Evaluation of sun dried sisal pulp (Agave sisalana Perrine) as feed for sheep in Eritrea

D Y Gebremariam* and D H Machin** 

School of Graduate Studies, University of Asmara, Asmara, Eritrea           
 *Present Address National Agricultural Research Institute, Ministry of Agriculture,P.O.Box 4627, Halhale, Eritrea
**Present Address Sandfields, Fenway, Steeple Aston, Oxford, OX25 4SS, UK
DavidMachin757@hotmail.com

Abstract

A study was carried out into the processing of Sisal pulp into animal feed using sun drying and a feeding trial was conducted to evaluate the sun dried sisal pulp (Agave sisalana) as a ruminant feed resource in Eritrea. The sisal pulp was obtained following the mechanical processing of sisal leaves using dry decortication. Short fibers were removed by hand before sun-drying the pulp on plastic sheets at a depth of approximately 20mm; the pulp was turned several times during drying. When dry, (after 24 hours) the pulp was sieved to remove the remaining short fibers, sacked and stored prior to being fed to animals. The feeding trial was carried out over 80 days using forty fat-tailed highland lambs weighing on average 22.5±1.7 kg and aged 5-7 months. Animals were allocated into four treatment groups with two replicates of 5 animals in each. The basal diet of barley straw fed ad libitum was supplemented with sun-dried sisal pulp at levels of: 0, 250g, 500g and 500g plus 50g ground cottonseed cake in treatments 1, 2, 3 and 4, respectively. All treatment groups had a free access to a mineral block to alleviate any mineral imbalances.  

Dried barley straw was found to have a crude protein of 5.2%, a crude fibre of 40.2% and an NFE content of 44.7%, whilst sisal pulp had a crude protein of 7.3%, a crude fibre of 15.2% and an NFE of 59.6%. The dry matter digestibilities of barley straw and sun-dried sisal pulp were determined using two lambs kept in metabolic cages, for 5 days for each feed type. These were shown to be 52.1 and 68.5, respectively. The voluntary consumption index (kg DM/100 kg live weight/day) of total DM were 3.09+ 0.25, 3.54 + 0.39, 3.74+ 0.56 and 3.88+0.45 for treatments 1,2,3 and 4 respectively. The average daily live weight gains were 22.5g, 41g, 53g and 69g respectively for the same treatments. In conclusion this study showed that dried sisal pulp was a good feed for sheep, whose performance improved increasingly where this was used to replace barley straw in their feed.  

Key Words: barley straw, cotton seed cake, weight gain

Introduction 

One of the most important constraints to animal production in the semi arid and arid regions of the tropics is shortage of feed. At the same time the production of sisal, one of the main cash crops in such areas has reduced due to the poor returns and demand for the sisal fibre, which is the main marketable product of the industry (Shamte 2000). However, in the last few years there has been a dramatic increase in the price of sisal fibre which has changed the overall potential of this crop.  

The fibre comprises approximately 4% of the weight of the harvested leaf, whilst the pulp which, makes up the remaining 96% of the leaf is either discarded or simply used as a mulch in the sisal fields. As a result many hundreds of thousands of tonnes of the pulp, which, could potentially be used as ruminant feed, are not being used in many arid and semi arid regions of the world, such as East Africa, where animals are dying or losing weight for lack of any form of feed. The fresh pulp has been used as an animal feed but with very little success in some sisal (or in Mexico related Henequen) growing areas, including Kenya, Tanzania and Mexico, (Herrera et al 1980). This lack of success with feeding sisal  pulp is largely a result of its inherent content of Oxalic Acid and the propensity of the high soluble carbohydrate content of the pulp to rapidly ferment generating even more acidity (principally Lactic acid) so reducing its palatability and nutritional value (Preston and Leng 1987).

Nearly two thirds of the African continent, is hyper-arid, arid, semi-arid and sub-humid (Gilani 2000).  In such countries crop residues such as straw, are the main source of feed for large ruminants (Leng 1992).  However, Leng (1997) also suggested that agro-industrial byproducts such as bagasse, molasses, sugar cane tops, sisal waste and oilseed cakes or meals could be significant sources of feeds in developing countries. Whilst all these resources might be available in significant amounts in the long term, sisal waste, which, is currently available in countries in East Africa, could offer an immediate or short term solution to the problem.

Analysis of a range of fresh sisal pulps from Kenya, Tanzania and Venezuela were carried out and reported by Machin (1991). These show that the dry matter composition of sisal pulp could provide significant amounts of nutrient if preserved without change to this composition (Table 1). In particular dry processing shows a greater degree of nutrient retention than wet processing.

The purpose of this study was firstly to determine a way by which sisal waste could be effectively processed and used as a ruminant feed in Eritrea and then to determine its nutritive value for sheep.

Materials and methods 

The study reported here took place at the College of Agriculture of the University of Asmara between June 2005 and June 2006 using sisal in the Eritrean Highlands (altitude 2300ms) which had been planted as an environmental improver. Laboratory analysis was carried out on pulp of leaves from several similar semi arid zones to determine any differences in the composition of leaves from different areas.

The leaves were processed using a motor driven sisal decorticator, which separated the pulp from the fibre in the leaves using rotating beaters within a static drum into which leaves were introduced by hand.  The pulp was blown out of the bottom of the drum whilst the fibre was held by the operator. The fiber was sun dried on wires and used by local women’s projects to make bags and handicrafts.

The pulp was dried on plastic sheets in the sun for a period of one day on sunny days and one and half days on cloudy days. To facilitate rapid drying the fresh pulp was laid out in 1 to 2 cm deep layers and turned regularly by hand. When completely dry, it was sieved through a mesh in order to exclude short fibers, which would become compacted into balls in the digestive tract of animals. The dried sieved product was then placed in sacks to be stored till used.

In order to determine the composition of the sisal leaves, 100 kg of fresh leaves were decorticated and the separate components, sisal pulp, long fibers and short fibers were weighed after sun drying. Samples of all these components were then oven-dried in the laboratory according to AOAC (1984).

Other materials used in the feeding trials included barley straw, which was purchased from farmers around Asmara, and a locally produced cotton seed cake which was ground using an 18 HP grinder with sieve size 3 mm.

The chemical composition (Ash, CP, CF, EE, Gross Energy and NFE) of each feed item was carried out according to the procedures of AOAC (1984).

In addition an imported mineral/vitamin lick was obtained with the following declared composition:- Sodium (Na) 34.5%, Calcium (Ca) 1.7%, Magnesium (Mg) 1.1%, Trace Minerals:- Zinc (Zn) 5g/kg, Manganese (Mn) 1.5g/kg, Iron (Fe) 300mg/kg, Copper (Cu) 750mg/kg, Iodine (I) 75mg/kg, Cobalt (Co) 50 mg/kg, Vitamins:- A 110,000IU/Kg, D3 30,000IU/kg, E (Alfa tocoferol)  30mg/kg. 

Feeding trials

Forty Eritrean Highland fat-tailed lambs, identified using ear-tags, with mean live weights of 22.5 ±1.7 kg, and ranging in age from 5-7 months were used in the experiment. All lambs were kept in 8 purpose built sheep pens for a 26 day adaptation period during which they were fed ad libitum barley straw and sun-dried sisal pulp. The sheep pens were located in a covered building with canvas walls, which were raised during the night to protect them from chilling. All lambs were de-wormed during the adaptation period using Ivermectin.

During the experiment, animals were randomly allocated to 4 treatment groups, using two replicates of 5 animals per pen.

Treatments

a)      Treatment 1= Ad libitum barley straw + free access to mineral lick.

b)      Treatment 2= Ad libitum barley straw + free access to mineral lick + 250g sun-dried sisal pulp per day.

c)      Treatment 3= Ad libitum barley straw + free access to mineral lick + 500g sun-dried sisal pulp per day.

d)      Treatment 4= Ad libitum barley straw + free access to mineral lick + 500g sun-dried sisal pulp + 50 g Cotton seed cake per day.     

The experimental design used was a randomized complete block design and the data was analyzed using GenStat Release 8.2 (2005) statistical software. The descriptive statistics for feed intake were computed using a Statistical Package for Statistical Sciences (SPSS 11.5 2002)

Each sheep was weighed weekly to calculate mean daily live weight gain. A known quantity of feed was offered every morning and the leftovers were weighed back the same time next morning in order to estimate the amounts of each feed consumed per pen per day. Water intake was recorded daily for each pen.

Determination of digestibility

A locally manufactured metabolic cage was employed to estimate the digestibility of the barley straw and sisal pulp used in the experiment. Two lambs which were adapted to both feeds and the crates were maintained in the metabolic cages for eleven days. During the first 5 days, straw and sisal pulp were fed together to the animals while in the last 5 days straw alone was given with a one day gap between the two five day feeding. The amounts of feed and water consumption per 24 hour period were recorded to calculate the intake/head/day. All the faeces, collected during each 24-hour period, were weighed and ten percent of these faeces were sampled for analysis. The faecal samples were stored in a refrigerator at 3 ^oC below zero for about a week before they were analyzed. The faecal samples were analyzed for ash, crude protein (CP), fat (EE), crude fiber (CF), gross energy (GE) and NFE.

Using these results the dry matter and organic matter digestibility of the straw were determined and then those of the sisal pulp were calculated by difference method using the following formula:

Where: D = “Digestibility,” T = “test feed,” N = “fraction of nutrient” and B = “basal diet”

Results 

In evaluating sisal pulp as an alternative animal feed resource, it was important to estimate the yield of the pulp on a dry matter basis that could be obtained from a given number of plants or leaves from each plant. This was carried out using 191 fresh sisal leaves, weighing 100kg and the mean composition of the components of sisal leaves estimated after processing which is shown in table 2

These results show that in order to produce each 100kg of dried sisal pulp 1854 leaves need to be processed, which is the annual yield from 70 to 80 plants. Each of these fresh leaves weighed on average 524g and had a dry matter content of 16.1%. Of this dry matter 10.3, 4.1 and 1.7% consisted of pulp, long and short fibre respectively. The pH was 4.8 which was largely a result of its content of oxalic acid.

Table 3. shows the chemical composition of feed components used in this experiment. Sisal pulp produced from leaves from two different semi arid zones of Eritrea showed only slight differences in composition; however, the CP, GE and NFE contents of sisal pulp were higher than those of barley straw. The EE content of both feeds were similar.   

The DM and OM digestibility of barley straw and sun-dried sisal pulp is shown in table 4. The results showed that the DM and OM digestibility of sisal pulp appear to be higher than those of straw. The DM and OM digestibility of the sisal pulp was also found to be higher than those of fresh sisal pulp reported in literature. (Ferreiro et al 1977a, Frank et al 1973, Godoy et al 1979 and Yerena et al 1977).

The results of the animal feed trials are shown in table 5. These show that when fed 500g of dried sisal pulp with ad libitum barley straw and access to mineral blocks the sheep in this study achieved a mean daily live weight gain (DLWG) of 53g, whereas those restricted to 250 g/day, achieved a DLWG of 41 g and those with only straw and mineral blocks had a DLWG of 22g. . Where the higher level of sisal pulp was fed with 50 g cottonseed cake a day the mean daily live weight gain of the sheep rose to 69 g. The live weight changes are shown in Figure 1.

These results show that when the basal diet of barley straw was supplemented with all levels of dried sisal pulp (treatments 2, 3 and 4) this resulted in a significantly higher (P<0.05) live weight gain compared to the basal diet alone (treatment 1). In fact supplementation of the barley straw basal diet with 250g sisal pulp led to an almost doubling in the weight gain, whilst doubling the supplementation level from 250g (treatment 2) to 500g (treatment 3) did not result in a significantly higher live weight gain. On the other hand, adding 50g cottonseed cake to the 500g pulp supplement (treatment 4) resulted in a significant difference in live weight gain (P<0.05) compared to both the 250g (treatment 2) and 500g (treatment 3) levels of supplementation.

As the level of sisal pulp supplementation increased from 250g (treatment 2) to 500g (treatment 3 and 4), the substitution level of straw intake by sisal pulp increased from 26% in treatment 2, to 45% and 48% in treatments 4 and 3, respectively. The consumption index for total DM was significantly lower (P<0.05) in treatment 1 compared to all the other treatment groups, though as before doubling the sisal pulp supplementation level from 250g in treatment 2, to 500g in treatment 3 did not result in a significantly higher consumption index. Doubling the sisal pulp intake from 250g to 500g accompanied by a further supplementation of 50g of ground cotton seed cake resulted in a significantly higher consumption index (P<0.05). Addition of 50g of cotton seed cake to the 500g sisal pulp level (treatment 4) did not result in a significant difference in consumption index compared to treatment 3.

The feed conversion efficiency (FCE) increased with increasing levels of sisal pulp supplementation with the highest FCE occurring when cotton seed cake was added to the 500g sisal diet in treatment 4.

Although no statistical analysis was carried out, the intake of water for each kg DM intake of feed increased in line with the increase in the consumption index, with animals fed straw alone tending to drink less water for each unit of DM straw they consumed.

Discussion 

Fresh sisal pulp contains at least 10% soluble sugars (DM), which falls to less than 1% after seven days (Herrera et al 1981) due to rapid fermentation producing lactic acid that starts immediately after fiber extraction (Preston and Leng 1987). Similarly when sisal pulp is ensiled, fermentation to organic acids and alcohol occurs and much of this is lost from silos; if the acids are retained they are not efficiently used in the rumen (Ferreiro et al 1977 a). Therefore given the abundance of drying conditions in areas where sisal is grown the best option seems to be to avoid fermentation by sun-drying since dried sisal pulp can be stored for long periods. At the same time the dried sisal feed is only about 3 times as bulky as grain making it easy to store and transport. The other advantage of drying is that the short fibers in the waste can be removed by raking or sieving to avoid the formation of balls in the digestive tract of animals. All researchers cited in this paper have used fresh or ensiled sisal pulp.

The CP content of sisal waste is shown to vary depending on the method of processing applied with the highest value resulting from dry decortication. Regardless of decortication and post-decortication-processes applied to the pulp, the overall CP content ranges reported range from 3.8% -15%, with the mean value being around 7%. Similarly the crude fibre (CF) content of sisal pulp is reported to range from 18% to 43% with a mean of approximately 25% (Machin 1991; FAO 1981; Preston and Leng 1987). The mean CP content of the sun-dried sisal pulp in this experiment was 7.3%, which is similar to the mean value reported in the literature. The slight variations in chemical composition of sisal pulp from the two different zones is probably due to variations in soils and climate as they were processed in a similar way.  While the CP was similar to the findings of other researchers, the CF values reported here were slightly lower which is probably due to removal of the short fibers by sieving from the dried pulp.

The fresh and dry sisal pulp was shown to have a pH of 4.8, which is within the range reported by Purseglove (1992) for fresh pulp. This shows that drying did not change the pH level in this experiment and confirms that the oxalic acid in the pulp does not volatilize during the drying process but remains there possibly with some crystallization (Bryant, pers. comm...). Although all sisal in Eritrea is Agave sisalana containing Oxalic Acid hybrid sisal varieties grown in many other countries are believed to lack Oxalic acid which could improve the potential of dried sisal pulp products.  

The NFE and GE content of fresh pulp in this experiment were shown to range from 56.3 to 62.9% and 11.2 to 12.1% respectively, which is similar to that reported by Machin (1991). This is higher than the 44.7% NFE content of the barley straw used in these trials.

Ferreiro et al (1977a) showed that fresh sisal pulp contained 10%-12% soluble sugars (DM), which fell to less than 1% seven days after ensiling. Similarly, Preston and Leng (1987) found that the water soluble carbohydrate content of fresh sisal pulp (Agave fourcroydes) was 21% (on DM basis) and this fell to 0% when the pulp was ensiled. This indicates that the high NFE and GE levels of dried pulp reported here is a result of sun drying the fresh pulp which has preserved the soluble sugars and hence the NFE and GE content.

In this experiment the CP content of the straw used was 5.2%. FAO (1981) reported that the CP content of similar samples of barley straw from Kenya and Iraq to be 6.0 and 2.5, respectively. It would therefore, appear that the CP content of the barley straw used in this experiment was of acceptable quality.

The CP content of the cotton seed cake used in this experiment was 35.9 per cent.  Oilcakes with hulls, processed by mechanical extraction in Uganda and Israel were reported to have CP contents of 26.2-26.9%, whilst similar samples from Zimbabwe had 30.5%. On the other hand, oilcake without hulls, mechanically extracted in Israel is reported to have a CP content of 47.7 per cent (FAO 1981). From this it would appear that sample of cotton seed cake used here was of acceptable quality.                                                              

It should be noted that, in this experiment, while the digestibility of straw was calculated independent of that of the sisal pulp, the latter was calculated by difference method using the straw as the basal feed resource, which could result in some interaction between the basal feed resource and the supplement (Preston and Leng 1987). Since the sisal pulp and straw are of similar nature it is not anticipated that any significant interaction will have occurred.

The DM digestibility of sisal pulp in this study was determined to be 68.5 % which is higher than that reported for fresh pulp, which was shown to be 64% by Yerena et al (1977) and 63% by Frank et al (1973). This was also much higher than the digestibility of ensiled pulp which was shown by Ferreiro et al (1977a) and Godoy et al (1979) using Agave fourcroydes to be 55% and 54% respectively. The dried sisal pulp DM digestibility was also shown to be higher than that of straw (52.1 %) in this study. The differences in digestibility between ensiled and dried sisal pulp probably reflects the difference in the physical form, the method of processing as well as other materials digested with the study material.

The DM digestibility of sun-dried sisal pulp in this experiment was shown to be 4 to5% higher than that reported for fresh sisal pulp which is probably a result of sieving the dry pulp to exclude the majority of the less digestible short fibers. It has been reported that when short fibers are left in the feed they form compact balls in the digestive tract of ruminants which cause digestive problems. Where ensiled sisal pulp, with the short fibers removed, has been fed to sheep the voluntary intake has been seen to increase (Rodriguez et al 1985a and b) which could imply that it had a higher digestibility though this was not determined.

The OM digestibility of straw in this experiment was found to be 57.4%, whilst that of the dried sisal pulp was 73.3%. Preston and Leng (1987) showed the in vitro digestibility of barley straw to be in the range of 34%-61%, which indicates that the straw used in this study was of good quality and that the dried sisal pulp had high nutritional potential for ruminants.

 Despite the low pH of the dry sisal pulp sheep fed  “ad libitum” barley straw and with access to a mineral block could consume up to 500 g/head/day of dried pulp without showing any observable ill-effects, showing that, nearly 50% of the basal straw feed can be replaced by dried sisal pulp. Also since no dried sisal pulp was left in the feeding troughs at the end of the day this indicates that the voluntary pulp consumption of sheep could well exceed the 500 g/day. This is supported by the experience of Rodriguez et al (1985b) who showed that the voluntary DM intake of sheep fed  fresh sisal pulp (Agave fourcroydes) could reach nearly 3% of their body weight, whilst the highest DM intake level used in this study was  2.2%.

When offered dried sisal pulp animals in treatments 2, 3 and 4 reduced their intake of straw. This is probably a result of the higher protein and NFE content as well as higher digestibility of sisal pulp compared with the straw.

Whilst the consumption of feeds may vary according to the type and nutritive value of other feedstuffs fed with the feed, the feeding of cotton seed cake with the dried pulp and straw did not affect the voluntary consumption of either of these products indicating that the nutrients provided by the cotton seed cake, primarily protein and energy, were not limiting or boosting the consumption of the other feeds.

No significant differences were observed in the DM consumption index between treatments 2, 3 and 4. Treatment 1, however, had a significantly lower (P<0.05) DM consumption index compared to the other three treatment groups. From these results, it is clear that sisal pulp has significantly increased the total dry matter intake and related live weight gain. This observation is in agreement with work carried out by Ferreiro et al (1977b) who showed that feeding African star grass to sheep fed fresh sisal pulp (Agave fourcroydes)  increased rumen liquid flow rates. This indicates the importance of including fibrous feeds to improve the use of sisal pulp as a ruminant feed.  

The increased live weight gain with the associated increased sisal pulp consumption of the sheep in this study shows that animals were able to get more nutrients from the sisal pulp than the straw. As can be seen from Table 3, the chemical composition of sisal pulp appears better than that of straw in most aspects other than crude fiber.

Table 3 shows the CP and energy value of cottonseed cake to be much higher than those of other feeds. This is clearly responsible for the significantly higher (P<0.05) weight gain of sheep fed the 50 g supplement of cotton seed cake in treatment 4 compared with those fed similar levels of straw and sisal pulp in treatment 3 showing the importance of bypass protein and possibly energy in straw and sisal pulp diets. However, no increase in levels of voluntary feed intake were observed as a result of cottonseed cake supplementation. In this respect Godoy et al (1979) suggested that when intake does not increase with supplementation of bypass protein and energy, animals are probably getting enough protein from such a supplement.   

Another reason for significantly higher (P<0.05) weight gain when the higher levels of sisal pulp was fed could be due to the provision of mineral supplementation. Deficiencies or excesses of nutrients can reduce the digestibility of feeds (McDonald et al 1995) and thereby affect live weight gain. Sisal-byproducts contain low levels of the minerals phosphorus (P), copper (Cu), cobalt (Co), manganese (Mn) and zinc (Zn) but are high in calcium (Ca) and magnesium (Mg) Rodriguez et al (1985a).  At the same time Sisal is known to contain oxalates (Preston and Leng 1987), which are reported to reduce the availability of calcium and other minerals in feeds. Although these can limit production ruminants adapted to such diets have been shown to have rumen bacteria that can degrade oxalates reducing or eliminating their effect (Preston and Leng 1987).

Similarly straws have a low and imbalanced mineral content (particularly calcium and phosphorus). Therefore it is generally agreed that minerals should be supplied for production of meat and milk, using such feeds (Preston and Leng 1987; Jayasuriya 1983).

It is also interesting to note that when sheep have been fed wheat straw, they lost weight (Leng 1992). In this experiment sheep fed barley straw alone gained 22 g of live weight daily. This is probably a reflection of the high digestibility of the barley straw, the straw was fed ad libitum so the sheep could select the more digestible leaves (Leng 1992) and the mineral blocks fed with the barley straw diet in this experiment, could correct limiting mineral deficiencies. 

The use of fresh sisal pulp as a feed for cattle has given slightly higher live weight gains and voluntary feed intakes compared with ensiled sisal pulp (Godoy et al 1979). This shows the importance of preserving the nutrients in the fresh pulp by avoiding ensiling. Although the results mentioned were observed in cattle, it is likely to be the same for sheep as both are ruminants. It is therefore clear that drying the fresh pulp has preserved its nutritive value and led to the better live weight gains recorded here using dried sisal pulp. 

Conclusions 

• The results reported here suggest that the nutritive value of sisal pulp is much better than that of barley straw and that the processing carried out here made it quite palatable for sheep.

• Carrying out cost-benefit analysis in this particular experiment was impractical because the leaves were purchased and were transported a long way to Asmara. However, in practice it is anticipated that the sisal would be grown and processed locally, which would significantly reduce costs. Although local use would be most cost effective, the dried sisal pulp has a reasonably high bulk density which would justify its transport to other locations. In this context the dried pulp could well be used widely as an alternative feed source in countries where sisal can grow and where frequent droughts occur since the pulp can be stored for use during such periods and the sisal can survive drought. At the same time planting sisal in semi arid and arid lands can significantly contribute to alleviating environmental degradation and water harvesting and offering other benefits such as the production of poles and honey.

• This study shows that moderate levels of performance can be achieved without the use of supplementary feeds providing that the sisal pulp is dried and fed with fibrous feeds and mineral blocks to correct any fiber and mineral deficiencies. Higher levels of performance would require the use of protein and energy supplements of higher quality.

• Of interest feeding similar feeds to small numbers of cattle on the project indicated a similar response to that of sheep which would need to be confirmed by appropriate experimentation. Also since sun-dried sisal pulp (Agave sisalana) has not previously been used as a supplement to crop residue based diets for all ruminants further experimentation is needed to develop the use of this feed for all ruminant animals.

Literature cited 

Association of Official Analytical Chemists (AOAC) 1984 Official Methods of Analysis. 4th Edition. AOAC, Washington D C

Ferreiro H M, Preston T R. and Herrera F 1977a Sisal By-products as Cattle Feed:  Effect of Supplementing Ensiled Pulp with Rice Polishing and Ramon (Brosimum alicastrum) on growth rate, digestibility and glucose entry rate by cattle. Tropical Animal Production 4 (1) 73-77 http://www.utafoundation.org/TAP/TAP41/4_1_13.pdf

Ferreiro H M, Elliott R. and Preston T R 1977b Rumen function and fermentation on diets based on sisal pulp. Tropical Animal Production 3 (1) 69-73 http://www.utafoundation.org/TAP/TAP23/TAP31/3_1_14.pdf

Food and Agriculture Organization (FAO) 1981 Tropical Feeds: Feed information summaries and nutritive values. FAO Animal Production and Health Series No. 12 Rome: FAO http://www.fao.org/ag/AGA/AGAP/FRG/afris/default.htm

Frank F, Meissner H H and Hofmeyr H.S 1973 Feeding value of sisal pulp for sheep. South African Journal of Animal Science 3 (2) 63-64

GenStat Release 8.2 2005 Lawes Agricultural Trust

Gilani A 2000 Aridity and Desertification in Africa. Second Training Course on the Use of Remote Sensing Techniques and the Geographic Information Systems in Monitoring and Combating Desertification. Damascus, Syria

Godoy R, Elliott R and Preston T R 1979 By-products of the sisal industry as cattle feed: effect of ground sorghum, fishmeal or rice polishings in cattle given diets based on sisal bagasse and ensiled sisal pulp. Tropical Animal Production 4 (3) 276-280 http://www.utafoundation.org/TAP/TAP43/4_3_10.pdf

Herrera F, Wyllie, D, Preston T R 1980 Fattening steers on a diet of ensiled sisal pulp and molasses/urea supplemented with sunflower meal and leucaena forage. Tropical Animal Production 5 (1) 18-23 http://www.utafoundation.org/TAP/TAP51/5_1_4.pdf

Herrera F, Ferreiro M, Elliot R and Preston T R 1981 The effect of molasses supplement on voluntary intake, live weight gain and rumen function in bulls fed basal diets of ensiled sisal pulp. Tropical Animal Production 6 (2) 178-185 http://www.utafoundation.org/TAP/TAP62/62_178.pdf

Jayasuriya M C N 1983 The use of fibrous residues in South Asia. In: Cyril A. Shacklady ed. The Use of organic residues in rural communities: Proceedings of the workshop on organic residues in rural communities. Bali, Indonesia, December 1979. The United Nations University, Japan  http://www.unu.edu/unupress/unupbooks/80362e/80362E06.htm

Leng R A 1992 Drought Feeding Strategies: Theory and Practice. R.M.Lilley, Penambul books. Armadale, New South Wales

Leng R A 1997 Trees - components of farming systems.. In Tree foliage in ruminant nutrition. FAO Animal Production and Health Paper 139 http://www.fao.org/docrep/003/W7448E/W7448E00.htm

Machin D H 1991 Report on the integration of livestock systems into sisal production. Report of a visit carried out to Kenya and Tanzania. GCP/RAF/258/SWE FAO

McDonald P, Edwards R A, Greenhalgh J F D and Morgan C A 1995 Animal Nutrition. Fifth edition. Longman Scientific and Technical, Longman Group Limited Harlow

Preston T R and Leng R A 1987 Matching Ruminant Production Systems with Available Resources in the Tropics and Sub-Tropics. Penambul Books, Armadale, New South Wales, Australia

Purseglove J W 1992 Tropical Crops: Monocotyledons. Harlow:  Longman Scientific and Technical, Longman Group UK Limited

Rodriguez A, Riley J A and Thorpe W 1985a Animal performance and physiological disturbances in sheep fed diets based on ensiled sisal pulp (Agave fourcroydes): I) The effect of supplementation with protein, forage and minerals. Tropical Animal Production 10 (1) 23-31 http://www.fao.org/ag/aga/agap/FRG/TAP101/101-23.pdf

Rodriguez A, Riley J A and Thorpe W 1985b Animal performance and physiological disturbances in sheep fed diets based on ensiled sisal pulp (Agave fourcroydes): II) The effect of forage source and removal of short fibers. Tropical Animal Production 10 (1) 32-38 http://www.fao.org/ag/aga/agap/FRG/TAP101/101-32.pdf

Shamte S 2000 Overview of the sisal and henequen industry: A producers’ perspective. Common Fund for Commodities - Alternative applications for sisal and henequen. FAO and CFC Technical Paper No. 14 http://www.fao.org/DOCREP/004/Y1873E/y1873e05.htm

SPSS 11.5 for Windows 2002 Statistical Package for Social Sciences (software)

Yerena F, Ferreiro H M, Elliott R, Godoy R and Preston T R 1977 Digestibility of ramon (Brosimum alicastrum), Leucaena leucocephala, buffel grass (Cenchus ciliare), sisal pulp and sisal bagasse (Agave fourcroydes). Tropical Animal Production 3 (1) 27-29 http://www.utafoundation.org/TAP/TAP23/TAP31/3_1_6.pdf

Received 9 July 2008; Accepted 8 September 2008; Published 6 November 2008

Go to top