| In this paper,the nutritional value of phragmites hay and common roughage（alfalfa hay,oat hay,millet straw,leymus chinensis）of dairy cows were evaluated comprehensively by CNCPS,nylon bag technology,improved three-step in vitro method and in vitro gas production method.The optimum ratio of alfalfa hay and phragmites hay was screened out by in vitro method,which provided data basis and theoretical support for the development and utilization of new roughage resources.The first part assessed the nutritional value of phragmites hay as roughage for dairy cows.1)The chemical composition and CNCPS parameters of common roughage of phragmites hay and dairy cows were evaluated by CNCPS.The results showed that the content of crude protein（CP）,neutral detergent fiber（NDF）and acid detergent fiber（ADF）in phragmites hay was 7.18%,73.07%and 38.11%,respectively.The availability of CP of phragmites hay（PC=21.32%）was significantly lower than that of millet straws,which was significantly greater than that of alfalfa hay,oat hay and leymus chinensis（P<0.05）.The content of non-structural carbohydrates（CA+CB1=14.34%）,and the digestible fibers（CB2=70.75%）were,lower in phragmites hay compared with millet straws,however,greater than alfalfa hay and oat hay（P<0.05）and had no difference with leymus chinensis.The content of unavailable fiber（CC=14.90%）was,greater than oat hay and lower than alfalfa hay,leymus chinensis and millet straws（P<0.05）.2)The rumen degradation characteristics of phragmites hay and common roughage for dairy cows were evaluated by nylon bag technology.The results showed that the effective degradability of dry matter in phragmites hay was 39.46%,which did not differ from millet straws and leymus chinensis,but lower than alfalfa hay and oat hay（P<0.05）;the effective degradability of CP in phragmites hay was 46.73%,which were significantly lower than other roughages（P<0.05）;the effective degradability of NDF in phragmites hay was lower than alfalfa hay,greater than oat hay and leymus chinensis（P<0.05）.The effective degradation rate of ADF in phragmites hay was 35.25%,significantly lower than millet straws（P<0.05）,greater than leymus chinensis and oat hay（P<0.05）,and no difference with alfalfa hay.3)The improved three-step in vitro method was used to evaluate the intestinal CP digestibility in dairy cows.The results showed that:The ruminal undedraded protein of intestinal digestibility（Idg of RUP）in phragmites hay was 58.25%,which was not different from leymus chinensis,but significantly lower than other roughages（P<0.05）.The content of intestinal digestible CP was 33.25 g/kg,which was greater than leymus chinensis,and lower than that of other roughages（P<0.05）.The ruminal methionine Idg in phragmites hay was significantly lower than other roughages（P<0.05）,but the ruminal lysine and total amino acid Idg in phragmites hay were significantly greater than leymus chinensis,significantly lower than other roughages（P<0.05）.4)The fermentation characteristics were evaluated by in vitro gas production method.The results showed that:The theoretical maximum gas yield in phragmites hay was 59.93 mL/g,significantly lower than oat hay and alfalfa hay（P<0.05）,but did not differ from leymus chinensis and millet straws;loss of DM（DML）was 48.19%in phragmites hay,which were lower than other roughage（P<0.05）;the pH and MCP in the ferementation liquid of phragmites hay was 6.52 and 4.18 mgN/dL,respectively,which was lower than alfalfa hay and oat hay,whereas greater than leymus chinensis and millett straws;the NH3-N concentraton in the fermentation liquid of phragmites hay was 14.75 mg/dL,significantly lower than alfalfa hay（P<0.05）,and was not different with other roughages.The concentration of total volatile fatty acids（TVFA）in the fermentation liquid of phragmites hay was 51.26 mmol/L,which was not different from leymus chinensis and millet straws,but significantly lower than alfalfa hay and oat hay（P<0.05）.According to the analysis of CNCPS patterns,rumen degradation rate,intestinal digestibility and fermentation parameters in vitro,phragmites hay,as an unconventional roughage resource for ruminants,though it is inferior to alfalfa hay and oat hay in quality,it can replace leymus chinensis and millet straws.The second part is the associative effect experiment.The study on the associative effect of phragmites hay includes two two-factor experiments.The first experiment was designed to study the best combination proportion of different whole corn silage,alfalfa hay and phragmites hay under the same concentrate-to-roughage ratio（60:40）.The concentrate-to-roughage ratio was set at 60:40 in this experiment,and the whole corn silage:hay at 40:60,50:50,and 60:40,respectively,and the alfalfa hay:phragmites hay at0:100,15:85,30:70,45:55,60:40,75:25,90:10,100:00,respectively.Triplicates were used for every treatment.Four Holstein fistula steers were used as rumen fluid donors.The results showed that:1)the theoretical maximum gas yield increased with the increase of the proportion of whole corn silage and alfalfa hay（P<0.05）.2)The DML tended to increase with the increase of whole corn silage proportion,but the loss of NDF（NDFL）and loss of ADF（ADFL）had no difference.With the increase of alfalfa hay addition,the disappearance patterns increased first and then decreased（P<0.05）.3)The pH of the whole corn silage decreased significantly with the increase of silage addition（P<0.05）.When the ratio of alfalfa hay to phragmites hay was 100:0,the pH of the alfalfa hay was significantly lower than that of the other proportion groups（P<0.05）.4)The MCP of Whole corn silage:hay 40:60 group was significantly greater than 50:50 and 60:40 groups by 1.26 mgN/dL and 1.30 mgN/dL,respectively（P<0.05）.MCP yield of 30:70,45:55 and 60:40 groups had no difference,while was significantly lower than that of other groups（P<0.05）.5)There was no significant effect on NH3-N with different whole corn silage-hays ratio and alfalfa-phragmites ratio.6)The concentration of acetic acid,propionic acid,butyric acid and TVFA increased with the increase of the proportion of whole corn silage（P<0.05）,and the ratio of acetic acid to propionic acid was not significant.The effects of different proportion of alfalfa hay and phragmites hay on the concentration of acetic acid,propionic acid and TVFA were different trend（P<0.05）,the maximum values were found in 15:85group（53.41 mmol/L）,45:55 group（26.53 mmol/L）and 90:10 group（87.27 mmol/L）.The acetic acid/propionic acid added by more than 85%of phragmites hay was significantly greater than that added by less than 70%of phragmites hay（P<0.05）.7)According to multiple factors associative effects index（MFAEI）,when the ratio of concentrate to roughage was 60:40,the hay ratio of different whole corn silage was the greatest in the group of alfalfa hay:phragmites hay at 75:25,and the MFAEI values were 0.0051,0.0922and 0.8500,respectively.According to the comprehensive evaluation of associative effect of MFAEI value,the maximum associative effect was obtained when the proportion of concentrate:whole corn silage:alfalfa hay:phragmites hay was 60:24:12:4.Combination Experiment 2 was designed to study the effects of different concentrate-to-roughage ratio,different alfalfa-phragmites ratio on the associative effect of whole corn silage at 60:40.The concentrate:roughage was set at 40:60,50:50,60:40,respectively.whole corn silage:hay was set at 60:40,and alfalfa hay:phrsgmites hay at0:100,15:85,30:70,45:55,60:40,75:25,90:10,100:00,respectively.Triplicates were used in every treatment.Four Holstein fistula steers were used as rumen fluid donors.The results showed that:1)The theoretical maximum gas production increased significantly with the increase of concentrate proportion（P<0.05）,and increased first and then decreased with the increase of alfalfa hay addition ratio.The maximum value was obtained at alfalfa hay:phragmites hay of 75:25（P<0.05）.2)DML disappearance,NDFL and ADFL increased with the increase of concentrate and alfalfa addition ratio.3)pH decreased significantly with the increase of concentrate addition ratio（P<0.05）,alfalfa-phragmites ratio had no significantly effect on pH;4)The effects of different concentrate-roughage ratio and alfalfa-phrsgmites ratio on MCP yield were not significant.5)When the ratio of concentrate to roughage was 50:50,the concentration of NH3-N was greater than other groups（P<0.05）,but the ratio of alfalfa to phragmites had no effect on it.6)The concentration of acetic acid,propionic acid,butyric acid and TVFA increased with the increase of concentrate addition ratio（P<0.05）,and the acetic acid/propionic acid decreased significantly（P<0.05）.With the increase of alfalfa hay addition ratio,the concentrations of acetic acid,propionic acid and TVFA increased first and then decreased trend（P<0.05）,acetic acid and TVFA were the highest in alfalfa hay:phragmites hay at45:55,propionic acid concentration was the highest in alfalfa hay:phragmites hay at 75:25,and the effect of the proportion of alfalfa hay and phragmites hay on acetic acid/propionic acid was not significant.7)According to MFAEI,when the ratio of concentrate to roughage was 40:60,50:50 and 60:40,the maximum positive effects were observed in groups of alfalfa hay:phragmites hay at 45:55（0.5061）,75:25（0.2003）,75:25（0.8500）.The optimum proportion of combined effects was screened according to multiple composite effect indices for different ratio of concentrate to roughage and different ratio of alfalfa hay to phragmites hay,concentrate:whole corn silage:alfalfa hay:phragmites hay is 60:24:12:4 ratio combination,the best associative effect,suitable for dairy cows;concentrate:whole corn silage:alfalfa hay:phragmites hay at 40:36:10.8:13.2 had the best associative effect,which should be suitable to be use in low concentrate diet in dairy cows. |
