Evaluation of Sapindus saponaria as a defaunating agent and its effects on
different ruminal digestion parameters
Diaz A, Avendano M and
Escobar A
Instituto de Producción Animal, Facultad de
Agronomía, Universidad Central de Venezuela, Maracay, Venezuela
Summary
The seed pericarp from Sapindus saponaria was evaluated as a
defaunating agent in terms of feed intake and pattern of
fermentation using three crossbred adult sheep. The experimental
design was a 3x3 Latin square with 30 days/period. Treatments
included 0, 25 and 50 g of S. saponaria in the diet. The
protozoal population was significantly (P<0.05) reduced (84%),
and a significant increase (P<0.05) in total viable bacteria,
cellulolytic bacteria and fungi was observed. The degradability
of the dry matter at 24 h also increased significantly
(P<0.05). An important implication of this study is the
possibility of developing a practical way to maintain a reduced
number of protozoa in ruminants while at the same time being a
source of nutrients.
KEY WORDS: Defaunating agent, Dry Matter degradability,
Protozoo, Ruminal digestion, Sapindus saponaria, Sheep.
Introduction
Venezuelan ruminant feeding systems rely on forages as the
major source of food. However, the main limitations of tropical
forages are their low contents of nitrogen, high-energy
carbohydrates and lipids, and their low digestibility (Minson
1981; Leng 1990). Feeding these forages to ruminants usually
results in reductions in voluntary feed intake and an imbalance
in the absorbed nutrients (protein to energy ratio, P/E) and, as
a consequence, growth, reproductive rate, and milk production are
reduced.
One way of improving the P/E ratio of the absorbed nutrients
might result from the elimination of the rumen protozoa
population (defaunation). Although these microorganisms
contribute to fibre digestion, therefore increasing the
availability of energetic substrates for the animal, it has been
shown that protozoa prey upon bacteria and that they are
selectively retained in the rumen (Weller and Pilgrim 1974;
Coleman 1975). As a result of protozoal activity, a significant
reduction in the flow of microbial biomass to the duodenum has
been documented (Bird and Leng 1978; Bird et al 1979; Hsu et al
1991).
Tropical countries are rich in flora that have developed
secondary metabolites, presumably as a protective mechanism
against grazing and browsing. Among these toxic compounds are the
saponins, which have been shown to exert a specific effect
against rumen protozoa while the rest of the rumen biomass
remains unaltered (Lu and Jorgensen 1987). Thus, the main
objective of this study was to evaluate the antiprotozoal
activity of Sapindus saponaria as a defaunating agent on the
rumen microbial biomass, volatile fatty acids, pH and
ammonia-nitrogen concentrations in the rumen fluid, in sacco
digestibility and feed intake in sheep.
Materials and methods
Experimental design
The treatments were arranged in a 3x3 Latin square. Each of
the experimental periods lasted 30 days. During the first day of
each period, 100 ml of cow rumen fluid was added to each sheep
via a rumen cannula. On day 11, each animal was fed its
respective test diet. Samples for analyses were taken during the
last 5 days of each period.
Animals
Three mature tropical crossbred sheep (37 " 5.2 kg
liveweight), fitted with permanent rumen cannulae were used, and
housed in individual pens. Each sheep was treated for the
prevention of ecto- and endoparasites with Ivomec (Merk, Sharp
and Dohne, Brasil) three weeks before the beginning of the study.
Diet and treatments
The basal diet consisted of chopped Cynodon nlemfuensis hay
(0.94% nitrogen, 91.2% dry matter) offered ad libitum daily
between 0700 and 0800 h and a supplement (315 g DM/animal/day)
which consisted of: 81% corn meal, 13% fish meal, 3% urea and 3%
of a mixture of salt and minerals. 0, 25 and 50 g of the Sapindus
saponaria's ground seed pericarp was incorporated to the
supplement, according to the treatments.
Measurements
Feed intake was calculated by weighing the feed offered and
refused each morning throughout the experimental period. Daily,
beginning on day 11 until the end of each experimental period, 4
ml of ruminal fluid were collected and immediately mixed with
equal amounts of formaldehyde-saline solution (37% formaldehyde
with saline solution 1:9). Subsequent dilutions were made with
Hungate solution (Hungate 1966) and protozoa were counted using a
Dollfus chamber, according to the method described by Jouany and
Senaud (1979). On day 25, ruminal fluid samples were withdrawn at
0, 1, 2, 4, 6, 9, 12 and 24 h before feeding the animals. The pH
was immediately determined and stored at -15EC in a 15 ml bottle
containing 5 drops of concentrated H2SO4 for later determination
of N-NH3 and VFA, according to the procedures described by FAO
(1986). In sacco digestibility of hay (Cynodon nlemfuensis,
chopped and passed through a 1 mm crib size) was determined on
day 26 during 48 h, according to the procedure described by
Mehrez et al (1977). During the last 2 days of each period and
prior to feeding the animals, a rumen fluid sample was taken for
the enumeration of total viable bacteria, cellulolytic bacteria
and fungi, following the most probable number technique described
by Dehority et al (1989) and Obispo (1990).
Results and discussion
The inclusion of 0, 25 and 50 g of S. saponaria seed pericarp
in the animals' diet had no significant effect (P>0.05) on dry
matter intake (Table 1). Also, no apparent metabolic disorders
were observed in animals consuming the higher levels of S.
saponaria.
| Table 1.
Effects of different levels of ground seed pericarp of Sapindus
saponaria on feed intake and different ruminal
fermentative parameters. |
 |
| |
Levels
of S. saponaria in the diet (g) |
|
| |
0 |
25 |
50 |
SEx |
|
| Feed intake |
|
|
|
|
| Hay (g DM/d) |
767.8 |
767.0 |
792.8 |
37.0 |
| Total (g
DM/d) |
1042.0 |
1059.3 |
1105.9 |
37.0 |
| Total (g
DM/LW^0.75) |
64.1 |
65.6 |
66.8 |
1.9 |
| Fermentative
parameters |
|
|
|
|
| pH |
6.4 |
6.4 |
6.4 |
0.0 |
| Ammonia (mg
N-NH3/100 ml) |
196.0 |
194.9 |
117.3 |
9.8 |
| VFAs (mol/100
mol VFA) |
|
|
|
|
| Acetate |
71.8 |
71.3 |
69.7 |
2.3 |
| Propionate |
17.0 |
17.9 |
18.4 |
1.3 |
| Butyrate |
10.0 |
9.6 |
10.0 |
1.0 |
| Microbial
populations |
|
|
|
|
| (log 1/ml of
ruminal fluid) |
|
|
|
|
| Protozoa |
5.4a |
5.0b |
4.6c |
0.1 |
| Fungi |
7.6a |
8.1b |
8.5c |
0.1 |
| Total
bacteria |
10.3a |
11.3b |
11.7c |
0.2 |
| Cellulolytic
bacteria |
7.5a |
8.1 |
8.8c |
0.1 |
| Dry matter
degradability (%) |
|
|
|
|
| 24 h |
12.5a |
18.6 |
25.9c |
0.9 |
| 48 h |
36.0 |
37.7 |
35.5 |
0.9 |
| T^1/2 |
72.9 |
69.7 |
66.6 |
5.7 |
|
The pH, molar proportions of VFA (mM/100 ml) and N-NH3 (mg
N/100 ml) concentrations in the ruminal fluid measured at 0, 1,
2, 4, 6, 9, 12 and 24 h after feeding the experimental diets were
not significantly (P>0.05) changed by dietary treatments.
Therefore, the results of each individual sampling time were
pooled and the means for each experimental treatment are
presented in Table 1.
There was no significant effect (P>0.05) of feeding
different levels of S. saponaria on rumen pH, ammonia
concentration and VFA molar proportions. However, there is a
negative relation between ammonia concentrations in the rumen
fluid and the level of S. saponaria incorporated in the
experimental diets. As it can be seen, there is a 40.14% decrease
in the concentrations of N-NH3 in the 50 g treatment with respect
to the control treatment. This marked reduction in ammonia
concentrations has also been reported in defaunated sheep and
cattle on a variety of diets (Eadie and Hobson 1962, Bird and
Leng 1984, Veira et al 1983), and in sheep which were given
extracted saponins from lucerne (Medicago sativa) included at 2
and 4% in the basal diet (Lu and Jorgensen 1987). This reduction
might result from a decrease in the digestibility of the diet,
insoluble protein and/or to the less predatory activity of the
protozoa on the rest of the microbial biomass.
The most important finding in this study was the change in the
distribution of the rumen microbial species with the
incorporation of different levels of S. saponaria seed pericarp
in the experimental diets. Although there were high variations in
the population size of protozoa among animals, there were
statistically significant differences (P<0.05) among
treatments with the inclusion of S. saponaria in the experimental
diets. The total number of protozoa decreased in comparison with
the control treatment, to 57 and 84% with the inclusion of 25 and
50 g of S. saponaria, respectively. On the other hand, the total
number of viable bacteria and fungi was significantly (P<0.05)
higher in animals fed S. saponaria than those fed the control
diets. These results indicate that the observed differences in
the microbial populations resulted mainly from the reduction in
protozoa populations. Coleman (1975) showed that protozoa are
able to ingest relatively large numbers of bacteria and it is
widely accepted that rumen fluid free of predatory protozoa is
characterized by a higher population density of bacteria (Eadie
and Hobson 1962, Demeyer and Van Nevel 1979, Hsu et al 1991).
This reducing effect of S. saponaria on protozoa population
persisted throughout the experimental period (data not shown).
The dry matter degradability (%) of hay (Cynodon
nlemfuensis) in the nylon bags after 24 h incubation in the
rumen increased significantly (P<0.05) with the inclusion of
S. saponaria in the diet. This increase represented 30.5 and
51.7% with respect to the control diet, with the inclusion of 25
and 50 g of S. saponaria in the diets, respectively. However,
this effect disappeared after a 48 h incubation period as
indicated in Table 1. The increase in the 24 h degradability of
hay might have been associated with the increased bacterial
biomass, especially cellulolytic bacteria and fungi, resulting
from the reduced number of protozoa on diets containing S.
saponaria.
The most important implication of this study appears to be the
possibility of developing a practical way to maintain a reduced
number of rumen protozoa by the addition of specific plants (such
as S. saponaria) in ruminant diets, while providing, at the same
time, nutrients to the animals. This could be particularly
important in the tropics where diets are characterized by
suboptimal protein levels. Therefore, a combination of a reduced
protozoa population and the utilization of by-pass protein
appears to be a promising means of increasing the amounts of
protein reaching the duodenum in ruminants.
Acknowledgements
This project was financed by the International Foundation for
Science and the Consejo de Desarrollo Científico y Humanístico
de la Universidad Central de Venezuela.
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