| In this experiment, we used the techniques including in situ and in vitro and combined with animal production experiment to study the rumen degradation characteristics of five types of forages degraded in dairy rumen and the effect of different NDF sources on performance and blood biochemical parameters of dairy cows. The methods and results were showed as follows:Experiment one:This study was conducted to investigate the rumen degradation characteristics of five types of forages degraded in dairy rumen. Three ruminally cannulated holstein dairy cows (650±25kg) were choosed and nylon-bag technique was used to evaluate alfalfa, oat hay, Leymus chinensis, rice straw and corn silage rumen degradation characteristics and effective degradabilities of dry matter (DM), crude protein (CP), neutral detergent fiber (NDF) and acid detergent fiber (ADF). The results indicated that:(1) Effective degradabilities of alfalfa DM and CP were more than50%and significantly higher than other forages (P<0.05), DM effective degradability was alfalfa> oat hay> corn silage> Leymus chinensis> rice straw (P<0.05) and NDF effective degradability was alfalfa> corn silage> oat hay> Leymus chinensis> rice straw (P<0.05).(2) Effective degradabilities of corn silage NDF and ADF were highest and alfalfa were lowest in all forages (P<0.05). NDF effective degradability was corn silage> oat hay> Leymus chinensis> rice straw> alfalfa (P<0.05), and ADF effective degradability was corn silage> rice straw> oat hay> Leymus chinensis> alfalfa (P<0.05). In conclusion, the degradability of alfalfa was much higher than grasses.Experiment two:This study was conducted to investigate the effect of dietary NDF sources on rumen fermentation, microbial protein synthesis and nutrient digestibilities of late lactation dairy cows in vitro. A completely random design was choosed and diets were formulated with similar concentrations of equivalent NDF and NFC contents. Diets of FNDFfrom forages was24.90g/100g, consisted of corn silage providing about20.25g/100g FNDF with either alfalfa hay, oat straw, Leymus chinensis or rice straw that provided about4.75g/100g FNDF. The results showed that:pH was varied between6.37-6.96, and had significant effect after12h,24h and48h of fermentation (P<0.05). The concentrations of ammonia nitrogen was highest in rice straw group and lowest in Leymus chinensis group at24h (P<0.05); Synthesis of microbial protein of rice straw group was highest and oat straw group was lowest (P<0.05). The acetate content of alfalfa was much higher than others after24h of fermentation, and propionate content of rice straw was highest while alfalfa was lowest (P<0.05), in addition, TVFA concentration of alfalfa was much higher than others (P<0.05). DM digestibility was highest in alfalfa group and lowest in rice straw group after6h of fermentation (P<0.05), but alfalfa group was significantly lower than others after24h (P<0.05), in addition, the ADF digestibility of rice straw was much higher than others (P<0.05). After fermentation of48h, ADF digestibility of Leymus chinensis group was much higher than oat hay (P<0.05). At the same time, NDF sources had no significant effect on the average of ruminal pH, ammonia nitrogen concentration and microbial protein synthesis (P>0.05),and also the digestibilities of DM, NDF and ADF (P>0.05). The results showed that diets were isonitrogenous and isocaloric with equivalent concentrations of FNDF and NFC result in similar ruminal fermentation, MCP synthesis and nutrient digestibilities after72h fermentation.Experiment three:Eight multiparous holstein cows were used in a replicated4×4Latin square design to evaluate the effect of NDF sources on performance and blood biochemical parameters of midlactating dairy cows. Each period consisted of21d, with14d for dietary adaptation followed by7d for sampling. Diets were isonitrogenous and isocaloric, and cows were fed with corn silage based total mixed rations with equivalent NDF, FNDF and NFC contents. The results showed that:Dry matter intake was not affected by sources of dietary forages, dietary treatments had no effect on the total tract apparent digestibilities of DM, organic matter (OM) and CP (P>0.05). However, digestibilities of NDF and ADF in rice straw diet were much higher than those in other groups(P<0.05). NDF sources had no effect on milk yield, fat, protein, lactose, non-fat solids (P>0.05), but the C4:0, C12:0, C14:0, C18:0, C18:2and C18:3concentrations of fatty acids had significantly differences in each group (P<0.05). The contents of TP and GLB (P<0.05) was affected by sources of dietary forages, other blood parameters were similar within each group (P>0.05). The quantities of rumen cellulolytic bacterials were General fungi>Fibrobacter succinogenes>Ruminococcus flavefaciens> Ruminococcus albus, Fibrobacter succinogenes was highest in rice straw group (P<0.01), but the quantities of general fungi, Ruminococcus flavefaciens and Ruminococcus albus were similar (P>0.05).Conclusion:diets were isonitrogenous and isocaloric, mid and late lactation dairy cows were fed with equivalent NDF, FNDF and NFC contents result in similar ruminal fermentation, nutrient digestibilities, performance and blood biochemical parameters (P>0.05). |
PDF Full Text Request