Feed Additives - Vemo 99

The effect of tribulus terrestris extract on egg yolk lipids and serum cholesterol content in guinea fowls

S. Grigorova1, D. Abadjieva1, M. Nikolova2, D. Penkov2

1Institute of Animal Science, Kostinbrod, Bulgaria
2Agricultural University, Plovdiv, Bulgaria
Corresponding author: svet.grigorova@abv.bg
Original scientific paper


With the aim to establish the effect of the product Vemoherb PT (dry extract of Tribulus terrestris L) on egg yolk lipids and serum total cholesterol content, the trial was designed with 30 Pearl gray Guinea fowls, at the age of 32 weeks, randomly distributed in control and experimental groups, 12 female and 3 male each. All birds received the same mixture for breeder Guinea fowls. The tested product was added to the compound feed of the experimental group in a dose of 10 mg/kg body weight for a period of 12 weeks. The total lipids, phospholipids, cholesterol content, fatty acids composition in the egg yolk and serum total cholesterol content were determined at the end of the trial. The results from this study indicate that Vemoherb PT (dry extract from Bulgarian Tribulus terrestris) does not have any influence on the total lipids and phospholipids content in the egg yolk. The addition of 10mg/kg body weight of the tested product to the forage of Guinea fowls decreased significantly the serum cholesterol level (P<0.01) and the cholesterol content in the egg yolk (P<0.05). It was observed the increase the content of linoleic acid in the yolk (P=0.05) in treated birds in comparison with control group.

Key words: Tribulus terrestris, Guinea fowls, egg yolk, cholesterol content, fatty acids


The eggs are one of the main sources of cholesterol and long chain Omega 6 (from the family of linoleic acid (18:2(n-6)) and Omega 3 (from the family of linolenic acid (18:3(n-3)) polyunsaturated fatty acids (PUFA) in human nutrition. That’s why they are an object of intensive research aimed at decreasing yolk cholesterol level and eggs’ enriched with Omega 3 and Omega 6 fatty acids (the ratio of Omega 6 and Omega 3 fatty acids has a positive effect on the prevention and medical treatment of the cardio-vascular disorders) by the use of suitable poultry feeding - inclusion of feeds containing high levels of essential long chain PUFA like linseed, rapeseed, algae, plant oils and extracts (Filev et al., 2001a; Filev et al., 2001b; Profirov and Toncheva, 2005; Surdjiiska and Grigorova, 2005).

The extract of the prostrate annual herb Tribulus terrestris L. (Zygophilaceae) contains biological active substances like saponins of the furostanol type (protodioscin and protogracilin), flavonoids, unsaturated fatty acids, vitamins etc. (Kostova and Dinchev, 2005). It was established that the herb has a sizable antioxidative (Asenov et al., 1998) as well as blood cholesterol reductive effect (Chu et al., 2003). Grigorova at al. (2008a,b) observed a clear cut trend towards decline of total serum cholesterol in laying hens and broiler parents. However, they didn’t find any changes of eggs’ cholesterol content and yolk’s fatty acids profile. There are no data concerning the effect of this extract on blood and yolk cholesterol levels, fatty acids profile in other poultry species.
The aim of our study was to investigate how the Bulgarian product Vemoherb PT (dry extract of Tribulus terrestris), produced by firm “Vemo 99”, Sofia changes the serum total cholesterol level and yolk lipid fractions in Guinea fowls.

Materials and Methods

The present investigation was carried out in the period April - June – 2008 at the Experimental base of Agricultural University - Plovdiv with 30 Pearl gray Guinea fowls at the age of 32 weeks, raised under extensive conventional method of production on a deep litter pen. The poultry were randomly distributed in control and experimental groups, 12 females and 3 males in each. The trial lasted 13 weeks – one-week adaptation and 12 weeks experimental period. All birds received the same compound feed for breeder Guinea fowls (table1) .The nutritive value of the diet was determined by the conventional Weende method. To the experimental diet was added Vemoherb PT (dry extract of Tribulus terrestris L.), produced by Vemo Ltd, Sofia, Bulgaria in a dose of 10mg/kg body weight for a period of 12 weeks. Serum total cholesterol content was measured with Pentra 400, biochemical analyzer at the end of the trial. The blood was taken from vena cutanea ulnaris. The amounts of total lipids, total cholesterol, total phospholipids and fatty acid content of yolk were determined for 15 eggs from both control and experimental groups at the end of the treatment. The total lipids were measured by the method of Bligh and Dyer (1959). The method of Shoenheimer-Sperry (1950) modified by Sperry and Webb (1950) was used for yolk cholesterol determination. The content of total phospholipids in the yolk was measured by the method of Bartlett (Kates, 1975). The fatty acid percentage was determined using the “Perichrom” gas chromatograph with capillary column Supelcowax-10 (0.32 mm –30 m).

Table 1. Ingredient and chemical composition of for breeder Guinea fowls














The obtained results were statistically processed using Excel 2000, single factor, Anova program.


Results and Discussion

The data about the content of serum total cholesterol and yolk lipid fractions from the both groups is presented in Table 2. The serum total cholesterol level in experimental Guinea fowls is significant lower (P<0.01) in relation to the control group. Similar results have been reported by Chu et al. (2003) who established significant decline (P<0,001) of total cholesterol content in mice given Tribulus terrestris extract supplemented diet. Lirette et al. (1993) suppose that the saponins and flavonoids contained in the Tribulus terrestris block the enzyme systems which have a key role in cholesterol synthesis. This leads to inhibition of cholesterol intestinal absorption and to its reduction. The total yolk cholesterol level of the treated birds was significantly lower (P<0.05) relative to that in control birds. These results are consistent with the reported by Clarenburg et al. (1971) positive relation between plasma and yolk cholesterol levels. An alternative explanation of the observed lower yolk cholesterol level in treated Guinea fowls could be related with their higher egg laying intensity (P<0.05) in comparison with the control group. Yolk cholesterol level in experimental group was within the normal range in those poultry species.
(Bair and Marion, 1978).


Table 2. Level of total cholesterol in blood serum and yolk lipid fractions of Guinea fowl











Table. 3. Total fatty acid composition of egg yolk of Guinea fowl (mol%)

The results about yolk fatty acids composition in Guinea fowls from the both groups are showed in Table 3. The concentration of linolenic acid (18:3(n-3)) was significantly higher (P < 0.05) in yolk of experimental birds than that in control group. Grohn et al. (1992). Suppose, that linolenic acid and the others Omega 3 fatty acids are preferred for combine with the biological membranes by exhausting of Omega 6 fatty acids. The results from this study indicated that Tribulus terrestris extract does not have any influence on the concentration of the others yolk fatty acids. Grigorova et al. (2008a) reported similar data in eggs of broilers’ parent receiving the same dose Vemoherb PT (dry extract from Bulgarian Tribulus terrestris) with the diet, but without significant difference about linolenic acid concentration between eggs from the both groups.


According to the obtained results it can be concluded the following:

  • The addition of the tested product Vemoherb PT (Bulgarian Tribulus terrestris dry extract) to the compound feed of Guinea fowls in dose of 10 mg/kg body weight for period of 12 weeks decreased significantly (P<0.01) total serum cholesterol content and yolk cholesterol content (P<0.05).
  • Vemoherb PT (Bulgarian Tribulus terrestris dry extract) did not chance significantly (P>0.05) the level of total lipids and total phospholipids in the yolk.
  •  It was observed the increase of the content of linolenic acid in the yolk (P<0.05) in experimental birds in comparison with control group


We would like to thank Mr. Hristo Zlatev and Mrs. Nina Zlateva (Firm Vemo 99 Ltd, Sofia, Bulgaria) for providing the Vemoherb PT (Bulgarian Tribulus terrestris dry extract) that was used in this Investigation


1.ASENOV I.V., GUSEV C.H., KITANOV G., NIKOLOV S.T., PETKOV T. (1998): Herb collecting, Biller, pp. 368.
BAIR C.W., MARION W.W. (1978): Yolk cholesterol in eggs from various avian species. Poultry science, 57, 5, 1260-1265.
BLIGH E.C., DYER J. W. (1959): A rapid method of total lipid extraction and purification. Cnad. J. Biochem. Physiol., 37, 911-917.
2.CHU S., QU W., PANG X., SUN B., HUANG X. (2003): Effect of saponin from Tribulus terrestris on hyperlipidemia. Zhong Yao Ca, 26, 26, 341-344.
3.CLARENBURG R., CHUNG K.A.I., WAKENFIELD M.L. (1971): Reducing the egg cholesterol level by including emulsified sitosterol in standard chicken diet. J. Nutr., 101, 289-298.
4.FILEV K., RIZOVA V., GJORGOVSKA N., LALEV M., NIKODINOVSKI M. (2001a): Influence of margine alga Schyzochitrium sp. on the production of enriched eggs with long chain polyunsaturated fatty acid DNA. Symposium of Livestock Production with International Participation, Struga, Republic of
Macedonia, May 23-25, 135-140.
5.FILEV K., RIZOVA V., GJORGOVSKA N., LALEV M., NIKODINOVSKI M. (2001b): Enriching table eggs with DHA by using conventional feed ingredients in the feed mixtures of layers. Symposium of Livestock production with International participation, Struga, Republic of Macedonia.
6.GRIGOROVA S., KASHAMOV B., VASILEVA D., SREDKOVA V., SURDJIISKA S. (2008a): Investigation the effect of Tribulus terrestris extract on the egg yolk lipids and some biochemical parameters of egg and blood serum in broilers’ parent. Conference with International participation ‘ecology and Health, Plovdiv, April 9-10, 93-98.
SURDJIISKA S. (2008b): Investigation of Tribulus terrestris extract on the biochemical parameters of egg and blood serum in laying hens. Archiva Zootechnica, 11, 1, 39-45.
8.GROHN M., CHRISTENSEN F., HAGVE T., CHRISTOFERSON O. (1992): Effects of dietary purified eicosapentaenoic acid (20:5(n-3)) and docosahexaenoic acid (22:6(n-3)) on fatty acid desaturation and oxidation in isolated rat liver cells. Biochem Byophys. Acta, 11, 25, 35-43.
9.KATES M. (1975): Technics of Lipidology, Mir, Moskow.
KOSTOVA I., DINCHEV D. (2005): Saponins in Tribulus terrestris – chemistry and bioactivity. Phytochemistry Reviews, 4, 1, 111-137.
10.LIRETTE A., ROBINSON R.A., CROBER C.D., LAWSON D.P., FIRTH L.N. (1993): Effect of oat bran, cottonseed hulls and guar gum on chicken egg and blood lipids during the early laying period. Can. J. Anim Sci., 73, 673-677.
PROFIROV Y.A., TONCHEVA E. (2005): Effect of Oregano essential oil on egg yolk lipids of laying hens. Journal of Animal Science., XLII, 5, 180-182.
11.SPERRY W., WEBB M. (1950): A revision of the Scoenheimer-Sperry method for holesterol determination. J. Biol. Chem., 187, 97-101.
12.SURDJIISKA S., GRIGOROVA S. (2003): Modification of cholesterol content and Omega fatty aciuds content in the egg. Ptitzevudstvo, 12, 4, 8-9.