Effects Of Dietary Non-Fibrous Carbohydrate/Neutral Detergent Fiber On Growth Performance And Intestinal Healthy Of Meat Rabbits

Dietary fiber is fermented and degraded in the cecum,which helps to improve animal intestinal microbial fermentation and improve animal growth performance.Since crude fiber is a rough component,research on precise fiber nutrition in diets has become a hot issue in recent years.In order to give full play to the nutritional role of fiber,more and more scholars have adopted the ratio of Non-Fiber Carbohydrates/Neutral Detergent Fiber(NFC/NDF)as an index of fiber nutrition in animal diets.This experiment was conducted to investigate the effects of different dietary NFC/NDF on growth performance,nutrient apparent nutrient digestibility,intestinal.development and cecal microflora in meat rabbits.A total of 135 healthy weaned meat rabbits with average body weight of(1.08±0.07)kg were randomly divided into 5 groups with 27 replicates in each group and 1 rabbit in each replicate.Under the condition of the same other nutrient levels,meat rabbits were fed experimental diets with NFC/NDF of 0.7(T1 group),1.0(T2 group),1.3(T3 group),1.6(T4 group),and 1.9(T5 group),respectively.The growth trial lasted for 28 days,and the digestion and metabolism trial lasted for 7 days.The results showed as follows:1)Different dietary NFC/NDF had certain effects on growth performance,apparent nutrient digestibility and blood biochemical indexes of meat rabbits.① The ADG and ADFI of meat rabbits in the T1,T2 and T3 groups were significantly higher than those of the T4 and T5 groups(P<0.05),and the F/G of the T5 group was significantly higher than that of the other groups(P<0.05).The diarrhea rates of meat rabbits in the T4 and T5 groups were 18.52%and 59.26%,respectively,which were significantly higher than those of the other groups(P<0.05).There was no significant difference in the Organ Development Index of meat rabbits in each group(P>0.05).② The digestibility of the CP of the meat rabbits in the T5 group was the lowest,which was significantly lower than that of the other groups(P<0.05).The EE digestibility was highest in the T3 group,which was significantly higher than the T1 and T5 groups(P<0.05).The digestibility of NDF in meat rabbits was the highest in the T2 group and the lowest in the T5 group.③ The WBC content of the meat rabbits in the T5 group was slightly higher than the other four groups(P>0.05).And the blood Gran content of the T5 group was significantly higher than that of the T1,T2,and T3 groups(P<0.05).The content of LYM in the blood of rabbits in each group was the lowest in the T5 group(P>0.05).The serum Glu content of meat rabbits were increased with the increasing of NFC/NDF,with the highest in the T5 group,and the lower in the T1 and T2 groups(P>0.05).The serum AST content of the meat rabbits in the T2 group was significantly higher than the other four groups(P<0.05).The serum ALP content was highest in the T2 group,and was significantly higher than that in the T5 group(P<0.05),and was not significantly different from the other four groups(P>0.05).2)Different dietary NFC/NDF had certain effects of intestinal healthy of meat rabbits.① The activities of Trypsin and α-amylase in the jejunum of meat rabbits in the T4 group were the highest,which were significantly higher than those in the T1 group(P<0.05).The activities ofJejunum Sucrase and Cecal Cellulase were the highest in the T2 group,which was significantly higher than that of the T4 and T5 groups(P<0.05).② The depth of the Jejunal Crypts of the meat rabbits in the T2 group was significantly lower than that in the T1 and T5 groups(P<0.05).The V/C of the meat rabbits in the T2 and T3 groups was significantly higher than that in the T1,T4 and T5 groups(P<0.01).The thickness of the Cecal Mucosa was the highest in the T2 group,extremely significantly higher than the T1 and T5 groups(P<0.01),and significantly higher than the T4 group(P<0.05).③ The relative expressions of cecal IL-1β and TNF-α in the T1,T2,and T3 groups were significantly lower than those in the T4 and T5 groups(P<0.05).The relative expression of Claudin in the T2 group was significantly higher than the other four groups(P<0.05),and the relative expression of Claudin in the T4 and T5 groups was the lowest.The relative expression of Occludin in the T1 and T4 groups was significantly lower than that in the T2 and T3 groups(P<0.05),and was significantly higher than that in the T5 group(P<0.05).The relative expression of ZO-1 was the highest in the T2 group,which was significantly higher than that in the T1,T4,and T5 groups(P<0.05).④Different dietary NFC/NDF had certain effects of caecal environmental parameters of meat rabbits.With the increasing of dietary NFC/NDF,the cecum pH,NH3-N concentration and acetic acid concentration of meat rabbits were decreased.The pH of the cecum in the T5 group was significantly lower than that in the T1,T2,and T3 groups(P<0.05).The concentration of NH3-N in T4 and T5 groups was slightly lower than T1(P>0.05).The concentration of Acetate was higher in the T1 and T2 groups,which was significantly higher than that in the T5 group(P<0.05).The concentration of Propionate in the cecum was highest in the T5 group,which was significantly higher than that in the T1,T2,and T3 groups(P<0.05).There was no significant difference in Butyrate content in the cecum of each group of meat rabbits(P>0.05).⑤ In terms of species richness,the Chaol and Observed_otus indexes of cecal microorganisms were lower in the T1 and T5 groups(P>0.05).In terms of species diversity,the Shannon and Simpson index of cecal microbes in the T5 group were significantly lower than those in the T2 and T3 groups(P<0.05).⑥At the Phylum level,the sum of Firmicutes and Bacteroidetes in the T1,T2,T3,and T4 groups was greater than 80%,and the T5 group was slightly lower(77.02%).The relative abundance of Firmicutes and Actinobacteria in the T2 group was the highest(P<0.05).The relative abundance of Proteobacteria in the T5 group was significantly higher than that in the other groups(P<0.05).At the Genus level,the relative abundance of Rumencoccaceae subgroups in the cecum of rabbits in the T2 and T3 groups was higher,and the T5 group was lower.⑦Through the analysis of the Differential Flora of the cecal microorganisms,it was found that the T2 group screened out 9 different flora which promoted the intestinal health and cecal fermentation.And the T5 group screened out 3 kinds of harmful and different bacterial groups symbiosis with the host.⑧ Through Joint analysis,it is found that cecal metabolites are related to the degradation of fiber matter and NFC.The phenotype related to cecal fermentation was significantly positively correlated with Firmicutes flora abundance(P<0.05).In conclusion,when the dietary NFC/NDF at 1.0 to 1.3,the meat rabbits showed good health and growth performance,and the expression of caecal inflammatory factors in the meat rabbits were decreased at 1.0 to 1.3,the expression of tight junction proteins were increased,and the cecum microbial diversity of the meat rabbits were increased,which ensures the balance of the intestinal flora and beneficial to intestinal health.