Effects Of Dietary Fats On The Growth And Intestinal Microecology In Rats

It has been suggested that dietary fats might reduce the number of microorganisms in rats. However, the effects of dietary fats on the intestinal microecology need to be further studied. The experiment was conducted to evaluate the effects of different dietary fats on the intestinal microecology in growing Sprsngue-Dawley rats fed isocaloric diets. Seventy-two Sprsngue-Dawley rats of about 122 g were randomly divided into six treatments receiving fat-free purified diet, typical practical diet with soybean oil, or purified diets with ten percent corn oil, beef tallow, palm oil and coconut oil as only fat sources. The experiment lasted 28 days. Six rats per treatment were euthanized on day 15 or 29 of the trial respectively to collect data or samples of body weight, blood, pancreas, small intestine digesta, duodenum and jejunum for analysis. The results showed that:1. The average body weight was different among groups at 1-2w, 3-4w and 1-4w. The average body weight of practical diet was higher than the purified diets, and that of purified diets with different fats was higher than the fat-free purified diet. The average body weight of 1-2w in rats fed diet with corn oil and palm oil were significantly higher than the fat-free purified diet (P<0.05), and the beef tallow and coconut oil were higher than the fat-free purified diet (P<0.05). However, the average body weight among the purified diets with different fats were not significantly different (P>0.05). The average body weight of 1-2w in each group were in the order of typical practical diet>corn oil>palm oil>coconut oil>beef tallow>fat-free diet group. The average body weight of 3-4w, 1-4w in rats fed different diets were similar as the 1-2w, but the average body weight of 1-4w in rats fed corn oil diet were higher than the beef tallow and palm oil (P<0.05).2. The postprandial lipid and glucose concentrations were different among groups on day 15 or .29. On day 15 of the trial, the postprandial lipid concentrations of typical practical diet were higher than the fat-free group (P>0.05). Among the purified diet groups, the concentrations of postprandial serum lipid were also higher than the fat-free group (P>0.05), and the TG, TC and NEFA in beef tallow and palm oil group were significantly higher than the fat-free group (P<0.01). The postprandial lipid concentrations of purified diet supplying fats were different being the TG and NEFA in coconut oil group were significantly lower than the beef tallow and palm oil group. However, no significant differences were observed on postprandial glucose among diets(P>0.05). The postprandial INS and PG in corn oil and coconut oil group were significantly lower than the beef tallow group(P<0.01) ,and the INS in palm oil group was lower than the beef tallow(P<0.05) .The postprandial lipid and glucose concentrations in each group on d 29 were similar to those on d 15.3. The digestion physiological functions of rats were different among groups on day 15 or 29. On day 15 of the trial ,the total activities of lipase in pancreas of rats fed typical practical diet were higher than the fat-free and palm oil group (P<0.01). The purified diet groups supplying different fats were higher than the fat-free group,and the total activities of lipase in pancreas of rats fed diet containing corn oil and coconut oil were signifieantly higher than the fat-free group (P<0.01),and the total activities of lipase in pancreas of rats fed diet containing beef tallow and palm oil were also higher than the fat-free group (P<0.05) .Among the diet supplying different fats, the total activities of lipase in pancreas of rats fed diet containing corn oil were higher than the palm oil group(P<0.05). The total activities of lipase in pancreas of rats fed diet containing corn oil were higher than the palm oil group(P<0.05). The total activities of lipase in each group were in the order of corn oil>coconut oil> typical practical diet>beef tallow>palm oil>fat-free diet group. The total activities of lipase in each group on d 29 were the similar to those on d 15.We also studied the digestibilities of energy, protein and fat in diets containing oils with different fatty acid composition and fat-free group. The digestibilities of energy, protein and fat of rats in each group were different. At the early stage of the trial, the digestibilities of energy were higher than the fat-free group (P<0.01) and beef tallow group (P<0.05) when rats were fed typical practical diet. The digestibilities of energy were higher than fat-free group when rats were fed purified diets containing fats, and the corn oil (P<0.01), coconut oil (P<0.01) and palm oil group (P<0.05) were higher than fat-free group. Among the purified diet containing fat, the corn oil, coconut oil and palm oil group were higher than the beef tallow group (P<0.05). The digestibilities of energy were in the order of typical practical diet>corn oil>coconut oil>palm oil>beef tallow>fat-free diet group.The digestibilities of protein were higher than the fat-free group (P<0.01) and beef tallow or palm oil group (P<0.05) when rats were fed typical practical diet. Among the purified diets containing fats, the corn oil group was higher than the palm oil group (P<0.05) . The digestibilities of protein were in the order of corn oil>typical practical diet>coconut oil>palm oil>beef tallow>fat-free diet group. However, the digestibilities of fat were relatively high but not significantly (P>0.05)when rats were fed diets containing coconut oil, corn oil, palm oil and beef tallow while that of the fat-free group was negative value. The digestibilities of fat were in the order of coconut oil>typical practical diet>corn oil>palm oil>beef tallow>fat-free diet group.The digestibilities of energy, protein and fat in diets containing oils with different fatty acid composition and fat-free group at the later stage were similar to those at early stage.The intestinal morphology of duodenum and jejunal were different among groups. On day 15 of the trial ,the villus height of duodenum in rats fed typical practical diet and the purified diet supplying fats was significantly higher than that of fat-free group (P<0.01). The villus height of duodenum in rats fed corn oil was higher than that of beef tallow (P<0.01) and palm oil (P<0.05). The villus height of duodenum in rats fed coconut oil and palm oil was significantly higher than that of beef tallow (P<0.01),and coconut oil was higher than the palm oil(P<0.05). On day 29 of the trial, the villus height of duodenum of rats in each group was similar as the before. Corn oil group was significantly higher than the beef tallow and palm oil group (P<0.01), but no differences were observed among the beef tallow, palm oil and the coconut oil group (P>0.05). The intestinal morphology of jejunum on 15d or 29 d was the similar to duodenum.4. The FFAs of the distal small intestine of rats was different among groups. On day 15 of the trial, the content of C18:2 in corn oil group was significantly higher than that of beef tallow and palm oil group (P<0.01), but the content of C16:0 was significantly lower than that of beef tallow, palm oil and the coconut oil group (P<0.01). The content of C18:1 in palm oil group was higher than that of corn oil and beef tallow group (P<0.05). The C10:0,C12:0 and C14:0 in digesta of distal small intestine in rats fed coconut oil diet was signifieantly higher than that of other groups (P<0.01). The FFAs of the distal small intestine of rats on day 29 among groups was similar to that on d 15.5. The numbers and microbial diversity of the proximal cecum in rats were different among groups on day 15 or 29. On day 15 of the trial, the numbers of Enterobacteria of cecum in the rats fed typical practical diet and purified diets with different fats were lower than that of fat-free diet group with corn oil, palm oil and coconut oil diet group (P<0.01) being significant. For all treatments, the numbers of Enterobacteria of cecum were in the order of fat-free diet group>beef tallow>palm oil>corn oil>typical practical diet>coconut oil. The numbers of Lactobacillus of cecum in the rats fed typical practical and fat-free diet were signifieantly higher than the purified diets with different fats (PO.Ol).The numbers of Lactobacillus were in the order of typical practical diet>fat-free diet group> coconut oil>cora oil>palm oil>beef tallow. The Bifidobacterium of rats in each group were not different (P>0.05). The numbers of Bifidobacterium were in the order of fat-free group>typical practical diet >coconut oil>corn oil> palm oil>beef tallow. On day 29 of the trial, the numbers of Enterobacteria, Lactobacillus and Bifidobacterium in digesta of cecum in the rats fed "different diet were similar to that on d 15.On day 29 of the trial, the DGGE profiles provided a snapshot of the bacterial population and allowed calculation of the degree of similarity in the predomint intestinal microflora of rats. In DGGE map, the microbial communities were rich in the cecum. The similarity of DGGE profiles of the cecum among typical practical diet group and the other groups was larger than 65%. The similarity of DGGE profiles of the cecum between the fat-free and corn oil group was larger than 86%. Between the palm oil and beef tallow group was about88%. However, the similarity of DGGE profiles of the cecum between coconut oil and corn oil group was about 70%.Compared with the palm oil and beef tallow group, the similarity of DGGE profiles of the cecum was about 80%.The results indicated that different fats showed different effects on the DGGE profiles.The results of present study showed that the effects of different fats on the growth, digestion physiological functions and the intestinal microecology were different .The effects of corn oil and coconut oil group on the growth were better than the palm oil and beef tallow group, and concerned with improving rat's digestion physiological functions and regulating intestinal microecology.