| Milk demand has increased in recent years, which in turn substantially increased dairy cattle production in southern China. Roughage for dairy cattle in this area is provided mainly by silage maize and Chinese Wildrye (Leymus chinensis) hay. However, the availability of corn and Chinese Wildrye hay is unable to meet the current demand and production cost in southern China. As a result of agricultural land is mainly used to product crop grains and natural grassland is scare in southern China, silage maize was not enough for the local need of the dairy cow industry and Leymus chinensis hay was generally purchased from northern China where natural grassland mainly distributed. Hence, developing alternate methods to increase forage production and exploring unconventional feed resources with main nutrients to balance diets and reduce cost has become an urgent matter in southern China. Spartina alterniflora was introduced to China in 1979 and total S. alterniflora saltmarshes have amounted to 34, 451 hm2 till 2009 in China due to its enormous seed production and root fragments. High biomass and rich in minerals and bioactive substances make this plant should be evaluated deeply as a ruminant potential feed resource. However, as a result of adapting to saline habitats, the stem and leaf of S. alterniflora contain high concentration of NaCl and crude fiber, which have produced less positive results when it was used as the forage of ruminants. So a dynamic analysis of nutritive values of S. alterniflora in different stages of maturity should be made and the amount of this plant that can be effectively used in livestock feeding would need to be carefully regulated to minimize any adverse effect on animal productivity.The present study aims at investigating the nutritive values and mineral contents of S. alterniflora in different stages of maturity to determine its optimum maturity used as a fodder and the optimal replacing rates of S. alterniflora in mixed diets by comparing the chemical composition of S. alterniflora with conventional mixed diets, and assessing the effect of using graded levels of S. alterniflora as dietary inclusion on feed intake,voluntary water intake, rumimal fermentation, bacterial diversity and degradation characteristics of S. alterniflora by feeding experiment of dairy cattle; and providing systematic data on the feeding of the unconventional plant, which can serve as resource for new breeding programs. The main research contents and results are as follows:1 Nutritive values of S. alterniflora in different maturity stagesIn this study, the IVDMD, organic and mineral contents of aboveground parts of S. alterniflora at seven different maturity stages collected from the upper intertidal area were analyzed to determine the optimal stage of S. alterniflora used as a fodder of ruminants. The results showed that the nutritive values of S. alterniflora continually changed as it matured. The CP, ash content, and IVDMD were negatively associated with increasing maturity, whereas DM, NDF, ADF content, and biomass were positively associated with increasing maturity. Higher CP, DM, EE content, and biomass, moderate ash, NDF, and ADF content of S. alterniflora were observed on June, July, and August, this means the S. alterniflora grass harvested on the three stages offering considerable potential as forage that is cost effective with middle-quality nutrient composition for dairy cattle during the summer feeding period in the coastal areas of the world. However, S. alterniflora should be considered as a supplement rather than a feed to be fed in monoculture for its high NaCl content at these stages.2 Effect of dietary S. alterniflora on rumen fermentation in dairy cattleIn this study, the chemical compositions of S. alterniflora and convetional mixed diets were analyzed to assess the nutrient level of S. alterniflora diets, and animal feeding trials were conducted with four late lactating dairy cattle (437 ± 23 kg BW) fitted with rumen cannulas to determine the effect of dietary S. alterniflora on the feed and water intake, and rumen fermentation in diary cattle. In the feeding experiments, S. alterniflora was incorporated into roughage at rates of 0%,5%,15%, and 25% on a dry matter (DM) basis, proportionally replacing equal amounts of corn silage and Chinese Wildrye in a mixed test diet. Four dairy cattle were randomly allocated to the four dietary treatments according to a 4 × 4 Latin square design. The results showed that there were higher ash, NDF, ADF, and Na content, moderate nutritive compositions, as well as comparable OM, CP, and GE contents in S. alterniflora diets compared with conventional diets; the DM and water intake of dairy cattle were linearly increased, rumen TVFA yield and molar percent of butyrate had a increasing trend, rumen pH had a decreasing trend in normal range, but the concentration of NH3-N, bacterial protein, acetate to propionate ratio and molar percent of acetate, propionate and isobutyrate had no significant change with increasing level of S. alterniflora inclusion in the diet.3 Degradation characteristics of S. alterniflora and activities of celluloses in dairy cattle fed with diets containing increasing levels of S. alternifloraBy nylon-bag technique, the study was conducted to determine the dynamics of activities of four cellulose enzymes with increased level of S. alterniflora in mixed diets and their influence on degradation characteristics of S. alterniflora in the rumen of diary cattle. The results showed that during 0-12 h after incubation in the rumen, DM and CP disappearance rates of S. alterniflora increased slowly and rapidly, while showed an opposite trends during 12 h-72 h, respectively, and CP disappearance rates increased with increasing level of S. alterniflora in the diets. Degradation characteristics of NDF and ADF had a similar trend, in which the disappearance rates of NDF and ADF increased slowly during 0-12 h, and increased rapidly during 12-72 h, and the rapid degradable fraction (a) of them were far below the slow degradable fraction (b), and the rapid degradable fraction of NDF and ADF in 5%SA and 15% SA group were higher than other groups. With increasing level of S. alterniflora in the diets, activities of avicelase and xylanase increased before feeding and decreased after feeding, whereas activities of CMCase and salicinase increased at 0 h,4 h and 6 h, and first increased then decreased at 2 h after morning feeding. Overall, there were no significant effect of dietary S. alterniflora on the activities of four cellulose enzymes.4 Effect of dietary S. alterniflora on diversity of bacterial community in dairy cattleTotal DNA of mixed rumen liquid collected from four experimental periods was extracted and analyzed by denaturing gradient gel electrophoresis (DGGE) with subsequent cluster and diversity analysis to determine the effect of increasing levels of S. alterniflora on bacterial diversity in dairy cattle. The results showed that dietary S. alterniflora had a significant effect on the diversity of bacterial community in the rumen of dairy cattle. DGGE profiles showed, compared with the control group, the DGGE bands in 5%SA and 15% SA group had a little change in the quantity but increased in optimal density, and Shannon-Weaver index showed no difference among the control,5%SA and 15%SA group; there are unique bacterial community and high diversity in 25%SA group, and the quantity and optimal density of the DGGE bands in this group were different from other three groups and changeable in different sampling time. Some bands from 25%SA group were less compared to other three groups. The DGGE fingerprints showed the control,5%SA, and 15%SA group with a overall similarity of 58%, and there were lower similarity being only 43% between 25%SA group and the other three groups. |
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