| Use of Cassava as Animal Feed |
Cassava (Manihot esculenta Crantz), an annual tropical tuber crop, was
nutritionally evaluated as a foliage for ruminants, especially dairy cattle.
Cultivation of cassava biomass to produce hay is based on a first harvest of
the foliage at three months after planting, followed every two months
thereafter until one year. Inter-cropping of leguminous fodder as food-feed
between rows of cassava, such as Leucaena leucocephala or cowpea (Vigna unculata), enriches soil fertility
and provides additional fodder. Cassava hay contain 20 to 25% crude protein in
the dry matter, and with very minimal HCN content.
Feeding trials with cattle
revealed high levels of DM intake (3.2% of BW) and high DM digestibility (71%).
The hay contains tannin-protein complexes which could act as rumen by-pass
protein for digestion in the small intestine. Therefore, supplementation with
cassava hay at 1-2 kg/hd/d to dairy cattle could markedly reduce concentrate
requirements, and increase milk yield and composition. Moreover, cassava hay
supplementation in dairy cattle could increase
milk thiocyanate which could possibly enhance milk quality and milk storage,
especially in small holder-dairy
farming. Condensed tannins contained in cassava hay have also been shown to
potentially reduce gastrointestinal nematodes and therefore could act as an
anthelmintic agent. Cassava hay is therefore an excellent multi-nutrient source
for animals, especially for dairy
cattle during the long dry season, and has the potential to increase the
productivity and profitability of sustainable livestock production systems in
the tropics.
Cassava or tapioca (Manihot
esculenta ,Crantz) is an annual
tuber crop grown widely in tropical and sub-tropical areas. It thrives in
sandy-loam soils with low organic matter, and in areas receiving low rainfall
and with high temperatures. It is therefore a cash crop cultivated by
small-holder farmers within the existing farming systems in many countries.
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 the high level of condensed tannins (Reed et al
1982; Onwuka 1992). Harvesting of
cassava at an early growth stage (3 months) to make hay reduces the condensed
tannin content and increases the protein content (to 25% of DM) resulting in a
higher nutritive value (Wanapat et al 1977).
Studies by
Wanapat et al (1997,2000a, 2000b, 2000c, 2000d) have revealed the details of
planting cassava and making hay. Planting cassava for hay is aimed at
increasing the whole crop digestible biomass, with the tuber root as a
by-product. Earlier work by Wanapat et al (1997) demonstrated that planting cassava at 60x40 cm between rows
and inter-cropping with cowpea or leucaena could enrich soil fertility and the
legumes could be used as food and feed for humans and livestock, respectively.
The initial cutting was at 3 months, and was followed by subsequent cutting at
every two months by 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 a dry matter level of 80-90%. This might
take 2-3 days, but chopping helps shorten the drying process. Sun-drying also
eliminated more than 90% of the hydro-cyanic acid (HCN) and enhanced the
palatability and long-term storage. Intercropping cassava with leguminous crops
such as cowpea could improve soil fertility and provide food for human
consumption, while the residue could be used as supplemental feed, especially
during the dry season (Polthanee et al. 2001). Planting space and frequent cutting
have been shown to affect the combined yield of the cassava hay (Petlum et al
2001). Furthermore, planting pattern, either with non-ridging or ridging, as
well as manure fertilization affects cassava hay production (Puangchompoo et al
2001).
It has been
found that cassava hay harvested at an early stage of growth (3 months)
contained up to 25% crude protein, and with a good profile of amino acids.
Digestibility and intake studies in cattle resulted in relatively high values,
which demonstrated that cassava hay was palatable and digestible. Condensed
tannins (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) and Reed (1995)
reported that if condensed tannins 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.
Cassava hay
contains condensed tannins(CT) or proanthocyanidins (PC), which are common in tropical plants. CT are
polyphenolics which can easily be solubilized in water and can precipitate
protein. The presence of condensed tannins and protein can result in the
formation of tannin-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 >8.0 (Jones and Mangan 1977). Condensed
tannins have been found to increase N-recycling in the rumen and saliva (Reed
1995) and moreover to improve rumen microbial protein synthesis (Makkar 1995).
However, McSweeney et al (2000) found reduced
rumen cellulolytic bacteria in sheep fed tannin-containing diets, although
microbial protein synthesis was not affected.
The mode of action of CT on rumen fermentation is yet to be elucidated
As has been reported by Claesson (1994), milk
thiocyanate is required in the lactoperoxidase system in milk to help increase
the shelf-life, although the optimal level of milk thiocyanate should not
exceed 20 ppm. Dairy cows fed with
cassava hay as a supplement, have been shown to have a milk thiocyanate content
of 19.5 ppm. However, more research is needed in order to pin-point the role of
residual HCN in cassava on milk thiocyanate.
Gastrointestinal
(GI) parasites or nematodes have been found widely in the tropics, and result
in poor performance of ruminants. Common GI nematodes found include Trichostrongylus colubriformis, Ostertagia
circumcincta, Haemonchus centortus and T. vitrinus. Animals infected with
these nematodes exhibited higher requirements for protein and minerals due to
the loss of endogenous nitrogen (blood, plasma, mucin and sloughed cells) and
lowered P adsorption (Poppi et al 1985; Kahn and Diaz-Hernandez 2000). Preliminary
work by 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 condensed tannins (CT), and were similar to the group that had been
drenched. Possible explanations are that the animals received supplemental
protein and /or that CT could have a direct effect on the internal parasites.
Possible mechanisms through which CT may reduce larval migration and
development remain to be elucidated, but the effect may be mediated through
ingestion of CT and interactions of CT with the external surface of the larvae
( Kahn and Diaz-Hernandez 2000).
Cassava hay has
been used successfully as a source of high protein roughage for lactating dairy
cows (Wanapat et al 2000a; Wanapat et al 2000b). Wanapat et al (2000a)(Table 1)
found that increasing levels of CH from 0.6 to 1.7 kg/hd/d reduced concentrate
use from 0.1 to 1.6 kg/hd/d, respectively, without affecting milk yield. Moreover,
feeding CH ad libitum gave a
similar result and could further reduce concentrate use.
|
Table
1. Effects of cassava hay (CH)
supplementation levels on ruminal pH, NH3-N, milk yield and milk
composition in late lactating cows fed urea-treated rice straw (UTRS) as a roughage |
||||||
|
CH replacement of
urea-treated straw |
CH0 |
CH8 |
CH15 |
CH18 |
CH100 |
SEM |
|
Cassava hay DM intake, kg/d |
- |
0.56 |
1.13 |
1.70 |
5.2 |
0.20 |
|
Condensed tannin intake, g/d |
0 |
1.44 |
2.90 |
4.37 |
13.36 |
5.26 |
|
Concentrate saving, kg/d |
- |
0.10 |
1.30 |
1.60 |
3.1 |
- |
|
Urea-treated rice straw, kg DM/d |
6.8 |
6.4 |
6.7 |
8.0 |
- |
0.28 |
|
Ruminal pH |
7.2 |
7.0 |
7.0 |
7.0 |
6.8 |
0.13 |
|
Ruminal NH3-N, mg/100 ml |
17 |
13 |
13 |
16 |
7.0 |
0.52 |
|
Milk yield, kg/d |
6.3 |
6.1 |
5.4 |
6.1 |
5.4 |
0.24 |
|
3.5% FCM,kg/d |
6.8ac |
6.2ab |
6.0b |
7.1c |
6.4ab |
0.13 |
|
Milk fat, % |
4.0a |
3.6b |
4.2a |
4.5c |
4.6c |
0.11 |
|
Milk protein, % |
4.4a |
4.0a |
3.8a |
4.1a |
5.3b |
0.17 |
|
Solids-not-fat, % |
8.6 |
8.8 |
8.4 |
8.6 |
8.4 |
0.12 |
|
Total solids, % |
12.6 |
12.3 |
12.0 |
12.2 |
12.6 |
0.18 |
|
abc Values on the same row with different superscripts differ (P<0.05).CH0= Urea-treated rice straw (UTRS0 ad lib.+ Conc: Milk yield(1:2) + 0 CH; CH8= UTRS ad lib. + Conc: Milk (1:2)+ CH at 0.56 kg DM/hd/d. CH15= UTRS ad lib. + Conc: Milk (1:3)+ CH at 1.13 kg DM/hd/d.; CH18= UTRS ad lib. + Conc: Milk (1:2)+ CH at 1.70 kg DM/hd/d.; CH100= Cassava hay ad lib. + Cassava root (cassava chip + 3% urea ) at 2 kg/d. |
||||||
Studies were conducted to examine the effect of
supplementation level of cassava hay (CH) in dairy cows. Six multiparous
Holstein-Friesian crossbreds were paired and randomly assigned in a change-over
design to receive three levels of CH supplement , at 0, 0.8 and 1.7 kg DM/hd/d.
Concentrate was supplemented at the same level (1:2, concentrate:milk yield)
while urea-treated (5%) rice straw was offered on an ad libitum basis. The results revealed that supplementation of CH significantly reduced
concentrate use, without affecting milk yield (12.5, 12.12 and 12.6 kg/hd/d)
and significantly improved 3.5% FCM (14.21, 15.70 14.9 kg/d, respectively).
Moreover, CH supplementation significantly increased milk fat and milk protein
percentages, especially at 1.70 kg/hd/d. Concentrate use was reduced by 27% at
1.7 kg/hd/d CH supplementation.
|
Table 2. Effect of level of chopped
cassava hay on milk yield and composition of
Holstein-Friesian crossbreds fed
urea-treated (5%) rice straw ad libitum |
||||
|
|
Chopped cassava hay , kg/d |
SEM |
||
|
|
0 |
0.8 |
1.70 |
|
|
Concentrate
DM Intake, kg/d |
5.53 |
5.00 |
4.03 |
0.25 |
|
Concentrate
saving, kg (% of control) |
0 |
0.53 (10) |
1.50 (27) |
0.30 |
|
Milk
yield, kg/d |
12.5 |
12.1 |
12.6 |
0.57 |
|
3.5%
FCM, kg/d |
14.2a |
15.7c |
14.9b |
0.67 |
|
Milk
composition |
|
|
|
|
|
Fat, % |
4.06a |
4.15a |
4.61b |
0.19 |
|
Protein, % |
3.40a |
3.34b |
3.50c |
0.08 |
|
Lactose, % |
4.64a |
4.82b |
4.62a |
0.05 |
|
Solids-not-fat, % |
8.74 |
8.80 |
8.81 |
0.09 |
|
Total solids % |
13.5 |
13.1 |
13.7 |
0.32 |
|
a,b,c, Values with
different superscripts differ (p<0.05); Wanapat et al (2000a) |
||||
In a later
experiment (Wanapat et al 2000b),
supplementation of cassava hay to replace concentrate use was studied in
lactating Holstein Friesian crossbreds grazed on Ruzi grass. Six multiparous
cows in mid-lactation were paired and
randomly assigned according to a change-over-design to receive three
combinations of cassava hay and concentrates (Table 3).
|
Table 3. Effect of cassava hay (CH)
supplementation on concentrate use and milk yield and composition |
||||
|
Conc
: Milk ratio |
1:2 |
1:3 |
1:4 |
SEM |
|
CH
supplement, kg DM/d |
0 |
2.85 |
4.02 |
|
|
Concentrate
DM Intake, kg/d |
4.56a |
3.20b |
2.64c |
0.25 |
|
Concentrate
saving, kg (% of control) |
0 |
1.36(30) |
1.92(42) |
- |
|
Milk
yield, kg/d |
10.7 |
10.1 |
10.4 |
0.58 |
|
3.5% FCM, kg/d |
12.6 |
12.5 |
12.6 |
0.75 |
|
Milk
composition |
|
|
|
|
|
Fat, % |
4.61a |
4.98 b |
4.80ab |
0.13 |
|
Protein, % |
3.36a |
3.60b |
3.45ab |
0.10 |
|
Lactose, % |
4.47a |
4.66b |
4.53 |
0.07 |
|
Solids-not-fat, % |
8.80a |
8.95b |
8.68c |
0.09 |
|
Total solids |
13.41 |
13.54 |
13.50 |
0.24 |
|
Thiocyanate, ppm |
5.3a |
13.3b |
17.8b |
0.77 |
|
abc Values with
different superscripts differ (P<.05). Wanapat et al (2000 a) |
||||
Milk yields
were similar among treatments, while protein, lactose and solids-not-fat
percentages were highest (P<0.05) in cows receiving CH at 1.0 kg/hd/d. The
most significant improvement from CH supplementation was that it allowed a
reduction in concentrate use of 42%, which would provide a higher income for small-holder dairy farmers (Table 4).
|
Table 4. Effect of cassava hay supplementation
on economical returns |
|||||
|
Conc
: Milk |
1:2 |
1:3 |
1:4 |
||
|
CH
suppl, kg DM/d |
0 |
2.85 |
4.02 |
||
|
3.5%
FCM, kg/d |
12.6 |
12.5 |
12.6 |
||
|
Milk
sales, Baht |
141 |
140 |
141 |
||
|
Concentrate
intake, kg/d |
5.15 |
3.62 |
2.97 |
||
|
Concentrate
cost, Baht/d |
60.9 |
21.7 |
17.8 |
||
|
Cassava
hay intake, kg/d |
0 |
2.85 |
4.02 |
||
|
Cassava
hay cost, Baht/d |
0 |
1.92 |
2.01 |
||
|
Total
feed cost |
30.9 |
23.6 |
19.8 |
||
|
Income over feed: |
|||||
|
Baht/hd/d |
1 |
116 |
121 |
||
|
Baht/hd/month |
3,324 |
3,494 |
3,652 |
||
|
$US |
92.3 |
97.1 |
101 |
||
|
1 kg milk = 11.20 Baht,
kg conc = 6.00 Baht, kg Cassava hay = 0.50 Baht.; 36 Baht = 1 $US |
|||||
In addition,
milk thiocyanate was increased from 5.3 in the control group to 17.8 ppm
(P<0.05) in the CH supplemented group (1.7 kg/hd/d). These results are in
line with the work of Woodward et al (1999), who reported that dairy cows fed
with Lotus corniculatus, which contained condensed tannins, had a 42%
improvement in milk yield and 57% increase in milk protein percentage, without
changing feed intake.
A participation
scheme involving small holder dairy farmers in improving dairy production
through the use of local feeds, on-farm established feeds and crop residues,
was carried out in Northeast, Thailand. At six milk collection centers, 63
farmers with 340 lactating cows participated in this study and demonstration of
feed supplements. Farmers and cows were
allotted to receive the following respective feed supplements: High-quality
feed block (HQFB); high-quality feed pellet (HQFP), dried cassava leaf/cassava
hay, dried lecuaena leaf and cottonseed meal. Rice straw treated with 5% urea
was fed as a source of roughage throughout the feeding period of the dry
season. Training courses and workshops were organized by the researchers at the
University, research station, demonstration sites and on-farms. Regular visits
to the farms by researchers and extension officers were made, and in addition
regular discussions and demonstrations were held. Participating farmers also
visited other farmers during the demonstrations, which offered a real practical
perspective and farmer-to-farmer interaction. As a result of this participation
and demonstration scheme, the farmers could learn more effectively and accepted
the technology more readily, especially the practical details of the feed
preparation, feed establishment, feeding method and feed preservation.
Strategic
supplementation of these feed supplements resulted in improved milk yield, milk
quality, overall condition of the cows and higher economic returns through
increased productivity and lower ratios of concentrate to milk yield, from 1:2 to 1:3 or lower. Based on this research
and demonstration/participation scheme, all feed supplements were shown to
enhance productivity. However, the establishment of cassava hay on farms requires
more attention and warrants a wider expansion among dairy farmers, since it
could be easily produced and be sustainable on farms (Wanapat et al 2000c)
(Table 5).
|
Table
5. Effect of local feed supplements
on milk yield and composition of lactating dairy cows*, conducted as on an
on-farm trial |
|
||||||||||||||
|
|
HQFB |
HQFP |
DCL |
DLL |
CSM |
|
|||||||||
|
|
P |
D |
P |
D |
P |
D |
P |
D |
P |
D |
|||||
|
Milk yield, kg/d |
9.80 +2.9 |
10.4+2.78 |
11.05 +3.21 |
12.0+4.55 |
9.08 +2.16 |
10.1+2.53 |
9.76 +1.78 |
10.7 +2.1 |
11.7+2.80 |
13.0 +3.10 |
|
||||
|
3.5% FCM,kg/d |
10.75+1.80 |
11.9+2.10 |
11.9 +2.80 |
13.9 +2.25 |
10.2+2.30 |
11.7+2.40 |
10.5+2.15 |
12.3 +2.90 |
10.9+2.65 |
12.6 +3.40 |
|
||||
|
Fat, % |
4.1 |
4.4 |
4.0 |
4.2 |
4.3 |
4.5 |
4.0 |
4.4 |
3.05 |
4.20 |
|
||||
|
Protein, % |
3.3 |
3.4 |
3.2 |
3.3 |
3.2 |
3.3 |
3.2 |
3.3 |
3.20 |
3.30 |
|
||||
|
Lactose, % |
5.1 |
5.1 |
5.0 |
5.0 |
5.0 |
5.0 |
5.1 |
5.0 |
4.90 |
5.00 |
|
||||
|
SNF, % |
9.1 |
9.2 |
8.8 |
9.0 |
8.8 |
9.0 |
9.0 |
9.0 |
8.85 |
8.90 |
|
||||
|
TS, % |
13.2 |
13.4 |
12.8 |
12.8 |
13.1 |
13.3 |
13.0 |
1.3.4 |
11.90 |
12.65 |
|
||||
|
*
Three farms within each group, 30 farms in all, with similar conditions were
randomly selected. P = pre-trial; HQFB = high-quality feed block; D= during trial, HQFB= High-quality feed
pellet; DCL = dried cassava leaf/hay
DLL= dried leucaena leaf; CSM=
cottonseed meal. Wanapat et al (2000c) |
|
||||||||||||||
As an
on-going research activity with small-holder
dairy farmers, the effect of planting cassava inter-cropped with cowpea to
produce hay has been investigated. Four groups of farmers, 4 farms each, were
randomly allotted to the following interventions: no cassava; with cassava;
cassava inter-cropped with cowpea and cassava inter-cropped with leucaena. Feed
biomass will be collected and measured
for the yield and nutritive values. Cassava hay will be collected throughout
the year. Cost of production and net profit, and on-farm input-output relations
will be analyzed (Wanapat et al 2001).
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