 |
|
Photo 1.
The pit holding an estimated 100,000 tonnes of cassava
pulp in the |
| Livestock Research for Rural Development 28 (1) 2016 | Guide for preparation of papers | LRRD Newsletter | Citation of this paper |
Eight local "Yellow" cattle (range 78 to 108 kg) were allocated according to live weight to two groups each of four animals. They were fed a basal diet of ad libitum ensiled cassava pulp enriched with urea at the rate of 3% of the cassava pulp dry matter (DM). The experiment was done in the dry season (April-May 2015). Fresh Brewer’s grains were used as a source of "bypass" protein. Rice straw was given as a source of “roughage”. A sulphur-rich mineral mixture was provided ad libitum. The urea was dissolved in water and sprayed on the cassava pulp. Brewers’ grains and rice straw were offered separately.
The 0.66 kg/day average growth rates over the 4 months of fattening, with a DM feed conversion of 6.67, confirmed that ensiled cassava pulp could be the basis of a successful diet for the intensive fattening of local "Yellow" cattle in Lao PDR.
Key words: Brewer's grains, bypass protein, rice straw, sulphur, urea
Cassava has become a major crop in Lao PDR mainly because of the export of starch that is extracted from the cassava root. There are five cassava starch factories with total planted area of 60,475 ha, giving an average yield of fresh roots of 27 tonnes/ha. Annual production is of the order of 1.6 million tonnes (Department of Agriculture 2014).
The cassava for the starch factory in Nashaw village, Pakngum District in Vientiane Capital is supplied by 235 households in 85 villages with total cassava harvested area of 5,207 ha producing 100.000 tonnes per year of cassava roots. During the 6 -7 month harvest season from October to March-April (the dry season in Lao PDR) this amounts to 480 tonnes of roots daily. The byproduct remaining after starch extraction, known as cassava pulp, represents from 10 to 15% of the original weight of fresh roots. Over the past 4 years, very little of the cassava pulp was bought by farmers and almost all of it had been stored in a pit adjacent to the factory, which had not been covered or protected in any way (Photo 1). Samples taken to a depth of 7 m (Photos 2 and 3) were found to have a pH of 3.5, indicating that the pulp had ensiled naturally and was perfectly conserved. Analyses conducted in the laboratory of Souphanouvong University showed that the potential feed value of the ensiled pulp was only slightly less than that of the fresh whole cassava root (Phanthavong et al 2014, 2015).
|
|
|
Photo 1.
The pit holding an estimated 100,000 tonnes of cassava
pulp in the |
 |
 |
|
Photos 2 and 3. Taking samples of the contents of the pit |
|
The cassava pulp is composed almost completely of non-structural carbohydrate, 65% of which is starch according to Sriroth et al (2000), and is very low in crude protein (less than 3% in the dry matter) and in minerals. To take advantage of the high carbohydrate content of cassava pulp it should be supplemented with:
The cheapest source of ammonia for rumen microbes is urea, which is produced and used as fertilizer. One of the best sources of "bypass" protein is brewers’ grains (Promkot and Wanapat 2003), a by-product from the beer factory. An excellent source of fiber is rice straw, most of which is presently burned, adding carbon dioxide to the atmosphere and thus contributing to global warming. Minerals are required only in small quantities (1-2% of the feed), and are available locally or can be imported. Sulphur is important as a component of the process of detoxification of HCN to thiocyanate.
With these resources it was hypothesized that cattle could be fattened intensively to produce quality beef for export, .
An experiment to test this hypothesis was carried out in Soukanya Farm, Xaythany District, situated some 20 km from the cassava factory in Nashaw village, Pakngum District in Vientiane Capital. Eight local "Yellow" cattle (range 78 to 108 kg) were allocated ccording to live weight to two groups each of four animals. They were fed a basal diet of ad libitum ensiled cassava pulp enriched with urea at the rate of 3% of the cassava pulp dry matter (DM) (Table 1). The experiment was done in the dry season (April-May 2015). Fresh Brewer’s grains were used as an alternative source of "bypass" protein (Promkot and Wanapat 2003). Rice straw was given as a source of “roughage” to stimulate rumen function. A sulphur-rich mineral mixture (50% common salt, 25% dicalium phosphate, 20% clacium carbonate, 5% sulphur) was provided ad libitum. The urea was dissolved in water and sprayed on the cassava pulp. Brewers’ grains and rice straw were offered separately.
|
Table 1. Composition of the diet fed to the Yellow cattle |
|
|
Ingredient |
kg/day |
|
Ensiled cassava pulp |
10 |
|
Urea |
0.070 |
|
Fresh brewers’ grains |
4 |
|
Rice straw |
1 |
|
Minerals# |
0.06 |
|
These quantities were provided on the basis of 100
kg live weight. They were increased proportionately as
the animals increased in weight
|
|
The data on growth rate, feed intake and feed conversion over the 4 months of the fattening period (Table 2) confirmed that ensiled cassava pulp could be the basis of a successful diet for the intensive fattening of local cattle. The excellent conformation (Photo 4), after 90 days of fattening on the cassava pulp diet, was confirmed by the high carcass yield of the first animal to be slaughtered which was 49% (carcass yields of local cattle in Lao PDR are of the order of 35%).
|
Table 2. Mean values for the feed intake, growth rate and feed conversion over the 120 days of the fattening period |
||
|
Group 1 |
Group 2 |
|
|
Live weight, kg |
||
|
Initial |
101 |
84.0 |
|
After 120 days |
185 |
158 |
|
Daily gain |
0.700 |
0.620 |
|
Feed intake, kg/day |
||
|
Cassava pulp |
11.3 |
9.57 |
|
Brewers' grains |
4.87 |
4.13 |
|
Urea |
0.11 |
0.090 |
|
Rice straw |
1.23 |
1.04 |
|
Minerals |
0.080 |
0.070 |
|
Total DM |
4.82 |
4.10 |
|
DM feed conversion |
6.43 |
7.05 |
|
On a DM basis, the diet contained: cassava pulp 51%, Brewers grains 23%, urea 2.2%, Rice straw 22%, minerals 1.4% |
||
 |
| Photo 4. Stages in the fattening of local cattle on ensiled cassava pulp, urea, brewers' grains and rice straw |
It is estimated that the five cassava starch factories in Lao PDR have a yearly production of 200,000 tonnes of pulp. The four breweries produce between 200 and 300 tonnes of brewers’ grains daily (about 150,000 tonnes per year).The availability of rice straw is 3 million tonnes per year. These resources would be sufficient to fatten some 200,000 cattle per year with an added value of USD 36 million. A similar feeding system could be developed with the 50,000 tonnes of molasses by-product from the four sugar factories, which could be the basis of fattening of a further 150,000 cattle per year. There are sufficient brewers’ grains to supplement both the cassava pulp (100,000 tonnes) and the molasses (50,000 tonnes).
The manure produced from cattle fattened in confinement, after being processed through biodigesters, will yield biogas which burned in an engine would generate enough electricity to supply the energy needs of the farm; the residual liquid effluent from the digesters would replace inorganic fertilizers for growing rice and other crops.
Intensive fattening of cattle in confinement will generate employment on large farms. In small scale family farms, a cattle fattening enterprise will generate additional income as well as the benefits from processing the manure into biogas for cooking and the use of the effluent as fertilizer.
The cassava pulp contains 75% water. It is not recommended to dry the pulp as this would require dehydration using fossil fuel, which is expensive and when burned produces carbon dioxide which contributes to global warming. The transport cost in trucks holding 15 tonnes is of the order of USD 0.20/tonne-km. Delivering the pulp within a radius of 100 km from the cassava factory would thus impose a maximum cost of US20/tonne. Facilities are needed on the farms to store the pulp so that it can be delivered in bulk. A load of 15 tonnes is sufficient for 10 cattle for 3 months. Silos of 15 m3 capacity would thus be required on a small farm fattening 10 cattle. For larger farms (100 cattle) a load of 15 tonnes would be enough for 10 days. Provided the pulp is protected from sun and rain it can be stored with no loss of nutritive value as it is safely conserved by the low pH.
A cassava factory processing 100,000 tonnes of roots per year will produce 12,000 tonnes of cassava pulp. This is sufficient to fatten 10,000 cattle over a period of 100 days. Assuming the fattening period is 100 days then three batches of cattle can be fattened per year. Thus a cassava factory, such as the one in Nashaw village, Pakngum District, could supply enough pulp for feedlots with capacity of 3000 heads (this equates to 300 small scale farms each with average capacity for 10 animals; or 200 small farms of 10 head capacity and two large farms each of 500 head capacity).
There is little experience in Lao PDR in the design of facilities for intensive fattening of cattle in confinement. The manure that the cattle produce is generally not taken into account in the design of these facilities, yet it is a potential source of renewable energy and fertilizer when correctly processed in anaerobic biodigesters. There is an urgent need to construct model feedlots to demonstrate and develop the appropriate way of managing cattle manure and transforming it into biogas and liquid fertilizer. It is proposed to construct a model unit for demonstration of the appropriate design: eg: shape of the feed troughs, floors with 7% slope leading to central “slatted” sections over deep (1m) drainage channels leading to lagoons covered with HDPE (High density polyethylene) plastic to facilitate anaerobic biodigestion to produce biogas and liquid effluent.
There appears to be an unlimited market for beef in neighbouring countries, especially Vietnam and China. Quality will be an increasingly important factor in order to secure highest prices for the product, either in carcass form or as live animals. Beef quality is achieved by ensuring fast rates of growth which increases growth of lean tissue and the content of the fat (marbling) in the meat, which ensures tenderness of the meat. Growth rates should be of the order of 600 to 700 g/day for local Yellow cattle, and 800 to 900 g/day for crossbred animals to achieve these standards. This in turn requires a diet of high nutritional value; high digestibility and adequate content of “metabolizable” protein. Grasses in tropical latitudes are much less digestible fiber than those in temperate latitudes; they are also lower in total protein, and the protein is “soluble” and rapidly fermented to ammonia in the rumen. Thus, in order to produce beef of high quality (and high price) it is essential to provide feeds that are: (i) highly digestible and have low fiber; and (ii) are rich in by-pass protein.
Cassava roots fulfill the requirements as being the main source of digestible energy, either as whole roots or as the by-product (cassava pulp) from starch manufacture. The existing cassava factories cover a restricted area of the country. Future developments for the areas of Laos not served by cassava starch factories could be based on ensiled cassava root as replacement for cassava pulp. Research is in progress to develop such a system. Brewers’ grains are one of the best sources of “by-pass” protein but, as in the case of the cassava pulp, access is restricted to the approximately 100km radius from the breweries. Cassava foliage (leaves and thin stems) have been successfully used as the only protein supplement in diets for cattle based on urea-treated rice straw (Sath et al 2008) or molasses-urea (Ffoulkes et al 1978). Initial attempts to use cassava foliage as the sole protein supplement in cassava pulp-urea diets have not yet been successful. However, 50% replacement of the brewers’ grains with fresh cassava foliage appears to be feasible, and 100% replacement can probably be achieved in the future, through ongoing research.
To further justify the emphasis on the cassava crop as the basis for intensive livestock production, it is relevant to emphasize the conclusions of a recent study in Africa which indicated that cassava would be least affected, or even benefitted, by global warming, whereas staple carbohydrate crops such as rice and maize would experience reduced yields (Jarvis et al 2012).
Department of Agriculture 2014 Crop statistic year book, Lao PDR
Ffoulkes D and Preston T R 1978 Cassava or sweet potato forage as combined sources of protein and roughage in molasses based diets: effect of supplementation with soybean meal. Tropical Animal Production, Volume 3, Number 3 pp186-192 http://www.utafoundation.org/UTAINFO1/TAP/TAP33/3_3_1.pdf
Jarvis A, Ramirez-Villegas J, Herrera Campo B V and Navarro-Racines C 2012 Is Cassava the Answer to African Climate Change Adaptation? Tropical Plant Biology.5 (1) 9-29.
Leng R A 2014 A paradigm shift in rumen microbial ecology and enteric methane mitigation. Animal Production Science (Perspectives on Animal Biosciences) http://dx.doi.org/10.1071/AN13381
Phanthavong V, Viengsakoun N, Sangkhom I and Preston T R 2014 Cassava pulp as livestock feed; effects of storage in an open pit. Livestock Research for Rural Development. Volume 26, Article #169. http://www.lrrd.org/lrrd26/9/phan26169.htm
Phanthavong V, Viengsakoun N, Sangkhom I and Preston T R 2015 Effect of biochar and leaves from sweet or bitter cassava on gas and methane production in an in vitro rumen incubation using cassava root pulp as source of energy. Livestock Research for Rural Development. Volume 27, Article #72. http://www.lrrd.org/lrrd27/4/phan27072.html
Promkot C and Wanapat M 2003 Ruminal degradation and intestinal digestion of crude protein of tropical protein resources using nylon bag technique and three-step in vitro procedure in dairy cattle. Livestock Research for Rural Development. Volume 15, Article #81. http://www.lrrd.org/lrrd15/11/prom1511.htm
Sath K, Borin K 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.lrrd.org/lrrd20/supplement/sath2.htm
Sriroth K, Chollakup R, Chotineeranat S, Piyachomkwan K and Oates C G 2000 Processing of cassava waste for improved biomass utilization. Bioresource Technolology 71(1):63-69.
Received 10 September 2015; Accepted 27 December 2015; Published 2 January 2016