Evaluation of ramie (Boehmeria nivea)  foliage as a feed for the ruminant

Dinh Van Tuyen, Pham Bao Duy and Hoang Van Huy

NIAH, Hanoi, Vietnam
vantuyen1973@yahoo.com

Abstract

The biomass potential of ramie foliage was investigated at three sites in the Red River Delta through harvesting, sampling and analyzing for chemical composition. Nutritive values of the leaves (fresh or dried  and whole plants fresh)  were determined in an in vivo digestibility trial with sheep while the in sacco degradation characteristics were examined using a ruminally cannulated steer.

The yield of ramie foliage grown in Red River Delta region could be as high as 126 tonnes of fresh matter/ha/year or 17.3 tonnes DM/ha/year. The yield of leaves only could reach 56 tonnes fresh matter/ha/year or 9.6 tonnes DM/ha/year. The ramie foliage either in whole plant or in the leaf portion only had high crude protein (>21% CP in DM)and ash (19-22% in DM), while drying reduced the CP content of the leaves. In vivo apparent digestibility coefficients of OM, CP, and NDF of fresh leaves were 78.5, 80.9 and 82.6%, respectively. Values for dried leaves and fresh whole plants were 63.1, 60.6, 76.1% and 66.1, 75.9, 62.5%, respectively.

It is concluded that ramie foliage has a relatively high nutritional value for the ruminant.

Key words: Biomass yield, crude protein, digestibility, in sacco degradability, sheep,

Introduction

Vietnam is a growing economy with a GDP growth rate which averaged approximately 7.5% annually over the last decade. The demand for meat is therefore increasing as consumption of red meet in general and beef in particular is on the rise, especially after the outbreak of bird flu pandemic. As a result, the population of cattle herd increased from 3.2 million in 1990 to 4.1 million in 2000 and 5.5 million in 2005 (General Statistics Office 2005).

Vietnam is a small country with a total area of 326,000 sq km² of which only 21% is arable land (Le Viet Ly 2005).  With such a limited arable land, and a high population of 80 million, the ruminant production in Vietnam is characterized by a household-based system in which only few animals are kept by each householder. Such a system has resulted in a tradition of feeding animals with whatever feed the farmer can collect. In this typical production system, it is necessary to diversify the supply of feed resources to the ruminant. To accommodate this approach, a number of unconventional feeds for ruminants have been investigated with variable results. However, the use of ramie plants, a native fiber crop to China (Liu Fei Hu et al 2003) , as a ruminant feed has not yet been studied. In Vietnam the crop is not produced in large scale for fiber purposes but rather in small area of the household with the main aim to use the leaves for making cakes for some special occasions (eg: Chinese New Year holiday, Mid-Autumn Festival . With up to 29% CP in the leaves (NIAH 2001) and a high yield of biomass (Wood 1999), ramie leaves may be a valuable protein source for the ruminant.

There is not much information on the nutritive value of ramie leaves as feed for the ruminant. Some studies reported that ramie plants can be a good feed for all type of livestock with nutritive value similar to Lucerne (Machin 1977). The only disadvantage which seems to be problematic to non-ruminants but not cattle is its high mineral content (Machin 1977).  In Vietnam there has been no research into the utilization of ramie forage or ramie leaves for the ruminant. Thus this project aimed to investigate biomass potential and nutritive value of ramie leaves and forage as a ruminant feed.

Materials and methods

Investigation of biomass of ramie foliage

The biomass potential of ramie foliage grown in the Red River Delta region was examined at three planting sites in Ha Tay, Ha Noi, and Nam Dinh provinces, respectively. The ramie plots of at least 300 m² each in the 2^nd (Ha Noi site)  and 4^th (Ha Tay and Nam Dinh sites)  year of growth and had been planted with row spacing of 40 cm. Fertilizer was not applied to any of the plots. The yield of ramie foliage in each plot was determined by cutting the whole plants at approximately 20 cm above the ground in 5 squares (4 m² each) of which four were located at the corners and one in the middle of the plot for each harvest. The harvesting time was determined as when the leaves of the plants covered the whole surface of the plot. Samples of whole plants and leaves were collected and analyzed to determine DM and CP contents which were then used for estimation of DM and CP yield of ramie foliage.

In vivo digestion trial

The trial was carried out with sheep to determine in vivo digestibility of two types of ramie leaves (fresh and dried leaves) and one type of whole ramie plant (5 weeks re-growth). The ramie leaves (or foliage)  was offered to five sheep at 90% of the ad libitum intake for a 10 day adaptation followed by a 10 day collection of feces. Aliquots of 10% of total feces were taken daily and stored at -20⁰C in a freezer. At the end of the collection period, feces samples were bulked and a sub-sample taken for analysis. Samples of feed offered and feed residue were also collected daily, and bulked and sub-sampled at the end of the 10 day collection period, for analysis. The samples of feces, feed offered and refused were analyzed for DM, OM, NDF, ADF and CP.

The nutritive value of the ramie foliage was calculated from chemical composition and in vivo digestibility data using formulae provided by INRA (1989).

In sacco digestion trial

Samples of fresh and dried ramie leaves and whole fresh plants of ramie were subjected to determination of DM degradability in an in sacco study. The samples of dried leaves were ground through a 2mm screen while the samples of fresh leaves and whole plants were chopped (5 cm length)  and crushed to a similar size as ruminated grass. The samples were then put (in triplicate  into nylon bags (approximately 4 g of DM/bag)  and incubated in the rumen of a ruminally cannulated steer for 0, 4, 8, 12, 24, 48 and 72h. DM contents of samples were determined by weighing approximately 200 g of the sample and drying in an oven at 60ºC,  after filling the nylon bags. All the bags were given the same washing procedure (10 times squeezing by hand under running tap water, then rinsed for 6 minutes, drained and spun for another 6 minutes in a semi-automatic washing machine  before being oven dried (60⁰C for 48h) , cooled in a desiccator, and weighed to determine the proportional DM loss. The potential by-pass protein content in ramie leaves and whole plants was estimated by the difference between N content in NDF and that in ADF of the sample.

Chemical analysis

DM content of samples was determined by drying in a forced draft oven at 60⁰C until the weight remained constant. Ash content was determined by combusting oven-dried ground samples in a muffle furnace at 550 ⁰C for 4.5 hours. The NDF and ADF contents were determined by the method of Van Soest et al (1991); crude protein, ether extract, ca and P were determined by the methods in (AOAC 1990).

Statistical analysis

Data on biomass yields of ramie foliage were subjected to Basic Statistics Analysis using the Minitab (version 14)  software. Data on in vivo digestibility were analyzed using the ANOVA program in the Minitab software, while data on DM disappearance of the test feeds were analyzed using the NEWAY software according to the exponential model, p = a + b (1-e^-ct) , described by Ørskov and McDonald (1979)  to predict potential degradability and rate of degradability of DM in the rumen. 
 

Results and discussion

Biomass yield of ramie foliage

Yields of fresh matter, DM, OM, and CP of ramie was measured for each cut and summed for a year. At each harvest, the fresh biomass of the whole plants was first measured and a sample taken for determination of DM, OM and CP. A sample (2 kg)  of the whole plants was also taken and all leaves were separated from the stems. Data for each cut were averaged from data collected at the three study sites (Table 1). The mean and SD values were for 7 cuts and the total was the yield of ramie/ha/year (sum of 7 cuts).

The DM yield of ramie foliage observed in the present study was lower than that of some grasses such as elephant grass (40 tonnes/ha/year) and atratum grass (27.9 tonnes/ha/year)  but comparable to the yield of some legumes such as Leucaena (13.7 tonnes/ha/year)  and stylo (15.9 tonnes/ha/year)  (Nguyen Van Quang et al 2005). Wood (1999)  also suggested that ramie can give a high yield with up to six cuts a year.

Chemical composition of ramie foliage

Data in Table 2 show that DM and CP contents of fresh ramie leaves were higher while CF, NDF and ADF contents were lower than those of fresh whole ramie plants. Other nutrients (EE and Ash)  as well as Ca and P contents were similar between fresh whole plants and fresh leaves. The fact that CP content of dried leaves was lower than that of fresh leaves (25.6 vs. 21.8% in DM)  indicates the reduction in quality of feeds due to the drying process. The content of ash (19.1-22.5% DM) in ramie foliage was high and in agreement with the observation of Machin (1977)  that ramie has a high capacity for mineral uptake.

In vivo digestibility and energy and protein values of ramie foliage

Coefficeints of apparent digestibility of proximate constituents in fresh ramie leaves were much higher than that in dried leaves and whole plants (Table 3). The higher digestibility of fresh as compared with dried leaves may be due to higher solubility of the nutrients in the fresh leaves. Meanwhile the lower digestibility of whole plants as compared with the leaves probaly reflects the higher content of cell wall constituents.

Data on energy values of different types of ramie foliage presented in Table 4 show that fresh leaves have the highest (2428 Kcal/kg DM)  and dried leaves the lowest (1851 Kcal/kg DM  ME) content. Likewise, the PDI content was highest in fresh ramie leaves (152.3 g/kg DM  and lowest in dried leaves (126.4 g/kg DM).  However, the PDIN values were higher than DPIE values in all type of ramie foliage, suggesting that when ramie foliage is used as feed for ruminants the energy content of the diet is likely the limiting factor to the growth of microorganisms in the rumen.

Degradability in sacco

The extent of rumen digestion of DM was greater for the fresh leaves than the dried leaves (Table 5 and Figure 1). Values for the fresh whole plant were only slightly lower than for the fresh leaves.

Conclusions

·        The yield of ramie foliage grown in the Red River Delta region can be as high as 126 tonnes of fresh matter or 17.3 tonnes DM/ha/year.

·        The yield of leaves only was 56 tonnes fresh matter or 9.6  tonnes DM/ha/year.

·        The ramie foliage either in whole plant or in the leaf portion only had high content of crude protein (>21% in DM)  and ash (19-22% in DM)

·        Oven-drying reduced the CP content of the leaves.

·        It is concluded that ramie foliage has a potentially high nutritional value for the ruminant.

References

AOAC 1990 Official Methods of Analysis. Association of Official Analytical Chemists. 15th Edition (K Helrick editor). Arlington pp 1230

General Statistics Office  2005  Statistical Year Book 2005. Statistic Publishing House. Hanoi, Vietnam.

INRA 1989 Ruminant Nutrition -Recommended allowances and feed tables. John Libbey Eurotext. Paris, France.

Liu FeiHu, Li Zong Ju, Liu Qi Yuan, He Han, Liang XueNi and Lai Zhan Jun 2003. Introduction to the wild resources of the genus Boehmeria Jacq. in China. Genetic Resources and Crop Evolution 50: 793-797.

Le Viet Ly  2005  The role of animal production in farming systems of Vietnam In: Improved utilization of agricultural by-products for animal feed in Vietnam and Laos. Publication No 1 of NUFU project. Pp: 7-14.

Machin D H 1977  Ramie as an animal feed: review. Tropical Science 19: 187-195.

NIAH  2001  Composition and Nutritive value of animal feeds in Vietnam. Hanoi Agricultural Publishing House. Hanoi, Vietnam.

Nguyen Van Quang, Le Hoa Binh, and Phung Duc Tuan  2005  Kết quả xây dựng mô hình trồng cỏ thâm canh phát triển chăn nuôi gia súc ăn cỏ tại hộ nông dân Định hóa-Thái nguyên. In Báo cáo khoa học năm 2005-Viện Chăn nuôi. Pp: 118-124.

Ørskov E R and McDonald I 1979  The estimation of protein degradability in the rumen from incubation measurements weighted according to the rate of passage. Journal of Agricultural Science, Cambridge 92, 499-503.

Van Soest P J, Robertson J B and Lewis B A  1991  Methods for dietary fiber, neutral detergent fiber and non-starch polysaccharides in relation to animal nutrition. Journal of Dairy Science 74: 3583-3593.

Wood I 1999  Ramie: the different bast fibre crop. The Australian new crops newsletter. Issue No 11, 1999. http://www.newcrops.uq.edu.au/newslett/ncn11162.htm

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