The Effects Of Different Ratios Of Millet Straw And Corn Straw Silage Diets On Fattening Performance,Rumen Fermentation And Rumen Microbial Flora In Beef Cattle

To investigate the effect of different ratios of millet straw and corn straw silage diet on fattening performance,blood index,slaughter performance,meat quality,rumen fermentation,rumen microbial flora and economic benefit of beef cattle.45 healthy Simmental crossbred cattle（440±38.49 kg）were randomly and equally assigned into 3groups.Each group had 15 Simmental crossbred cattle.Each group had the same concentrates and concentrate-roughage ratio.The proportions of millet straw and corn straw silage were:10:90（groupⅠ）,20:80（groupⅡ）,30:70（groupⅢ）.The experiment lasted for 90 days.The results showed:（1）Among the three experimental groups,the average daily gain（ADG）of group II was the highest（1.56 kg/d）,which was improved12.23%compared with group III（P<0.05）.The feed-to-gain ratio（F/G）of group II was the lowest（7.38）,but there was no significant difference among the three groups of cattle（P>0.05）.（2）The apparent digestibility of nutrients such as crude protein（CP）,neutral detergent fiber（NDF）,acidic detergent fiber（ADF）,calcium（Ca）,and total phosphorus（P）were the highest in Group II（P>0.05）.（3）The serum GH and IGF-1 were also the highest in Group II beef cattle,which was 1.86%（P>0.05）,8.34%（P<0.05）higher than group I and 5.38%（P>0.05）,11.03%（P<0.05）higher than group III.（4）There were no significant differences in body weight,slaughter rate and net meat rate among the three groups（P>0.05）,but the slaughter indicators of Group II were better than those in group I and group III.（5）There were no significant differences in pH,shear force and water loss rate of meat`（P>0.05）,but meat color a*gradually decreased with the increasing of the proportion of millet straw,group III had a relative decrease of 13.10%and 9.77%（P<0.05）compared with group I and group II.（6）There were no significant differences in saturated fatty acids（SFA）,monounsaturated fatty acids（MUFA）,and polyunsaturated fatty acids（PUFA）among the three groups of cattle（P>0.05）.With the increase of the proportion of millet straw,SFA and PUFA had a downward trend;MUFA had a rising trend.（7）With the increase of the proportion of millet straw,the MCP production of beef cattle decreased gradually.Group II had lower NH₃-N concentrations than Group I and III.The concentration of acetic acid in the rumen increased gradually with the increase of the proportion of millet straw,propionic acid concentration gradually decreased with increasing proportion of millet straw,The total volatile fatty acids（TVFA）and acetic-propionate ratio（A/P）were increased gradually with increasing proportion of millet straw.（8）There were no significant differences among the three groups in rumen microbial species richness index Observed-species,Chao1,ACE,and community diversity index Shannon and Simpson（P>0.05）.At the phylum level,the top3 rumen bacteria in the rumen of each group were Bacteroidetes,Firmicutes,and Proteobacteria,which were dominant flora.The highest proportion of Bacteroidetes in group II was47.42%,which was greater than those of group I and group III（P>0.05）.At the genus level,Prevotella₁was the largest proportion,group II>group I>group III,there was no significant difference among the three groups（P>0.05）.（9）From the economic benefit,the group II had the highest economic benefit,which was 15.78%higher than group I and37.34%higher than group III.In summary:under the experiment conditions,the optimal ratio of millet straw and corn straw silage was 20:80,ADG was the highest,F/G was the lowest,apparent digestibility of nutrients and slaughter performance has also been improved.Rumen fermentation environment was the best.Economic benefit was the best.