Study On Growth And Development Law And Energy Requirment Of Growing Hu Sheep

Hu sheep is a unique local breed in China,which has the characteristics of simultaneous use of meat and wool,high yield of multiple litter,suitable feeding,strong adaptability and fast growth rate.In recent years,the breeding scale has been expanding continuously.In order to improve its economic benefits,it is of great significance to explore its growth and development law and energy requirement.In this study,Hu sheep aged from 0 to 5 months were selected as the research object.Sixty healthy Hu sheep were randomly selected to measure body weight（BW）,body height（BH）,body length（BL）,chest circumference（CG）and tube circumference（SC）at 0,0.5,1,2,3,4and 5 months of age,respectively.The Logistic,Gompertz and Von Bertalanffy nonlinear growth models were used to fit the growth process of 0～5 months old Hu sheep.The results showed that:（1）The growth rate of Hu sheep at 4～5 months of age was the fastest,followed by 1～2 months of age;（2）The fitting degrees of Logistic,Gompertz and Von Bertalanffy models for the early growth and development of Hu sheep were all higher than 0.98,and the theoretical values of each body size in Von Bertalanffy model were closest to the actual measured values,and the fitting results were the best;（3）The curve equation Y=48.579（1-0.601e-0.259t）³was obtained by fitting the body weight data to the Von Bertalanffy model.The age at the inflection point was 68d,the body weight at the inflection point was 14.39kg,and the maximum daily gain was 186.4g.In this study,the ewe of Hu sheep aged from 3 to 5 months were selected as the research object,and the digestion and metabolism experiment were conducted at 80 to 90 days,110 to120 days and 140 to 150 days,respectively.A completely randomized design was used in the experiment,and 12 ewes at each month of age were randomly divided into three groups:fed ad libitum（AL）,70%（IR70）or 50%（IR50）of the ad libitum intake.Feeding experiment and digestion and metabolism experiment were combined to study the law of energy metabolism of ewe in the growing period of Hu sheep,and the regression equation of energy requirement was obtained.The results show that:（1）Feeding level had a significant effect on the growth of Hu ewes.Dry matter intake,net gain and average daily gain of free feeding group at 3 months of age were significantly higher than those of the two restricted feeding groups（P<0.01）.（2）At 3 months of age,the acid detergent fiber（ADF）digestibility of AL group and IR70group was significantly higher than that of IR50 group（P<0.01）.At 4 months of age,the digestibility of dry matter（DM）,crude protein（CP）,neutral detergent fiber（NDF）and acid detergent fiber（ADF）in AL group and IR70 group was significantly lower than that in IR50group（P<0.05）.At 5 months of age,the crude fat（CP）digestibility of AL group was significantly lower than that of IR50 group（P<0.05）.（3）At 3 months of age,the ammonia nitrogen（NH3-N）concentration in AL group was significantly lower than that in IR70 group and IR50 group（P<0.05）.At 4 months of age,the ammonia nitrogen（NH3-N）concentration in AL group and IR70 group was significantly lower than that in IR50 group（P<0.05）.At 5 months of age,p H of AL group was significantly lower than that of IR50 group（P<0.05）,and acetic acid concentration of AL group and IR70 group was significantly higher than that of IR50 group（P<0.01）.The propionic acid concentration in AL group was significantly higher than that in IR50 group（P<0.05）,the valerate acid concentration in IR70 group was significantly higher than that in IR50 group（P<0.05）.The total acid concentration in AL group and IR70 group was significantly higher than that in IR50group（P<0.01）.（4）At 3 months of age,the gross energy intake（GEI）,fecal energy（FE）,digestible energy（DE）and metabolizable energy（ME）of ewes in AL group were significantly higher than those in the two restricted feeding groups（P<0.01）.At 3 months of age,gross energy metabolic rate and digestible energy metabolic rate in AL group were significantly higher than those in IR50group（P<0.05）.（5）To establish the regression equation of DE requirement or ME requirement with metabolic weight and average daily gain of Hu sheep female lambs at different months of age:3 months（15-19kg）DE（MJ/d）=0.896W^0.75+16.147ADG（P<0.001,R²=0.975）ME（MJ/d）=0.722 W^0.75+14.940ADG（P<0.001,R²=0.963）4 months（20-25kg）DE（MJ/d）=0.611W^0.75+20.861ADG（P<0.001,R²=0.993）ME（MJ/d）=0.366W^0.75+21.611ADG（P<0.001,R²=0.984）5 months（26-30kg）DE（MJ/d）=0.729W^0.75+18.429ADG（P<0.001,R²=0.992）ME（MJ/d）=0.581W^0.75+15.061ADG（P<0.001,R²=0.990）The results showed that the maintenance metabolizable energy requirements of Huyang ewes at 3 months（15-19 kg）,4 months（20-25 kg）and 5 months（26-30 kg）were 0.722,0.366and 0.581 MJ/BW^0.75·d,respectively.According to the above regression equation,digestible energy and metabolizable energy requirements of Hu-sheep ewes with different body weights（15-30kg）under different daily gain conditions（100,200,300 and 350g/d）were estimated.（6）To establish the regression equation of DE requirement or ME requirement with metabolic weight and average daily gain of ewe of Hu sheep during the growing period:DE（MJ/d）=0.783W^0.75+15.515ADG（P<0.001,R²=0.983）ME（MJ/d）=0.6W^0.75+13.588ADG（P<0.001,R²=0.971）The regression equation of DE requirement or ME requirement with monthly age and average daily gain of Hu sheep was obtained:DE（MJ/d）=0.783{48.579（1-0.601e-0.259t）³}^0.75+15.515ADG ME（MJ/d）=0.6{48.579（1-0.601e-0.259t）³}^0.75+13.588ADG...