Effects Of Folic Acid Supplementation On Ruminal Fermentation,Nutrient Digestion And Metabolism In Jinnan Steers Based On Different Energy Diets

This study was conducted to investigate the effects of folic acid supplementation on ruminal fermentation,nutrient digestion and metabolism in Jinnan steers based on different energy diets.Four Jinnan steers(average BW 397 ± 20 kg,2.5 years old)with permanent ruminal cannula consuming a corn silage diet were used in two 4x4 Latin square design and supplemented with four concentrations(0,0.07,0.14,0.21 mg/kg BW/d)of rumen protected folic acid based on two different energy diets(NEmf were 5.69 and 6.23 MJ/kg,respectively).The results showed that the interaction between rumen protected folic acid and energy of the diets had no significant effects on each parameters(P>0.05).Rumen proteinase activity and serum glucose,total cholesterol,triglyceride,glutamic-pyruvic transaminase,lactate dehydrogenase concentration in high energy feeding conditions were significantly higher than those in standard energy feeding conditions(P<0.05).But energy levels had no significant effects on rumen fermentation,ruminal degradabilities of nutrients,celluloytic bacteria,synthesis of microbe protein,nutrients digestibility and nitrogen balance(P>0.05).Ruminal pH and ammonia nitrogen in groups supplemented folic acid at 0.14 mg/kg BW/d and 0.21 mg/kg BW/d were significantly lower than that of control group(P<0.05).Total volatile fatty acid in group supplemented folic acid at 0.14 mg/kg BW/d was significantly higher than that of control group(P<0.05).In standard energy feeding conditions,ruminal acetate and the ratio of acetate to propionate in group supplemented folic acid at 0.14 mg/kg BW/d were higher than those of control group significantly(P<0.05),while isobutyrate was lower than that of control group significantly(P<0.05).In high energy feeding conditions,the supplementation of folic acid increased the ratio of acetate to propionate;reduced the ruminal isobutyrate and isovalerate significantly(P<0,05).The digestibility of dietary dry matter,ether extract,nitrogen free extract,neutral detergent fibre,and the effective degradabilities of dry matter,crude protein and neutral detergent fibre in group supplemented folic acid at 0.14 mg/kg BW/d were significantly higher than those of control group(P<0.05),while no significant differences were found between groups supplemented folic acid at 0.14 mg/kg BW/d and 0.21 mg/kg BW/d.The activities of xylanase,cellobiose enzymes of steers supplemented folic acid at 0.14 mg/kg BW/d were significantly higher than those of control group(P<0.05).Supplemented folic acid had no significant effects on the activities of filter paper enzymes,carboxymethyl cellulase,pectinase,a-amylase and proteinase in rumen(P>0.05).The population of R.Albus,R.flavefaciens,F.Succinogenes in groups supplemented folic acid were significantly higher than those of control group(P<0.05),and the population of B.Fibrisolvens in groups supplemented folic acid at 0.14 mg/kg BW/d and 0.21 mg/kg BW/d were significantly higher than that of control group and 0.07 mg/kg BW/d(P<0.05).Synthesis of microbe protein,retention nitrogen and the ratio of retention nitrogen to digestible nitrogen in groups supplemented folic acid at 0.14 mg/kg BW/d and 0.21 mg/kg BW/d were higher than those of control group(P<0.05).Urine nitrogen and the ratio of urine nitrogenin to total nitrogen excretion in groups supplemented folic acid at 0.14 mg/kg BW/d and 0.21 mg/kg BW/d were lower than those of control group(P<0.05).The concentrations of homocysteine,folic acid and methylene tetrahydro folate reductase in serum of steers supplemented folic acid at 0.14 mg/kg BW/d and 0.21 mg/kg BW/d were higher than those of control group(P<0.05).Concentrations of glutamic-oxaloacetic transaminase,methionine synthase,growth hormone-releasing factor and growth hormone in serum of steers supplemented folic acid at 0.14 mg/kg BW/d were higher than those of control group,while no significant differences were found between groups supplemented folic acid at 0.14 mg/kg BW/d and 0.21 mg/kg BW/d(P>0.05).These results indicated that the optimum dose of folic acid was 0.14 mg/kg BW/d in standard energy feeding conditions.