Evaluation Of Nutrient Values Of Different Carbohydrate Composition Dietary For Dairy Cattle

Three experiments were conducted to research nutrient values of different neutral detergent fiber/starch raito diets for dairy cattle.Trial 1:This experiment was conducted to evaluate the nutritive value of different neutral detergent fiber/starch raito diets for Dairy Cattle by Cornell net carbohydrate and protein system.Experiment 1 was used to compare the nutritive value of different feed ingredient (alfalfa hay,oat hay,corn silage,corn,sugar beet pulp,soybean meal,extruded soybean,cottonseed fuzzy) experiment 2 was used to compare the nutritive value of different feed combinations, corn silage,oat grass and corn grain were used to adjust the NDF/starch ratio. Four total mixed rations were fed with different NDF/starch in ratios of 0.86(I),1.13(II),1.56(111) and 2.38(IV),respectively..The basic nutrient contens were analyzed,and the carbohydrate and protein fraction were calculated respectively according to the CNCPS method.The feed ingredient and feed combinations samples were analyzed by category. The results showed as follows:1) the characteristic of CNCPS carbohydrate fractions and CNCPS protein fractions of various feed ingredient were different.2) CHO、 CNSC、CA、CB1、PB1 and PB2 were gradually decreased with the increase of dietary neutral detergent fiber/starch raito, but CB2、CC、PA、PB2 and PC were gradually increased with the increase of NDF/starch raito.Therefore,based on this study, the nutritive value of different neutral detergent fiber/starch raito diets was:Ⅰ> Ⅱ>Ⅲ>Ⅳ.Trial 2:This experiment was conducted to evaluate the rumen degradation characteristics of four different neutral detergent fiber/starch raito diets. Corn silage,oat hay and corn grain were used to adjust the NDF/starch ratio. Four total mixed rations were fed with different NDF/starch in ratios of 0.86(Ⅰ),1.13(Ⅱ),1.56(Ⅲ) and 2.38(IV),respectively.Three healthy Holstein cows in midlactation (600+21 kg body weight) with permanent ruminal cannulas were selected as experimental animals, and the rumen degradation rates of dry matter (DM),organic matter (OM),crude protein (CP),neutral detergent fiber (NDF) and acid detergent fiber (ADF) of four rations were measured using nylon bag method.The culture time of rations in the rumen was 2,4,8,16,24,36,48 and 72 ^respectively. The results showed as follows:DM degradation rate of grouop Ⅰ and Ⅱ were the highest at 72 h among four types of rations,but very significantly higher than group III and Ⅳ(in descending order) (P<0.01);The effective degradability(ED) of group Ⅰ, Ⅱ and ⅢI was not significantly different (P>0.05),and the ED of group I and II was significantly higher than that of group IV (P<0.05),but there was no significant difference between group Ⅲ and IV (P>0.05); OM degradation rate and ED had the same trend with DM at 72 h; CP degradation rate of grouop I and II were the highest at 72 h among four types of rations,but very significantly higher than group Ⅲ and Ⅳ(in descending order) (P<0.01); CP effective degradability showed group Ⅱ> Ⅰ> Ⅳ>Ⅲ,and the differences among groups were not significant (P>0.05); NDF degradation rate at 72 h among four types of rations ranked in the following order:group Ⅱ>Ⅲ>Ⅰ>Ⅳ, and there was no significant difference among four treatments (P>0.05); NDF effective degradability of grouop I was the highest among diets, but significantly higher than group Ⅱ,Ⅳ and Ⅲ (in descending order) (P<0.05), and the latter three groups were not significant (P>0.05); ADF degradation rate at 72 h among four groups were not significant (P>0.05); ADF effective degradability showed group Ⅰ>Ⅳ> Ⅲ> Ⅱ.and there was no significant difference among four treatments (P>0.05). In conclusion, ruminal degradation characteristics of rations are dissimilar, dietary ratio of NDF/Starch between 0.86 and 1.13, have the higher nutritive value among the four types of testing rations.Trial 3:This experiment was conducted to examine the effects of different neutral detergent fiber/starch raito diets on rumen fermentation in vitro. Corn silage.oat hay and corn grain were used to adjust the NDF/starch ratio.Four total mixed rations were fed with different NDF/starch in ratios of 0.86(Ⅰ),1.13(Ⅱ),1.56(Ⅲ) and 2.38(Ⅳ),respectively. Three healthy Holstein cows fitted with permanent ruminal cannulas were used as the donor of rumen fluid.Accumulative gas production in 2,6,12,24,36,72 h, fermentation kinetic parameters and fermentation characteristic indexes for these diet samples were determined by combining the method of in vitro rumen fermentation and the technique of real-time recording of gas production. The results showed as follows:1) The IVDMD in 48 incubation time was decreased with the increase of dietary neutral detergent fiber/starch raito, and group Ⅰ and group Ⅱ were very significantly higher than group Ⅲ and group Ⅳ (P<0.01). Gas production (GP)in 48 h and theoretical maximum GP ranked in descending order, and there was a vere significant difference among four treatments(P<0.01). No significant difference on the time of reaching 1/2 of theoretical maximum GP and the maximum GP rate among all treatments were observed (P>0.05).2) The concentrations of ammonia mtrogen(NH3-N) and microbial protein concentration were not affected by dietary neutral detergent fiber/starch raito.3) pH, acetate, acetate/propionate and acetate/TVFA were gradually increased with the increase of dietary neutral detergent fiber/starch raito, but TVFA, propionate, butyrate and propionate/TVFA were gradually decreased with the increase of NDF/starch raito.4) Correlation between nutritional level of different NDF/starch ratio diets and fermentation parameters in vitro showed that the GP in 48 h and theoretical maximum GP were a very significantly positive related to starch, neutral detergent soluble(NDS), NDS/CP and non-fiber carbohydrate(NFC) contents (P<0.01),but also had a very significantly negative related to neutral detergent fiber(NDF) and acid detergent fiber contents(P<0.01). In conclusion, the results of in vitro GP method indicate that dietary NDF/starch ratio between 0.86 and 1.13 can promote rumen microbe fermentation under the experimental conditions.