Effects Of Low Protein Diet Supplemented With Rumen Protected Methionine On Nutrients Metabolism At Rumen And Post-rumen Using In Vitro Techniques

Protein quality plays a vital role in growth,production,and reproduction of ruminants.Application of high concentration of dietary crude protein(CP)can improve dairy performance and balance the required amount of limiting amino acids(AA)at duodenal digesta of the high producing dairy ruminants.Usually,high dietary CP diet also increases excessive nitrogen(N)excretion by urine and faeces,and occasionally,increases gases production into the environment.However,the protein which reaches at the small intestine is adequate in cystine but deficient in methionine(Met)and making it the first limiting AA for high yielding dairy ruminants.Thus,the addition of limiting AA in the way of rumenprotected is highly recommended by many researchers to meet the AA requirement for high yield dairy animals.For endorsement of these all referential data our hypothesis behind this study is that: the flow of Met in the small intestine is the first limiting AA.And the Met came from rumen undegradable protein(UDP),microbial crude protein(MCP)and supplemented rumen-protected methionine(RPMet)for the “low CP diet+RPMet” could meet the requirement for medium yield dairy ruminants.Because the heat increment accelerates with the upsurge of dietary CP in diet and rise loses of energy with high N excretion.“Low CP diet+RPMet” diets not only decrease feed cost but also improve nutrients metabolism,increase nitrogen and energy utilization.The methodology of the 1st experiment(Rusitec),followed as described by Kajikawa et al.(2003),using rumen simulation technique(Rusitec,Sanshin,Tokyo,Japan).Furthermore,the 2nd and 3rd experiment in vitro one step abomasum and ileum digestibility were followed as modified procedure proposed by Boisen and Fernandez(1995)using thermostaticcontrolled heating chamber(RDM,CM22 6JX the United Kingdom).The research was randomly designed and repeated over two independents 15 d incubation periods at Rusitec with 7 d for adaption and 8 d for samples collection followed by in vitro one step abomasum(6 h)and ileum digestibility(18 h).The four groups were designed as(1)the positive control group,high protein diet without RPMet(HP,163.39 g/kg CP),(2)the negative control group,low protein diet without RPMet(LP,146.33 g/kg CP),(3)low protein diet(141.80 g/kg CP)supplemented with low concentration of RPMet(0.11 g/kg DM)(LPLMet),and(4)low protein diet(143.30 g/kg CP)supplemented with high concentration of RPMet(0.81 g/kg DM)(LPHMet).Based on NRC(2001)recommendation for dairy cows HP diet formulated as a positive normal control.The test product was provided as mepron? as a rumen-protected DLmethionine 85.00 %(CAS-RN:59-51-8;DL-methionine)and has rumen bypass rate 80.00% developed by Evonik Germany.The results of the current study stated below.Results of the current research represent that,the CP disappearances of LPLMet and LPHMet diets were significantly improved at Rusitec and post-ruminal.However,NDF and GE disappearances of LPLMet,LPHMet,and HP were unaffected at Rusitec,but postruminal NDF disappearances of LPHMet were significantly higher than HP(P<0.05).Furthermore,the RPMet supplementation promotes the 16 S r DNA gene copy numbers in the Rusitec fluid and residue(solid)significantly(P<0.05),but not affect the copy number of R.flavefaciens and F.succinogenes or total bacterial species numbers except R.albus.However,values of microbial crude protein synthesis,total or short chain fatty acids and R.albus population were similar(P>0.05)between LPHMet and HP groups.Production of total gas and methane volume and NH3-N were significantly(P<0.05)higher in HP than LP,LPLMet and LPHMet at Rusitec.However,p H before or after feeding was not significantly changed(P>0.05)of each Rusitec fermenter among all groups with RPMet supplementation.The flow of total AA from the fluid portion at ileum(small intestine)in LPHMet was found nonsignificant(P>0.05)different compared with HP than other groups.Furthermore,the flow of methionine was also significantly(P<0.05)increased in LPHMet than LPLMet,LP and HP at ileum.However,from residue portion the total AA and some essential and non-essential AA were pointedly higher(P<0.05)in HP residue than other groups.In summary,the dietary supplementation of RPMet with low CP at a level of(0.11 g/kg DM;LPLMet),the most of studied parameters were unaffected at post-ruminal.But at a level of(0.81 g/kg DM;LPHMet)inclusion in the current study could significantly improve MCP yield,concentrations of total and short chain fatty acids in a Rusitec fluid,the disappearances of NDF and GE,and rumen specific species R.albus population.Furthermore,production volume of total and methane gas was significantly higher in HP than other groups at Rusitec.However,the CP disappearances of supplement groups were significantly improved at Rusitec and post-ruminal(abomasum and ileum).Although,post-ruminally at abomasum and ileum NDF disappearance potently higher in LPHMet than other groups.The total and some essential and non-essential AA were pointedly higher excreted in HP residue at small intestine than other groups.Based on the results of present research,we concluded that for the medium yield ruminants “low CP diet+RPMet”(LPHMet)can replace HP diet.