Comparison Of The Nutritive Value Of Different Kenaf (Hibiscus Cannabinus) Varieties And The Study On Silage Utilization Technology Of Kenaf

Kenaf(Hibiscus cannzzbinus L.), an annual herbaceous bast fiber crop, is an important raw material for the traditional textile industry. Nowadays, the utilization of the fiber of kenaf is restricted with the development of chemical fiber and container. Protein feed shortage is one of the most important factors that limit the development of animal husbandry in China. Many studies have shown that kenaf has a high nutritional value and can be a high quality source of plant protein feed. Little domestic study is about kenaf forage nutritive value, and most of them are in the phase of preliminary exploration; hence, studies on Kenaf as forage have obvious ecological and economic benefits.The first part of this study aimed to evaluate the harvesting mode depending on stubble height of kenaf and the yield and quality characters of seven Kenaf varieties harvested on the basis of stubble height and to identify varieties with high nutritive value; the second part aimed to carry on the preliminary exploration of the silage utilization technology of kenaf, and to evaluate the quality of the kenaf silage when the when the sucrose and formic acid were added.The results of the study were as the follows:1. Kenaf can be harvested multiple times in one growing season depending on stubble height to ensure sustainable yield and high nutritive value. The results of our trial analysis revealed that 90 cm stubble height was the most suitable for harvesting kenaf, but since this study is a preliminary exploration, the stubble height and harvest time need to be further optimized.2. The dry matter yield of the whole plants, crude protein content, and crude fiber of the kenaf varieties ranged from 15,359.31 kg/hm2 to 18,502.18 kg/hm2, 8.99% to 16.23%, and 16.71% to 37.43%, respectively. The nutritive value of the seven kenaf varieties was the same during the first two harvests, but was slightly different during the third harvest because of the cold climate during this harvest time. D(SZHP35) variety had the highest nutritive value with the highest dry matter yield(18,502.18 kg/hm2) and crude protein yield(2,027 kg/hm2), and F(4A-4B) had higher leaf proportion(44.82%) and yield and significantly higher crude protein(P<0.05) than the other varieties. Correspondence analysis results suggested that F(4A-4B) was closely related to leaf yield and crude protein content, and D(SZHP35) was closely related to high yield. Our findings suggested that both the varieties could be used as a forage material in China.3. To establish a method of determining four kinds of organic acids(Lactic acid, Acetic acid, Propionic acid and Butyric acid) in kenaf silage by high performance liquid chromatography(HPLC). Dionex Ultimate 3000 was used to separate organic acids; the chromatographic column was Thermo Hypersil BDS C18. 0.02 mol/mL NaH2PO4(pH=2.70) and methanol were used as mobile phase with a flow rate of 0.5 mL/min. The column temperature and UV detection wavelength were set as 30℃ and 210 nm respectively. The results showed that four organic acids could be separated successfully, all the calibration curves for these organic acids displayed a good linear relationship with correlation coefficients above 0.9982(R2≥0.9982), and the coefficient of variation of four kinds of organic acids was under 5%(n=6). The recovery rates of six organic acids were in the range of 98.73%~102.79%.This method is convenient, rapid, accurate and applicable to determine organic acids in kenaf silage.4. Adding the sucrose or formic acid can significantly increase the crude protein content(P<0.05) and soluble carbohydrate content(P < 0.05). The pH of the kenaf silage of all the treatments was less than 4.0, lactic acid content increased significantly(P<0.05), ammonia nitrogen content decreased significantly(P<0.05), butyric acid was not detected in all of the treatments; the silage fermentation quality was good. Hence, the fermentation quality and nutritive value of kenaf silage was improved with additives of sucrose and the quality of kenaf silage with 20g/kg of sucrose added is better than the other groups in the range of this study and the quality of kenaf silage with 9mL/kg of formic acid added is better than the other groups in the range of this study.