Study On The Energy And Protein Nutrient Requirements Of Tan Sheep Ewes During Growing Period

Tan sheep is a unique local sheep breed for fur in China,and is one of the sheep breeds developed and protected by the state.However,with the implementation of the policy of closing mountains and banning grazing,the feeding method of Tan sheep has also changed from traditional grazing to house breeding.Due to its living conditions and lifestyle changes,the intensive breeding of Tan sheep also has problems such as unbalanced nutrition,slow growth rate and low feed remuneration,but the current feeding standards for Tan sheep have not been formulated and released.In this study,the effects of diets with different energy and crude protein levels on the growth performance,energy and protein digestion and utilization efficiency and serum biochemical indexes of Tan sheep ewes during growing period were investigated by feeding experiment and digestion and metabolism experiment,in order to preliminarily determine the energy and protein nutrient requirements of Tan sheep ewes during growing period,and provide basic data for the establishment and release of feeding standards for Tan sheep in intensive houses.The main results of this study are as follows:1.Sixty-four 4-month-old Tan sheep ewes with good body condition and similar weight were randomly divided into 4 groups of 4 replicates each,with 4 replicates each.The digestible energy of the four test diets was set to 10.32（80%）,11.61（90%）,12.9（100%）,and 14.08 MJ/kg（110%）,and the crude protein level was 174 g/kg.An 80-day feeding experiment was carried out,and after the feeding experiment,digestion and metabolism experiment was carried out by whole feces and urine collection.It was found that with the increase of energy level in diet,the gross energy digestibility,metabolic rate and digestible energy metabolic rate of ewes in the four test groups gradually increased.The gross energy digestibility and metabolic rate of the test ewes increased linearly with the increase of energy level（P<0.05）,but the dietary energy level had no significant effect on the digestive energy metabolic rate of the test ewes（P>0.05）.The average daily weight gain of ewes in the four test groups increased linearly with the increase of gross energy,digestible energy and metabolizable energy intake（P<0.05）,and the correlation coefficients were 0.9736,0.9988and 0.9986,respectively.Among them,the average daily gain of ewes in the energy level group with 14.08 MJ/kg was the largest,reaching 215.59 g/d.The ratio of feed to gain of ewes in the four test groups showed a significantly decreased trend with the increase of energy intake（P<0.05）.With the increase of energy level,the serum total cholesterol content of ewes in four test groups gradually increased（P<0.05）,and the content of urea nitrogen gradually decreased（P<0.05）.Based on the above data,the regression equations for digestible energy and metabolizable energy nutrient requirements and metabolic body weight and average daily weight gain of Tan sheep and ewes during growing period were constructed as follows:DE（MJ/d）=0.5343 W^0.75+0.042 ADG（P<0.01 R²=0.9781）ME（MJ/d）=0.4230 W^0.75+0.037 ADG（P<0.01 R²=0.9900）2.Sixty-four 4-month-old Tan sheep ewes with good body condition and similar weight were randomly divided into 4 groups of 4 replicates each,with 4 replicates each.The crude protein levels of the four test diets were set to 119（70%）,144.5（85%）,170（100%）,and195.5 g/kg（115%）,and the energy level was 12.5 MJ/kg.An 80-day feeding experiment was carried out,and after the feeding experiment,digestion and metabolism experiment was carried out by whole feces and urine collection.It was found that the crude protein level of the diet had no significant effect on the apparent digestibility of crude protein in the test ewes（P>0.05）.The average daily weight gain of ewes in the four test groups showed a linear increase with the increase of crude protein and digestible crude protein intake（P<0.05）,and the correlation coefficients between them were 0.9900 and 0.9638,respectively.Among them,the average daily weight gain of the 195 g/kg protein level group was the largest,reaching 205.75 g/d.The ratio of feed to gain of the test ewes showed a significantly decreased trend with the increase of protein intake（P<0.05）.With the increase of crude protein level,the serum urea nitrogen content of ewes in four test groups increased significantly（P<0.05）,but the total cholesterol and triglyceride contents did not increase linearly with the increase of protein level（P<0.05）.Based on the above data,the regression equations for crude protein and digestible crude protein nutrient requirements and metabolic body weight and average daily weight gain of Tan sheep ewes during growing period were constructed as follows:CP（g/d）=3.8581 W^0.75+0.6975 ADG（P<0.01 R²=0.9162）DCP（g/d）=2.3167 W^0.75+0.4932 ADG（P<0.01 R²=0.9480）In summary,this study synthesized the growth performance,digestion and metabolic efficiency and serum biochemical indexes of Tan sheep ewes during growing period,and established the energy and protein nutrient requirement regression equation of Tan sheep ewes during growing period,which provided an important reference basis for the intensive feeding of Tan sheep and provided some data support for the establishment and release of feeding standards of Tan sheep in the later stage.