Effects Of Dietary Linoleic Acid Level On Production Performance And Lipid Metabolism Of Blue Foxes

In this paper,we studied the effect of linoleic acid level on growth performance and lipid metabolism of blue foxes in growth period.The optimum level of linoleic acid in the blue fox dry-powder was determined,which built the foundation for the study of fatty acid metabolism and the improvement of blue fox fatty acid model.This study was divided into four parts.Part1: Effect of dietary linoleic acid level on growth performance,nutrient digestibility and nitrogen metabolism of blue fox in growing periodSixty healthy male blue foxes,with similar body weight and 90-days-old were selected,to divide into 6 groups randomly,and each group had 10 repeat while each repeat had one fox.They were fed with the dietary containing different level of linoleic acid(group? 0.11%,group? 0.52%,group? 0.92%,group? 1.33%,group? 2.14% and group ? 3.36%)separately.And the official period was 63 days.The results showed:(1)The level of dietary linoleic acid had a highly significant effect on the average daily gain and feed/gain(P<0.01),and had no significant effect on the dry matter intake(P>0.05).The average daily gain was increased with dietary linoleic acid level increasing,while feed/gain was declined gradually.(2)Dietary linoleic acid level had significant effects on fat digestibility,carbohydrate digestibility and dry matter digestibility(P<0.01),and had no significant effect on the digestibility of protein(P>0.05).The fat and carbohydrate digestibility ware increased with dietary linoleic acid level increasing.The dry matter digestibility had a trend of first increase and then decrease.(3)Dietary linoleic acid level had no significant effects on nitrogen intake(P>0.05),nitrogen retention(P>0.05),and net protein utilization(P>0.05),and had significant effects on fecal nitrogen(P<0.05),urea nitrogen(P<0.01),and biological value of protein(P<0.05).The fecal nitrogen was the highest in 3.36% of linoleic acid level group and the lowest in 0.11% of linoleic acid level group,and a significant difference was found between group ? and ?(P<0.05);the nitrogen retention,net protein utilization and biological value of protein in 3.36% of linoleic acid were the highest and those in 0.52% of linoleic acid were the lowest and significant differences were found between group ? and ?(P<0.05).Part2: Effect of dietary linoleic acid level on production performance,nutrient digestibility,nitrogen metabolism and fur quality of blue foxes in fur development periodThey were fed with the dietary containing different level of linoleic acid(group? 0.10%,group? 1.32%,group ? 2.13%,group ? 2.94%,group ? 3.76% and group ? 4.97%)separately.And the official period was 67 days.The results showed:(1)The level of dietary linoleic acid had a significant effect on the average daily gain(P<0.01),and had no significant effect on the dry matter intake(P>0.05).The average daily gain was increased with linoleic acid level increasing,while feed/gain was declined gradually.The fresh fur length and the fur weight in group ? were significantly higher than other groups(P<0.05).And no significant effects on other fur properties(P>0.05).(2)Dietary linoleic acid level had significant effects on fat digestibility,carbohydrate digestibility and dry matter digestibility(P<0.01),and had no significant effect on the digestibility of protein(P>0.05).The digestibility of fat,carbohydrate and dry matter were increased with dietary linoleic acid level increasing.The digestibility of fat was highest in group ?(3.76%)and lowest in group ?(0.10%).(3)Dietary linoleic acid level had no significant effects on nitrogen intake,fecal nitrogen,urea nitrogen,nitrogen retention,net protein utilization and biological value of protein(P>0.05).The nitrogen retention was increased with dietary linoleic acid level increasing.Group ?(0.10%)was the lowest,while group ?(4.97%)was the highest.The net protein utilization and biological value of protein fed group ?(3.76%)were the highest.Part3: Effect of dietary linoleic acid level on serum biochemical parameters and the activity of intestinal digestive enzyme of growing blue foxes(1)The level of dietary linoleic acid had a significant effect on the serum TG,TP and ALB(P<0.01),and the serum TG had a trend of decrease during growing period,and the serum TP and ALB in group ?(4.97%)was the highest.The serum TP in group ?(0.10%)was the highest,ALB in group ?(1.32%)was the highest during fur development.(2)Dietary linoleic acid level had no significant effects on the activity of lipase(LPS)and trypsin in the jejunum chime of fur development period blue fox(P>0.05),and with the increase of linoleic acid level,the activity of lipase rose.It affected significantly the activity of amylase(AMS)(P<0.01).and The amylase activity in group ?(2.13%)was the highest.Part4: Effect of dietary linoleic acid level on fatty acids composition of tissues and lipid metabolism of growing blue foxes in fur development period(1)The level of dietary linoleic acid had a significant effect on the proportion of subcutaneous fat ratio(FAS and PUFA)(P<0.01),and the ratio of SFA in muscle(P<0.01),and had no significant effects on PUFA(P>0.05).With the increase of linoleic acid level,the ration of SFA(e.g.,C16:0 and C18:0)were reduced.And the ration of PUFA(e.g.,C18:2n-6 and C20:2n-6)were increased,but the ratio of MUFA had no significant different(P>0.05).(2)CPT-? expression was up-regulated(P<0.01)with increasing dietary linoleic acid levels,and in group 4.97% of linoleic acid were the highest,however,the dietary linoleic acid levels had no significant effects on FAS gene(P>0.05).In summary,needs and metabolism in different growth periods and gender of the blue fox to dietary linoleic acid levels are different.Under the experimental condition,dietary linoleic acid level from 1.33% to 2.14% is considered to be an optimal supplemental level for blue foxes in terms of reducing feed expenses and maintaining growth performance;The 3.76% dietary linoleic acid level is considered to be an optimal supplemental proportion for blue foxes in terms of reducing feed expenses and maintaining growth performance.In addition,the supplement of dietary linoleic acid not only has the effect on serum biochemical indexes and lipase activity,but also can affect the composition of fatty acids in muscle and subcutaneous fat,and play an important role in the regulation of fatty acid synthesis and metabolism in vivo.