| In these series of research, meat sheep were used as animal models to study. First, in vitro gasproduction experiment was used to explore the suitable fermenting NDF level of cultivation substratewith5different NDF forage sources. In this context, we designed different NDF levels diets withChinese wildrey hay and alfalfa being the forage source, aimed at achieving the suitable dietary NDFlevel after doing animal feeding trails with these diets. The present research consists of threeexperiments which were listed as follows.Experiment1: The influence of in vitro gas production experiment by SiO2.This experiment was divided into two parts. The first part, we compared the gas production andfermentation parameters of different additions of SiO2to the blank control group. The second part, wecompared the gas production and fermentation parameters of different additions of SiO2with basesubstrate (soybean meal/Chinese hay NDF/corn starch=70mg/100mg/30mg) to the base substrate. Theadditions of SiO2are25mg,50mg,75mg,100mg. The results showed, different addition of SiO2haveno significant effects on both gas production and fermentation parameters (P﹥0.05). The base substratewith different addition of SiO2also have no significant effects on both gas production and fermentationparameters(P﹥0.05).Experiment2: The influence of in vitro gas production by cultivation substrates withdifferent NDF forage sources and levelsThis experiment was adopts in vitro gas production to determine the pH, gas production after72hincubation(GP72h), in vitro organic matter digestibility(IVDOM), microbial protein(MCP), NH3-N, andvolatile fatty acid(VFA). To search the most suitable dietary NDF level of Dorper×thin-talied Hancrossbred lambs and compare the different effects on the results of in vitro gas production by differentNDF sources. After72h in vitro incubating of Chinese wildrey hay NDF, wheat straw NDF, alfalfa NDF,corn straw NDF, corn silage NDF, the results showed as follows, different sources of NDF have thesignificant effects on in vitro gas production. The GP72hand TVFA of corn straw NDF and corn silageNDF were significantly higher than alfalfa NDF（P﹤0.05）, but pH were significantly lower than alfalfaNDF（P﹤0.05）. The MCP of alfalfa NDF was significantly higher than others（P﹤0.05）. We usedsoybean meal as the CP source, corn starch as the NSC source and5forage NDF as the NDF source, torespectively make the cultivation substrate with NDF levels form10%to60%. The CP levels wererespectively designed on14.10%and11.70%. after72h in vitro incubating, the results showed, as theincreasing of NDF level, GP72hwas significantly increasing（P﹤0.05）, pH was significantly decreasing（P﹤0.05）. TVFA has a rising trend. When the NDF level was during30%～40%, NH3-N was lowerthan other NDF levels but MCP was higher than other NDF levels. The values of all the indexes in CP11.70%were lower than CP14.50%. Experiment3: To establish the suitable dietary NDF level of Dorper×thin-talied Hancrossbred lambs with Chinese wildrey hay and alfalfa as the forage source.Fifty female lambs and twenty-five male lambs were randomly assigned to five groups with tenfemale lambs and five male lambs each (five lambs/replication). Female and male lambs were separatedto feed. Each group feed one of the five diets which have same crude protein level and different NDFlevels. When the live weight of sheep was25to35kg, the dietary crude protein level was14.50%andthe dietary NDF levels were25%,30%,35%,40%,45%respectively. When the live weight of sheepwas35to5o kg, the dietary crude protein level was11.90%and the dietary NDF levels were30%,35%,40%,45%,50%respectively. Growth performance was measured, and digestive trails were conductedwhen the live weight of sheep was30or50kg. The results showed as follows: NDF levels hadsignificant effects on DMI and apparent nutrient digestibility（P﹤0.05）. Dry matter intake of lambs hada positive correlation with NDF levels, and apparent nutrient digestibility had quadratic parabolacorrelation with NDF levels. Average daily gain and apparent nutrient digestibility were highest whenthe NDF level was33.35%during25～35kg live weight or43.21%during35～50kg live weight. |
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