Effects Of Physically Effective Neutral Detergent Fiber On Chewing Activity,Rumen Fermentation,Digestibility And Milk Production Of Dairy Cows Fed A Total Mixed Ration

Two parts of experiments included in this research work:Experiment 1:Effects of different peNDF content on rumen fermentation and nutrients digestion in dairy cowsThree dairy cows fitted with permanent rumianl cannulas,duodenum cannula and ileum cannula were used by 3×3 Latin Square design,to study ruminal internal environment parameters of dairy cows fed with three diets which were chemically similar but varied in peNDF content (H-high, M-medium, and L-low) by altering corn silage particle length. The results indicated:1.Increased dietary peNDF content improved the mean ruminal pH,ruminal mean NH3-N concentration significantly between L and H,M and H group (P<0.05); total volatile fatty acid also increased but no significantly between groups(P>0.05);the concentration of acetate, acetate-propionate ratio increased respectively in accordance with the peNDF content(P<0.05), whereas the concentration of propionate and butyrate decreased respectively(P<0.05). No significant difference was observed between groups for total volatile fatty acid (P>0.05).2. There was no significant effects on DM intake, duodenal flows, ileum flows, fecel flows, the amount of digestion in tract and DM digestibility both in small intestine and in total digestive tract by peNDF content (P>0.05); the digestibilities of DM in rumen between L and H treatments were improved in agreement with peNDF content in diets (P<0.05).3. .No significant effect was observed on OM intake,OM flows in different site of tract (P>0.05) as increasing peNDF content in TMR; the amount of digestion in rumen was improved significantly between groups(P<0.05), the digestibilities of OM both in rumen and in small intestine were echanced significantly in accordnace with peNDF content(P<0.05); the digestibilities of OM in total tract were improved too, but no significant impact presented on the amount of OM digestion(P >0.05).4. There were no significant effects on NDF intake, duodenal flows, ileum flows, fecel flows (P>0.05); the amount of digestion in rumen and total tract were improved significantly between groups(P<0.05), the digestibilities of NDF in rumen and total tract were also improved respectively as increasing dietary peNDF content.5. No significant effects were observed on ADF intake,ADF flows and amount of ADF digestion in different site of tracts (P>0.05) by peNDF, the digestibilities of ADF in rumen were elevated while receiving higher peNDF content(P<0.05), the digestibility of ADF in small intestine tended to decrease whereas the digestibility in total tract tended to increase combined with elevated peNDF content(>0.05).6. Increased the dietary peNDF content ,the digestibilities of N in rumen was significantly improved(P<0.05), the digestibilitles of N either in small intestine or in total tract were not affected respectively by peNDF content(P>0.05).Experiment 2: Effect of different dietary peNDF content on chewing activity,milk production and composition in dairy cowsThe objective of this research was to investigate the effects of physically effective neutral detergent fiber(peNDF) content in TMR on feed intake, chewing activity, milk performance and mild compositon of dairy cows. The experiment was designed as a replicated 3×3 Latin square using 6 lactating dairy cows. Cows were received 3 diets which were chemically similar but varied in peNDF content (H-high, M-medium, and L-low) by altering corn silage particle length. The results indicated: reduced dietary peNDF content decreased intake of peNDF,ingestion, ruminating and total chewing time significantly between H and L group (P<0.05 or P<0.01) but did not affect intake of DM ,NDF and ADF respectively. The milk fat content increased significantly while increasing dietary peNDF content between H and L group (P<0.05), but no apparent changes recorded in milk production ,milk protein and milk lactose towards treatments(P>0.05) .