| High quality forage resources deficiency is one of the serious problems of dairy industry.Replacing alfalfa hay with fibrous non conventional feed resources such as dry corn gluten feed(DCGF)may have important significance to alleviate the pressure of the shortage of forage resources.On the other hand,the physical properties of feed is another kind of nutritional characteristics that affect the nutritional value of feed,and different from those of conventional chemical composition,rumen degradation characteristics and intestinal digestion of feed,but it is often neglected in scientific research and production.Thus,The objectivse of this research were to:(1)investigate therelationships between physical parameters,chemical components,and degradation characteristics,which will reveal the physical characteristics of the importance to feed nutritional value evaluation,and provide a novel ideafor feed evaluation.(2)Comparison nutritional propertiesamong DCGF,alfalfa hay,and Chinese Leymus for dairy cows in: chemical compositions,physical parameters and metabolic characteristics,which will provide a scientific proof for the rational use of DCGF.(3)determine theeffects on in vitro fermentation,lactating performance,nutrient digestibility and metabolism,andeconomic benefits when a portion of alfalfa hay wasreplaced with the combination of DCGF and Chinese Leymus in thediets of lactating Holstein cows,which will provide a theoretical basis for replacing alfalfa hay with DCGF in dairy cows,and provide a new idea to alleviate the shortage of alfalfa hay resources in china.Experiment 1: Relationship between the physical parameters,chemicalcompositions and rumen degradation kinetics parameters ofcertain feedstuffs for ruminantsThirteen kinds offeedstuffs were selected to analyze the physical properties(including water holding capacity(WHC),swelling,bulk density,and feed solubility),chemical compositions and degradationparameters.The PROC CORR procedure of SAS 9.2 was used for correlation analyses.The results showed that physical parameters,chemicalcompositions and rumen degradation kinetics parameters were widely altered among the feedstuff varieties.Correlation analysis indicated that WHC was negatively correlated with thecontents of starch and crude protein(CP)(P<0.05).However,WHC had a highlypositive correlation with the level of neutral detergent fiber(NDF),acid detergent fiber(ADF)andacid detergent lignin(ADL)(P<0.01).Swelling had a high negativecorrelation with contents of starch and EE,and had a positive correlation with ash content.Bulk density wasnegatively correlated with the level of NDF(rSpearman=-0.720,P<0.0001),ADF(rSpearman=-0.761,P<0.0001)and ADL(rSpearman=-0.727,P<0.0001).Dry matter solubility(DMSol,% DM)was negatively correlated with NDF,ADF and ADL,but highly positive correlated with CP content(rSpearman=0.772,P<0.0001).Additionally,there was a positive association between the effective degradability of DM(EDDM)andbulk density(rSpearman=0.336,P=0.037)and DMsol(rSpearman=0.560,P=0.001).Bulk density had a significantly correlation with degradation parameters of CP,but highly positive correlated withthe potentially degradable fraction of NDF(DNDF)(rSpearman=0.647,P<0.001).DMSol was positively correlated with the degradation rate of DM and CP.Also,the effective degradability of CP(EDCP)was negatively correlated with WHC(rSpearman=-0.460,P=0.003)and positively correlatedwith DMSol(rSpearman=0.503,P=0.001).Experiment 2: Comparison of nutrient profiles among dry corn gluten feed and three common roughagesThe conventional chemical compositions of dry corn gluten feed(DCGF),alfalfa hay and Chinese Leymuswere determined,andprotein and carbohydrate fractions were partitioned by CNCPS system.The rumen degradation kinetics of DM,CP and NDF and the intestinal CP digestibility of rumen undegraded protein were determined respectively using in situ nylon bag technique and three-step in vitro method.Truly digestible nutrient and energy value were estimated based on NRC(2001)model.Addationally,the physical characteristics of DCGF,alfalfa hay and Chinese Leymuswere determined in this study.The results showed that the content of CPof DCGF was similar with alfalfa hay,and higher than Chinese Leymus(P<0.05).The NDF content of DCGF was significantly higher than alfalfa hay(P<0.05).However,the contents of ADF and ADL of DCGF were remarkably lower than alfalfa hay and Chinese Leymus(P<0.05).DCGF contains rich amino acids,and methionine content of DCGF was higher than alfalfa hay and Chinese Leymus.The total amino acid andlysine contents of DCGF were lower than alfalfa hay,but higher than Chinese Leymus.According to CNCPS system,the level of true protein(PB)of DCGF was lower than alfalfa hay(P<0.05).Compared with alfalfa hay and Chinese Leymus,DCGF had lower content of unavailable protein(P<0.05).The contents of intermediately degraded carbohydrate(CB1)and slowly degraded carbohydrate(CB2)of DCGF were significantly higher than alfalfa hay(P<0.05).The unavailable carbohydrates(CC)of DCGF was lowest.The WHC level of DCGF and alfalfa hay were similar,which were significantly lower than Chinese Leymus(P<0.05).The bulk density of DCGF was significantly higher than other roughages(P<0.05),and there was no difference between alfalfa hay and Chinese Leymus.DCGF had higher solubility than alfala hay and Chinese Leymus,including DMSol and Ash Sol(P<0.05),and the solubility of Chinese Leymus was lowest.Compared with alfalfa hay and Chinese Leymus,the rumen degraded DM content of DCGF was higher than alfalfa hay and Chinese Leymus,andChinese Leymus wes lowest.DCGF had higher soluble protein fraction S than alfala hay and Chinese Leymus(P<0.05).Compared with Chinese Leymus,the rumen undegraded protein(RUP)contents of DCGF and alfala haywere higher.The rumen degraded NDF for DCGF was significantly higher than Chinese Leymus(P<0.05),and the lowest was alfalfa hay.The intestinal digestibility of rumen ungradable feed protein in DCGF was no difference with alfalfa hay(P>0.05),and significantly higher than Chinese Leymus(P<0.05).The intestinable digestible protein(IDP)and total digestible protein(TDP)contents of alfalfa hay were higher than DCGF and Chinese Leymus(P<0.05).According to NRC(2001)model estimation,DCGF had higher total digestible NDF(td NDF)and total digestible nutrients at maintenance level(TDNm)than alfalfa hay,and Chinese Leymus was lowest.Therefore,the estimated microbial protein(MCP)and energy values for feeds had same trend with TDNm.The supply of protein metabolism of DCGF was similar with alfalfa hay(P>0.05),and significantly higher than Chinese Leymus(P<0.05).Experiment 3: Effects of replacing alfalfa hay with dry corn gluten feed and Chinese Leymus on in vitrorumen fermentation and gas parametersThis experiment was conducted to investigatein vitro rumen fermentation and gas parameters when different portion of alfalfawas replaced with combinations of dry corn glutenfeed(DCGF)and Chinese Leymus in the diets.There were five diets:(1)0% of DCGF(0DCGF);(2)3.0% of DCGF(3DCGF);(3)7.0% of DCGF(7DCGF);(4)11.0% of DCGF(11DCGF);and 15.0% of DCGF(15DCGF).In vitro fermentation device in Altech IFM laboratory was used and gas production was continuously monitored for 48 h.The results showed that the cumulative gas production of 11 DCGF at different time points was significantly higher than other diets(P<0.05).Campared with 0DCGF and 3DCGFdiet,the gas production for 15 DCGF diet was significantly higher(P<0.05),and no difference with 7DCGF(P>0.05).11 DCGF had highest slowly gas production,and higher than other diets(P<0.05).Compared with 0DCGF diet,in vitro dispeparence of DM(IVDDM)for 11 DCGF and 15 DCGF were increased(P<0.05).11 DCGF and 15 DCGF diets had higher NH3-N concentration,but 0DCGF and 3DCGF were lowest.The MCP production of 7DCGF and 11 DCGF was higher than 0DCGF diet(P<0.05).Compared with 0DCGF diet,a portion of alfalfa hay was replaced with DCGF and Chinese Leymusincresedthe production of total volatile fatty acids(VFA),acetate,propionic and butyrate production.Experiment 4: Effects of replacing alfalfa hay with the combination of dry corn gluten feed and Chinese Leymus on lactating proformance,nutrient metabolism,and economic benefits in lactating dairy cowsSix multiparous and 3 primiparous Chinese Holsteins were arranged in a replicated 3 × 3Latin square experiment for 21-d periods.The animalswere fed 1 of 3 treatment diets during each period:(1)0% of DCGF(0DCGF);(2)7.0% of DCGF(7DCGF);and(3)11.0% of DCGF(11DCGF).Diets were isonitrogenous,a portion of alfalfa hay was replaced with DCGFand Chinese Leymus,with similar concentratemixtures and corn silage contents.The dry matterintake(DMI)was greater for 11 DCGF than for0 DCGF or 7DCGF.The treatment diets did not result in difference in milk production,fat and lactose concentration.Comparedwith 0DCGF,cows fed 11 DCGF improved the milk protein concentration.Additionally,DM and NDF digestibility was greaterfor 7DCGF(62.7% and 45.6%)and 11DCGF(63.1%and 47.2%)than for 0DCGF(59.4% and 42.3%),andthe nitrogen digestibility was similar for the 3 treatments.The concentration of rumen VFAwas higher in cows fed the 11 DCGF diet than in thosefed the 0DCGF diet,with no difference between the7 DCGF and 11 DCGF diets.The estimated microbialcrude protein yield was greater for the 11 DCGF diet(1985.1 g/d)than for the 0DCGF diet(1745.0 g/d),with no difference between the 0DCGF and 7DCGFdiets.The feed costper kilogram of milk for 7DCGF(1.51 ?/kg)and 11DCGF(1.47?/kg)were significantly lower than 0DCGF(1.64 ?/kg),which increased the economic benefits.Therefore,it was concluded that:(1)The chemical,physical and degradation properties of feedstuffs were widely different.The physical parameters were significantly correlated with thechemical parameters and degradation parameters,which might be used as new information for the estimation of the nutritive values of the feedstuffs and applied in a ration formulation.(2)DCGF had high contents of available fiber and crude protein.Themetabolic energy supply for DCGF was higher than alfalfa hay,and metabolizable proteinsupply was similar with alfalfa hay.On the physical properties,the bulk density and solubility of DCGF were higher alfalfa hay,and the water hold capicity of DCGF was similar with alfalfa hay.The swelling of DCGF waslower than alfalfa hay.(3)There was no adverse effect on production performance when 17 percent of alfalfa hay was replaced with the combination of DCGF and Chinese Leymus in lactating cows' ration.The feed costper kilogram of milk was decreased and the benefit was increased when a portion of alfalfa hay was replaced.Thus,it appeared that feeding DCGF and Chinese Leymus in combination can effectively replace a portion of alfalfa hay in rations for lactating dairy cows. |
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