4. General discussion
4.1. Cattle in the farming system in Lao PDR
4.2. Feed resources for ruminant in Lao PDR
4.3. Constraints for livestock production in Lao PDR
4.4. Advantages of cassava in agriculture
4.5. Cassava production and utilization in Lao PDR
4.6 The present and future of cassava production and utilization for ruminant production
4.7. Planting, cutting and cultivation for leaf / hay making
4.8. The role of cassava hay as ruminant feed
4.9. Dietary protein and rumen microbial protein synthesis
4.10. Rumen ammonia and blood urea nitrogen
4.11. Structural carbohydrate, digestion and utilization by growing cattle
5. Conclusions
6. Acknowledgments
7. References
4. General discussion
4.1. Cattle in the farming system in Lao
PDR
Farming in Lao PDR involves 90% of the overall population and
this situation is unlikely to change significantly in the
foreseeable future even if there is considerable amalgamation of
small properties into bigger units. However, there is some urban
drift occurring, due largely to lack of work opportunities in the
rural areas. In Paper I, also was found that during dry season
which no cultivation, most farmer husband worked for another
regular job in town.
Smallholder production dominates the farming system in the
country and there are few individual farmers in Lao PDR with
"commercial" beef herds. Most farmers who own cattle have only 2-3
animals. They buy an individual animal and try to slowly increase
their numbers. Beef cattle are used solely as a direct source of
income rather than slaughtered for village consumption whereas the
buffalo are used for ploughing the paddy fields and slaughtered for
village consumption. (DLF, 2002).
The total cattle population in the year 2002 was found to be
1,213,500 heads;(DLF, 2002) the major part of cattle production in
Lao PDR will still remain for long as an integrated part of
crop-livestock production system. The industry is primarily
smallholder based; intensive and intensive farms of cattle
production are still at an initial stage of development, the
existing cattle farms in the country are run on pilot schemes.
Small holders livestock practices are still very traditional using
minimum inputs or none at all. This leaves the cattle industry with
numerous constraints. Primaries amongst these are the incidence of
disease and inadequate nutrition. Cattle productivity is therefore
rather low. Constraints of lesser consequence, though nonetheless
important include poor technology, staff skill deficiencies, poor
database, an insufficiently competitive marketing network and
insufficient access to credit.
Livestock production is integrated to crop production systems
(mainly rice). Cattle graze the paddies when rice is not being
grown and are usually tethered. When the rice crop is grown in the
paddies, the animal's diet is often supplemented with rice straw,
which is low in nutritive value. Communal land in adjacent forested
or scrubland areas is also often available for grazing generally
the smallholder farms operate at a subsistence level and frequently
they are unable to satisfy the household demands for food and
protein within the local village.
There is huge potential for the exporting of beef from Laos to
Thailand, Cambodia, Vietnam, Burma and China. The live export trade
(legal) alone into Thailand of both cattle and buffalo was
estimated to be worth almost USD 670,000 in 1993. Currently there
is also a large unofficial export trade (illegal) of live animals
across the Mekong River onto the "black market" in Thailand but
both governments are endeavoring to take steps to control and
reduce this border trade.
In Paper I, it was also found that native beef cattle raising
has been closely associated with farmers' livelihood for both
irrigated and rain-fed farmers and cattle raised were average 17
and 7 heads/household in field rain-fed and irrigated areas,
respectively. In addition, market price of cattle is very
attractive in these areas.
2. Feed resources for ruminants in Lao
PDR
Feed sources for beef cattle in central region areas are based
on native forages that are available in rangelands, forests,
fallows, wastelands, roadsides and cultivated areas after crop
harvest. Rice straw and some other crop residues such as sugar cane
tops, sweet potato vines and tree leaves etc. are also available.
In the past, farmers recognized that cattle and buffaloes could
graze freely in the natural grassland without the competition of
human food (grain or crops) and with crops in term of land use. The
sufficiency of grazing land in the past has generally meant that it
animals have been left to forage on grassland. Wanapat, (1999)
reported that rice straw is high in structural carbohydrate but
contained low level of crude protein and essential minerals.
However, rice straw is still used by farmers as an essential feed
for ruminants. Devendra et al. (1997) estimated that rice straw is
the principal fibrous residue fed to over 90% of the ruminants.
Rice straw is especially important during periods when other feeds
are scarce from time of planting through harvest, when animals have
limited or no access to grazing and whenever drought or some other
factor causes crop losses. The maximum intake of rice straw per 100
kg live weight in Asia was about 1.5-3.0 kg. Feeding methods
including use of crop-residues such as rice straw, sugarcane tops
and cassava leaf (dried) should be highly exploited.
In Paper I, farmers both in irrigated and rain-fed lowland areas
are facing problems of keeping livestock in these cropping systems
where grazing land is becoming less available. Problems become more
severe during the dry season when green forages are not available
with limited choice of suitable grasses, legumes and fodder tree
species for use. Therefore, rice straw is a common crop residue,
available during rice harvesting time. Normally, farmers collect
straw and store it for dry season feeding. However, feed quality
based on any energy measurements for ruminants are clearly
misleading when they are applied to poor quality forage or
non-conventional feedstuffs. (Leng, 1990).
3. Livestock development: Constraints and
potential
In general, low animal productivity, inappropriate technologies,
inadequate research and extension support; poor infrastructure and
unfavorable external condition have contributed to the poor
performance of the livestock sector and cattle sub-sector in Lao
PDR (de Leeuw et al., 1999). There are many constraints on cattle
production by the smallholder farmer, in Lao PDR particularly in
areas where subsistence farming is practiced (MAF, 2002). Moreover,
poor management is also one of the constraints for Lao cattle
production such as insufficient legal framework and related
regulations on livestock such as veterinary laws. Moreover,
insufficient livestock extension works, coupled with lack of
competitive extension professionals for feeding, grazing land
management, cultivation of fodder crops, feed storage, ect. Poor
marketing and processing system without market information services
and lack of farmers' knowledge on epidemic diseases and reluctance
to receive vaccination, feed in the dry season, could result in a
lower resistance against diseases (Bouahom, 1995). These results
were in agreement with Preston and Leng, (1987) who reported that
the feed problem in tropical countries is exacerbated by seasonal
variation. In the dry season, the available feed is low
digestibility and low total nitrogen. Animal loss weighs in dry
season because of the nutritional imbalance. Therefore, crop
residues become major feed sources for ruminant production in
developing, particularly in the dry season (Preston and Leng,
1987).
Diseases and parasites in mature bovine animals are also a major
problem. Food and mouth diseases cause heavy economic loss now and
then in cattle. Haemorrhagic Septicaemia and Blackleg are also a
problem. Internal parasites do not cause sudden death in ruminants
but they could affect growing ability of the animals. Vaccination
against certain diseases and deworming is always advantageous but
often ignored by smallholders, while government services are also
not readily available.
Despite the above constraints that require time to solve, Lao
PDR has the following competitive advantages for livestock
development. There are many potential grazing lands suitable for
livestock raising, represented in Boloven and other plateaus.
In Paper I, the constraints and problems confronting small
farmers have been identified. Problems involved not only technical
aspects but also socio-economic condition. Technical aspects
include lack of breeding bull, poor body condition of breeding
animal due to lack of feeds, reproductive diseases, ect. While
socio-economic factors involve lack of incentives for farmers to
increase herd size, traditional confinement of animal during
cropping season, or lack of market for young (weaned) animals.
However, major problems encountered were those of shortage of feeds
during the dry season.
4. Advantages of cassava in agriculture.
Cassava is a perennial vegetative propagated shrub grown through
the low land to dry/humid tropic. Originating in Central and South
America, cassava spreads rapidly and arrived on the West Coast of
Africa via the Gulf of Benin and the River Congo at the end of the
Sixteenth century. It arrived on the East Coast of Africa via the
Reunion Island, Madagascar, and Zanzibar at the end of the
Eighteenth century. The crop then spread into the main land from
both sides. Cassava plant came to Asia probably in the
17th century (James et al., 1982). This plant could be
able to adapt to different ecological conditions. It could grow
well in sandy and low organic matter soil in the tropic. It is
famous for drought tolerance, pest and disease resistance. The crop
can thrive well during the dry season in tropical area. Cassava was
traditionally used as a root crop; it was also regarded as an
important source of energy in the tropic. In an integrated farming
system, cassava can be grown with other cash crop such as beans,
maize and cucumber by "intercropping"(Leihner, 1983: Silvestre,
1989). Polthanee et al. (2001) reported that cassava - cowpea
intercropping and cassava-peanut inter-cropping increased land use
efficiency by 72-76% and 30-98%, respectively. In economic term,
cassava intercropping with both cowpea and peanut gave higher
return than sole cropping. Previously, cassava has been
characterized as an "exploitive" crop, destructive of soil
fertility. However, when cassava is grown as a component of farming
system, in which livestock and crop are closely integrated, its
capacity to "exploit" the nutrients in livestock manure becomes a
valuable asset (Preston, 2001). Cassava contributes to economic
diversity and creates opportunity for development of other
processing industries for example the cassava industry in Thailand
and Brazil as well as in several African countries on a smaller
scale (FAO, 1997). They also used it as a cash crop and a material
to produce industrial starches, tapioca, and livestock feeds.
Cassava in integrated system contributes to the strategy of making
an optimal use of natural resources with the efficiency in using
solar energy for food and fuel and improving the environment and
reducing pollution (Preston, 2001).
5. Cassava production and utilization in Lao
PDR
Lao PDR has about 5 million hectares of land that is suitable
for cultivation. Of that land, farmer plant only 800,000 hectares
with rice or secondary food crops. They use other 750,000 hectares
as pastureland and 50,000 hectares of ponds for freshwater fish
farming (The fishery sector provides an importance source of
protein.)(MAF, 2002)
Cassava is traditionally grown for root harvest. Cassava root is
regarded as a reserve food for people in case of other crop fail
and also cash crop. During 1988 to 1999, an average of increasing
rate of production per 1000MT in Lao PDR was 1.1 %, whereas an
average of increasing rate of root yield was 0.8%. (MAF, 2002).
Recently, the use of cassava root and leaf for animal production
has been increasing. In May 2001 two cassava variety trials was
planted in Lao PDR, i.e. one trial in Houy Khot station in Luang
Prabang province and one in the NamSuang Livestock Research Center,
about 40 km north of Vientiane. Twelve plots of eight varieties
introduced from Thailand and two local varieties, were planted. As
a result cassava in Houy Khot grew very well, reaching a height of
4-5 meters resulting in relatively low yields and very low harvest
index (HI). This was most likely due to application of fertilizers
to an already fertile soil. Highest root yields of 20-25 ton/ha
were obtained with introduced varieties (Rayong 72 and Rayong 90),
versus 13-15 ton/ha for the two local varieties, while in Namsuang
cassava top growth was not very vigorous but root growth was quite
good, resulting in high root yields and HI. Highest yields of 25-30
ton/ha were obtained with introduced varieties (Rayong 72, Rayong
60 and KU50), versus 15-20 ton/ha for the two local varieties. In
addition many research projects started to use leaf and root of
cassava for animal feeding in Lao PDR.
6. The present and future of cassava production and
utilization for ruminant feed
World cassava production has been grown at annual rate of 2%
during the last decade (1987-1997), slightly faster than during the
previous decade (1977-1987), when it grew at annual rate of 1.7%.
Area expansion has generally been driven the growth in cassava
production during the last decade (1.7% annual growth rate in area
and only 0.3% in yield). Projection for the 1993-2020 period was
expected at growth rate between 1.93-2.15% per year, of which more
than 1% is expected to come from yield increases, while the rest
(0.74-0.95) from area expansion. Therefore, cassava production will
continue to grow at almost the same rate, but more due to increases
in yield than before (CGIAR, 1999).
Cassava is planted on about 16 million hectares, with 50 percent
in Africa, 30 percent in Asia and 20 percent in Latin America.
Total root production was 152 million tons. Under favorable
experimental conditions, cassava as a mono crop can yield as much
as 90 tons of fresh roots per hectare. But it is usually grown in
poor soils and harsh climates and in association with other crops,
such as maize, beans, or cowpeas. Under these conditions average
yield in tons of fresh roots per hectare were much lower: 9.6 tons
worldwide: 7.7 to Africa; 12.7 in Latin America; and 12.9 in Asia.
Cassava is produced mainly by small holder farmers, who are often
women, heads of households, generally used traditional farming
methods, and live in some of the poorest and most difficult areas
of the tropics. The crop offers these farmers several major
advantages. It is relatively tolerant of poor soils and seasonal
drought and has an unrivaled ability to recover from damage by
pests and diseases. In addition, it can be safely left in the
ground for 7 months to 2 years after planting and then harvested as
needed.
Cassava root is an excellent energy source because of its highly
digestible carbohydrate (70-80%), mainly in the form of starch;
however, it's low in protein content (2-4%) and all other
nutrients. Cassava root is low in amino acids particularly amino
acids, which contained sulfur (Gomez, 1991; Khajarern, 1991).
Cassava tubers contain high levels of energy and minimal levels of
crude protein and have been used as readily fermentable energy in
ruminant rations. Cassava leaves have been used as a protein source
when collected at tuber harvesting time. However, the intake and
digestibility was low due to high level of condensed tannins (Reed
et al.,1982; Onwuka 1992). Harvesting of cassava at an early growth
stage (3 months) to make hay could reduce the condensed tannin
content and increased protein content (25% of DM), which can result
in a higher nutritive value (Wanapat et al., 1997). Cassava leaf
(dried) contained high level of nutrients 90% DM, 18-20% CP, 55-60%
TDN, 26.9% NDF, 25% ADF, 1.45% Ca, 0.45% P (Ravindran, 1993;
Wanapat, 2001). Several reports have been shown when dried cassava
leaves were supplemented to ruminants; digestibility, intake, and
average daily gain were improved (Wanapat, 1983; Devendra, 1985;
Bezkorowajnyi et al., 1986). Cassava foliage has been shown to be
an excellent source of protein, as a direct supplement or in
concentrates mixtures (Wanapat, 1995). In the Dominican Republic,
fresh cassava leaves as the only source of foliage in a diet of
molasses-urea, supported good growth rates (>800 g/day) in
fattening cattle (Ffoulkes et al., 1978; Ffoulkes and Preston,
1978; Ffoulkes and Preston, 1979). However, limitations of using
cassava leaf have been found due to its high level of condensed
tannins (CT) (Reed et al., 1982; Onwuka, 1992). CT are
polyphenolics which can easily be solubilized in water and can
precipitate protein. Potential and manipulations of using CT could
be shown by Ravindran (1993); Reed (1995); Wanapat (2001). If CT in
the feed exceeded 6% of dry matter, feed intake and digestibility
would be reduced. If the CT level was between 2-4% DM it would help
to protect protein from rumen digestion, thereby increasing by-pass
protein. Moreover, CT have been found to increase N-recycling in
the rumen and saliva (Reed, 1995) and thus to improve rumen
microbial protein synthesis (Makkar, 2000). The presence of
condensed tannins and protein can result in the formation of
tannins-protein complexes (TPC) by hydrogen bonding, especially
under alkaline pH conditions. TPC will maintain its complex at pH
3.5-7.0, and will dissociate under pH<3.0 and pH>8.0 (Jones
and Mangan, 1997). In addition, Netpana et al. (2001), showed that
the fecal parasitic egg counts in cattle and buffaloes were
significantly lower when fed with cassava hay that contained CT and
were similar to the group that had been drenched. CT has also been
reported to have potential as a means of reducing nematodes in the
gastrointestinal tract (Kahn and Diaz-Hernandez, 2000). Currently,
more interests have been given on the use of cassava leaf as animal
feed as shown by Preston (2001); Preston et al. (2001); Wanapat
(2001). However, CT were generally found in higher concentrations
in matured cassava leaf, but levels were lower in cassava hay
harvested at a younger stage (Barry and Manley, 1984). Cassava hay
contained 25% CP and with minimal HCN content (0.348 mg%). Feeding
trials with cattle revealed high levels of DM intake (11.2 kg/hd/d,
3.2% BW) and DM digestibility (71%). Ruminal protein degradation of
cassava hay was relatively low (48.8%) since it contained
tannin-protein complex, which would render higher by-pass protein
in small intestine.(Wanapat, 2001)
7. Planting, cutting and cultivation for leaf/hay
making
The studies by Wanapat et al. (1997, 2000a, 2000b, 2000c, 2000d)
have revealed the detail of planting and cassava hay making.
Planting cassava for hay making was aimed to increase the whole
crop digestible biomass and the tuber root as a by-product. The
initial cutting at 3 months was made and followed by subsequent
cutting at every two months by hand breaking of the stem about 10
cm above the ground. The fresh whole crop was directly sun-dried or
chopped before sun-drying to obtain dry matter 80-90%. This might
take 2-3 days but chopping helps shorten the drying process. Sun
drying also eliminated hydro-cyanic acid (HCN) more than 90% and
enhanced the palatability and long-term storage. In addition,
Condensed tannins (CT), were generally found in higher value in
matured cassava leaf but was lower in cassava hay harvested at
younger stage. Intercropping cassava with leguminous crop such as
cowpea could improve soil fertility and to provide as food for
human consumption and the residue used as supplemental feed
especially during the dry season (Polthanee et al., 2001). Planting
space and frequent cutting have been shown to affect on combined
yield of the cassava hay (Petlum et al., 2001). Furthermore,
planting pattern either with non-ridging or ridding as well as
manure fertilization could affect cassava hay production
(Pouangchompu et al., 2001)
In Paper II, it was found that cassava foliage for hay making
(CH) could be harvested at 3 months and followed by 2 months.
Results revealed that fresh, dry matter (DM) and protein yields of
cassava variety RY72 at each harvest were significantly higher
(P<0.001) than local variety. As a consequence, 35.1, 7.7, 1.9
and 15.2, 3.5, 0.8 ton/ha for total fresh, DM and protein yield of
RY72 and local varieties, respectively.
The chemical analysis of Cassava foliage (CF) on DM, CP, fiber
components (NDF, ADF, ADL) and levels of CT were found differently
in RY72 and local varieties. Concentration of chemical composition
was highly different among varieties and cassava hay making was
possible under Lao condition.
8. The role of cassava hay as ruminants
feed
Cassava hay could contribute to the sustainable livestock-crop
production systems in the tropics. It has been used successfully as
a source of high protein roughage in lactating daily cows Wanapat
et al. ( 2000a, 2000b). Furthermore, cassava hay also can be used
as a source of concentrate replacement for dairy cattle. According
to Wanapat et al. (2000b) found that increasing levels of CH from
0.6 to 1.7 kg/hd/day could reduce levels of concentrate from 0.1 to
1.6 kg/hd/d, respectively without changing levels of milk yield but
protein and fat content in milk was increase. These results were in
agreement with the work by Woodward et al. (1999) who reported that
dairy cows fed with Lotus Coniculatus that contained
condensed tannins had contributed to 42% improvement in milk yield
and 57% increase in protein percentage without changing feed
intake. Moreover, Nguyen et al. (2002) found that cassava hay could
be produce at initial 4 months after planting and subsequently at 1
month. Supplementation of cassava hay could lower concentrate use
improve milk yield and milk compositions. In addition, Koakhunthod
et al. (2001) used CH as a major source of protein in high-quality
feed block and supplemented to lactating dairy cows. The results
were found that rumen ecology, milk yield and milk compositions
were improved. Therefore, cassava hay could be a good supplement to
combine with the low protein roughage such as grass, rice straw to
improve feed intake, digestibility and production of cattle,
especially in dry season.
Moreover, CH supplementation on native beef cattle fed on rice
straw was enhanced weigh gain. (In Paper II,) The result shows that
improved ADG were obtained at 400, 600 g CH/head/d supplementation
group. Apparently, In term of intake levels of CH supplementation
were affect on rice straw intake and total DM intakes in terms of
%BW and g/kg W0.75 and enhancing of CH supplementation
could significantly (P<0.05) increase the total DM and OM intake
without decreasing the intake of RS. They were highest in treatment
at 600g/hd/d supplementation.
9. Dietary protein and rumen microbial protein
synthesis
In temperate areas, it has been reported that over half of the
amino acids absorbed by ruminants are derived from rumen microbial
protein (Clark et al., 1992). Rumen microbial protein synthesis
cannot totally provide the needed amino acids to achieve efficient
and maximum structural growth of the dietary heifer. Dewhurst et
al. (2001) agreed by explaining that while the ruminant animal is
unique in its ability to survive on a diet consisting entirely of
non-protein nitrogen, the efficiency of rumen microbial growth and
animal performance is enhanced by the addition of dietary amino
acids and peptides particularly in high concentrate rations. Still
it is desirable economically and from efficiency standpoint to
maximize the amount of microbial growth in the rumen. Maximizing
microbial growth require maximizing the activity of the rumen
microbe population. Understanding the activity and dynamics of the
rumen microbial population is a key first step toward maximization.
The attempts to increase microbial protein synthesis for animals
raised in the tropics have been emphasized.
The rumen microbial ecosystem comprises at least 30 predominant
bacterial species at a total concentration of 1010 to
1011 /ml of rumen fluid, some 40 species of protozoa
105 to 107 /ml and five species of fungi
<105 /ml (Czerkawski, 1986; Orpin and Joblin, 1997;
Sttewart et al., 1997; Williams and Coleman, 1997). Bacterial
species of the rumen are considered more important than protozoa
and fungi in determining the extent and rate of feed degradation
and utilization for the production of microbial protein and VFA
(Leng, 1982; Sttewart et al., 1997)
Hodson and Stewart (1997) reported 30 to 50% of the bacteria
isolated from rumen fluid possess proteolytic activity toward
extracellular protein. Ruminobacter amylophilis is one the
most active proteolytic species. Other predominant protiolytic
bacteria include: Butyrivibrio fibrisolvens, Prevotella
ruminicola, Clostridium and Eubacterium. Ciliate
protozoa have been known to be proteolytic, however the role of
ciliate protozoa in the digestion of soluble dietary protein is not
entirely known (Hodson and Stewart, 1997). The main role of
protozoa may be the predatory activity against rumen bacteria,
which greatly affects bacterial protein turnover.
High producing ruminants require considerable amounts of protein
flow to the small intestine. In general feeding practice, dietary
by-pass protein is often costly. Therefore, it is important to
maximize microbial protein synthesis within the rumen before
supplementation with any dietary by-pass protein.
Manipulation of ruminal fermentation has been shown as a major
step in improving ruminal degradation, fermentation and increasing
overall feed utilization (Nolan and Leng, 1989).
In Paper II, Cassava hay supplementation for
native cattle can improve rumen ecology, for Ruminal temperature
and pH were found in normal range (38-39° C) (pH = 6.4-6.6),
Moreover, CH supplementation were linearly increased (P<0.05) in
bacterial and fungal zoospores population than the control,
respectively. Meanwhile, protozoal population were found slightly
decreased as levels of CH supplemented increased 5.0 to
3.7x105 cell/ml, in control and treatment with CH
supplementation, respectively.
10. Rumen Ammonia and blood-urea
nitrogen
Rumen ammonia concentrations are the result of not only rumen
microbial protein degradation but also of rumen microbial
utilization. Ammonia is the preferred nitrogen source for fiber
digesting bacteria and also is required by starch, sugar, and
secondary rumen microbial fermenters for protein synthesis (Song
and Kennelly, 1990). Mehrez et al., (1997) states the optimal
ammonia concentration of rumen fluid may be defined as that which
results in either the maximum rate of fermentation in the rumen or
ammonia concentrations that allows maximum production of rumen
microbial protein per unit of substrate fermented. Considerable
debate has been made on the relationship between rumen ammonia
concentration and ruminal microbial growth. The debate has not
necessarily focused on single optimum value of rumen ammonia
concentration for maximum rumen microbial growth, but upper and
lower limits of rumen ammonia concentrations. Mizwicki et al.
(1980) attempted to attenuate rumen ammonia release by varied and
continuous intraruminal infusion of feed urea, a readily available
ammonia source. Mizwicki et al. (1980) reported no advantage from
this technique but attributed the lack of results to restricted
feeding conditions. Recently, Arelovich et al. (2000) reported
increase utilization of rumen ammonia and energetic efficiency of
ruminal fermentation through zinc supplementation at concentration
of 250 ppm. Arelovich et al. (2000) explains that the additional
zinc supplementation inhibited rumen urease activity, retarding
rumen ammonia accumulation and thus allowed a more consistent and
maximum utilization of rumen ammonia by the rumen microbes. When
ammonia accumulates in the rumen, rate of ammonia production has
exceeded utilization (Arelovich et al., 2000). An excess of ruminal
ammonia reduce fermentation of the diet, nitrogen retention, and
consequently efficiency of diet nutrient
utilization.
Bunting et al. (1987) explains bacteria associated urease
activity within rumen epithelium appears to facilitate the transfer
of urea from blood into the rumen by hydrolysis of urea to more
readily diffused and absorbed ammonia. Bunting et al. (1987) later
reported that net incorporation of blood urea nitrogen (BUN) by the
rumen into bacterial protein is inversely related to level of CP
intake and cattle receiving low CP intakes may actually
preferentially utilize BUN derived ammonia. Hutjens and Jordon
(1994) outlines several factors that impact BUN concentrations: 1)
amount of dietary CP intake along with the solubility and
degradability of the CP; 2) the amount of fermentable carbohydrates
in the diet; and 3) the physical characteristics of the diet and
feeding system fed is offered to cattle.
Effect of level of cassava hay (CH) supplementation on rumen
parameters (In Paper II) could incrase NH3-N
(11.8-13.9), and BUN(10.2-12.4). All those values were in normal
range as reported, as an optimal range for microbial digestion of
fiber (Horver, 1986), digestion of protein (Wanapat,
1990).
11. Structural carbohydrate digestion and utilization
by growing cattle
In the last 30 years dietary structural carbohydrates for cattle
have been analytically characterized as neutral or acid detergent
fiber (NDF, ADF). These analysis have been used in ration
formulation as a guideline to set the energy density of ration to
achieve proper intake for given level of production. NDF measures
the sum of the cellulose, hemicellulose, and lignin fraction of
feed. NDF is not chemically pure entity, but represents structural
carbohydrate components of feed that commonly require chewing
activity for particle size reduction and passage. Forage NDF
content was related with DMI of forage. Waldo (1986) and Mertens
(1994) suggested that NDF content is the best single chemical
predictor of DMI by ruminants, with DMI positively correlated with
NDF concentration when energy limits intake. Changing the NDF
content of a dietary by substituting grain for forage should result
in a quadratic response in DMI. The primary components of the ADF
fractions of feedstuffs include cellulose and lignin.
Concentrations of ADF and lignin are more highly correlated with
digestibility than intake (r2= -0.75 and -0.46 for ADF
digestion and intake, respectively, Van Soest et al. (1978). NRC
(1989) recommendation are a minimum of 19-21% dietary ADF and of
25-28% dietary NDF, 75% of which is supplied from forage. Early
report Allen (2000) indicated that a general decline in DMI with
increasing NDF concentration in diet when diet exceeded 25% NDF.
Dado and Allen (1995) indicated that 35% NDF diets restrict DMI in
early lactating cow because of feed bulkiness and rumen fill, but
DMI was not limited when 25% NDF diet were fed with or without
inert bulk in rumen. Beauchemin et al. (1994) showed that DMI was
reduced nearly 3 kg/d when forage content was increase from 35 to
65%, but less than 0.5% kg/d with diet containing the short chop
forage.
In Paper II, it was found that the data on intake and
digestibility of nutrients, intakes in terms of % BW and g/kg
W.75/d were significantly enhanced by CH supplementation
(P<0.05). Digestion coefficients of DM, OM, CP, NDF and ADF were
also found significantly increased (P<0.05). Overall energy
intakes with regards to ME (by calculation) were significantly
different (P<0.05) and were subsequently improved by level of CH
supplementation.
5. Conclusions
Based on these experiments, the following points could be
concluded;
1). Native beef cattle raising has been closely associated with
farmers' livelihood for both irrigated and rain-fed farmers, which
provided as source of protein food, source of family income, as
saving bank, and social status.
2). It was also found that most of farmers in irrigated area
paid more attention and manage beef herd better e,g. use of
vaccination, better feedings and feed use. Grazing cattle on
roadside, forest area and paddy fields are found common
practices.
3). Seasonal pattern has influenced cattle productivity since
only native grasses, fodder, tree leaf, rice stubble and straw are
often offered. However, crop residues are available e.g. sugarcane
tops, dried cassava leaf particularly rice straw has been collected
and use for cattle. However, other sources have been limitedly
used.
4). Group forming and support from government in relation to
promoting and supporting beef cattle raising as well as extension
were highly required by the interviewed farmers.
5). Cassava hay (CH) harvested at 3 months and
followed by 2 months resulted in higher DM and protein yields in
RY72 than in local variety.
6). Cassava cultivation to produce cassava hay
for ruminant feeding could be practiced under Lao
condition.
7). Cassava hay supplementation increased
intake, digestibility and ME of feed especially when fed with rice
straw diet.
8). Cassava hay supplementation for native
cattle can improved rumen ecology by maintaining normal pH,
temperature, increasing bacterial and fungal zoospore population
and decreasing protozoal population particularly at 600 g/hd/d
group.
9). Feeding of beef cattle based on cassava hay is highly
potential and should be developed especially for small holder
farmers.
Moreover, future research in this area of suing cassava hay
should be undertaken in more experiments for both digestion and
feeding trials in Lao PDR.
6. Acknowledgements
I would like to acknowledge the following people for their
contributions to my Master degree program. First, the financial
assistance of the Swedish International Development Agency (SIDA)
and Swedish Agency for Research Cooperation with Developing
Countries (SAREC), which made possible the implementation of the
program and this work.
To extend my most sincere gratitude to my supervisor, Prof. Dr.
Metha Wanapat for his endless support in correcting, making
constructive comments, inspiring, encouraging me during the study
period. He has not only served as my advisor, but has provided so
many valuable recommendations beyond just advising, teaching, and
supervising. Most importantly, he has allowed me to make mistakes,
learn from those mistakes, and grow as a student and
person.
I wish to express the special thanks to Dr. Boonthong Bouahom,
Mr. Bounleang Koudsavang, Directors of the National Agriculture and
Forestry Research Institute (NAFRI) and Livestock Research Center
(LRC) for giving me permission to participate in this study program
and providing facilities for conducting experimental work.
Cordial appreciations are specially extended to the surgery team
from Khon Kaen University, Thailand, led by Professor Metha
Wanapat, Chamnanwit Promkot and the graduate students who kindly
advised and performed rumen fistulation of cattle for the first
time in Lao, PDR for these experiments.
I am deeply indebted to the Ruminant Nutritional Laboratory,
Department of Animal Sciences, Faculty of Agriculture, Khon Kaen
University, Thailand for giving me great opportunity to carry out
the chemical analyses of samples.
I would like to express my gratitude to Assoc. Prof. Dr. Brian
Ogle the Course Director and Assoc. Prof. Dr. Iger Ledin the Course
Co-ordinator who spent time to facilitates the smoothly and
efficiency running of the course.
I would like to make a special thank to Prof. Dr. Luu Trong
Hieu, the Regional Course Coordinator, Mr. Coung and all his staffs
for assistance, kind help, support and warm hospitality while
studying in Vietnam.
Appreciation is extended to all of the lecturers for their
encouragement, invaluable knowledge as well as many informal
discussions, particularly to learn of theory and research work in
linking with smallholder farmers. I enjoyed not only academic but
social and culture, as well.
I also like to thank all Ph.D and MSc. students at Khon Kaen
University, Thailand and my friends in this course, my field
assistant, who helped and supported in all important research
activities, shared suggestions, and warmly
cooperated.
Most importantly, the support and the encouragement from my
wonderful families have been always treasured. My parents, my
parent-in-law, my elder brothers, my younger brother and sister who
have been constantly supportive. Finally, my loving family, my
wife, Sirisopha and my son, Sirixay for their continued love,
forever caring and standing by my side through thick and thin and
cheering on, I was always deeply touched by them.
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