Effects Of Dietary Arginine Level On Production Performance And Immune Function Of Blue Foxes

This thesis was conducted to investigate the effects of dietary arginine level in dry-powder diet on production performance and immune function of blue foxes(Alopex lagopus) in growth period. A combined strategy comprising of feeding trials, digestion and metabolism experiments, slaughter experiment, immunological stress, histology, molecular biology and chromatography of amino acid were employed to study the mechanisms of arginine digestion, absorption and metabolism in foxes at different growth period. The nutritional requirements of arginine in foxes were estimated to provide the data for dry-powder feed application in animal husbandry. This study was divided into three parts.Part1: Effects of arginine level on performance and serum biochemical indexes of growing blue foxesOne hundred and twenty healthy weaned 60-day foxes were randomly assigned into six treatments,the average body weight of each treatment had no significant difference(P>0.05), half male and half female. Every group had 20 replications, with one fox in each replication. Each fox was fed in an individual pen. Foxes from six groups were fed basic diets supplemented with 0%(group Ⅰ), 0.2%(group Ⅱ), 0.4%(group Ⅲ), 0.6%(group Ⅳ), 0.8%(group Ⅴ) and 1.0%(group Ⅵ) arginine,respectively. The main results were as follow:(1) When arginine was supplemented up to 0.8% in female foxes’ diet and 1.0% in male foxes’ diet,average daily gain was highest(P<0.01) and feed: gain ratio was lowest(P<0.01 or P<0.05).(2)There was a rising tendency in fat digestibility with the decreasing of dietary arginine levels(P<0.01).The digestibility of dry matter and ingested nitrogen of female foxes in group Ⅴ were the highest(P<0.01 or P<0.05). Ingested nitrogen, the digestibility of dry matter and protein of male foxes in group Ⅳwere the highest(P < 0.01 or P < 0.05).(3) When the dietary arginine level was increased, the digestibility of arginine was also increased(P<0.01), the digestibility of methionine, lysine, aspartic acid, glycine, tyrosine and total amino acids of female foxes and methionine of male foxes were increased first and then decreased(P<0.01 or P<0.05).(4) The concentration of arginine, proline,ornithine and citrulline in serum were increased but glutamic acid and urea were decreased as dietary arginine level increased(P < 0.01 or P < 0.05).(5) When arginine level increased in diet, blood ammonia was decreased(P < 0.01), insulin in female fox and growth hormone in male fox were increased(P<0.01 or P<0.05).Part2: Effects of arginine levels on performance and serum biochemical indexes in growing-furring blue foxesDuring growing-furring period, the basic diets were changed into this period. And all foxes were regrouped, the average body weight between each treatment of the same gender had no significant difference(P>0.05). The groupings and arginine supplemented levels were same with the growing period. The main results were as follow:(1) When arginine was supplemented up to 0.6% in female foxes’ diet and 0.8% in male foxes’ diet,average daily gain was highest(P<0.01) and feed: gain ratio was lowest(P<0.01), and both of the body length and fur length were best.(2) There was a rising tendency in fat digestibility with the increasing of dietary arginine levels(P<0.01). The digestibility of dry matter and ingested nitrogen of female foxes in group Ⅳ were the highest(P<0.01 or P<0.05). The digestibility of dry matter male foxes in group Ⅴ were the highest(P<0.01).(3) When the dietary arginine level was increased, the digestibility of arginine was also increased(P<0.01), the digestibility of methionine was increased first and then decreased(P<0.01 or P<0.05), the digestibility of serine of male foxes was decreased(P<0.01).(4) The concentration of arginine, proline, ornithine and citrulline in serum were increased(P<0.01) but urea were decreased(P<0.01) as dietary arginine level increased.(5) When arginine level increased in diet, NO in serum blood was increased(P<0.01), ammonia was decreased(P<0.01).Part3: Effects of arginine levels on anti-immunological-stress capability in LPS stressed blue foxesBased on the original feeding test, the test diets followed growing-furring period. Twenty five foxes were assigned into five treatments, every group had 5 replications, with one fox in each replication.Test groups were injected intramuscularly with 100 μg/kg BW lipopolysaccharide(LPS), the groups, and were fed basic diets supplemented with 0%(control group), 0.2%(group ARG0), 0.6%(group ARG0.6), and 1.0%(group ARG1.0) arginine; foxes in the control group were fed basal diet, and injected with sterile saline. The foxes were taken blood and slaughtered after 48 h. The results as follow:(1) LPS increased Alb, TP, CHO and HDL in serum(P<0.01), but reduced IL-2 and IL-4 by36.66% and 43.82% respectively(P<0.01). Activity of ALT, total NOS and iNOS in group ARG1.0were significantly higher than other groups(P < 0.01).(2) After LPS challenged, the content of methionine, arginine, serine, glycine, alanine, proline and citrulline in serum were decreased(P<0.01),but ornithine, glutamic acid and urea were increased(P<0.01 or P<0.05). Serum arginine in group ARG0 was decreased by 74.80% compared with the control group(P<0.01). Serum amino acid changes eased after adding arginine.(3) The content of sIgA in group ARG0 wad significantly lower than that of group ARG0.6 and ARG1.0(P<0.01), group ARG1.0 of jejunum villus length was significantly higher than that of group ARG0(P<0.01).(4) After LPS stimulated, the expression of NF-κB1 in mesenteric lymph node and TLR4 mRNA in spleen were increased(P<0.01), the PPAR-γ mRNA expression were decreased(P<0.01), iNOS mRNA expression of the control group and ARG0 group were significantly lower than that of the other groups(P<0.01).In summary, needs and metabolism in different growth periods and gender of the blue fox to dietary arginine are different. Under the experimental conditions, female and male foxes’ diet in growing period supplemented respectively with 0.8% and 1% arginine(total arginine level is 2.41% and2.61%), in growing-furring period supplemented respectively with 0.6% and 0.8% arginine(total arginine level is 2.04% and 2.24%) can improve the growth performance of blue foxes, and be beneficial for animal health. In addition, the blue foxes after LPS challenge increase demand of arginine,long-term adding arginine in diet can alleviate damage to blue fox caused by LPS stress.