Effect of different levels and particle sizes of perlite on serum biochemical factors of broiler chicks

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Introduction
Perlite is an aluminosilicate volcanic rock which is made of rapid solidification of acidic magma.The volume of perlite rock increases from 4 to 20 times at temperature of about 860 to 1200°C and produces expanded perlite (Anonymous, 2006).As displayed in Figure 1, expanded perlite has porous texture which gives it unique characteristics.Perlite chemical composition is given in Table 1.
Aluminosilicates can be used as a feed additive to increase the absorption of cations, provide minerals in diets, improve the health of gastric tract and detoxificate aflatoxins (Anonymous, 2006).One of the recent applications of perlite is its usage in livestock and poultry feed industry.However, reports in this research area are scarce.Hence, a few studies about aluminum silicates, such as Zeolite, Bentonite and Clinoptilolite have been referred to.Due to the similarity of these materials and perlite, it is expected that perlite will have similar effect on broiler chick's feeding (Tatar, 2006).Lotfollahian et al. (2004) used two types of aluminosilicates and different levels of dietary calcium (Ca) and phosphorus (P) and *Corresponding author.E-mail: hrebadi@yahoo.com.obtained a significant increase in broilers' serum Ca.However, they did not observe any significant difference between experimental treatments for serum P. Ward et al. (1991) examining the role of aluminosilicates in broiler chicks diet, reported a reduction in serum Ca and P levels.On the other hand, Frost et al. (1992) investigated the effect of zeolite on serum Ca and P levels of Leghorn strain laying hens and concluded that the dietary intake of this substance did not have any significant role on the dependent variables under study.Furthermore, Santurio et al. (1999) reported that the use of bentonite in broilers diet did not have any major impact on the blood biochemical variables.
The objective of this study was to investigate the effects of different levels and particle sizes of perlite in diet, on serum biochemical characteristics of broiler chickens, with the aim of finding a cheap and plentiful substitution for mineral diet ingredients in comparison with other aluminosilicates.

Materials and methods
In this study, 280 day-old Ross 308 broiler chicks were allocated to seven treatments and four replications in a factorial design on the basis of randomized complete block design.Factors were particle  (Anonymous, 1993).size (1.5 and 3 mm) and levels (1, 3 and 5% of diet) of perlite.In addition, a treatment with no perlite was included as the control group.Therefore, experimental treatments consisted of seven treatments.In order to control the possible differences in environmental factors such as light, they were divided into four complete blocks and the treatments were randomly allocated to each block.The perlite used in this study was extracted from Azerbaijan perlite mine and its purity was proved by chemical analysis based on the recommendations of the relevant factory.At day 42, blood samples were randomly collected from two chickens per cage (experimental unit) and the remaining chickens were sent to slaughterhouse at day 49.serum levels of calcium (labtest method), phosphorus (basques-lustosa's method), magnesium (tonks' method), sodium (ion-selective method), potassium (ion-selective method) and chlorine (labtest method) were determined by commercial kits (labtest) using a clinical chemistry analyzer (au 5000 olympus, hamburg, germany).serum iron concentration was determined by colorimetric method with a commercial kit (boehringer mannheim) using an automatic analyzer (hitachi 911, boehringer mannheim, germany).energy and protein content of the diets were similar and they only differed for the levels and particle sizes of perlite.nutritional requirements of broiler chickens during the growing periods were balanced according to the tables of nutritional requirements of national research council (NRC) (1994) and were balanced by the user friendly feed formulation done again (uffda) software.the diets used in this research and supplied nutrients in starter and grower periods are given in table 2, respectively.analysis of variance and mean comparisons by duncan's new multiple range test (5% probability level) were performed using mstatc 11 and spss 16.0 softwares.performance traits such as body weight, body weigth gain and feed conversion rate were published elsewhere (ebadi et al., personal communication).

Results and Discussion
Statistical analysis of data obtained from blood serum biochemical examination (Table 3) indicated that different levels and particle sizes of perlite did not affect serum concentrations of calcium (Ca) and phosphorus (P).Ward et al. (1993) also, examining the effect of zeolite on broilers' blood elements, showed that adding this substance to diet, did not have any significant influence on blood serum Ca and P. Santurio et al. (1999) added 0.25 and 0.5% bentonite to dietary ration of broilers and did not observe significant change in blood calcium.Some other researchers also reported that using aluminosilicates in dietary rations had no effect on serum phosphorus levels of broiler chicks (Roland et al., 1990;Scheideler, 1993;and Dwyer et al., 1997).Scheideler (1993) found that adding an aluminosilicate substance called zeobrite reduced serum Ca in broiler chicks.Furthermore, Tatar (2006) added 2.5 and 5% perlite to broilers' diets and examined serum biochemical characteristics.It was found that despite a non-significant difference between treatments in terms of blood serum Ca, serum P increased when a diet containing 5% perlite was used.
In broilers' diets, decreased the Cl levels of blood serum.Scheideler (1993) in the study of effects of four diffe-rent types of aluminosilicates in diets impregnated by aflatoxin on serum characteristics of broilers, also indicated that regardless of the existence or lack of aflatoxin in the diet, aluminosilicate substance decreased the serum Cl level.
Based on the results of serum biochemical analysis (Table 3), it could be seen that the amount of serum † Supplying per kg food: 900 µg retinol, 15 µg cholecalciferol, 2 mg menadione sodium bisulphate, 2 mg thiamine, 5 mg riboflavin,15 mg calcium pantothenate,30 mg niacin: 3.5 mg pyridoxine, 0.2 mg biotin, 0.6 mg folic acid, 0.02 mg vitamin B12, 200 mg choline chloride.magnesium (Mg) and potassium (K) of broilers were influenced by the dietary perlite and the levels of these two elements reached the highest value by adding 3% perlite.Although in an investigation by Pond and Yen (1983), Mg level was not affected by the use of zeolite in swine's diets, Kayongo Male and Jia (1999) observed that adding zeolite to the diet, increased blood Mg of turkeys.Furthermore, according to the results of Santurio et al. (1999), serum Mg increased by feeding broilers with 0.25% bentonite.It seems that the Mg in the structure of perlite is absorbed from gastrointestinal tract of broilers which increases the serum content of Mg.In addition, perlite having ion exchange properties and the ability of bivalent cations absorption, increases blood Mg.Meanwhile, Rabo (1976) stated that aluminosilicates are thermodynamically unstable and tend to generate insoluble aluminate and soluble silicate in acidic and water environments and this transformation easily occurs in chicks' gastrointestinal tract with pH 5. It seems that in the condition of increasing dietary perlite level to 5%, silicate produced in the gastrointestinal tract, combines with Mg ions and prevents their absorption.Santurio et al. (1999) reported that adding 0.25% bentonite to the diet, caused an increase in blood K but the amounts more than 0.25% decreased blood K. Kleiner et al. (2000) in an investigation on the effects of aluminosilicates on serum biochemical characters, found that the use of these substances in diets of mice increased serum K.This seems to be due to the existence of K in aluminosilicates' structure and due to its In each column and for each factor, the numbers which are not marked with the same characters, are significantly different (P < 0.05).
absorption from the gastrointestinal tract.On the other hand, based on some studies, aluminosilicates used in diets had no effect on serum content of K of broiler chicks (Pond and Yen, 1983;Roland et al., 1993).None of the blood elements were influenced by the particle size of perlite (Table 3).Kasim and Edwards (2000) also reported that particle size of diet do not play any role on serum Ca and P in broilers.It is possible that the perlite structure is destroyed in the upper parts of the gastrointestinal tract, particularly the gizzard.Furthermore, only 7% of aluminosilicates appears unsolved, maintaining its primary structure in terminal parts of the digestive tract (Roland et al., 1993).
In conclusion, the results of the present research showed that adding 3% of perlite to diet increased the Mg and K content of serum.Overall, different levels and particle sizes of perlite did not have any major impact on the serum biochemical values in broilers.

Table 1 .
Chemical composition of perlite.

Table 2 .
Composition of the experimental diets in the experiment.

Table 3 .
Mean values of some serum biochemical parameters in 42-day old broiler chickens fed on diets containing different levels and particles sizes of perlite.