition and intestinal morphology.The results showed that:(1)In terms of growth performance and digestibility : there was no significant difference in the initial weight,final weight,average daily gain and feed to gain ratio of lambs in each group(P>0.05).The average daily feed intake of CS1 group and CS2 group was significantly higher than that of control group(P<0.05).The apparent digestibility of crude protein,crude fat,neutral detergent fiber and acid detergent fiber of lambs in each group was not significantly different(P>0.05).(2)In terms of plasma biochemical indexes: there was no significant difference in the contents of glucose,triglyceride,total cholesterol,total protein,globulin and albumin in lamb plasma among groups(P>0.05).The white ball ratio of CS1 group was significantly higher than that of control group(P<0.05).There were no significant differences in plasma growth hormone,insulin-like growth factor-1,glutathione peroxidase,superoxide dismutase,malondialdehyde and total antioxidant capacity among groups(P>0.05).(3)In terms of slaughter performance and meat quality: There were no significant differences in live weight,carcass weight,slaughter rate,eye muscle area,organ weight and organ index among groups(P>0.05).Except that the L*45min of meat color in CS2 group was significantly lower than that in control group and CS1 group(P<0.05).There were no significant differences in p H,shear force and meat color of lamb meat in each group(P>0.05).There was no significant difference in the contents of dry matter,crude ash,crude fat and crude protein in the longest back muscle of lambs in each experimental group(P>0.05).(4)Rumen fermentation parameters,microbial composition and gastrointestinal morphology : There was no significant difference in the concentration of acetic acid,propionic acid,butyric acid,isovaleric acid and p H in rumen fluid among groups(P>0.05).The concentration of valeric acid in rumen fluid of lambs in CS2 group was significantly higher than that in control group and CS1group(P<0.05),the concentration of ammonia nitrogen was significantly higher than that of the control group(P<0.05).Compared with the control group,the number of OTU in rumen microbial community of lambs in CS1 group and CS2 group decreased,and there was no significant difference in sample coverage,Chao1 index and Obersve species index(P>0.05),the Shannon index of CS2 group was significantly lower than that of control group(P<0.05).At the phylum level,the relative abundance of rumen Bacteroidetes decreased significantly with the increase of cumin straw replacement ratio(P<0.05),The relative abundance of Proteobacteria in rumen of lambs in CS2 group was significantly higher than that in control group(P<0.05),there was no significant difference in the other bacteria(P>0.05).At the genus level,the relative abundance of Prevotella in the rumen of the CS1 group was significantly lower than that of the control group(P<0.05),there was no significant difference in other genera(P>0.05).There were no significant differences in villus length,crypt depth and villus length / crypt depth in ileum and jejunum among groups(P>0.05).There was no significant difference in the rumen papilla width and muscle thickness between the groups(P>0.05),the rumen papilla length of the CS2 group was significantly higher than that of the control group and the CS1 group(P<0.05).In summary,the content of crude protein,neutral detergent fiber and acid detergent fiber in cumin straw is better than that of wheat straw,which can replace wheat straw as roughage.In vitro fermentation experiments showed that cumin straw had higher total gas production,ammonia nitrogen,acetic acid and other volatile fatty acids than wheat straw,indicating that the fermentation effect in the rumen was better than that of wheat straw.The replacement of wheat straw with cumin straw had no negative effect on the growth and development,production performance,rumen microbial composition and gastrointestinal tissue morphology of lambs,and could increase the feed intake of lambs.After the replacement of 60 % wheat straw with cumin straw,the content of valeric acid and ammonia nitrogen in the rumen and the length of rumen papilla were improved.Therefore,cumin straw can be used as roughage instead of wheat straw to feed herbivorous ruminants.In this experiment,24 % cumin straw(replacing 60 % wheat straw)was better for lamb feeding. |
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