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The Effects of Different Fractions of Yucca Plant Extract (De-Odorase) on the Fermentation of Hay in Ovine Ruminal Fluid In Vitro
J. Philip Ryan, PhD
Teresa Quinn, BSc
Joann Mullally, MSc
Barry F. Leek, BVM, PhD, MRCVS
Department of Veterinary Physiology and Biochemistry, Faculty of Veterinary Medicine, University College Dublin, Belfield, Dublin 4, Ireland
KEY WORDS: Yucca shidigera plant extract, saponin and glyco-fractions, ruminal fluid, pH, ammonia, SCFA
Yucca shidigera plant extracts contains both a glyco-fraction and a saponin fraction. The beneficial effects of yucca plant extracts in ruminants have been attributed to their ability to bind ammonia and enhance ruminal fermentation. The ammonia-binding ability of the extract is associated with the glyco-fraction. The extract has also been shown to increase short chain fatty acid (SCFA) production during fermentation of hay in ruminal fluid in vitro. This study was carried out to determine which fractions of the extract are responsible for these effects on ruminal fermentation. The effects of a commercial extract, De-Odorase (Alltech Ireland Ltd. Dunboyne, Co. Meath, Ireland), were compared with the saponin-free glyco-fraction and the saponin fraction of De-Odorase. Samples were analyzed for pH, ammonia, and SCFA (mmol/L). Significant differences were determined using the Student paired two-tailed t-test. The effects on pH were very slight. The saponin fraction significantly decreased the pH (P <0.05). Neither De-Odorase nor any of the fractions tested had significant effects on ruminal ammonia levels. Both the saponin fraction (P <0.01) and glyco-fraction of De-Odorase (P <0.05) were found to enhance SCFA production to a similar extent as De-Odorase itself (P <0.001). This suggests that they work through a common mechanism and consequently do not have an additive effect.
Yucca shidigera plant extracts are routinely used in pig and poultry systems to reduce ammonia arising from decomposing manure in storage lagoons. A number of studies in vitro and in vivo1–3 have shown that yucca extracts can decrease ruminal ammonia levels and increase short chain fatty acid (SCFA) production. There are 2 fractions of yucca extracts that might affect ammonia metabolism in the rumen, namely a glyco-fraction (a mixed complex carbohydrate system) which binds ammonia 3 and a steroidal saponin fraction.4 On the basis of ammonia-binding estimations by Wallace5 and Leek,6 the effect of the glyco-fraction would not be expected to be significant at normal ruminal ammonia concentrations so it is difficult to explain the observed enhancement of livestock performance, particularly in ruminants, in terms of this effect alone. On the other hand, the saponins in yucca extracts might indirectly affect ammonia concentrations because of their toxicity to bacteria and ruminal ciliate protozoa.5 Ryan et al.2,3 observed a decrease in pH together with a marked increase in the level of SCFA in samples treated with De-Odorase (Alltech Ireland Ltd. Dunboyne, Co., Meath, Ireland), and they attributed much of the benefits to this effect. This study was carried out to determine which fractions of the extract are responsible for these effects on ruminal fermentation. The effects of the extract, De-Odorase, were compared with the saponin-free glyco-fraction of De-Odorase and the saponin fraction itself.
MATERIALS and METHODS
Dry De-Odorase and the glyco-fraction (liquid saponin-free De-Odorase) were supplied by Alltech Ireland Ltd. The amount of De-Odorase added was 100 mg/L. The amount of glyco-fraction added was 300 ml/L, which is equivalent to 100 mg/L saponin-free yucca extract solids.
The saponin fraction was extracted from the dry De-Odorase as follows: De-Odorase (20 g) was mixed thoroughly in approximately 75 mL butanol and the supernatant decanted. The procedure was repeated 3 times and the solution pooled. The butanol was then evaporated at 50˚C and the residue redissolved in 20 mL distilled water. The amount of saponin fraction added was 200 ml/L, which is equivalent to the saponin content of 100 mg/L De-Odorase.
For the ammonia-binding studies, artificial saliva buffered at pH 7.0 containing 350 mmol/L ammonium chloride, with or without fractions when indicated, were incubated at 39˚C. Samples were taken for analysis at zero time and after 24 hours and 48 hours.
The effects of the fractions on ruminal fermentation were compared using the in vitro technique as previously described by Ryan.7 During the fermentation, 50-mL aliquots of each solution were placed in small polypropylene fermenters containing 0.8 g of milled hay and incubated at 39˚C with or without fractions as indicated. Samples were taken for analysis at zero time and after 24 hours.
Ammonia was determined using an enzymatic UV-method (Boehringer Ingelheim harm Gmbh & Co, Ingelheim, Germany).
The pH of ruminal fluid samples was determined using a pH Meter with a Russell pH Combination Electrode (Russell pH Ltd. Fife, Scotland, UK).
Short chain fatty acids in ruminal fluid were determined using a Unicam 610 Gas Chromatograph with a Chromosorb-101 column (SGE Europe Kiln Farm, Milton Keynes, UK).
The F-test was used to test the overall significance between treatments and the Student two-tailed t-test was used to test the significance of mean differences between the controls and each treatment.
RESULTS and DISCUSSION
Effect of De-Odorase Fractions on Ammonia Binding
The effects of various fractions of the yucca plant extract on ammonia binding were compared in artificial saliva buffer as shown in Table 1. Saponin-free De-Odorase, which contains the natural glyco-fraction, bound the most ammonia, whereas saponins extracted from De-Odorase have been shown to have no ammonia-binding activity.3 As shown in Table 1, 200 ml/L saponin fraction bound no ammonia after 24 hours and only a negligible amount (22 mmol/L) after 48 hours, from a standard 350 mmol/L ammonium chloride solution. A decrease of 139 mmol/L in ammonia was found in the glyco-fraction solution buffered with artificial saliva (pH 7.0 rising to 8.1) after 48 hours. This is comparable to the ammonia binding found by Quinn and Leek8 under slightly different conditions. Furthermore, Leek6 showed that ammonia binding was independent of initial ammonia concentration.
Effect of De-Odorase Fractions on Ruminal Fermentation
The effects of De-Odorase and its fractions on ruminal fermentation in vitro are summarized in Table 2. The ammonia levels were all slightly decreased. However, the decreases were nonsignificant. In our previous work,2 it was shown that after 24 hours incubation with De-Odorase (100 mg/L), ammonia was decreased from 13.6 to 13.0 mmol/L, and after 48 hours, the ammonia decreased from 17.0 to 15.6 mmol/L in vitro.
From our binding studies (Table 1), it could be concluded that reductions in ammonia cannot be attributed to ammonia binding by the glyco-fraction. However, the antibacterial and antiprotozoal activity of the saponin fraction5 could lead to the observed reduction in ammonia levels. Suppression of the peptidolytic microbial population could decrease the fermentation of dietary protein, thereby reducing ruminal ammonia levels. Decreased predation of bacteria by protozoa could also lead to lowered ruminal ammonia levels.
Similar increases in total SCFA occurred with De-Odorase (P <0.001), saponin-free De-Odorase (P <0.05), and the saponin fraction (P <0.01). In each case, these changes were accompanied by nonsignificant slight decreases in the acetate:propionate ratios. Several authors have reported that yucca extracts specifically increase fiber degradation.9,10 Increases in dry matter degradation should lead to enhanced SCFA production as found in this study. Ryan et al.3 suggested that the enhanced degradation could be the result of the surfactant properties of the saponin fraction in De-Odorase. Initially, increased wetting of the feedstuffs could encourage greater microbial adhesion, leading to improved fiber degradation. In the long-term, this could lead to enhanced proliferation of the microbial population, particularly the cellulolytic bacteria. Although this could account for the effect of De-Odorase and its saponin fraction, it does not explain the effect of glyco-fraction in enhancing SCFA production. Because both the saponin fraction and glyco-fraction of De-Odorase were found to enhance SCFA production to a similar extent as De-Odorase itself, and do not show an additive effect, this suggests that they work through a common mechanism.
The authors thank Alltech Ireland Ltd., Dunboyne, Co. Meath, Ireland, for supplying samples of standard De-Odorase and saponin-free De-Odorase for this study.
1. Gibson ML, Preston RL, Pritchard RH, et al: Effect of sarsaponin and monensin on ruminal ammonia levels and in vitro dry matter digestibilities. J Anim Sci 61:492, 1985.
2. Ryan JP, Quinn T, Leek BF: Comparison of the effects of Yucca shidigera plant extract and Saccharomyces cerevisiae yeast culture on pH, short chain fatty acids and ammonium, during fermentation of hay by sheep’s ruminal fluid in vitro. Irish Vet J 50:422–429, 1997.
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10. Valdez FR, Bush LJ, Goetsch AL, et al: Effect of steroidal sapogenins on ruminal fermentation and on production of lactating dairy cows. J Dairy Sci 69:1568–1575, 1986.
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TABLE 1. Ammonia
Binding to Various Fractions
(mmol/L) Ammonia binding
24 hours 48 hours
De-Odorase (200 ml/L)
Each value represents the mean of 3 experiments.
The International Journal of Applied Research in Veterinary Medicine • Vol. 1, No. 2, Spring 2003
Table 2. Effect of Various Fractions of De-Odorase on Ruminal Fermentation of Hay In Vitro
± 0.03 6.21
± 0.02NS 6.20 ± 0.03* 6.20 ± 0.03NS
8.2 ± 0.5NS 8.3
± 0.6NS 8.4 ± 0.5NS
Total SCFA (mmol/L)
71.4 ± 3.3‡ 72.2
± 3.6† 71.2 ± 3.4*
4.31 ± 0.34 4.24 ± 0.32NS 4.24 ± 0.35NS 4.23 ± 0.36NS
Each value represents
the mean ± standard error of mean of observations from 8 sheep.
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