CASSAVA FORAGE AS A PROTEIN SOURCE IN SUGAR CANE DIETS FOR CATTLE: EFFECT ON RUMEN FERMENTATION OF DIFFERENT LEVELS OF CASSAVA FORAGE AND UREA

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Trop Anim Prod 1977 2:3
CASSAVA FORAGE AS A PROTEIN SOURCE IN SUGAR CANE DIETS FOR
CATTLE: EFFECT ON RUMEN FERMENTATION OF DIFFERENT LEVELS OF
CASSAVA FORAGE AND UREA1
Luz Meyreles, N A MacLeod2 and T R Preston


3
Centro Dominicano de Investigación Pecuaria con Caña de Azúcar,
CEAGANA, Sonto Domingo, R D
In a 4 x 4 latin square design, sugar cane/urea was substituted by cassava forage (levels of cassava
were 0, 20, 40 or 60%). The diets were balanced for N content by adding a solution of urea and
ammonium sulphate. The sugar cane had 27.5% DM and 14.2 Brix, the cassava had 20% DM and 2.4%
N in the DM. The only other dietary supplement was a mineral mixture. There were no differences in the
principal parameters of rumen fermentation (pH, protozoal biomass, total VFA, VFA molar proportion
ammonia concentration) or in blood urea levels on the different dietary treatments. Voluntary intake of
DM was significantly higher on the three cassava diets compared with the control containing only sugar
cane/urea. Rumen fermentation parameters varied according to time of feeding following the pattern
established by other workers in this field.
Key words: cattle, sugar cane, cassava forage, urea, rumen fermentation
The potential of cassava forage as a protein source has been established at the
agronomic level (Moore 1976, Meyreles et al 1977a). However the early claims as to
its nutritive value in sugar cane based diets (Moore 1976) have not yet been
substantiated. In fact, at this Centre, growth rates have never exceeded 300 g/d when
cassava has been the only protein source (Meyreles et al 1977 b,c,d).
Cassava leaf protein is of good quality and it has been suggested that the principal
problem may be one of too high solubility in the rumen (Meyreles et al 1977b).
The following experiment was carried out to provide more information on rumen
digestion end products with different dietary ratios of cassava forage and sugar
cane/urea.
Materials and Methods
Treatments and Design: The 4 dietary treatments were chopped sugar cane/urea
substituted by 0, 20, 40 or 60% chopped cassava forage. The diets were balanced for
N content by the addition of varying quantities of a solution of urea and ammonium
sulphate as shown in table 1. The experiment was a 2 x 2 latin square design with
periods of 14 days.
This work was supported in paint with funds provided by the Organization of American States
1
through the project Fondo Mar del Plato
On secondment from Rowett Research Institute, Aberdeen, Scotland
2
Scientific adviser to CEAGANA partially financed through the UNDP/FAO project
3
DOM/71/504

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301
Table 1:
Daily intake of cane, cassava forage and nitrogen by Zebu bulls given different levels of cassava forage
Proportion of Cassava, %
72
48
26
0
SEx
Daily intake
Chopped whole cane, kg
4.9
9.7
12.7
14.3
±.55
Cassava forage, kg
12.4
8.7
4.4
-
±.17
Total dry matter, kg
4.8
5.2
5.0
4.2
±.19
Total N, g
74
77
73
69
Proportion of diet N (%) as:
Cassava forage
84
56
29
-
Cane
8
14
20
23
Urea/(NH ) SO
8
30
51
77
4
4
Animals and Diets: 4 Zebu bulls of 18 months of age fitted with permanence rumen
cannulas were used. The sugar cane had an average DM of 27.5% and a Brix of
14.2!. The Brix level corresponds to a sugar content of 43.6% in cane DM (see
Ferreiro et al 1977). The cassava forage was from the variety Zenon and consisted of
the aerial part of the plant cut about 30 cm above ground level. It had a DM of 20%
and contained 2,4% N in DM. The urea and ammonium sulphate were given as a
solution (18 urea: 5 ammonium sulphate: 77 water) (w/w) which was mixed with the
fresh sugar cane. The animals also received a mineral mixture containing equal parts
of sodium chloride and dicalcium phosphate.
Procedure: The animals were kept in individual concrete floored stalls in a large open
sided building. They were fed once daily in the morning. The sugar cane was available
ad libitum and the quantity of cassava forage adjusted on the basis of the cane
consumption the previous day. On the last day of each period, rumen samples were
taken immediately before and 1, 2, 3 and 4 h after feeding. Blood samples were taken
from the jugular vein immediately before, and 2 and 4 hr after feeding.
Measurements and Analyses: Rumen samples were analysed for pH (pH meter),
protozoal biomass using the index method developed by Leng et al (1976), ammonia
using a modification of the diffusion technique of Conway, total VFA by steam
distillation, and the proportion of VFA by gas chromatography (see Minor et al 1977 for
details of the methods).
The DM, pH and Brix of the cane and DM of the cassava were measured daily and N
content of the cassava at intervals.
Results and Discussion
Overall means for the rumen parameters and urea levels in blood were remarkedly
uniform (table 2); the changes observed were due mainly to time of feeding (figures
1-7).

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Figure 1-4:
The effect of different levels of cassava forage ( ,0%; , 26%; , 48%; ,72%) on rumen pH and VFA
proportions at 0, l, 2, 3 and 4 hours after feeding.

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Trop Anim Prod 1977 2:3
303
Figures 5-7:
The effect of different levels of cassava forage ( ,0%; , 26%; , 48%; ,72%) on rumen NH , blood urea
3
rumen protozoal index (Biomass) at 0, 1,2, 3 and 4 hours after feeding.

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Trop Anim Prod 1977 2:3
Table 2:
Rumen parameters and brood urea levels in Zebu given cane diets supplemented
with different levels of cassava forage. Values ate means of four samples taken
1, 2, 3 and 4 hr after feeding (rumen), or 2 and 4 hr after feeding (blood)
Proportion of cassava in diet,
% of fresh basis
72
48
26
0
SE of mean1
Rumen pH
6.75
6.66
6.68
6.71
± .49
Rumen VFA, mM/litre
166
218
183
182
± 14
Molar proportions, %
Acetate
66
66
65
66
± 4.2
Propionate
19
20
21
20
± 1.3
Butyrate
15
14
14
13
± 1.1
Biomass, % in rumen fluid
0.26
0.53
0.51
0.29
± .14
Rumen ammonia, mg/100 ml
36.7
54.7
60.4
30.0
± 12.7
Blood urea, mg/100 ml
11.1
14.0
10.6
15.6
± 2.2
Average of standard errors of individual means
1
Inevitably, in experiments of this kind, there is considerably confounding of dietary
treatments with overall nutritional characteristics of the ration. Thus one effect of
replacing sugar cane with cassava forage is to reduce the amount of fermentable
carbohydrate (sugars) in the diet which, in turn, could mean a less favourable
environment for the up-take of ammonia by the rumen microorganisms, Nevertheless,
taking into account this limitation caused by the design of the experiment, the results
would appear to lend support to the hypothesis that the protein present in cassava
forage is readily soluble; since there were no significant differences in rumen ammonia
and blood urea over the range of treatments (from 77% of dietary N as urea to 84% as
cassava). The only indication of a "by-pass" protein effect was the significantly lower
intake of total DM on the treatment which contained no cassava. As the principal
effect of "by-pass" protein on sugar cane diets is to raise voluntary intake (Leng and
Preston 1976), this difference could be interpreted as having been caused by some of
the cassava protein by-passing the rumen,
There were considerable differences in the different parameters of rumen
fermentation according to the time that the rumen samples were taken, These trends
with time (figures 1-7) are typical of those reported by other workers for diets based on
sugar cane (Montpellier et al 1977; Meyreles et al 1977c; Priego and Sutherland 1977;
Silvestre et al 1977).

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References
Ferreiro H M, Sutherland T M & Preston T R 1977 Brix and dry matter content as indices of
urea requirement in diets based on sugar cane Trop Anim Prod 2: 213-21B
Leng R A & Preston T R 1976 Sugar cane for cattle production: present constraints
perspectives and research priorities Trop Anim Prod 1: 1-22
Leng R A, Valdez R E, De Gonzalez E & Minor S 1976 A method for assessing protozoal
biomass in rumen fluid Trop Anim Prod 1: 42 abs
Meyreles L, MacLeod N A & Preston T R 1977a Cassava forage as a source of forage protein:
effect of population density and age of cutting Trop Anim Prod 2: 18-26
Meyreles L, MacLeod N A & Preston T R 1977b Cassava forage as a protein supplement in
sugar cane diets for cattle; effect of different levels on growth and rumen fermentation
Trop Anim Prod 2: 73-80
Meyreles L, MacLeod N A & Preston T R 1977c Cassava forage as a protein a in sugar cane
diets for cattle: effects of different levels without urea on growth and on rumen
fermentation Trop Anim Prod 2: 200-205
Meyreles L & Preston T R 1977d Cassava forage as a protein source in sugar cane diets for
cattle: effect of supplementary sulphur and dried cassava root Trop Anim Prod 2:
Minor S, MacLeod N A, Preston T R & Leng R A 1977 Studies on digestion in different sections
of the intestinal tract of bulls fed sugar cane/urea with different supplements Trop Anim
Prod 2: 163-174
Montpellier F A, Valdez R E and Preston T R 1977 Processing of sugar cane: effect of
derinding and coarseness of chopping on animal performance and rumen fermentation
Trop Anim Prod 2: 206-212
Moore C P 1976 El uso de forraje de yuca en la alimentacion de rumientes Seminario
Internacional de Ganaderia Tropical, Acapulco, Mexico (FIRA, Banco de Mexico)
Priego A & Sutherland T H 1977 The effect of propionic acid on pattern of ruminal fermentation
Trop Anim Prod 2: 189-194
ilvestre R, MacLeod N A & Preston T R 1977b Effect of meat near, dried cassava root and
groundnut oil in diets based on sugar cane/urea, or molasses/urea Trop Anim Prod 2:
151-157
Received 20 July 1977

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