Study On The Low-protein Diets And The Ideal Protein Pattern Of Growing Blue Foxes

This thesis contains two parts. The first part observerd the effects of diets reduced the protein level and supplemented with Lysine and DL-methionine on growth performance and digestive metabolism of growing blue foxes. To study the feasibility of low CP diet on growing blue fox and to make sure how low the CP level can reduce of the diet with the supplement of Lys and Met. The second part was at the groundwork of first part, and the experiment was conducted with growing-fur blue foxes to determine the optimum level of Lys and Met(SAA) and the influence of the low protein diets on production performance.According to feeding trail, nitrogen balance trail and slaughter trail, it was studied the initial approach of building the optimum ideal protein pattern.Exp.1: Single Factor design was adopted. 75 8-week-old healthy growing male blue foxes were randomly divided into five groups, each groups had 15 blue foxes. The foxes in the control groups were fed on with high protein diet of 28.7%, and the foxes in trail groups were fed on with low protein diets of 27.4%, 24.5%, 23.2% and 22.4%, and the low protein diets respectively supplemented with Lys and Met which as the diets protein level reduced. So did feeding trail and nitrogen trial on each group, the experiment was lasted for 72 days.The results indicated that:(1)While the Lys and Met were added in diet and protein level was reduced to 27.4%, the final weight, the average daily gain, the day N retention in this group were significantly higher than control group and other treatment groups(P< 0.01); the feed conversion ratio, the N retention ratio, the N biological value were significantly higher than control group (P< 0.05); No significant differences were observed in the performance and digestive metabolism of blue foxes compared with control group( P> 0.05) when the Lys and Met added in diet and protein level was reduced to 23.2%.(2)Considering of all factors, As the Lys and Met were added in diet and protein level was reduced by 1%~1.5%, it could significantly improve the performance and digestive metabolism of growing blue foxes, and could save the cost of diet about 1.3%~1.5%; while Lys and Met were added in diet and protein level was reduced by 2%~4%, there were no significant effects on the performance and digestive metabolism of growing blue foxes and could save the cost of diet about 7.4%~8.0%; low protein level diet could reduce the pollution of N 10%~15%, and it also save the feed protein resource.Exp.2: The high protein diets operate as control groups, Lysine and Methionine were supplemented to the low protein diet with 0.3%, 0.5%, 0.7% Lys and 0.4%, 0.6%, 0.8% Met, which adopted an entirely random experiment designation of two factors (3×3), totally 10 groups, each of which was composed of 12 heathy 17 weeks male blue foxes. The two basal diets contained 27% and 19% CP respectively did feeding trail, nitrogen trial and slaughter trail on each group. The experiment was lasted for 78 days.The results indicated that:(1)If consider the average daily gain(ADG), day N retention, N retention ratio, N biological value, digestible EE, 0.6% Met was optimum; If consider the day N retention, N biological value and the quality of the fur, 0.3% and 0.5% Lys were optimum; If consider the N apparent digestibility day FN output and digestible EE, 0.3% Lys was optimum; Considering of all the factors L1M2( 0.3% Lys×0.6% Met) group's blue foxes's production performance was optimum.(2)While the appropriate number and proportion Lys and Met were added in diet and CP level was reduced to 19%, the blue foxes could get the same growth performance as CP 27% and could reduce the pollution of N 23.29%; There is no significant difference in feeding low protein diets supplementing restrictive performance of growing-fur blue foxes.(3)While the 0.3% Lys and 0.6% Met were added in diet and CP level was reduced to 19%, the production performance of growing-fur blue foxes were better than control group and other trial groups; Show as optimum number is each fox everyday need to supply 1035mg Lys and 2070mg Met; As the optimum level in the diet is 1.13% Lys and 1.08% Met.(4)Based on the amino acid analysis of carcasses and fur, blood serum free amino acid(FAA), ideal protein pattern for growing blue foxes was obtained. Supposing that the lysine is 100, the optimum pattern of some main total amino acids was as follow:Lys: Met+Cys: Ser: Val: Ile: Leu: Phe: His: Arg: Thr=100: 159: 120: 86: 46: 147: 68: 33: 123: 89.