The Effects Of Dietary Fat Level On The Fat Digestion And Metabolism And Production Performance In Silver Foxes

This study was conducted to evaluate the effects of dietary fat level on the lipid metabolism and production performance in silver foxes. Hopefully, this paper could provide a reliable basis for development and utilization of fodder as well as lay a foundation for the research on the fat digestion and metabolism in silver fox by determination of growth performance, nutrient utilization, serum parameters, digestive tract enzyme activity, fat deposition, and genes expression of lipid digestion and metabolism.Fifty male silver foxes aged 12 weeks with a similar body weight were randomly divided into 5groups with 10 replicates per group and 1 fox per replicate, and they were fed diets supplementing 8%,10%, 12%, 14% and 16% mixed oils(Chicken oil:soybean oil=1:1) respectively, the experiment lasted for 60 days. Based on the growing period experiment, all foxes were divided into 5 new groups in the winter and they were fed diets supplementing 10%, 12%, 16%, 20% and 24% mixed oils(Chicken oil:soybean oil=1:1) respectively, the experiment lasted for 90 days.The results were as follows:1. Dietary fat level had no significant effect on the ADG, ADFI and F/G(P>0.05); The digestibility of EE and GE were significantly increased(P<0.01 or P<0.05) and the digestibility of CC was decreased with increasing the dietary fat level(P<0.05); The UN was increased but the UN and BV of protein were decreased when the dietary fat level was increased(P<0.01); Dietary fat level had no effect on the serum TG、TC、HDL-C、LDL-C、GLU(P>0.05).2.The ADFI was significantly decreased(P<0.01) as the dietary fat levels increased, the foxes fed with diet supplemented with 24% lipid has the significantly poorer(P<0.01 or P<0.05) ADG and higher F/G compared with other groups; The the digestibility of EE was significantly increased(P<0.01) and the digestibility of CC and CP was decreased(P<0.01) when the dietary fat level increased; The IN and UN were decreased as the dietary fat level increased,the foxes fed diets supplemented with 24% fat showed the lowest RN and BV of protein compared with the other four groups(P<0.01); Foxes fed with diet supplemented with 16% lipid showed the the best pelt quality(P<0.05).3. Serum TG and GLU were increased(P<0.05) as dietary fat level increased; Not only the weight of liver, subcutaneous fat, hepatic fat weight but also the hepatic somatic index, liver fat percentage and subcutaneous fat percentage were significantly increased as dietary fat level increased(P<0.05 or P<0.01); Serum TG was significantly positive correlated to liver fat percentage, subcutaneous fat percentage and hepatic somatic index; Different dietary fat level also affect the activity of pancreatic lipase in jejunum chyme(P<0.05), but no difference between the activity of trypsin and amylase(P>0.05).4.The proportion of liver PUFA(e.g., C18:2n-6 and C18:3n-3) and MUFA(e.g., C18:1-n9) significantly increased(P<0.01 or P<0.05) with increasing dietary fat level. The proportion of SFA(e.g., C18:0)decreased(P<0.05) with increasing dietary fat level the proportion of muscle SFA was increased(P<0.05) as dietary fat level increased, however, the proportion of MUFA was decreased(P<0.05);Dietary fat level had no effect(P>0.05) on the fatty acid composition of abdominal subcutaneous fat of silver foxes.5.The expression of L-FABP and I-FABP m RNA were increased(P<0.01 or P<0.05) as dietary fat level increased.In conclusion, based on this study, considering the production performance and feed cost, the optimum dietary fat supplement level in silver foxes of growing period is 8%(total fat content was9.9%) and the supplement level of optimal fat in winter fur-growing period is 16%(total fat content was18.7%);The fatty acid composition in different body tissues of silver foxes were different; When the dietary fat level was increased the silver foxes could change the related enzyme activity and gene expression to regulate the lipid metabolism in order to avoid the harm to the body. The serum TG can be preliminary predictive index of degree of body fat accumulation in silver foxes.