|Livestock Research for Rural Development 5 (2) 1993||
Citation of this paper
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
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.
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
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.
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.
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)|
|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|
|Ammonia (mg N-NH3/100 ml)||196.0||194.9||117.3||9.8|
|VFAs (mol/100 mol VFA)|
|(log 1/ml of ruminal fluid)|
|Dry matter degradability (%)|
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.
This project was financed by the International Foundation for Science and the Consejo de Desarrollo Científico y Humanístico de la Universidad Central de Venezuela.
Bird S and Leng R A 1978 The effects of defaunating the rumen on the growth of cattle on low-protein, high-energy diets. British Journal of Nutrition 40:163-167
Bird S H, Hill M K and Leng R A 1979 The effect of defaunation on the growth of lambs on low-protein, high energy diets. British Journal of Nutrition 42:81-87
Bird S H and Leng R A 1984 Further studies on the effects of the presence or absence of protozoa in the rumen on live-weight gain and wool growth in sheep. British Journal of Nutrition 52:607-611
Coleman G S 1975 The interrelationship between rumen ciliate protozoa and bacteria. IN: Digestion and Metabolism in the Ruminant (Eds. I W McDonald and A C I Warner) pp149-164. University of New England Publishing Unit, Armidale
Dehority B A, Tirabasso P A and Grifo A P Jr 1989 Most-probable- number procedures for enumerating ruminal bacteria, including the simultaneous estimation of total and cellulolytic numbers in one medium. Applied and Environmental Microbiology 55:2789-2792
Demeyer D I and Van Nevel C J 1979 Protein fermentation and growth of rumen microbes. Annales de Recherches Veterinaires 10:275-279
Eadie J M and Hobson P N 1962 Effect of presence or absence of ciliates on the total rumen bacterial count in lambs. Nature 193:503-505
FAO 1986 Better Utilization of Crop Residues and By-products in Animal Feeding: Research Guidelines. 2. A Practical Manual for Research Workers. FAO, Rome, 154pp
Hsu J T, Fahey G C Jr, Berger L L, Mackie R I and Merchen N R 1991 Manipulation of nitrogen digestion by sheep using defaunation and various nitrogen supplementation regimens. Journal of Animal Science 69:1290-1299
Hungate R E 1966 The Rumen and Its Microbes. Academic Press, New York
Jouany J P and Senaud J 1979 Role of rumen protozoa in the digestion of food cellulosic materials. Annales de Recherches Veterinaires 10:261-263
Leng R A 1990 Factors affecting the utilization of poor-quality forages by ruminants particularly under tropical conditions. Nutrition Research Reviews 3:27-91
Lu C D and Jorgensen N A 1987 Alfalfa saponins affect site and extent of nutrient digestion in ruminants. Journal of Nutrition 117:919-927
Mehrez A Z, Orskov E R and McDonald I 1977 Rates of rumen fermentation in relation to ammonia concentrations. British Journal of Nutrition 38:437-443
Minson D J 1981 Nutritional differences between tropical and temperate pastures. IN: Grazing Animals (Ed. F H W Morley), pp143-157. Elsevier, Amsterdam
Obispo N E 1990 Most-Probable-Number method for enumeration of rumen fungi with studies on factors affecting numbers in the rumen. MSc Thesis. The Ohio State University. Ohio, USA. 64pp
Veira D M, Ivan M and Jui P Y 1983 Rumen ciliate protozoa: Effects on digestion in the stomach of sheep. Journal of Dairy Science 66:1015-1022
Weller R A and Pilgrim A F 1974 Passage of protozoa and volatile fatty acids from the rumen of the sheep and from continuos in vitro fermentation system. British Journal of Nutrition 32:341-351
(Received 6 August 1993)