| Four experiments were conducted to investigate the fermentation quality and chemical composition of Pennisetum sp. silage, the effects of different cutting height on the quality of the Pennisetum sp. hay and silage, and to determine the rumen degradation characteristics of Pennisetum sp. hay and silage, in order to explore the proper levels of Pennisetum sp. hay and silage in the diets of dairy cows.The first experiment: The Pennisetum sp. with same plot and growth period was used as material to make silage, trial group adding silage additive(lactic acid bacteria preparation), control group without any additives, comparison the dynamic fermentation level and nutrition composition in 1 d, 3 d, 9 d, 30 d, 57 d. The results showed as follows: 1) the contents of water soluble carbohydrate(WSC), water and nutrition conducive to making silage. 2) pH less than 4.2 in two groups, the contents of lactic acid in trial group were significantly higher than those in control group(P<0.05), However, the contents of acetic acid and ammonia nitrogen to total nitrogen ratio were significantly lower than control group(P<0.05), propionic acid had no significant difference(P>0.05). 3) The contents of DM and CP in trial group were significantly higher than those in control group(P<0.05), but compare with the control group, NDF and WSC were significantly reduced(P<0.05), ADF had no significant difference(P>0.05).The second experiment: This experiment was conducted to investigate the effects of different cutting height on the quality of the Pennisetum sp. hay and silage, in order to determine the optimum cutting time of the Pennisetum sp.. Pennisetum sp. was used as material to make silage and hay, to compare the nutrient composition of different cutting height hay and silage, the fermentation quality of Pennisetum sp. silage. The results showed as follows: 1) with the increase of the Pennisetum sp. hay cutting height, the contents of DM, NDF and ADF were significantly increased(P<0.05), However, the relative feed value(RFV) was significantly decreased(P<0.05), meanwhile, the contents of CP and Ash were significantly decreased gradually(P<0.05). 2) The pH less than 4.2 in all Pennisetum sp. silage, and the pH in 1 m silage was significantly higher than other height(P<0.05). The quality of silage made of Pennisetum sp. cutting on 1 m and 1.5 m were lower. The content of lactic acid in 2.5 m silage was significantly higher than other height(P<0.05), and the acetic acid was lowest. The proportion of ammonia nitrogen in 2 m and 2.5 m silage were significantly lower than 1.5 m and 3 m silage(P<0.05). 3) The contents of CP and Ash were significantly decreased as cutting height increased(P<0.05), the same as RFV. But the NDF and ADF contents were significantly increased gradually(P<0.05). The content of WSC in 2.5 m silage was significantly lower than 1 m silage(P<0.05).The third experiment: This experiment was conducted to determine the rumen degradation characteristics of 7 types of roughages: 2 kinds of Pennisetum sp. hay(different cutting height), 2 kinds of Pennisetum sp. silage(different cutting height), Chinese wildye, alfalfa hay and whole corn silage. Four Holstein cows with permanent ruminal cannulas were used, Nylon-bag technique was used to evaluate the ruminal degradability and effective digestibility of DM, CP, NDF and ADF. The results showed as fllows: 1) the contents of CP in Pennisetum sp. hay were significantly high than those in Chinese wildye(P<0.05), but compare with the Chinese wildye, the contents of NDF were significantly reduced(P<0.05); The contents of CP and NDF in Pennisetum sp. silage were significantly high than those in whole corn silage(P<0.05). 2) The DM effective degradability of alfalfa hay was significantly higher than that of whole corn silage, 2 m Pennisetum sp. sliage, 2.5 m Pennisetum sp. silage, 2 m Pennisetum sp. hay, 2.5 m Pennisetum sp. hay and Chinese wildye(P<0.05), which were decreased in the above order, Chinese wildye had the lower DM effective degradability than others(P<0.05); CP effective degradability of alfalfa hay and 2 m Pennisetum sp. silage was not significantly different(P>0.05), and was significantly higher than that of 2.5 m Pennisetum sp. silage, 2 m Pennisetum sp. hay, whole corn silage, 2.5 m Pennisetum sp. hay and Chinese wildye(P<0.05), which were decreased in the above order; NDF effective degradability of whole corn silage and Pennisetum sp. silage was not significantly different(P>0.05),and was significantly higher than that of other roughages; ADF degradation rate of Pennisetum sp. silage at 72 h was significantly higher than that of other roughers(P<0.05).The fourth experiment: This experiment was conducted to investigate the effects of dietary supplementation of Pennisetum sp. silage and Pennisetum sp. hay on ruminal fermentation, nutrient digestibility, serum indices and performance of dairy cows. Forty-five healthy Chinese Holstein lactating dairy cows were randomly assigned into 3 groups with 15 cows in each group by milk yield, parity and days in milk. Roughages in control group(CG) were whole corn silage, Chinese wildrye and alfalfa hay, those in trial group ? were Pennisetum sp. silage, whole corn silage, Chinese wildrye and alfalfa hay, those in trial group ? were Pennisetum sp. hay, whole corn silage and alfalfa hay. Nutrient levels of the three diets were close. The pre-trial lasted for 10 days, and the lasted for 60 days. The results showed as follows: 1) compared with CG, the content of ammonia nitrogen of acetate in rumen fluid, and milk protein percentage in trial group ? were significantly increased(P<0.05). The other milk composition, DMI, milk yield, nutrient digestibility and serum indices had no significant difference(P>0.05). The benefit per cow per day improved 1.19 yuan. 2) Compared to CG, the milk composition, nutrient digestibility and serum indices in trial group ? were not significantly changed(P>0.05), and the content of ammonia nitrogen in remen fluid was significantly decreased(P<0.05). The DMI and milk yield was slightly increased(P>0.05). The benefit per cow per day improved 2.07 yuan.In conclusion, cutting 2 m to 2.5 m Pennisetum sp. to make hay and silage are the best, Pennisetum sp. by making silage can save the nutrition composition of silage, adding lactic acid bacteria preparation in silage can promote the fermentation process of Pennisetum sp. silage, and reduce the nutriment losses, it also can improve the rumen degradation of nutrition composition. Partial replacement of whole corn silage with Pennisetum sp. silage and partial replacement of alfalfa hay with Pennisetum sp. hay in diets can bring in better economic benefit without influencing cows performance. |
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