Study On Two-stage Net Energy Requirement Of Maintenance And Net Energy Value Of Chinese Wildrye Hay For Dorper And Thin-tailed Han Mutton Sheep

The purpose of this study was to determine the net energy requirements for maintenance of mutton sheep and the net energy value of Chinese Wildrye Hay by different methods,so as to provide methods and theoretical basis for the net energy system and precise nutrition of mutton sheep.Having determined two-stage net energy requirement of maintenance by using the method of regression and fasting and compared them subsequently for Dorper and Thin-tailed Han F1 progeny mutton sheep.At the same time,the net energy value of Chinese Wildrye hay during the fattening period of the sheep was determined by substitution method.This research consisted of three parts,and the details were as follows:ExperimentⅠ:The net energy for maintenance of Dorper and Thin-tailed Han lambsThe purpose of this study was to determine the NEm of the lambs by regression and fasting method.A total of twenty four lambs（12♂+12♀）were randomly allotted to four groups with 6 sheep（3♂+3♀）for each.Four groups included 1 fasting group and 3 regression groups in which fed ad libitum（AL group）,80%of ad libitum（AL80 group）and 60%of ad libitum（AL60 group）,carrying out fasting in the respiration calorimetry for fasting substitution group.Nutrient apparent digestibility,energy utilization,gas metabolism and net energy for maintenance of the lambs at different feeding levels were determined.The results showed that there were no differences in apparent digestibility of dry matter,organic matter and nitrogen in regression groups,but had extremely significant differences in gross energy and fecal energy among all groups（P<0.01）.The methane energy of AL group was higher than the other two groups（P<0.05）.There were no significant differences in digestible energy,metabolizable energy,gross energy,as well as the ratio of digestible energy and metabolic energy to gross energy,the ratio of metabolic energy to digestible energy among feeding levels（P>0.05）,but gas production was significantly different（P<0.05）;The net energy for maintenance during lamb stage was 224.08 k J/kg BW^0.75 by regression method,232.84 k J/kg BW^0.75 by fasting method.There was no significant differences between two methods（P>0.05）.ExperimentⅡ:The net energy for maintenance of Dorper and Thin-tailed Han fattening sheepThe purpose of this study was to determine the NEm of the fatting sheep by regression and fasting substitution method.A total of twenty four fatting sheep（12♂+12♀）were randomly allotted to four groups with 6 sheep for each.The grouping method and measurement index were same as experimentⅠ.The results were as follows:There were no significant differences in the apparent digestibility of dry matter,organic matter and nitrogen among regression groups（P>0.05）,and had no significant effect on urinary energy（P>0.05）,but had significant effects on gross energy intake and fecal energy（P<0.05）;The methane energy,digestible energy,the rate of metabolic energy to digestible energy and oxygen consumption in AL group were significantly different from those in restricted feeding groups（P<0.05）.The net energy for maintenance during fatting sheep was 271.33 k J/kg BW^0.75 by regression method,and 279.20k J/kg BW^0.75 by fasting method.There was no significant difference between two methods（P>0.05）.ExperimentⅢ:The net energy value of Chinese Wildrye Hay for Dorper and Thin-tailed Han fattening sheepThe purpose of this study was to determine the NE value of Chinese Wildrye Hay for fatting sheep.A total of sixteen lambs（8♂+8♀）were randomly allotted to two groups which were basal diet group and Chinese Wildrye Hay replacement group（35%Chinese Wildrye Hay+65%basal diet）with 8 sheep for each.The results were as follow:Different dietary composition had no significant effects on apparent digestibility of dry matter,organic matter and nitrogen（P>0.05）,and had no significant effects on digestible energy,metabolizable energy,and the ratio of digestible energy and metabolic energy to gross energy,but had significant effects on the gross energy,fecal energy and methane energy（P>0.05）;The net energy value of Chinese Wildrye Hay was 6.50 MJ/kg DM.