Effects of supplements of water hyacinth and cassava hay on the performance of local “Yellow” cattle fed a basal diet of rice straw

Cheat Sophal, Khieu Borin* and T R Preston**

Faculty of Animal Science and Veterinary Medicine,
Royal University of Agriculture (RUA), Phnom Penh, Cambodia
sophalcheat@yahoo.com
* Centre for Livestock and Agriculture Development (CelAgrid), Phnom Penh, Cambodia
** Finca Ecológica, UTA-Colombia, AA#48, Socorro, Santander, Colombia

Abstract

Eighteen male local “Yellow” cattle with average weight of 101±14.5 kg were allocated in a randomized complete block design (RCB) to a 3*2 factorial combination of 6 treatments, with three replicates of each treatment. The factors were: 3 sources of rumen supplement (water hyacinth leaves, water hyacinth leaves + stem and urea-mineral mixture), and supplementation or not with cassava hay. The basal diet was untreated rice straw fed ad libitum. The rumen supplements were offered at levels to provide 100 g crude protein (CP) per 100 kg live weight. The cassava hay was offered at levels equivalent to 200 g CP per 100 kg live weight.

Live weight gain was increased dramatically when cassava hay was fed. However, there was a significant interaction between the effect of the cassava hay and the rumen supplements. When cassava hay was fed growth rates were higher when the leaves of water hyacinth were given as the rumen supplement with no difference between water hyacinth leaves plus stem and the urea-mineral mixture. In the absence of cassava hay, the cattle fed either leaves or leaves plus stem of water hyacinth lost body weight while those fed the urea-mineral mixture gained in weight.

It is concluded: (i) that water hyacinth leaves can be used effectively as a source of rumen nutrients for growing cattle on a basal diet of rice straw provided a source of bypass protein (in this case cassava hay) is also fed; and (ii) that the limiting factors in water hyacinth foliage are the presence of anti-nutritional factors the negative effects of which are exacerbated at low levels of CP intake.

Key words: Anti-nutritional factors, bypass protein, protozoa, rumen ammonia, rumen supplements, urea-minerals

Introduction

Livestock are very important for the livelihood of the majority of people in developing countries, and also as a source of renewable energy for draft purposes and as a source of organic fertilizer for their crops (Steinfeld 2006).

Cambodian farmers, like those in other developing countries in SE Asia; have various sources of livelihood, which range from rice farming, vegetable and fruit cultivation in home gardens, other non-rice crop cultivation in upland areas, animal husbandry and fishing (Yang Saing Koma 2001). In the farming system, livestock play a crucial function. Cattle and buffaloes provide most of the draught power and the manure is used to fertilize crops in the system. Moreover, they are an important social asset and prestige for the rural farmers.

The total number of cattle and buffaloes in Cambodia was reported to be around 3 million and 0.7 million, respectively (MAFF 2004). The number of cattle has fluctuated while buffaloes have declined slightly during the period 1994-2004. The feeding of cattle and buffaloes mainly relies on grazing on common areas but at present this has been significantly declining. Among the constraints for their development appears to be a lack of fodder supply, particularly in the dry season, which affects the performance and the production of cattle and buffalo. Due to shortage of grazing, rice straw plays an important role as a feed source albeit of low nutritional value. In the rainy season, the feed supply remains poor because the grazing area used in the dry season is needed for rice production. As a result of poor management, community land is heavily overgrazed and degraded (Yang Saing Koma 2001).

Poor-quality feed and fluctuating feed supplies are the biggest constraints to increasing livestock productivity in many tropical countries (ILRI 2009). In order to improve this situation, there is a need to look at ways for extending the availability and quality of the available feed resources.

Water hyacinth (Eicahronia crassipes) is a water plant that can be collected locally from rivers, lakes and ponds in Cambodia, as in other tropical countries. It is one of the fastest growing plants, which is known to double its biomass in two weeks (Upadhyay et al 2007). The plant impacts dramatically on water flow, blocks sunlight from reaching native aquatic plants, starves the water of oxygen, and often kills fish. Based on these reasons, it has been recommended that water hyacinths should be removed from water surfaces to limit the disadvantages attributed to this plant (Skinner 2007). This process would be facilitated if it could be used as a feed for animals.

Utilization of water hyacinth as an animal feed has been reported by Hentges (1970), Salveson (1971) and Stephens (1972). When land forages were limited, cattle have been noticed grazing floating water hyacinths (Little 1968). Hentges (1970) reported that the amount of water hyacinth voluntarily consumed by cattle was less than the  requirement for maintenance. In order for water hyacinth to be fed as the basis of the diet it therefore needs to be complemented with other nutrient-rich feeds. Water hyacinth foliage is rich in protein and minerals (Abdelhamid  and  Gabr 1991), thus the other approach to the use of this plant is to consider it as a rumen supplement to complement crop residues such as rice straw which are deficient in such nutrients. For this purpose it needs to supply readily fermentable nitrogen and minerals as well the “unknown” factors often associated with green feeds (Preston and Leng 2009). However, even when the needs of rumen micro-organisms are met, basal diets such as rice straw must also be supplemented with sources of  “bypass” or “escape” protein (Preston and Leng 2009) in order to meet the requirements for production. In this respect cassava foliage has proved to be a valuable supplement in diets that otherwise supply only “rumen” nutrients (Ffoulkes and Preston 1978). These authors showed that fresh cassava foliage supported the same growth rate as soybean meal for fattening cattle fed a basal diet of molasses-urea. On diets of rice straw fed to growing cattle, rates of live weight gain were increased by supplements of fresh cassava foliage (Seng Mom et al 2001), cassava leaf meal (Ho Thanh Tham 2008) and sun-dried cassava hay (Keo Sath et al 2007).

For the above reasons it was decided to evaluate the potential advantages of combining fresh water hyacinth and sun-dried cassava foliage (hay) as respective sources of rumen nutrients and bypass protein in a basal diet of rice straw fed to growing cattle of the  local “Yellow” breed.

Hypotheses

The hypotheses to be tested were:

·         Giving water hyacinth foliage as a supplement to rice straw fed to local “Yellow” cattle will have a similar effect as a “rumen” supplement containing urea, and minerals

·         Water hyacinth leaves will have a better feeding value than the whole aerial part containing stems as well as leaves

·         Cassava hay will supply bypass protein and therefore, because all diets are devoid of bypass protein,  will enhance performance on all the diets

Materials and methods

Location

The experiment was carried out at the Animal Research Station of the Faculty of Animal Science and Veterinary Medicine, Royal University of Agriculture (RUA), Phnom Penh capital city, Kingdom of Cambodia, for 72days from November 08, 2009 to January 17, 2010.

Experimental design

The experiment was designed as a randomized complete block (RCB) with 3 replicates per treatment. The treatments were arranged as a 3*2 factorial, in which the factors were:

Rumen supplement:

·         Water hyacinth leaf (WHL)

·         Water hyacinth leaf and stem (WHLS) and

·         Urea-mineral mixture (UM)

Bypass protein supplement

·         With cassava hay (CH)

·         Without cassava hay

Experimental feeds

All animals received a basal diet of untreated rice straw ad libitum and either supplements of WHL, WHLS or UM (Table 2) each of which was provided at a level to supply 100g of crude protein (N*6 25) per 100kg LW.

Animals on three of the six treatments (WHL-CH, WHLS-CH and UM-CH) received an additional supplement of cassava hay at 1% of live weight (DM basis). This was planned to provide approximately 200g/day of additional crude protein to a 100 kg live weight animal.

Ingredients for making urea-minerals mixture were bought from a local market near the experimental site while fresh cassava foliage was obtained from plants that were three months old from farm households in Kampong Cham province. Cassava leaves and petioles were separated from the hard stem and sun dried for about 5 to 7 days on a plastic sheet placed on the ground until the leaves became crisp (>85% DM) (Photo 1). Rice straw of the same variety was bought from farmers at the harvest time. Water hyacinth (Photo 2) was collected daily from the lagoon located close to RUA.

Animals and management

Local male “Yellow” cattle (Photo 3) with mean live weight of 101±14.5 kg were housed in individual pens (photo 4) where they could have free access to the rice straw and water. Before starting the experiment, the cattle were drenched with Ivermectin (1% of Ivermectin concentration) and vaccinated against foot and mouth disease (FMD) and Pasteurellosis (Heamorraghic Septicaemia). The water hyacinth and urea-minerals mixture were given as the first feed in the morning at 07:00h. At 09:00h and 16:00h the cattle were offered the cassava hay and rice straw.

Photo 1. Sun-dried cassava (hay)	Photo 2. Water hyacinth collecting from lagoon	Photo 3. The experimental local “Yellow” cattle
Photo 4. Experimental cattle kept in individual pens	Photo 5. The stomach tube and gag	Photo 6. The way of taking rumen fluid

Data collection

Feeds offered were weighed before giving them to the cattle. Feed refusals were collected each morning prior to offering fresh feed and weighed to measure the feed intake. Representative samples of feeds offered and refusals were collected for chemical analysis. The live weights of the cattle were taken at the beginning, every 2 weeks and at the end of the experiment. Samples of rumen fluid were taken by a stomach tube (Photos 5 and 6) two hours post feeding in the morning at 4, 8 and 10 weeks for counting of protozoa and determining rumen ammonia and pH. The samples for counting of protozoa were stabilized by adding formaldehyde saline solution (10% formaldehyde and 0.9% NaCl) at the rate of 1ml per 10 ml of rumen fluid and kept in the refrigerator at -20^oC for later counting. For rumen ammonia analysis, 0.3 ml of 50% H₂SO₄ was added to 15.0 ml of rumen fluid (Korhonen et al 2002).

Chemical analyses

Water hyacinth leaves plus stems, water hyacinth leaves, cassava hay and rice straw and the urea-mineral mixture and feed refusals were analyzed for dry matter (DM), nitrogen (N) and ash following the methods of AOAC (1990). Acid detergent fiber (ADF), and neutral detergent fiber (NDF) were determined by the methods of Van Soest et al (1991). The numbers of rumen protozoa were counted using a Whitlock universal (worm egg counting) chamber under a microscope at 10x magnification. Rumen pH was measured immediately after taking rumen fluid from the animal with a digital pH meter.

Data analyses

Data for feed intake, growth and feed conversion were analyzed with the Generalized Linear Model option of the ANOVA program in the MINITAB software (Version 13.31) (Minitab 2000). Sources of variation were rumen supplements, with or without cassava hay (bypass protein supplement), interaction between rumen supplement and with or without cassava hay and error. When there was a significant difference at P<0 05, the means were compared using Tukey’s procedure in the same MINITAB software. When there were trends in animal responses, linear regressions were calculated using the MINITAB software.

Results and discussion

Chemical composition of feeds

The DM and crude protein (CP = N*6 25) contents of water hyacinth leaves+stems (whole aerial part) were higher than was reported by Aboud et al (2005) but values for ADF, NDF and ash were lower (Table 3). Leaves of water hyacinth had higher DM, CP and lower ADF and NDF than the combined leaves+stems. On an “as fed” basis the water hyacinth aerial part was only 35% leaf (Table 4). In the cassava hay the proportion of leaf was 71%.

The chemical composition of water hyacinth varies considerably, according to where it grows and when it is harvested. The comparisons made here are with water hyacinth growing in Tanzania and in Thailand. The high CP content of the leaves can be considered as favorable for feeding to ruminants thus the leaves may be regarded as a valuable fermentable N supplement for animals fed on low protein crop residues. For cassava hay, the ash, ADF and NDF contents were higher, but CP was comparable to that reported by Wanapat et al (1997).

Feed intake

Total DM intakes were increased by feeding cassava hay and by feeding water hyacinth leaves compared with leaves+stems (Tables 5 and 6; Figures 2 and 3). DM intake on the UM rumen supplement treatment was lower than when water hyacinth was fed – in the presence of cassava hay. The opposite was observed in the absence of cassava hay, when rice straw intake and total DM intakes were higher for the UM treatment than for treatments with water hyacinth. The CP levels of the diets were lower in the absence of cassava hay and were only marginally above the minimum level needed for efficient rumen function (Perdok and Leng 1989). In this situation the water hyacinth treatments were inferior to the urea-mineral treatment, because of the lower total  DM intake of the former compared with that of the  UM treatment group.

Figure 1. Dry matter intake of dietary ingredients for “Yellow” cattle fed rice straw supplemented with water hyacinth leaves, water hyacinth leaves+stems or urea-mineral mixture, in each case with or without cassava hay

Figure 2. Total DM intake for “Yellow” cattle fed rice straw supplemented with water hyacinth leaves, water hyacinth leaves+stems or urea-minerals mixture, in each case with or without cassava hay	Figure 3. CP intake for “Yellow” cattle fed rice straw supplemented with water hyacinth leaves, water hyacinth leaves+stems or urea-minerals mixture, in each case with or without cassava hay

Figure 4. Proportion of CP in DM for “Yellow” cattle fed rice straw supplemented with water hyacinth leaves, water hyacinth leaves+stems or urea-minerals mixture, in each case with or without cassava hay

Rumen parameters

 The concentration of rumen ammonia was increased by feeding cassava hay and was higher when urea-minerals was the rumen supplement rather than water hyacinth (Tables 7 and 8; Figure 4). The pH values varied only slightly among treatments and all were within the normal range for adequate rumen function (Preston and Leng 2009). Protozoal populations were not affected by dietary treatments but were lower by a factor of 10 compared to data reported by Seng Mom et al (2001) (populations of protozoa  (3-4*10⁴/ml) for similar animals fed similar diets.

Figure 5. Mean values of rumen ammonia for “Yellow” cattle fed rice straw supplemented with water hyacinth leaves, water hyacinth leaves+stems or urea-minerals mixture, in each case with or without cassava hay

Growth rate

Live weight gain was higher when cassava hay was fed (Table 9). However, there was a significant interaction between the main treatments (Figures 6 and 7). When cassava hay was fed growth rates were higher when the leaves of water hyacinth were given as the rumen supplement with no difference between water hyacinth leaves plus stems and the urea-mineral mixture (Table 10). In the absence of cassava hay, the cattle fed either leaves or leaves plus stems of water hyacinth lost body weight while those fed the urea-mineral mixture gained in weight (Table 10; Figures 6 and 7). The growth rate on the best treatment of cassava hay and water hyacinth leaves (243 g/day) was similar to that (250 g/day) reported by Seng Mom et al (2001) for “Yellow” cattle fed rice straw supplemented with urea minerals and cassava foliage, and is probably close to the genetic potential of this “small” breed.

The differences in rate of live weight gain (or loss) reflected the differences in DM intake (Figures 8) and the crude protein intake (Figure 9).

Figure 6. Growth curves for “Yellow” cattle fed rice straw supplemented with water hyacinth leaves, water hyacinth leaves+stems or urea-minerals mixture, in each case with or without cassava hay

The positive growth response to the cassava hay supplement is in agreement with a wide body of recent reports in which cassava foliage was supplemented to rice straw as the basal diet (Seng Mom et al 2001, Ho Thanh Tham 2008; Keo Sath et al 2007). The better growth on water hyacinth leaves compared with leaves+stems may in part be due to the greater concentration of cell wall compounds in the stems, resulting in a lower digestibility, The interesting result, however, is in the interaction between cassava hay and the rumen supplements (Figure 7).

Figure 7. Mean values for live weight change for “Yellow” cattle fed rice straw supplemented with water hyacinth leaves, water hyacinth leaves+stems or urea-mineral mixture, in each case with or without cassava hay

When cassava hay was fed, there were no differences between the rumen supplements of water hyacinth leaves+stems and urea-. However, in the absence of cassava hay, growth was positive with the urea-mineral supplement and negative with water hyacinth leaves and leaves+stems. The implication for these findings is there may be anti-nutritional compounds in the water hyacinth which exerted negative effects on animal metabolism when the protein status of the animal was low (ie: in the absence of cassava hay supplementation). That these negative effects were not evident when cassava hay was fed can be explained by the known positive effects of higher dietary protein levels in animals subjected to disease stress, including that induced by intake of toxic compounds (Leng 2005).

The critical role of the protein supply is evident from the positive relationships between the crude protein consumed and the DM intake and the live weight gain (Figures 8, 9 and 10). The positive relationship between rumen ammonia concentration and live weight gain (Figure 11), supports the idea that the N supply to rumen micro-organisms, as well as the protein supply to the animal, were important factors determining animal growth responses.

Figure 8. Relationship between dry matter intake and live weight change for “Yellow” cattle fed rice straw supplemented with water hyacinth leaves, water hyacinth leaves+stems or urea-mineral mixture, in each case with or without cassava hay	Figure 9. Relationship between crude protein intake and live weight change for “Yellow” cattle fed rice straw supplemented with water hyacinth leaves, water hyacinth leaves+stems or urea-mineral mixture, in each case with or without cassava hay

Figure 10. Relationship between proportion of crude protein in dray matter and live weight change for “Yellow” cattle fed rice straw supplemented with water hyacinth leaves, water hyacinth leaves+stems or urea-mineral mixture, in each case with or without cassava hay

Figure 11. Relationship between rumen ammonia and live weight change for “Yellow” cattle fed rice straw supplemented with water hyacinth leaves, water hyacinth leaves+stems or urea-mineral mixture, in each case with or without cassava hay

Support for the concept of the presence of anti-nutritional compounds in water hyacinth can be found in the report of Hentges (1970) that cattle could not eat enough fresh water hyacinth to cover their maintenance requirement. Kahn (1977) also found that green water hyacinth alone was insufficient for the maintenance of bullocks as the animals lost 23 g/day of live weight during a period of 60 days. However, when rice straw was given together with the water hyacinth (1:1 ratio) the bullocks increased their DM intake by 67% and gained 68g/day of live weight. On the basis of proximal analysis, rice straw has a much lower nutritive value (less crude protein and more cell wall compounds) than water hyacinth. In this case, the positive effects from adding a feed of lower nutritional value could be due to the diluting effect of the rice straw on the anti-nutritional compounds in water hyacinth.

There is confusing evidence on the presence of anti-nutritional compounds in water hyacinth. Lareo and Bressani (1982) stated: “that the levels of anti-physiological factors present in the plant are either very low or non-existent. We found tannins in amounts of only about 1 per cent of the dry matter from the whole plant and 2 per cent in the leaves. The plant as a whole does not have trypsin inhibitors. The tests for saponins and alkaloids were negative, and the level of oxalates was only 0.8 per cent”. Abdelhamid and Gabr (1991) also reported low levels of total tannins of only 0.13% in the DM of water hyacinth leaves. In marked contrast, Dutta et al (1984) reported total tannins of 2% in DM in the leaves of water hyacinth. No information was given on the condensed tannin fraction, which can combine with protein to make it insoluble. In any event, even 2% of tannins are not likely to be a problem as the safe upper level of condensed tannins was indicated to be of the order 5 to 6% in DM by Reed (1995), while levels of 4% were considered by Barry (1987) to be advantageous in enhancing the “bypass” characteristics of the protein.

The presence of toxic heavy metals – lead and mercury – in water hyacinth was reported to be a risk factor by Skinner (2007). However, there seems to be no evidence linking these elements with ruminant animal responses to feeding water hyacinth. What appears to be consistent is the depression in animal growth responses when water hyacinth leaves are fed in increasing amounts up to the point of being the sole diet. Thus Abdelhamid  and  Gabr (1991) fed sheep on diets of rice straw and concentrates, with increasing proportions of fresh water hyacinth leaves until the sole diet was water hyacinth. DM intake decreased linearly with increasing proportions of water hyacinth in the diet being only 420 g DM/day with 100% water hyacinth compared with 1290 g/day on the control diet of 30% concentrates and 70% rice straw. They showed that these responses were not related to the apparent nutritive value of the diets as apparent DM digestibility (56-58%) was similar on the control and 100% water hyacinth diets, while the DCP was 13% for water hyacinth compared with 5% for the control diet. These same authors also quoted reports from farmers who used water hyacinth as a green fodder that all rabbits and geese died, soon after eating water hyacinth. The toxicity for rabbits of water hyacinth as the sole diet was recently reported in Vietnam (Bui Phan Thu Hang 2010, personal communication). There were no problems when the water hyacinth was diluted with 50% of its weight as water spinach. Osman et al (1975) came to the same conclusion that feeding with the fresh plant alone is not possible. The physiological problems caused by the biochemical components of the water hyacinth remained the same after drying the plants according to Becker et al (1987). This would seem to rule out calcium oxalate as a factor limiting intake since drying Taro (Colocacia esculenta) leaves eliminates the limitations to intake caused by the high levels of calcium oxalate in the leaves of  this plant (Pheng Buntha et al 2008). At the same time many authors did not find health problems from feeding water hyacinth (Moursi 1976 and El-Serafy et al 1980) but they, along with other authors (Hathout et al 1980; Tagel-Din et al 1989; Zahran et al 1989) recommended its use with appreciable amounts of concentrates.

Conclusions

• Supplementation of a rice straw diet with water hyacinth leaves and cassava hay supported normal growth in local “Yellow” cattle
  
  
• In the absence of cassava hay, the cattle lost weight when the rumen supplement  was water hyacinth leaves or leaves+stems, while those given a urea-mineral supplement gained weight
  
  
• It is postulated that there are anti-nutritional compounds present in water hyacinth leaves which at low overall protein intakes lead to reduced feed intake and loss of body weight
  
  
• Water hyacinth foliage should never be fed as the sole diet of ruminants but may be fed at up to 25% of the diet DM along with protein-rich supplements

Acknowledgements

The authors are grateful to the MEKARN project, financed by Sida, Sweden for the support for this research. The Royal University of Agriculture, Phnom Penh, Kingdom of Cambodia is acknowledged for provision of research facilities.

References

Abdelhamid  A M and  Gabr A 1991  Evaluation of water hyacinth as a feed for ruminants  Archives  Animal Nutrition • Berlin 41 (1991) 7/8  745-756

Aboud A A O, Kidunda R S and Osarya J 2005: Potential of water hyacinth (Eicchornia crassipes) in ruminant nutrition in Tanzania  Livestock Research for Rural Development  Vol  17, Art  #96  Retrieved April 30, 2010, from http://www lrrd org/lrrd17/8/abou17096 htm

AOAC 1990   Official Method of Analysis  Association of Official Analytical Chemists  15^th edition (K Helrick editor)  Arlington pp 1230

Barry T N 1987 Secondary Compounds of forages in Nutrition of herbivores. Hacken J B and Termouth J H (editors). AP Sydney. Pp. 91-120.

Becker K, Mahler F and Gall C  1987  Animal Research Development  25, 45

Dutra R K, Sahu B K, Panda N C and Nayak B C 1984  Indian Journal of Animal Science 54, 594 Egypt.-British Conf. on Anim., Fish and Poultry Prod., Alexandria, Egypt

El-Serafy A  M, Allam S  M, El-Ashry M  A,  Kilaltab H  M,  SowIan H  S  and Swidan F  Z 1980   Dry matter intake and nutrients digestibility of water hyacinth hay, haylage and silage by buffalo steers. Indian Journal of Animal Science. 57: 698-701.

Ffoulkes D and Preston T R 1978  Cassava or sweet potato forage as combined sources of protein and roughage in minerals based diets: effect of supplementation with soybean meal  Tropical Animal Production (3): 186-192  http://www.utafoundation.org/TAP/TAP33/3_3_1.pdf

Hentges J  F Jr  1970  Processed aquatic weeds for cattle nutrition  Proceedings Aquatic Plant Research  Conference,  University of Florida, Gainesville

ILRI 2009  Forage diversity  http://www.ilri.org/ForageDiversity

Kahn M J 1977 Studies on the composition, voluntary intake and digestibility of water hyacinth (Eichhornia crassipes) and its effect on the growth of cattle MSc Thesis submitted to Bangladesh Agricultural University

Keo Sath, Khieu Borin and Preston T R  2008 Effect of levels of sun-dried cassava foliage on growth performance of cattle fed rice straw. Livestock Research for Rural Development. Volume 20, supplement. http://www.cipav.org.co/lrrd/lrrd20/supplement/sath2.htm

Lareo L and Bressani R 1982 Possible utilization of the water hyacinth in nutrition and industry. Food and Nutrition Bulletin. Volume 4, Number 4, United Nations University, Tokyo, Japan.
http://www.unu.edu/unupress/food/8f044e/8F044E00.htm#Contents

Leng R A 2005 Metabolisable protein requirements of ruminants fed roughage based diets. In Proceedings of AHAT/BSAT International Conference   Integrating Livestock-Crop systems to meet the challenges of globalisation (Editors: P Rowlinson, C Wachirapakorn, P Pakdee and M Wanapat), November 14-18, 2005, Khon Kaen, Thailand.

Little E C S  (Editor) 1968  Handbook of Utilization of Aquatic Plants  F A O  of the U N  Rome, Italy

MAFF 2004  Ministry of Agriculture, Forestry and Fisheries  http://www maff gov kh/eng/statistics/livestock html#a1

Moursi H  A  1976 Symposium on Nile water and Lake Dam Projects, Cairo, P: I

Osman H  E, El-Hag G  A   and Osman M K 1975 Aquatic weeds in the Sudan with special reference to water hyacinth. National Council for Research  In: Obeid M  (Ed ) Aquatic weeds in the Sudan

Perdok H B and Leng R A 1989  Rumen ammonia requirements for efficient digestion and intake of straw by cattle. In: Protozoa and Fungi in Ruminant Digestion: Proceedings of an OECD/UNE International Seminar, 26- 29 September 1988. pp. 291-293 (J V Nolan, R A Leng and D I Demeyer. editors]. Armidale, NSW: Penambul Books.   

Pheng Buntha, Khieu Borin, Preston T R and Ogle B 2008  Survey of taro varieties and their use in selected areas of Cambodia  Livestock Research for Rural Development  Volume 20, supplement  Retrieved May 25, 2010, from http://www.lrrd.org/lrrd20/supplement/bunt1 htm

Preston T R and Leng R A 2009  Matching ruminant production systems with available resources in the tropics and subtropics  http://www utafoundation org/P&L/preston&leng htm

Reed J D 1995 Nutritional toxicology of tannins and related polyphenols in forage legumes. Journal of Animal Science 73:1516 http://jas.fass.org/cgi/reprint/73/5/1516.pdf

Salveson, R  E  1971  Utilization of aquatic plants in steer diets: Voluntary intake and digestibility  MSA  Thesis  University of Florida, Gainesville

Seng Mom, Preston T R, Leng R A and Meulen U ter 2001 Response of young cattle fed rice straw to supplementation with cassava foliage and a single drench of cooking oil  Livestock Research for Rural Development (13) 4: http://www lrrd org/lrrd13/4/seng134 htm

Skinner Kathleen 2007  "Mercury uptake and accumulation by four species of aquatic plants"  Environmental Pollution (Elsevier) 145 (1): 234–237  doi:10 1016/j envpol 2006 03 017  http://en wikipedia org/wiki/Water_hyacinth

Steinfeld Henning 2006  Rearing cattle produces more greenhouse gases than driving cars, UN report http://www un org/apps/news/story asp?NewsID=20772&Cr=global&Cr1=environment

Stephens E  L  1972  Digestibility trials on ten elements and three toxicants in aquatic plant diets fed steers  M S A  Thesis  University of Florida,

Tagel-Din A  E, Nour A  M  , Nour A  A   and Ahmed A  H   1989  Proc  3rd Egypt -British Conf  on Anim., Fish and Poultry Prod., Alexandria, Egypt.

Tham H T, Man N V and Preston T R 2008  Performance of young cattle fed rice straw sprayed with mixture of urea and minerals supplemented with different levels of cassava leaf meal  Livestock Research for Rural Development  Volume 20, supplement  Retrieved May 25, 2010, from http://www cipav org co/lrrd/lrrd20/supplement/tham1 htm

Upadhyay, Alka R and Tripathi B  D  2007  "Principle and Process of Biofiltration of Cd, Cr, Co, Ni & Pb from Tropical Opencast Coalmine Effluent"  Water, Air, & Soil Pollution (Springer) 180 (1 - 4): 213–223  http://en wikipedia org/wiki/Water_hyacinth

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 74:3583-3597 http://download.journals.elsevierhealth.com/pdfs/journals/0022-0302/PIIS0022030291785512.pdf

Wanapat M, Pimpa O, Petlum A and Boontao U 1997 Cassava hay: A new strategic feed for ruminants during the dry season  Livestock Research for Rural Development (13) 4: http://www lrrd org/lrrd9/2/metha92 htm

Yang Saing Koma 2001  Assessment of the current state of agriculture, forestry and marine resources: Sustainable Agriculture, Japan International Volunteer Centre,

Zahran S  M, Ahmed M  H , Tagel-Din A  E  , Nour A  M   and Abou-Akkada A  R 1989  Proceedings 3rd Egypt -British Conference  on Animal, Fish and Poultry Production, Alexandria, Egypt.

Go to top