Effects Of Dietary Protein Levels On Reproductive Performance And Metabolism Of Nutrients In Blue Foxes

Primiparous blue foxes were studied in this experiment, which were fed with different dietary protein levels at the reproduction period. The effects of reproductive performance, digestive physiology and serum biochemical parameters of blue foxes were investigated in order to provide a theoretical basis for increasing the reproductive performance of primiparous blue foxes. This thesis was comprised of three trials:Experiment.1: The objective of this experiment was to determine whether the regularity of digestibility and metabolism and serum biochemical parameters of blue foxes were affected by different dietary protein levels at prepare breeding period. 180 healthy female blue foxes were randomly assigned to four groups (Ⅰ,Ⅱ,Ⅲ,Ⅳ) containing approximately 21.64%,26.21%,30.43%和35.10% crude protein by analysis, respectively. The experiment lasted for 52 days, including preset period for 7 days and test period for 45days. The results showed as follows: (1) With the increase of dietary protein levels, dry matter intake and dry matter digestibility were higher firstly, and then lower (P<0.05), when the protein level of diet arrived at 30.43%, they got the highest. (2) The digestibility of fat and protein of blue foxes also showed the same change law, when protein level arrived 30.43%, foxes in different groups had no significance in the digestibility of protein. (3) With the increase of dietary protein levels, net protein utilization and biological value of protein were higher firstly, and then lower (P>0.05). (4) The BUN and TP of high protein group were higher than the low group (p<0.05). Foxes in different groups had no significant difference in GOT, GPT and GLU (P>0.05). (5) In conclusion, when the protein level of diet arrived at 30.43%, the nutrient digestibility was optimal.Experiment.2: The experiment was conducted to study the reproductive performance of diets with different protein levels in fox at pregnancy period. Choose the same foxes as the experiment 1, the dietary composition and protein level in each group were the same as which in prepare breeding period. The results showed as follows: (1) Different protein levels had significant influence on DM digestibility, protein digestibility and fat digestibility of pregnant blue foxes (P>0.05). Nutrient digestibility rose with the increase of dietary protein levels. It is not significantly enhanced when the content of dietary protein reached or over the 30.43%. (2) The oestrus time of blue foxes was advanced with the increase of dietary protein levels. Conception rate had showed the trend of gaussian distribution in different time, from February 27 to March 18, it arrived the highest. (3) Foxes in different groups had no significant difference in litter size (P>0.05). With the decrease of dietary protein levels, litter weight and conception rate were higher firstly, and then lower; the birth survive rate was not obviously decreased (P >0.05). The birth weight of high protein group was significantly higher than that of low protein group (P <0.05) (4) With the decrease of dietary protein levels, the breeding rate and conception rate were both higher firstly, and then lower, they got the highest at the diet of 30.43% protein level. (5) In conclusion, combined productive performance with growth performance, the optimal protein percentage was 30.43% for blue fox at the period of reproduction. Experiment.3: This experiment was to study the growth performance and survive rate of larva fox, serum biochemical parameters and body weight change of primiparous blue fox at different dietary protein levels during the lactation period. 60 litters of healthy blue foxes were randomly assigned to four groups (Ⅰ,Ⅱ,Ⅲ,Ⅳ) containing approximately 28.19%,32.49%,35.69%,39.84% crude protein by analysis, respectively. The result showed that: (1) Foxes in different groups had significant difference in weight gain. With the similar birth weight and birth litter weight, the high dietary protein level increase the weaning weight of litter (P<0.05), weaning average individual weight (P>0.05) and the litter weight daily gain (P<0.05). (2) With the increase of dietary protein levels, the survive rate of larva fox at each stage increased (P>0.05). (3) Fox in the lactation period mobilized much protein of itself to satisfy enough milk yields for larva fox. (4) The GOT and GPT increased significantly (P<0.05), when the dietary protein level decreased to 21.64%, lead to liver damage. (5) In conclusion, foxes in lactation period needed more protein to satisfy production requirement and maintenance requirement. When the protein level of diet arrived at 39.84%, the suckling performance was optimal.In conclusion, this experiment was conducted to study the effects of different dietary protein levels on reproduction period of blue foxes by feeding experiment and digestion metabolism experiment. When the protein level of diet arrived at 30.43% in prepare breeding period and pregnancy period, the nutrient digestibility and reproductive performance was optimal; when the protein level of diet arrived at 39.84% in the lactation period, foxes had the best suckling performance.