Evaluation of the ability of Saccharomyces cerevisiae and mannan oliosaccharides to ameliorate the adverse effects of aflatoxin B1 in broiler chickens

INTRODUCTION

Feed is the major input in poultry production. Supply of high quality feed is must to obtain optimum performance. Presence of mycotoxins in feed is one of the major constraints in maintain feed quality because the mycotoxins are widely present in feedstuffs around the world and may affect production even in very low concentration. The most widespread and in most studied group of mycotoxins, aflatoxins are of great concern in warm and humid climatic conditions like India (Singh et al., 2010). The occurrence of aflatoxins in agricultural commodities depends on region, season and the conditions under which particular crop is grown, harvested or stored. Singh et al. (2010) conducted a survey in Uttar Pradesh and reported that ninety per cent of the maize samples were found to be positive for aflatoxin B₁ and the values ranged from 0.00 to 0.80 ppm with an average of 0.14 ppm of aflatoxin B₁ . Aflatoxicosis in poultry causes listlessness, anorexia with lowered performance and increased mortality (Miazzo et al., 2000), anemia (Oguz et al., 2000), reduction of immune function (Oguz et al., 2003), hepatotoxicosis and haemorrhage (Ortatatli and Oguz, 2001). Thus, aflatoxins are deleterious to poultry and their contamination in feed is practically unavoidable (Coulombe et al., 2005). When contamination cannot be prevented, detoxification of aflatoxins is required while using contaminated feed. In-vitro studies showed an AFB₁ dose-dependent binding capacity of SC upto 77 per cent (Galvano et al., 2001). MOS derived from the cell wall of Saccharomyces cerevisiae was reported to have high binding capacity (95%) for aflatoxin (Mahesh and Devegowda, 1996). Therefore, the present study was undertaken to evaluate the ability of Saccharomyces cerevisiae and Mannan Oligosaccharides (MOS) in ameliorating the toxic effects of aflatoxin.

MATERIALS AND METHODS

Production and analysis of Aflatoxin

Aflatoxin was produced using the fungal strain Aspergillus flavus NRRL 6513 that was obtained from U.S Department of Agriculture, Illinois, U.S.A. To get the fresh spores, the culture was regularly subcultured on Potato Dextrose Agar (PDA) medium slants and stored at 5ºC. Aflatoxin was produced on maize substrate. Fermentation was carried out in batches as per the method described by Shotwell et al. (1966). The extraction and estimation of aflatoxin was done as per the procedure of Pons et al. (1966). Aqueous acetone was used for extraction of the toxin. Aflatoxin contents were finally quantified using a spectrophotometer.

Experimental design

Experimental design was completely randomized design (CRD). There were 10 dietary treatments. Each dietary treatment had 4 replicates and each replicate had 8 chicks. The experiment was conducted in broiler chickens from day-old to 6 weeks of age. The various dietary treatments were prepared by mixing the required quantity of adsorbents and mouldy maize to get the desired concentration of 300 ppb AFB₁. The MOS and SC were obtained from Kothari Fermentation and Biochem Limited, New Delhi (India).

Evaluation of the ability of Saccharomyces cerevisiae and mannan oliosaccharides to ameliorate the adverse effects of aflatoxin B1 in broiler chickens - Image 1

Biological experiment and analysis

Three hundred and twenty, day-old broiler chicks were obtained from experimental hatchery, CARI, Izatnagar and distributed randomly into 10 groups. All birds were reared under standard managemental conditions from 0-6 weeks. All birds were fed with broiler starter ration from 1-21 days and broiler finisher ration from 22 to 42 days. Weekly individual body weight and feed consumption of each group were recorded. The composition of broiler starter and broiler finisher rations are presented in Table 1.

The protein (AOAC, 1990) and calcium (Talapatra et al., 1940) contents were estimated, while the concentrations of lysine, methionine, available P and metabolizable energy values were calculated. Data were analyzed following completely randomized design following Snedechor and Cochran (1980). Differences among the treatments were determined with Duncan’s multiple range test (Duncan, 1955).

RESULTS AND DISCUSSION

Body weight gain (BWG)

The BWG at different weeks of age as influenced by various dietary treatments is given in Table 2. At first week of age, the BWG did not differ statistically (P<0.05) among various dietary treatments. Significant (P<0.05) differences in BWG among were recorded from second week of age. At second week of age, the BWG in control group (T₁ ) was 171.57g which significantly (P<0.05) reduced to 135.06 g in aflatoxin alone fed group (T₂ ). The BWG in T₃ to T₁0 was significantly (P<0.05) higher compared to T₂ indicating that supplementation of MOS and SC to the AF contaminated diet significantly (P<0.05) improved the BWG. The BWG in T₄ , T₅ , T₈ , T₉ and T₁₀ was statistically (P<0.05) similar to that of control. However, the BWG in T₃ , T₆ and T₇ was statistically (P<0.05) lower than that of control. The BWG in T₃ was significantly (P<0.05) higher than that of T₆ and comparable to that of T₇ . At third week of age, the body weight in control group was 218.68 g, which significantly (P<0.05) reduced to 175.22 g in T₂ . The average BWG in T₄ , T₅ , T₇ , T₈ , T₉ and T₁₀ was comparable to that of control (T₁ ). The BWG of group T₃ and T₆ was significantly (P<0.05) higher than that of T₂ but could not match with the control diet. Thus, addition of binders in various concentrations significantly (P<0.05) increased the weight gain compared to toxin alone fed group. During fourth week of age, the average BWG of control group was 265.30g, whereas, the average BWG in T₂ was 201.40 g which was significantly lower than that of control. The average BWG in other treatments (T₃ to T₁₀) was significantly (P<0.05) similar to that of control. Thus, addition of toxin binders at different doses significantly improved the BWG. During fifth week of age, the BWG of control group (T₁ ) was 300.30 g which significantly (P<0.05) reduced to 229.32 g in T₂ . Inclusion of aflatoxin binders to the aflatoxin contaminated diet significantly (P<0.05) increased the BWG and the gains recorded in various dietary dietary treatments (T₃ to T₁₀) were comparable to that of control diet (T₁). During sixth week of age, the average BWG of control group (T₁ ) was 400.90 g which significantly (P<0.05) reduced to 295.11 g due to aflatoxin feeding (T₂ ). The BWG in other treatment (T₃ to T₁₀), was similar to that of control diet (T₁ ). During overall growth period (0-6 weeks), the weight gain of broiler in control group (T₁ ) was 1450.0 g as against 1131.0 g in aflatoxin alone fed group (T₂ ). The BWG in other treatments (T₃ -T₁₀) varied from 1268.4 g in T₆ to 1432.1 g in T₈ and the values recorded were statistically similar to that of control group.

The present study revealed that addition of 300 ppb of aflatoxin in the diet of broiler chickens caused significant reduction in body weight gain. The present observation was in agreement with the previous researchers who also observed significant reduction in body weight gain at 300 ppb level of dietary aflatoxin (Silambarasan, 2011; Sapocota et al., 2007; Raju and Dewegowda, 2000). In the present study, inclusion of MOS at 0.05, 0.1 and 0.2% level in the aflatoxin contaminated diet showed significant (P<0.05) increase in the overall BWG and the gain was statistically (P<0.05) similar to that of control. Similar findings were also reported by Oguz and Parlat (2004) where addition of MOS (1 g/kg) to the AF containing diet (2 mg/kg) completely ameliorated the adverse effect of AF on BWG in Japanese quails. These beneficial effects of MOS are due to their AF binding capacity. Mahesh and Devegowda (1996) in an in-vitro study observed that the addition of 0.05% MOS to a diet containing 200 ppb AF bound 79% of the toxin. In the present study, supplementation of SC at 0.05, 0.1 and 0.2% level in the AF contaminated diet showed significant (P<0.05) improvement in the BWG of broilers. Similar results were reported by Stanley et al. (1993) where inclusion of SC (1 g/kg) to the AF containing diet (5 ppm) provided significant improvement on BWG in broiler chicks fed for 28 days. Modirsanei et al. (2004) reported that supplementation of SC at a level of 0.5% to the diet containing 1 ppm AFB₁ significantly diminished the deleterious effect of aflatoxicosis on BWG of broiler chicks.

Feed intake (FI)

The data pertaining to weekly feed consumption are presented in Table 3. During first week of age, comparable feed consumption was observed among groups T₁ , T₂ , T₃ , T₄ , T₆ , T₇ and T₈ . Feed consumption in groups T₅ , T₉ and T₁₀ was significantly (P<0.05) higher than that of control. During second week of age, FI in control group was statistically comparable to all other treatments barring T₆ wherein the FI was statistically (P<0.05) lower than that of control. During third week, the FI in various treatments was statistically similar to that of control except group T₂ . During fourth, fifth, and sixth week the FI in all the treatment group was statistically (P<0.05) similar. The overall feed consumption in all the treatment groups was statistically similar to that of control group, however, the FI in groups T₈ and T₉ was statistically higher than that of aflatoxin alone fed group (T₂ ). Decreased feed consumption at 300 ppb aflatoxin was also reported by Silambarsan (2011); and Raju and Devegowda (2000). In the present study, addition of MOS and SC alone or in combination significantly improved the FI which was statistically (P<0.05) similar to that of control. Zhao et al. (2010) also reported that addition of Yeast cell wall (0.1 or 0.2% level) to the AF contaminated diet (1 ppm) recovered 90% of the feed consumption. Oguz and Parlat (2004) also reported that the addition of MOS (0.01%) to the AF containing diet (2 ppm) completely ameliorated the adverse effect of aflatoxin on feed consumption in Japanese quails.

Feed conversion ratio (FCR)

The data pertaining to weekly FCR are given in Table 4. During first week of the growth period, there was no significant (P<0.05) difference among various dietary treatments in FCR which varied between 1.536 and 1.645. During second week of trial, the FCR in control group (T₁ ) was 1.599 which significantly increased to 1.868 in aflatoxin alone fed group (T₂ ). The FCR in other treatment groups (T₃ to T₁₀) did not vary significantly (P<0.05) to that of control. During third week of trial, the FCR in control group (T₁ ) was 1.729 which significantly increased to 2.056 in aflatoxin alone fed group (T₂ ). The FCR in other treatment groups was statistically similar to that of control barring group T₆ wherein statistically higher FCR (1.877) was recorded compared to control. At fourth week of age, the control bird FCR was 1.980 which significantly (P<0.05) increased to 2.325 due to administration of aflatoxin. Both MOS and SC alone or in combination decreased the FCR compared to T₂ and the FCR were statistically similar to that of control barring treatment T₃ and T₆ where significantly (P<0.05) higher FCR compare to control was recorded. During fifth week, there was no significant (P<0.05) difference among the different dietary treatment in feed conversion ratio. At sixth week of age, the FCR of control group (T₁ ) was 2.119. Addition of aflatoxin in the diet of broilers significantly (P<0.05) increased the FCR to 2.416. With regard to other treatment groups, the FCR in T₄ , T₅ , T₈ , T₉ and T₁₀ was comparable to that of control group, however, the FCR of T₃ , T₆ and T₇ was significantly higher than T₁ and significantly lower than that of T₂ . The overall FCR in groups T₃ , T₆ and T₇ was statistically higher than that of control group indicating that supplementation of MOS at 0.05% and SC at 0.05 and 0.1% level to the aflatoxin contaminated diet may not be sufficient to curb the harmful effect of aflatoxicosis in broiler diet.

Poor feed efficiency is a common feature in poultry exposed to aflatoxins. In the present study also adverse effect of aflatoxin on feed efficiency were recorded. Silambarsan (2011); and Raju and Devegowda (2000) also reported significantly poor feed efficiency in broiler chickens with 0.3 ppm level of dietary aflatoxin. In the present study, addition of MOS and SC (alone or in combination) at any level resulted in significant improvement in feed conversion ratio. Oguz and Parlat (2004) also reported that the addition of MOS (1 g/kg) to the aflatoxin containing diet (2.0 mg/kg) completely ameliorated the adverse effect of aflatoxin on feed efficiency in Japanese quails. Suksombat et al. (2011) reported that yeast supplementation to the aflatoxin contaminated diet (250 ppb) significantly improved feed efficiency in broiler chickens. Modirsanei et al. (2004) also reported that supplementation of SC at a level of 0.5% to the diet containing 1 ppm aflatoxin improved the feed efficiency which was comparable to the control diet in broiler chickens. Parlat et al. (2001) also observed that supplementation of SC at a level of 1g/kg to the diet containing 2.5 ppm aflatoxin improved the feed efficiency significantly. In the present study, both MOS and SC appeared to be equally efficient in ameliorating the adverse effects of aflatoxicosis in broiler chickens from 1-42 days of age.

Livability percentage

The results on week-wise livability in broilers kept on different dietary treatments are presented in Table 5. During first, second and third weeks of age, there was no significant difference in livability percentage among various dietary treatments. During fourth week of age, the livability percentage varied between 87.50 in T₂ to 100 in T₅ . The livability percentage was significantly (P<0.05) lower in T₂ compared to T₅ . The livability percentage in other groups remained statistically comparable to that of control. During fifth week of age, the livability percentage in T₂ was significantly (P<0.05) lower than that of T₄ and T₅ indicating that addition of MOS at 0.1 and 0.2 level significantly (P<0.05) improved the livability percentage. During sixth week of age, the livability percentage in control group was 93.75 which significantly (P<0.05) reduced to 81.25 in T₂ . The livability percentage in groups T₃ , T₄ , T₅ , T₈ , T₉ and T₁₀ was significantly (P<0.05) higher compared to toxin alone fed group (T₂ ). Increased mortality is one of the main features of aflatoxicosis in poultry. In the present study significantly (P<0.05) higher mortality due to 300 ppb level of aflatoxin was recorded. Silambarasan (2001) also reported significant increase in mortality due to 300 ppb of aflatoxin in the diet of broilers. Occurrence of mortality due to aflatoxin contamination in the diet has also been reported by Denli et al. (2009) and Gopi (2006). In the present study, addition of MOS and SC (alone or in combination) improved the livability percentage in broiler chickens. This may be due to the effective adsorption of aflatoxin in the gastrointestinal tract before absorption into the blood stream. MOS at 0.1 and 0.2% level of inclusion was more effective than their SC counterparts in improving the livability percentage in broiler chickens. Significant improvement in livability percentage of broiler due to Yeast supplementation to the 250 ppb aflatoxin contaminated diet was earlier reported by Suksombat et al. (2011).

It is concluded that aflatoxin in feed at 300 ppb level impaired the performance in terms of body weight gain, feed intake, feed efficiency and livability in broiler chickens during period of 0-6 weeks. Use of binders MOS and SC (at the rate 0.05%, 0.1%, 0.2%) and their combination ameliorated the effect of aflatoxin partially or completely in dose-dependent manner. The 0.2% level of MOS and SC is more effective than 0.05% and 0.1% levels in counteracting the 300 ppb of aflatoxin in the feed.

This article was originally published in Indian Journal of Poultry Science (2012) 47(2): 176-182.