Feeding value of steam treated sugar cane bagasse in ruminant rations
Fernando Basile de Castro and
Pablo Fernando Machado
Fundacao de estudos agrarios Luiz de
Queiroz, Av. Padua Dias 11, 13400 Piracicaba - SP, Brazil.
Sponsered by International Foundation for
Science (Research Grant Agreement B/1220-1)
Summary
In order to evaluate the effects of steam treatment upon sugar
cane bagasse three experiments were conducted. The first was to
determinate the best conditions to treat the bagasse. Four
pressures were tested (13; 15; 17 and 19 kgf/cm2)
during 3 to 10 minutes in a factorial design. The condition that
gave the highest in situ digestibility was 19/6 (kgf/cm2)/(min).
The second experiment was to evaluate the potencial and the
effective degradation of the bagasse treated under the best
condition set above. The results indicate a high potential
degradation (68.96% in 48 hr), a value very close to 74.22% in
48hr from a high quality hay. Nevertheless, the effective
degradation was only 47.90% in 48hr, indicating poor rumen
conditions. The third experiment was to study the effects of
treated bagasse upon the rumen environment. It was concluded that
the main constraint of using steam treated bagasse was its fast
rate of passage through the rumen.
Key words: Sugar cane bagasse, steam treatment, rumen
degradation, rumen environment, cattle
Introduction
A series of trials was carried out to determine the effect of
steam treatment of sugar mill bagasse on its potential and
achieved degradability in the rumen of steers.
Materials and methods
Experiment 1: Determination of optimum conditions to
steam treat sugar cane bagasse to be fed to ruminants
Sugar cane bagasse was steam treated under pressure in a
commercial sugar cane mill. The treatments were: 13, 15, 17 and
19 kg/cm2 of pressure during 3 to 10 minutes. Samples
were conveniently collected and submitted to in vitro and
in situ degradation by rumen microorganisms. The in vitro
system was the one developed by Tilley and Terry (1963) and the in
situ by Orskov et al (1980).
The in situ test was done in two fistulated Jersey cows
receiving hay. These animals were also the source of inoculum for
the in vitro analysis. Three assays were run for
each determination.
Experiment 2: Determination of potencial and effective
degradation of steam treated sugar cane bagasse by ruminants.
Sugar cane bagasse treated under 19 kg/cm2 steam
pressure during 6 minutos was put into nylon bags and allowed to
be degraded by rumen microorganisms in the rumen of two
fistulated Jersey cows. The animals received hay, or raw bagasse,
plus grain (47:53), or steam treated sugar cane bagasse (19 kg/6
minutes) plus grain (65:35). Each diet was fed for 4 weeks.
During the last 20 days, three in situ assays were run.
For each assay, besides the treated bagasse, hay and raw bagasse
were used as standards.
Experiment 3: Study of the effect of steam treating
sugar cane bagasse upon its digestion by ruminants and rumen
physiology.
Six fistulated dry cows received two diets: raw bagasse plus
grain (47:53) or steam treated bagasse (19 kg/6 minutes) plus
grain (65:35). The animals received those diets for 30 days and
then the diets were interchanged. The experiment consisted of
three periods of 30 days, 10 days of adaptation to the new diet
and 20 days of sample collection. During the first day after
adaptacion, Folley catheters were introduced into the gallblader
of the animals; the following 6 days, feces and urine were
collected for total dry matter determination. Afterwards, a
serial sample collection during 24hr was used to determine
volatile fatty acids, ammonia nitrogen, and pH; another serial
sample collection for 76 hr was for rate of passage of solids and
liquids through the rumen.
Results and discussion
Experiment 1:
The results are given in Table 1.
| Table 1:
Effect of steam treating sugar cane bagasse on total in
situ (TISD), insoluble in situ (IISD) and in
vitro dry matter degradation (IVD) by rumen
microorganisms (% 48hr) |
 |
| Treatment
(kg/cm2) |
TISD |
IISD |
IVD |
|
| 13/6 |
70.12 |
55.36 |
60.82 |
| 13/8 |
71.12 |
58.08 |
59.57 |
| 13/10 |
75.52 |
62.45 |
62.71 |
| 15/4 |
76.70 |
62.13 |
61.32 |
| 15/6 |
75.83 |
62.05 |
61.05 |
| 15/8 |
76.99 |
63.50 |
61.49 |
| 17/3 |
71.88 |
56.47 |
61.20 |
| 17/5 |
74.62 |
60.53 |
60.98 |
| 17/7 |
79.10 |
67.43 |
62.52 |
| 19/2 |
78.52 |
64.08 |
62.88 |
| 19/4 |
81.61 |
68.87 |
64.01 |
| 19/6 |
80.59 |
60.58 |
63.69 |
| |
|
|
|
| STANDARD |
79.40 |
73.72 |
73.99 |
|
It can be seen from Table 1 that the best treatments were
19kg/cm2 pressure for 6 minutes (19/6) and 19/4. The
values represented an improvement of 20% above the treated
bagasse receiving commercial steam processing at the mill.
Another important observation was that the in vitro dry
matter degradation was not a sensitive enough method to evaluate
the effect of the treatment.
Experiment 2:
It was assumed that animals receiving a high quality hay would
have an adequate environment in the rumen for degradation of cell
wall carbohydrates; and that therefore in situ dry matter
degradation would represent the potential degradability of the
material. On the other hand, in situ dry matter
disappearance in animals receiving treated bagasse would
represent the effective degradation.
The results obtained can be seen in Tables 2, 3 and 4.
| Table 2:
In situ degradation (% in 48 hr) of a high quality
hay, raw and steam treated sugar cane bagasse (19 kg/cm2;
6 minutes) in cattle receiving hay or treated (19/6) or
untreated bagasse. |
|
| |
--------------------------
Diet of host animal -------------------------- |
| Sample |
Hay |
Raw bagasse |
Treated
bagasse |
|
| Hay |
74.22 |
75.30 |
68.58 |
| |
|
|
|
| Raw bagasse |
36.27 |
35.70 |
17.29 |
| |
|
|
|
| Treated
bagasse |
68.96 |
67.76 |
47.90 |
|
| Table 3: Degradation
rate (%/hr) of high quality hay, raw and steam treated
sugar cane bagasse (19/6 kg/cm2) in cattle
receiving hay or treated (19/6 kg/cm2) or
untreated bagasse. |
|
| |
--------------------------
Diet of host animal -------------------------- |
| Sample |
Hay |
Raw bagasse |
Treated bagasse |
|
| Hay |
9.19 |
8.54 |
6.06 |
| |
|
|
|
| Raw bagasse |
5.89 |
5.50 |
3.71 |
| |
|
|
|
| Treated
bagasse |
7.49 |
5.92 |
4.41 |
|
| Table 4:
Lag time (hr) in digestion of a high quality hay, raw and
steam treated sugar cane bagasse (19/6 kg/cm2)
in cattle receiving hay or treated (19/6 kg/cm2)
or untreated bagasse. |
|
| |
--------------------------
Diet of host animal -------------------------- |
| Sample |
Hay |
Raw bagasse |
Treated bagasse |
|
| Hay |
0.68 |
1.57 |
2.55 |
| |
|
|
|
| Raw bagasse |
1.23 |
3.50 |
|
| |
|
|
|
| Treated
bagasse |
3.23 |
4.68 |
3.40 |
|
From the data shown in Table 2 it can be seen that the
potential degradation of the treated bagasse is very close to
that of the high quality hay (69 vs 74 % in 48 hr). The
potential degradation of raw bagasse is 36% in 48 hr. This means
that steam treating the bagasse almost doubles its potential
degradability. Nevertheless, the effective degradation of the
treated bagasse is only 48% in 48 hr.
It would appear that something in the diet containing the
treated bagasse is interfering with its degradation since on the
raw bagasse diet no such depressing effect was observed.
The data in Table 3 show similar results indicating a lower
rate of degradation in animals receiving a diet based on treated
bagasse. Date from Table 3 and 4 indicate that despite almost the
same degradation after 48 hr, lag time was longer (3.23 vs
0.68 hr) and rate of degradation lower (7.49 vs 9.19 %hr)
for treated bagasse and hay, respectively. It shows that in order
to be degra- ded at the same rate, the bagasse would have to stay
longer in the rumen; this in turn, almost certainly would
decrease feed intake.
Experiment 3:
Data on intake and dry matter digestibility of the diets are
given in Table 5.
Dry matter digestibility was higher for raw bagasse than for
the steam treated material (Table 5). However, digestible dry
matter intake was 38.4% higher for treated bagasse. This could
explain the higher body weight gain observed for animals
receiving treated bagasse compared with the untreated material.
Assuming that the digestibility of the grain component was 85%,
it can be calculated that the effective degradation of the
bagasse was 40 and 30% for the treated and raw material
respectively, a value very close to the one observed in situ.
| Table 5:
Dry matter digestibility (DMD), intake (DMI) and
digestible dry matter intake (DDMI); rumen fermentation
parameters and rumen kinetics for diets based on raw and
steam treated bagasse. |
|
| |
Raw bagasse |
Treated
bagasse |
|
| DM
digestibility (%) |
60.2 |
54.7 |
| DM intake
(kg/d) |
7.36 |
10.8 |
| Digest DM
intake (kg/d) |
4.42 |
5.92 |
| |
|
|
| Molar %
VFA |
|
|
| Acetic |
70.0 |
66.1 |
| Propionic |
18.2 |
22.1 |
| Acetic/propionic
|
4.0 |
3.0 |
| Total VFA
(meq/100ml) |
8.5 |
12.0 |
| N-NH3
(mg/100ml) |
3.47 |
4.19 |
| pH |
6.90 |
5.89 |
| |
|
|
| Liquid
phase kinetics: |
|
|
| Dilution rate
(%/hr) |
5.97 |
8.36 |
| Turnover time
(hr) |
16.8 |
12.3 |
| |
|
|
| Solid
phase kinetics: |
|
|
| Retention
time (hr) |
47.3 |
33.5 |
|
In an attempt to identify factrs affecting rumen degradation,
samples from the rumen of the animals were analyzed for VFA, NH3-N,
pH and rate of passage of liquids and solids (Table 5).
The data show that the fermentation pattern is almost the same
on both diets, but that the intensity of fermentation is 32%
higher for the treated bagasse. This is in agreement with the
higher rate of intake of digestible dry matter.
Ammonia nitrogen levels were similar to those recommended by
Satter and Slyter (1974) but lower than the minimum value (15
mg/100 ml) suggested by Preston and Leng (1987) as being
necessary for optimum rates of digestion of fibrous feeds. The
rumen pH in the animals receiving the treated bagasse was below
the critical level (6.5) considered as providing a good
environment for cellulolytic bacteria.
The rate of passage of liquids and solids and therefore the
rate of turnover was higher for the diet of treated bagasse than
for the raw bagasse (Table 5). This means that the time available
for microorganisms to degrade the feed was shorter on the diet
with treated bagasse, which may explain the lower effective
degradation.
References
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