Effects of dietary inclusion of natural zeolite and flaxseed on broiler chickens’ body fat deposition in an extended fattening period
Einfluss von natürlichem Zeolite und Flachssaat im Futter auf die Fetteinlagerung beim Broiler bei verlängerter Mast
Efterpi V. Christaki, Panagiota C. Florou- Paneri, P. D. Fortomaris, Angeliki S. Tserveni- Gousi and A. L. Yan- nakopoulos
Department of Animal Production, Ichthyology, Ecology and Protection of the Environment, School of Veterinary Medicine, Aristotle University of Thessalon- iki, Thessaloniki, Greece
Manuskript eingegangen am 22. Dezember 2004, angenommen am 26. Februar 2005
Introduction
Zeolites occur in nature in specific kinds of rocks, mostly of volcanic origin (DONGARE and SABDE, 1996). They are com- posed of a negatively charged crystalline hydrated alumi- no- silicate framework, including alkali and alkaline earth counter cations along with small amounts of various other elements (MUMPTON and FISHMAN, 1977). Because of their three- dimensional pore structure, zeolites are able to ab- sorb and trap molecules of proper size, analogous to a sieve, as well as selectively release, specific molecules by ion exchange (SHURSON et al., 1984). Zeolites are either natural or synthetic in origin having quite different compo- sitions and therefore different physical properties (ELLIOT
and EDWARDS, 1991). Evidence in the literature suggests that there is a growth promoting effect when zeolites are used as additives in animal nutrition (SWEENY et al., 1979;
HEMKEN et al., 1984; OLVER, 1997; POND, 1984; BERGERO et al., 1997; POULSEN and OKSBIERG, 1995; TSERVENI-GOUSI et al., 1995; YANNAKOPOULOS et al., 1995; TSERVENI-GOUSI et al., 1997; YANNAKOPOULOS et al., 2000; CHRISTAKI et al., 2001). It should be mentioned here that zeolites per se have no nu- tritive value and the minerals they contain are not digesti- ble. The beneficial effects of their addition to animal ra- tions should be ascribed to the facilitation of digestion by slowing the passage of the digesta through the digestive tract (EVANS and FARRELL, 1993; OLVER, 1997).
Flaxseed or linseed (Linum usitatissimum L.) is grown in the Northern United States and Southern Canada, and it is cultured as a source of linseed oil. There are studies on the addition of flaxseed in broiler chickens diets and most of them are related to birds performance or to the effects on the fatty acid composition of the broiler meat (AJUYAH et al., 1991; LEE et al., 1991; ROTH-MAIER and KIRCHGESSNER, 1995; RODRIGUEZ et al., 2001; ALZUETA et al., 2003). Flax- seed is a potentially valuable source of energy, protein and α- linolenic acid (LNA). There is evidence that LNA (C18:
3, n-3) has beneficial effects on human health, and parti- cularly in vascular disorders prevention (HARRIS, 1997), or
in early neural development (UAUY et al., 1996). Hence, the need for increase in the LNA and the other unsaturated fatty acids in foods of animal origin for human consump- tion has been emphasized (DEPARTMENTOF HEALTH NUTRI-
TIONAL ASPECTS, LONDON, 1994).
By changing the fatty acid content in broilers’ diets, the fatty acid composition of the broiler meat produced can be modified (YAU et al., 1991; CRESPO and ESTEVE-GARCIA, 2001). However, there are still very few studies about the effects of dietary fat saturation on body fat deposition in broiler chickens, although the lipid deposition control is an issue matter of particular research interest in poultry meat production (FISHER, 1984; HERMIER, 1997). It has been shown that the incorporation of saturated fatty acids in broilers’ diets results in higher intra- muscular and abdo- minal fat accumulation in comparison to the incorporation of unsaturated fatty acids (SANZ et al., 1999; CRESPO and ES-
TEVE-GARCIA, 2001).
The objective of the present study was to investigate the effect of the dietary inclusion of natural zeolite (a clinopti- lolite- rich tuff) in combination to flaxseed (source of po- lyunsaturated fatty acids), on body fat deposition of broiler chickens in an extended fattening period.
Materials and Methods Zeolite and flaxseed
The natural zeolite (NZ) used in this study was obtained from Metaxades, a territory in Northern Greece. Its miner- alogical composition was determined by the X- ray Diffrac- tion (XRD) analysis (TSERVENI-GOUSI et al., 1997) as fol- lows: Clinoptilolite 60%, Clay minerals 12%, Cristobalite 10%, Feldspars 8%, Micas 5%, Quartz 5%, and traces of Moissanite, Ilmenite and Amphibole. Recently, it has been registered, in accordance to the 70/524 EEC Directive, as a feed additive (COMMISSION REGULATION 1245, 1999).
Flaxseed is used in animal nutrition either in grounded form or after procession (mechanical expellers, solvent ex- traction), which is made in order to separate the oil from the residual flaxseed meal. The grounded flaxseed (FX) used in the present study was analyzed for its chemical composition using the standards procedures of AOAC (AOAC, 1990). The chemical analysis of FX had as follows:
Crude protein 220.0 g/ kg, Crude fat 340.0 g/ kg, Crude fiber 65.0 g/ kg, Total lysine 9.2 g/ kg, Total methionine and cystine 7.7 g/ kg, Calcium 2.5 g/ kg, Total phospho- rous 5.0 g/ kg and Metabolisable Energy 16.55 MJ/ kg.
Experimental study
Sixty, a day- old, broiler chickens of both sexes from a com- mercial strain (Ross 308) were used. The birds were indi- vidually weighed and were randomly allocated into five treatments (A, B, C, D, and E) of twelve (six females and six males) birds each, according to the experimental diets used. In each treatment three replicates (four birds- two fe- males and two males, per replicate) were ensured by the use of especially designed floor pens covered with straw.
Broilers in treatment A, served as control, were fed a com- mercial diet. In treatments B and C the birds were fed diets contained 3% and 10% FX, respectively, while in treat- ments D and E they were fed diets containing 3% FX plus 2% NZ and 10% FX plus 2% NZ, respectively. Diets were all-mash and were fed from the beginning in all the exper- imental groups. Diets, consisted mainly of maize and soya- bean, were isonitrogenous and isoenergetic and were for- mulated according to the National Research Council (NRC, 1994) nutrient requirements (Table 1). The experiment lasted for ten weeks in order to obtain the greatest lipid deposition in broilers’ carcasses. Food and water were available in broilers, for ad libitum consumption through- out the experimental period. The experimental room was ventilated throughout the experimental period and artifi- cial light was continuously provided. At the end of the ex-
periment all broilers were weighed individually, starved for 12 h and then slaughtered. Abdominal fat pad, from the proventriculus surrounding down to the cloaka (CAHANER
et al., 1986), as well as breast and thigh meat were dissect- ed and weighed (UIJTTENBOOGART and GERRITS, 1982). The total fat content in twin samples (10 g) of breast and thigh meat was determined according to the AOAC procedures (AOAC, 1990). The remaining quantities of both breast and thigh meat were mixed and homogenized. For the determi- nation of the LNA content (%) in the total lipids of breast and thigh meat fat was extracted form the homogenous mixture (FOLCH et al., 1957) and methylated using a mix- ture of boron-trifluoride, hexane and methanol (MORRISON and SMITH, 1964) for gas chromatographic identification (5890 Hewlett- Packard gas chromatographer). Retention time was compared by the use of standard solution for LNA (Sigma Chemical Co Ltd, Poole, UK). All data were ana- lyzed by the analysis of variance (Statistix for Windows, version 7.0). Means were compared by the LSD test.
Results and Discussion
In this study the extended fattening period resulted in dif- ferences in almost all the measured traits among broilers of different sex. Male broiler chickens were heavier and de-
Table1.Composition and contents of nutrients of experimental diets Zusammensetzung und Nährstoffgehalte der Versuchsrationen
Ingredients (g/ kg) Treatments
A B C D E
Maize, grains 473.9 462.2 434.0 432.3 406.9
Soyabean meal (44% protein) 303.2 289.7 258.3 303.4 272.7
Poultry fat 56.9 52.1 41.4 65.0 53.5
Yeast 25.0 25.0 25.0 25.0 25.0
Maize gluten feed 100.0 100.0 100.0 83.4 80.7
Flaxseed, ground - 30.0 100.0 30.0 100.0
Zeolite (clinoptilolite) - - - 20.0 20.0
Avatec (15 in lasalocid) 0.5 0.5 0.5 0.5 0.5
Limestone, pulverized (37% in Ca) 12.7 12.8 12.8 14.6 12.5
Dicalcium phosphate (24% in Ca, 18% in P) 14.4 14.2 13.7 12.5 14.1
Sodium chroride iodized 3.3 3.3 3.3 3.3 3.3
Natuphos (phosphatase) 0.1 0.1 0.1 0.1 0.1
Endox (antioxidant) 0.1 0.1 0.1 0.1 0.1
Choline chloride 0.6 0.6 0.6 0.6 0.6
Biolysine 3.1 3.4 4.1 3.0 3.6
DL- Methionine 2.3 2.3 2.3 2.4 2.4
Vitamin premix1 0.1 0.1 0.1 0.1 0.1
Trace minerals premix2 0.1 0.1 0.1 0.1 0.1
Calculated analysis
Metabolisable Energy – ME (MJ/ kg) 12.97 12.97 12.97 12.97 12.97
Crude protein (g/ kg) 206.0 206.0 206.0 206.0 206.0
Lysine (g/ kg) 12.2 12.2 12.2 12.2 12.2
Methionine- cystine (g/ kg) 9.5 9.5 9.5 9.5 9.5
Calcium (g/ kg) 9.3 9.3 9.3 9.3 9.3
Total Phosphorus (g/ kg) 6.6 6.6 6.6 6.6 6.6
1Supplying per kg of feed: 4.82 mg all-trans retinol acetate, 0.625 cholecalciferol, 80 mg a-tocopheryl acetate, 3 mg menadione sodium bisul- phite, 1 mg thiamin hydrochloride, 5 mg riboflavin, 3 mg pyridoxine hydrochloride, 0.02 mg cyanocobalamin, 30 mg niacin, 10 mg pan- tothenic acid, 0.8 mg folic acid, 0.15 mg biotin, 10 mg ascorbic acid, and 480 mg choline chloride.
2Supplying per kg of feed: 100 mg Zn, 120 mg Mn, 30 mg Fe, 15 mg Cu, 0.2 mg Co, 1 mg I, and 0.3 mg Se.
posited less abdominal fat compared to the female ones.
There are many studies in the literature to support this finding (see e.g. SANZ et al., 1999), but this effect is beyond the scope of this paper. The interaction treatment x sex was not significant nor was the replicate effect. For this reason the specific means related to broilers sex and replicates used, are no further discussed.
Initial body weight, final body weight and the average weights of breast meat, thigh meat and abdominal fat pad according to treatment are shown in Table 2. There were not any significant differences on the initial body weight and the final body weight as well as the breast meat weight between different treatments. The combination of NZ and FX increased thigh meat weight (P<0.05) into the treat- ment E compared to treatment C. Abdominal fat pad weight in treatments B and C (dietary FX inclusion) and in treatments D and E (NZ and FX combination) was signifi- cantly lower in comparison to the control treatment. Die- tary fatty acids play an important role in lipid deposition in broilers. LEYTON et al. (1987) suggested that polyunsatura- ted fatty acids lead high-energy absorption because of their faster in vivo oxidation than saturated fatty acids. Accor- ding to CRESPO and ESTEVE-GARCIA (2001), such differences can be ascribed to the inhibition of lipogenesis or to the re- distribution of lipids in body lipid stores.
Significant (P<0.001) differences were also observed between treatments B and D and treatments C and E, re- spectively. Mean values of abdominal fat pad weight were 51.0 g and 33.7 g, for treatments B and D, and 44.5 g and 35.5 g for treatments C and E, respectively. The reduction on the abdominal fat pad weight in treatments where FX was added into the diet (diets B and C) was 20.6% and 30.7%, respectively, compared to the control group. Simi- larly, in treatments where NZ was involved the reduction was even higher ranging to the level of 47.5% for treatment D and 44.7% for treatment E when compared to the con- trol group. Given that there was no differences in the die- tary ME levels between treatments, the variation in the ab- dominal fat pad content can be attributed to the different metabolic use of the dietary fat sources (SANZ et al., 1999).
Broilers fed FX, which contains more unsaturated fatty acids, deposited less abdominal fat pad compared to those fed the control diet which contained more saturated fatty acids. This is in agreement to the findings of KEREN-ZVI et al. (1990) and SANZ et al. (1999) who reported significant decrease in abdominal fat pad weight by the increase of the dietary vegetable oils levels. CRESPO and ESTEVE-GARCIA
(2001), reported that polyunsaturated fatty acids produce lower abdominal fat pad deposition compared to saturated or monounsaturated fatty acids.
Furthermore, there was a significant difference between treatments B and C in abdominal fat pad weight (51.0 g vs 44.5 g) and this should be ascribed to the difference in the dietary FX level. Interestingly this trend was not observed in the treatments where NZ was included suggesting that the inclusion on NZ enhances the reduction of the abdo- minal fat pad weight regardless of the source of dietary fat.
However, there is a lack of relevant studies in the literature and more systematic research is needed in this filed to cla- rify the physiological mechanism(s) responsible for such differences in fat accumulation when NZ is involved.
Since less abdominal fat pad in heavier thigh meat was observed, the regression analysis results (Table 3) were helpful in demonstrating the negative relationship bet- ween thigh meat weight and abdominal fat pad weight (r=
- 0.5319, P<0.05). Abdominal fat pad, containing about 15% of the total body lipids, represents the largest fat de- posit in broiler chickens (LEESON and SUMMERS, 1980). Re- duction of the abdominal fat pad can affect broiler meat quality and the leaner meat is more preferable by consu- mers (FISHER, 1984; HERMIER, 1997).
In order to evaluate whether the experimental diets affec- ted other body lipid stores, the intramuscular fat content of breast and thigh meat was estimated (Table 4). The results suggest that the fat content of the breast meat was lower into the experimental treatments compared to the control one, and this content was even lower to the treatments where NZ was involved. The same trend was observed in the intramus- cular fat content of the thigh meat. Similar results have been reported from CHRISTAKI et al. (2001), when NZ was incorpo- rated in broilers rations at levels of 2% or 4%. Furthermore, Table2.Initial body weight (IBW), final body weight (FBW) in broiler chickens and breast meat weight (BMW), thigh meat weight (TMW) and abdominal fat pad weight (AFPW) in broiler chickens carcasses (n=12 per treatment)
Kükengewichte (IBW) und Mastendgewichte (FBW) der Broiler sowie Gewichte von Brustfleisch (BMW), Schenkelfleisch (TMW) und Ab- dominalfett (AFPW) am Schlachtkörper
Treatments
A B C D E SEM Effect
IBW (g) 42.7 a 44.5 a 42.8 a 42.9 a 43.7 a 0.81 NS
FBW (g) 3900.0 a 4333.3 a 4191.7 a 4058.3 a 3975.0 a 188.4 NS
BMW (g) 882.3 a 937.6 a 857.5 a 866.0 a 987.0 a 51.7 NS
TMW (g) 724.5 a, c 693.0 a, c 671.6 b, c 764.8 a, c 807.7 a 41.1 *
AFPW (g) 64.2 a 51.0 b 44.5 c 33.7 d 35.5 d 1.21 ***
a, b, c, d Means in rows with the same superscript do not differ significantly (P>0.05)
* P<0.05
*** P<0.001
Table3.Regression equations between breast (BM) and thigh (TM) meat weight and abdominal fat pad (AFP) weight Regressionen zwischen Brustfleisch- (BM) sowie Schenkelfleisch- gewicht (TM) und dem Gewicht des Abdominalfettes
Dependent Equation r Effect
Y (AFP) 86.0146 - 0.441859 X (BM) -0.1929 NS Y (AFP) 135.4255 - 0.122217 X (TM) -0.5319 *
* P<0.05
the LNA content in the total fat of breast and thigh meat pro- spectively increased in treatments where FX was involved (treatments B, C, D and E) and this is consistent to the fin- dings reported by GONZALEZ-ESQUERA and LEESON (2000) and CRESPO and ESTEVE-GARCIA (2001). Between treatments com- parison, no significant differences were found in treatments B and D and treatments C and E suggesting that the inclusion of NZ did not affect the LNA content of the broiler meat.
Conclusions
It has been demonstrated that dietary fatty acid profile plays an important role in lipid deposition. This study also showed that the dietary inclusion of natural zeolite com- bined to flaxseed resulted in abdominal fat pad reduction and in a beneficial body fat deposition in broiler chickens.
The expectation is that the addition of natural zeolite into the diets of broiler chickens would have beneficial effect in fat deposition with respect to the dietary fat sources and, hence, there is a need for further research to understand and clarify the mechanism(s) involved.
Summary
The effect of the dietary inclusion of natural zeolite (a clinoptilolite- rich tuff) and flaxseed on body fat deposition was assessed. Sixty broiler chickens, from a commercial strain (Ross) were randomly allocated into five treatments (A, B, C, D, and E) according to the experimental diets used (n=12 birds per treatment). In treatment A, served as control, a commercial diet was used. In treatments B and C the birds were fed diets contained 3% and 10% flaxseed, respectively. In treatments D and E the broilers were fed diets containing 3% flaxseed plus 2% natural zeolite and 10% flaxseed plus 2% natural zeolite, respectively. All diets, consisting mainly of maize and soyabean, were iso- nitrogenous and isoenergetic. The experiment lasted for ten weeks. At the end of the experiment the abdominal fat pad and the breast and thigh meat were dissected and weighed. Total fat content of breast and thigh meat as well as the α-linolenic acid content in the total lipids of breast and thigh meat were determined.
The addition of the natural zeolite resulted in a signifi- cant increase on thigh meat weight. Furthermore, abdo- minal fat pad was significantly reduced in treatments where natural zeolite was added in the diets. The results
from this study suggest that the dietary inclusion of natural zeolite and flaxseed in broiler chickens has a beneficial ef- fect on body fat deposition.
Key words
Broiler, nutrition, natural zeolite, flaxseed, body fat depo- sition, extended fattening period
Zusammenfassung
Einfluss von natürlichem Zeolite und Flachssaat im Futter auf die Fetteinlagerung beim Broiler bei ver- längerter Mast
In der vorliegenden Studie wurde der Einfluss von natürli- chem Zeolite (einem Clinoptilolit reichem Gestein) und Flachssaat im Futter auf die Fetteinlagerung von Broilern untersucht. Hierzu wurden 60 Broiler einer kommerziellen Herkunft (Ross) zufällig auf die 5 Behandlungen (A, B, C, D, E) verteilt. Behandlung A diente als Kontrolle. Hier wur- de eine kommerzielle Ration eingesetzt. In den Behand- lungen B und C enthielten die Rationen 3 bzw. 10% Flachs- saat. Die Behandlung D erhielt ein Futter mit 3% Flachs- saat und 2% Zeolite, die Behandlung E mit 10% Flachssaat und 2% Zeolite. Alle Rationen enthielten in erster Linie Mais und Sojaschrot und wurden auf isoenergetischer und isonitrogener Basis kalkuliert. Der Versuch dauerte 10 Wo- chen. Am Versuchsende wurden die Tiere geschlachtet und die Menge an Abdominalfett, Brust- und Schenkelfleisch bestimmt. Bei Brust- und Schenkelfleisch wurde der Ge- samtfettgehalt sowie der Gehalt an α-Linolensäure in den Gesamtlipiden ermittelt.
Die Zugabe von natürlichem Zeolite führte zu einer sig- nifikant größeren Brustfleischmenge. Ferner war beim Zu- satz von natürlichem Zeolite das Abdominalfett signifikant vermindert. Die Ergebnisse deuten darauf hin, dass der Zu- satz von natürlichem Zeolite und Flachssaat zum Futter ei- nen günstigen Einfluss auf die Fetteinlagerung in den Schlachtkörper von Broilern hat.
Stichworte
Broiler, Fütterung, natürliches Zeolite, Flachssaat, Fettein- lagerung, verlängerte Mast
Table4.Intramuscular fat content of breast (BMF) and thigh meat (TMF), and LNA content of the total intramuscular fat of the mixture of breast and thigh meat in broiler chickens carcasses (n=12 per treatment)
Intramuskulärer Fettgehalt von Brust- (BMF) und Schenkelfleisch (TMF) sowie LNA-Gehalt im gesamten intramuskulären Fett von ge- mischtem Brust- und Schenkelfleisch der Broilerschlachtkörper
Treatments
A B C D E SEM Effect
BMF (%) 2.20 a 1.60 b 1.46 b 1.45 b 1.40 b 0.13 ***
TMF (%) 7.10 a 5.40 b 4.30 b, c 4.10 c, d 3.93 c, d 0.41 *
LNA (%) 1.01 a 2.95 b 5.10 c 2.70 b 5.30 c 0.21 ***
a, b, c Means in rows with the same superscript do not differ significantly (P>0.05)
*P<0.05
*** P<0.001
References
ASSOCIATION of OFFICIAL ANALYTICAL CHEMISTS, 1990: Official Methods of analysis (15th edn.). (Washington DC, AOAC).
AJUYAH, A.O., K. LEE, R.T. HARDIN and J.S. SIMS, 1991: Chang- es in the yield and in the fatty acid composition of whole carcass and selected meat portions of broiler chickens fed full-fat oilseeds. Poulr. Sci. 70, 2304-2314.
ALZUETA, C., M.L. RODRÍGUEZ, M.T. CUTULI, A. REBOLÉ, L.T. OR-
TIZ, C. CENTENO and J. TREVINO, 2003: Effect of whole and demucilaged linseed in broiler chicken diets on digesta viscosity, nutrient utilization and intestinal microflora.
Br. Poult. Sci. 44, 67-74.
BERGERO, D., G. RUMELLO, C. SARRA and A. D’ANGELO, 1997:
Effect of natural clinoptilolite or phillipsite in the feeding of lactating dairy cows. Proccedings of the Sofia Zeolite Meeting, G. KIROV, L. FILIGOVA, O. PETROV (Eds) pp. 67-72.
CAHANER, A., Z. NITSAN and I. NIR, 1986: Weight and fat con- tent of adipose and nonadipose tissue in broilers selected for and against abdominal adipose tissue. Poult. Sci. 65, 215-222.
CHRISTAKI, E., P. FLOROU-PANERI, A. TSERVENI-GOUSI, A. YANNA-
KOPOULOS and P. FORTOMARIS, 2001: Effects of dietary in- clusion of natural zeolite on broiler performance and car- cass characteristics. Proceedings of the 13th International Zeolite Conference, Montpellier, France, A. Galarneau, F.
Di Renzo, F. Fajula, J. Vedrime (Eds), pp. 373-379.
COMMISSION REGULATION, 1999: No 1245, 70/ 524/ EEC, 16 June 1999.
CRESPO, N. and E. ESTEVE-GARCIA, 2001: Dietary fatty acid profile modifies abdominal fat deposition in broiler chick- ens. Poult. Sci. 80, 71-78.
DEPARTMENTOF HEALTH NUTRITIONAL ASPECTSOFCARDIOVASCU-
LAR DISEASE, 1994: Report of the cardiovascular review group committee on medical aspects of food policy. Re- port on Health and Social Subjects, No 46 (London, De- partment of Health).
DONGARE, M.K. and D.P. SABDE, 1996: Zeolite a unique ma- terial for poultry industry. Proceedings of XX World’s Poultry Congress, New Delhi, India, Vol. II, pp. 377-385.
ELLIOT, M.A. and H.M. EDWARDS JR., 1991: Comparison of the effect of synthetic and natural zeolite on laying hen and broiler chicken performance. Poult. Sci. 70, 2115-2130.
EVANS, M. and D.J. FARRELL, 1993: Are there economic ben- efits to adding zeolites to poultry diets? in: FARRELL, D.J.
(Edt.) Recent advances in animal nutrition in Australia, Armidale, University of New England, pp. 303-316.
FISHER, C., 1984: Fat deposition in broilers, in: J. Wiseman (Ed.), Fats in Animal Nutrition (Nottingham, England:
Butterworths).
FOLCH, J., M. LEES and G.H.S. STANLEY, 1957: A simple meth- od for the isolation and purification of total lipid from an- imal tissues. J. Biolog. Chem. 226, 497-509.
GONZALEZ-Esquera, R. and S. LEESON, 2000: Effects of men- haden oil and flaxseed in broiler diets on sensory quality and lipid composition of poultry meat. Br. Poult. Sci. 41, 481-488.
HARRIS, W.S., 1997: n-3 fatty acids and serum lipoproteins:
human studies. Am. J. Clin. Nutr. 65, 1645S-1654S.
HEMKEN, R.W., R.J. HARMON and L.M. MANN, 1984: Effect of clinoptilolite on lactating dairy cows fed a diet containing urea as a source of protein, in: W.G. Pond and F.A. Mump- ton (Eds), Jeo Agriculture, Use of Natural Zeolites in Ag- riculture and Aquaculture, pp. 171- 176.
HERMIER, D., 1997: Lipoprotein metabolism and fattening in poultry. J. Nutr. 127, 805S-808S.
KEREN-ZVI, S., I. NIR, Z. NITSAN and A. CAHANER, 1990: Effect of dietary concentrations of fats and energy on fat depo- sition in broilers divergently selected for high or low ab-
dominal fat tissue. Br. Poult. Sci. 31, 507-516.
LEE, K., J.M.OLOMU and J.S. SIMS, 1991: Live performance, carcass yield, protein and energy retention of broiler chicken fed canola and flax full-fat seeds and the restored mixtures of meal and oil. Can. J. Anim. Sci. 71, 897-903.
LEESON, S. and J.D. SUMMERS, 1980: Production and carcass characteristics of the broiler chicken. Poult. Sci. 59, 786-978.
LEYTON, J., P.J. DRURY and M.A. CRAWJOED, 1987: Differential oxidation of saturated and unsaturated fatty acids in vivo in the rat. Br. J. Nutr. 57, 383-393.
MORRISON, W.R. and M.L. SMITH, 1964: Preparation of fatty acid methylesters and dimethylacetals from lipid with bo- ron fluoride methanol. J. Lipid Res. 5, 600-608.
MUMPTON, F.A. and P.H. FISHMAN, 1977: Application of nat- ural zeolites in animal-science and aquaculture. J. Anim.
Sci. 45, 1188-1203.
NRC, NATIONAL RESEARCH COUNCIL, 1994: Nutrient Require- ments of Poultry. Ninth Revised Edition, National Acad- emy Press, Washington, D.C., pp. 19-34.
OLVER, M.D., 1997: Effect of feeding clinoptilolite (zeolite) on the performance of three stains of laying hens. Br.
Poult. Sci. 38, 220-222.
POND, W.G., 1984: Response of growing lambs to clinoptilo- lite or zeolite NAA added to corn, corn-fish meal and corn-soybean meal diets. J. Anim. Sci. 59, 1320-1328.
POULSEN, H.D. and N. OKSBIERG, 1995: Effects of dietary in- clusion of a zeolite (clinoptilolite) on performance and protein metabolism of young growing pigs. Anim. Feed Sci. Techn. 53, 297-303.
RODRÍGUEZ, M.L, C. ALZUETA, A. REBOLÉ, L.T. ORTIZ, C. CENTENO
and J. TREVINO, 2001: Effect of inclusion level of linseed on the nutrient utilization of diets for growing broiler chickens. Br. Poult. Sci. 42, 368-375.
ROTH-MAIER, D.A and M. KIRCHGESSNER, 1995: Feeding of full-fat flaxseed and sunflower seed to fattening chicken.
Arch. Geflügel. 59, 319-322.
SANZ, M., A. FLORES, P. PEREZ DE AYALA and C.J. LOPEZ- BOTE, 1999: Higher lipid accumulation in broilers fed on satu- rated fats than those fed on unsaturated fats. Br. Poult.
Sci. 40, 95-101.
SHURSON, G.C., P.K. KU, E.R. MILLER and M.T. YOKOYAME, 1984: Effect of zeolite A or clinoptilolite in diets of grow- ing swine. J. Anim. Sci., 59, 1536-1545.
SWEENEY, T.F., L.S. BULL and R.W. HEMKEN, 1979: Effect of zeolite on ammonia availability and rumen microbial pro- tein-synthesis in vitro. J. Dairy Sci. 62, 209-209.
TSERVENI- GOUSI, A.S., A.L. YANNAKOPOULOS, N.K. KATSAOUNIS, A. FILIPPIDIS and A. KASSOLI-FOURNARAKI, 1997: Some inte- rior egg characteristics as influenced by addition of Greek Clinoptilolitic rock material in the hen diet. Arch. Geflü- gel. 61, 291-296.
TSERVENI-GOUSI, A.S, A.L. YANNAKOPOULOS, N.K. KATSAOUNIS, A. FILIPPIDIS, A. KASSOLI- FOURNARAKI and P. FORTOMARIS, 1995: Influence of Greek clinoptilolite bearing rocks on the egg-shell quality in the early stage of laying. Interna- tional Symposium and Exhibition of Natural zeolites, So- fia, Bulgaria. Extended Abstracts, pp. 118.
UAUY, R., P. PEIRANO, D. HOFFMAN, P. MENA, D. BIRCH and E.
BIRCH, 1996: Role of essential fatty acids in the function of the developing nervous system. Lipids 31, S167-S176.
UIJTTENBOOGART, T.G. and A.T. GERRITS, 1982: Method of dis- section of broiler carcasses and description of parts.
Spelderholt Report 370 (Beekbergen, The Netherlands).
YANNAKOPOULOS, A., A. TSERVENI-GOUSI, A. KASSOLI- FOURNAR-
AKI, A. TSIRAMBIDES, K. MICHAELIDIS, A. FILIPPIDIS and U. LU-
TAT, 2000: Effects of dietary clinoptilolite- rich tuff on the performance of growing- finishing pigs. in: C. COLELLA, F.A. MUMPTON (Eds), Natural Zeolites for the Third Mille-
nium, (De Frede, Napoli, Italy), pp. 471- 481.
YANNAKOPOULOS, A.L., A.S. TSERVENI-GOUSI, N.K. KATSAOUNIS, A. FILIPPIDIS, A. KASSOLI-FOURNARAKI and A. TSOLAKIDOU, 1995: The influence of Greek clinoptilolite bearing rocks on the performance of laying hens, in the early stage of laying. International Symposium and Exhibition of Nat- ural zeolites, Sofia, Bulgaria. Extended Abstracts, pp.
120.
YAU, J.C., J.H. DENTON, C.A. BAILEY and A.R. SAMS, 1991: Cus- tomizing the fatty acid content of broiler tissues. Poult.
Sci. 70, 167-172.
Correspondence: Dr P.D. Fortomaris, School of Veterinary Medicine, Aristotle University of Thessaloniki, 54124 Thessaloniki, Greece; e-mail:
fortomap@vet.auth.gr