Seasonal Dynamics Of Condensed Tannin Content And Structure Of Lespedeza Bicolor And Their Effects On The In Vitro Rumen Fermentation

The proper amount of condensed tannins in forage has a beneficial effect on livestock production.For example,condensed tannins can increase bypass protein in ruminants,reduce methane emission,which is of great significance in promoting animal husbandry production and protecting the environment.However,due to the large differences in the content of condensed tannins and their types in different forages,condensed tannins of different sources and contents have great differences in increasing bypass protein in ruminants and reducing methane emissions.In the research on the effects of condensed tannins on the rumen fermentation characteristics,the international research mainly focus on cultivated forages such as Onobrychis viciaefolia and Lotus corniculatus,while the reports on wild Lespedeza bicolor which is rich in tannins are very limited.Therefore,in the present study,wild L.bicolor in the Loess Plateau was used as the research objective.The content and chemical structure of condensed tannins of L.bicolor leaves were determined and characterized.The combination of in vitro gas production technology and polyethylene glycol(PEG)addition method was used to explore the effects of condensed tannin of L.bicolor on rumen fermentation.L.bicolor and alfalfa(Medicago sativa)were mixed in different ratios for fermentation to determine the best combination of the ration.The aim of the study was to develop natural forage that contains condensed tannins,to provide more beneficial options for the selection of livestock feed,and to provide the theoretical and practical basis for the development of animal husbandry in the local region.The main results of this study are as follows:(1)The condensed tannin content of L.bicolor was 150-250 g/kg DM.The content and protein-complexation ability of condensed tannins decreased during the growth period,whereas the structural changes of the condensed tannin were not significant.(2)The results of the in vitro rumen fermentation study showed that L.bicolor samples collected in June had higher total gas production,total volatile fatty acids and dry matter digestibility than those collected in other months.By analyzing the effects of the addition of PEG on the in vitro fermentation,it was found that the condensed tannins of L.bicolor significantly inhibited the production of fermentation gases,reduced methane emission,and reduced the concentration of ammonia nitrogen in the fermentation broth.(3)The in vitro fermentation results of the mixed ration of L.bicolor and alfalfa showed that compared with other treatments,the treatment that had 20:80 dry weight ratio of L.bicolor and alfalfa showed good fermentation characteristics,such as low methane production,low ammonia nitrogen content,high dry matter degradation rate and high volatile fatty acid yield.This study has the following conclusions: The wild L.bicolor in the Loess Plateau is rich in condensed tannins.The sample collected in the early stage of the growing season had better rumen fermentation performance.In addition,when L.bicolor and alfalfa are mixed in an appropriate ratio,the ration may be more beneficial to the production of ruminants than a single forage feed.The results of this study will provide a theoretical basis for the development and utilization of L.bicolor as new forage,which is of great significance for alleviating the shortage of forage in the Loess Plateau region and promoting the development of local animal husbandry.