Changes Of Rumen Methanogen Diversity And Quantity Associated With Different Sources Of Forage And Protein In Diets

Methane from ruminants is an undesirable end product of rumen fermentation as itrepresents an3-12%of total energy loss to the host animal and it accounts for30%ofthe global methane emissions. Methanogens are the major microbial for methaneemission in rumen. The objective of this study was to compare the methanogencommunity and number in the rumen of cows fed with different sources of forage andprotein in diet.Forty-eight Chinese Holstein dairy cows were randomly assigned into three groupsaccording to milk yield and day in milking (DIM). The diets in three treatments wereas follows: MF (alfalfa and corn silage, soybean meal), CSA (corn stover, soybeanmeal), CSB (corn stover, cottonseed and rapeseed meal). The experiment wasconducted for107days and consisted2periods. In Period1, the cows were fed withassigned diets for91days. Then in Period2，all animals were fed with MF diet. Allthe cows are free to water and fed three times a day. Rumen fluid samples werecollected before and after feeding using stomach-tube on day91and day107. Theexperiment consist two parts:Part1: The effects of different sources of forage and protein on the methanogencommunity structure. mcrA gene clone library was used to reveal the diversity of rumenmethanogen. Mothur Software was used to assign clones to operational taxonomic units(OTUs) based on a94%sequence identity cutoff.763clones were examined and25OTUs were found. In the library before feed. ten OTUs were represented in all threelibraries, ten OTUs were only found in the CSA and CSB, and eleven OTUs wereshared between MF and CSA. In the library after feed, ten OTUs were represented inall three libraries,13OTUs were only found in the CSA and CSB, and12OTUs wereshared between MF and CSA. We found that the squences belong to Rumen clusterC(RCC) and Methanobrevibacter-related sequences were the most abundant in allgroups library. Libshuff software analysis and PCA analysis showed methanogencommunity of CSA and CSB, MF and CSA were different (P=0.03and P=0.04, respectively). MF and CSB had lower diversity based on Shannon index and Ace index,Compared with CSA. CSA had higher richness than MF and CSB, according toShannon and Simpson index. Additionally, CSA had a high proportion ofMethanobrevibacter.smithii, MF had high proportions of M.gottschalkii andM.ruminanium, while CSB had a high proportion of M. millerae.Part2: The effects of different sources of forage and protein on the number ofrumen methanogen. qPCR was used to detect the quantity of methanogen. The resultsshowed during Period1the quantity of methanogen of CSA and CSB was different(p=0.049), while MF and CSA had no differences; The quantity of methanogen of CSAand CSB, MF and CSA had no differences during Period2.In conclusion, the different sources of forage and protein in diet changed thecommunity structure of rumen methanogen; Alfalfa and corn silage diet and corn strawdiet have no effects on the number of methanogen, but the soybean diet promoted thequantity of methanogen, compared with rapeseed diet.