Research On Nutrition Value Assessment Of Various Forage Silage And Their Effects On Fattening Beef Cattle

The feeding management of herbivorous livestock in China is undergoing a transition from“low quality roughage+high concentrate”to“high quality forage+low concentrate”,and the transition has also profound impact on the grass industry.There is an inevitable requirement for safe and efficient production of herbivorous livestock that research and development of high-quality forage and its utilization technology.As far as Chinese beef cattle production is concerned,it shows a new pattern which is regional layout,large-scale development and industrialized operation.However,there is no synergistic development between grass industry and new-type livestock industry,and those are not moderate that feeding theory and supporting technology of new forage products in animal husbandry production process.Therefore,the present study was conducted in the grassland agricultural demonstration zone?the hilly and gully region of the Loess Plateau?through systematic research on the nutritional assessment of grass products and their effects of fattening beef cattle.The purpose was to establish nutritional parameters and matching technology of fattening beef cattle of the wrapped silage,and more,explore the regulating mechanism that the silage type diet affects beef cattle nutrition.To study the nutritional quality and combination effects of forage silage,it was used as research materials that the stretch wrapped silage of corn,oat,alfalfa and alfalfa hay.Based on previous results,the total mixed ration?TMR?was made up,and a series of experiments were carried out as cattle feeding,digesting and slaughtering.For the in vitro,to study the combined effect of forages,the various combinations were:C₁?50%corn silage+50%oat silage?,C₂?50%corn silage+50%alfalfa silage?,C₃?80%corn silage+20%alfalfa hay?,C₄?50%oat silage+50%alfalfa hay?,C₅?70%corn silage+10%oat silage+20%alfalfa silage?,C₆?65%corn silage+15%?Oat silage+25%alfalfa silage)and C₇?50%corn silage+20%oat silage+30%alfalfa silage?.For in vivo,to explore the regulating mechanism that the silage type diet affects beef cattle nutrition,thirty Simmental bulls?initial body weight is 440.5±3.5kg?were randomly divided into two groups in the comparative fattening experiment,and they were fed with single corn silage TMR?SS?and silage combination?corn silage,alfalfa silage,oat silage?TMR?MS?,respectively.The period a 180-day fattening trial was divided into three stages as P1?1d to 60d?,P2?61d-120d?,P3?121d-180d?,and the formula for each group was adjusted according to the nutritional requirements of different growth stages in each stage.The blood and rumen fluid were collected on the 60^th,120^th,and 180^th day.At the end of the fattening trial,those animals were slaughtered that six beef cattle of similar final body weight from SS or MS,and the right longissimus dorsi muscle was used for the slaughtering performance,meat quality,and histological characteristics determination;In addition,the tissue samples of gastrointestinal tract and kidney were collected to determine the histological characteristics and the relative expression of nutrient transporter.Mainly results as following showed that:?1?The results in vitro indicated that for single forage:the gas production?GP?for corn silage was the highest and alfalfa silage was the lowest at 3h,6h,9h,12h,24h,36h and 48h?P<0.05?;the dry matter 48h disappearance rate?DMD?of corn silage was higher than others?P<0.05?;the pH was differences among the groups?P<0.05?;it was the highest that ammonia nitrogen?NH₃-N?concentration for oat silage?P<0.05?;the total volatile fatty acid?TVFA?of corn silage was higher than that of alfalfa silage and alfalfa hay?P<0.05?.For seven combination groups,the DMD of C₂was lower than C₅ and C₇?P<0.05?;TVFA concentrations of C₂ and C₄ were lower than C₅ and C₆?P<0.05?.?2?The ADG of MS group was increased by 8.6%compared with SS group,and F:G of MS group was decreased by 23.65%;And it was interesting that fattening MS group was more conducive to reduce the stress caused by dietary conversion than that of SS group.?3?The P1 stage digestibility of NDF and ADF in the two groups were lower than that others?P<0.05?.The relative expression of PepT1mRNA and PepT2mRNA in the rumen epithelium of SS group was higher than that of MS group?P<0.01?.?4?It was respectively lower 33.2%,11.5%and 12.5%for MS group than SS group of the average daily methane emission and fecal dry mater and nitrogen excretion.And there was significant reducing emission effect for silage combined TMR fattening beef cattle.?5?TVFA and propionic acid in MS group?3.22 mg/dL and 4.33 mg/dL?were lower than those in SS group?9.63 mg/dL and 13.45 mg/dL??P<0.01?during the whole experiment period,and its in SS group was increased with the extension of fattening time?P<0.05?.The thickness of inner circular muscle layer of duodenum in MS group was higher than that in SS group?P<0.05?,and the ratio of villus length to crypt height in ileum?V/C?in MS group was higher than that in SS group?P<0.05?.Bacteroidetes and Firmicutes were the dominant bacteria in three stages;Prevotella 1and Rikenellaceae_RC9_gut_group were the dominant bacteria in three stages.?6?The loin-eye area in MS group was higher than that in SS group?P<0.05?,the ratio of connective tissue in MS group was lower than that in SS group?P<0.05?,and the content of histidine in MS group was higher than that in SS group?P<0.05?.There was no significant difference in fatty acid composition of longissimus dorsi between the two groups?P>0.05?.In summary,there were significant differences in rumen gas production,kinetic parameters and rumen fermentation parameters that corn silage,oat silage,alfalfa silage and alfalfa hay.The combination of 50%oat silage and 50%alfalfa hay was better based on the level of MFAEI.Compared with the single corn silage TMR,the various forage silage combined TMR could improve the average daily gain and feed conversion efficiency,and reduce the fecal excretion and methane emissions of beef cattle.Long-term fattening beef cattle with silage combination TMR was more conducive to reducing the stress caused by dietary conversion and making the small intestine more helpful to nutrient absorption,and modifying microflora environment of gastrointestinal tract.In addition,silage combination TMR fattening beef cattle can also regulate beef qualities.