Study On The Regularity Of Fat Digestion And Metabolism In Blue Foxes Of Growing-furring Period

Blue foxes (Alopex lagopus) are well-known carnivorous mammals of the Canidae family and are precious fur-bearing animals. They mainly live on animal feedstuff of high protein and high fat. This study focused on the effects of dietary lipid levels and fat species on the nutrient absorption and metabolism in Blue foxes.Hopefully, this paper could provide a reliable basis for development and utilization of fodder as well as prevention and control of fat related disease by determination of reproductive performance, nutrient utilization, serum biochemical indices, digestive tract enzyme activity, fat deposition, tectology and genes expression of lipid metabolism and systematic research of the assimilation and metabolism mechanism of fat. The dietary lipid levels are 12%。The paper consists of two parts:PartⅠThe Effect Of Different Fat On Digestion And Metabolism Of Blue Foxes In Growing Period48 larva foxes, which were healthy, and roughly the same age and body weight, were allotted into 3 treatments randomly, each treatment consisted of 8 male and 8 female, fed with diet containing fish oil, lard and tallow seperately.①Blue foxes fed with diet containing fish oil had the lowest daily weight gain, which was significantly lower than the ones fed with diet containing lard and tallow(P<0.05). Feed conversion ratio and energy/gain ratio of fish oil group were significantly higher than the other two groups during the early growing period. However the male blue foxes of the three groups showed extremely significant differences in feed conversion ratio and energy/gain ratio, with the lowest in fish oil group and highest in tallow group(P<0.01).the fish oil fed group had the significant poorer fur quality compared with the other two(P<0.05).②Comparing with the other two treatments, diets with fish oil can shorten the intestinal mucosae(P<0.01) and deepen the recess(P<0.05). The treatments with lard and tallow showed no significant differences (P>0.05).All type of dietary had no significant effect on activity of intestinal digestive enzyme.③The TG, TC, HDL-C and LDL-C of blue foxes in fish oil treatment all with high on centration, the index of fat deposition were significantly raised especially the hepatic fat rate and liver/body ratio(P<0.01). The treatments with lard and tallow showed no significant differences in these indexes (P>0.05). Lard and tallow had no bad effects on liver while the fish oil caused damage to the structure of liver.④Extremely significant difference was observed in expression quantity of ChREBP,reaching the highest in fish oil group and lowest in tallow group(P<0.01). The expression quantity of MTP in group fed with fish oil contained diet was significantly higher than those of lard group and tallow group (P<0.05), between which no significant differences were observed (p>0.05). The expression quantity of SREBP-1c in group fed with fish oil contained diet was significantly lower than those of lard group and tallow group (P<0.01),between which no significant differences were observed (p>0.05).PartⅡThe Affect of Fat Level On Digestion and Metabolism In Blue Foxes In Growing Period 64 larva foxes, which were healthy, and roughly the same age and body weight, were allotted into 4 treatments randomly, each treatment consisted of 8 male and 8 female, fed with diet containing 12%,26%,40% and 54% fat.①Average daily feed intake and feed conversion ratio decreased as the dietary fat increased, d metabolizable energy tended to increase at first then remained stable. The daily metabolizable energy of 40% treatment was significantly higher than 12% treatment (P<0.01). Male foxes in 26% treatment and female in 40% treatment grew most rapidly.As the fat in dietary increased, pelt quality increased at first and then decreased. Pelt quality of male foxes in 26% treatment was significantly better than other treatments (P<0.01) while that of female in 54% treatment was significantly worse than other treatments (P<0.01).②The nutrient-use efficiency increased as the dietary lipid level rose except carbohydrate during growing period. The digestibilities of crude protein, ether extract, dry matter and gross energy of 12% treatment was significantly lower than those of treatment 40% and 54%.As the fat in dietary increased, there was a decline of nitrogen intake, fecal nitrogen and urinary nitrogen, while net protein utilization and biological value of protein increased. High level of fat in dietary would cause morphological change in intestinal canal such as shorter intestinal villi, deeper recess and more lipase activity, but trypsinase and amylopsin were not affected.③With 54% fat in dietary, the index of fat deposition were significantly raised especially the hepatic fat rate and liver/body ratio (P<0.05), hyperlipoidemia and hyperglycosemia were detected, the liver was badly damaged.The TG and HDL-C of serum can be preliminary predictive index of degree of liver fat accumulation, liver/body ratio and visceral adiposity in blue foxes in growing period.④In sum, this study suggested optimum dietary fat level of blue fox in growing period is 26%.④The expression quantity of MTP increased with the fat level and the 54% group was extremely significantly higher than the other groups(P<0.01), 40% group was extremely significantly higher than 12% and 26% group(P<0.01).No significant difference was observed between 12% and 26% group(P>0.05).In conclusion, based on this study, the optimum dietary fat level in blue foxes of growing-furring period is 26%, higher fat level could cause pathological changes. The expression quantity of MTP increased with the fat level. Feeding effect of lard and tallow were equally good. Most physiological performance and production performance of fish oil group were significantly lower than those of lard group and tallow group, between which no significant differences were observed. The expression quantity of SREBP-1c in liver in group fed with fish oil contained diet was significantly lower than those of other groups, but the liver of foxes in fish oil group were morphologically damaged, so fish oil was not recommended at this period.