Effect of Methionine Supplementation in Ameliorating Aflatoxicosis in Broiler Chickens

INTRODUCTION

There is increasing evidence that cereal grains used for poultry feed are commonly contaminated with mycotoxins. Mycotoxins are toxic compounds produced by fungi, when present in the feed depress nutrient quality of the feed and hence the health and performance of poultry. The tropical and subtropical climate with hot and humid condition prevailing in India coupled with poor harvesting of crops, inadequate drying and storage facilities, and insect infestation make feedstuff susceptible to fungal contamination that result in greater economic losses to poultry industry through mycotoxicosis. Aflatoxins are toxic secondary metabolites produced by certain strains of fungi (Aspergillus flavus and Aspergillus parasiticus). Among the main aflatoxins (aflatoxin B₁, B₂, G₁, and G₂ ), AFB₁ is known to be the most toxic metabolite, especially in sensitive species such as poultry (Hussein and Brasel, 2001). Aflatoxin in poultry causes reductions in growth performance (Silambarasan et al., 2013), suppressed immunity (Manegar et al., 2010), carcinogenesis, hepatotoxicity (Busby and Wogan, 1984), anaemia (Oguz et al., 2000) and increased mortality (Miazzo et al., 2000). Thus, aflatoxin contamination in feed is practically unavoidable (Coulombe et al., 2005). Changes in the composition of poultry diets (dietary modifications) alleviate the adverse effects of aflatoxin in the poultry. Inclusion of slightly higher methionine in feed of coloured broiler chickens was beneficial to counteract the adverse effects of aflatoxin (Singh et al., 2013). The aim of this study was to evaluate the efficacy of methionine in counteracting the deleterious effects of aflatoxin B₁ (AFB₁ ) in broiler chickens.

MATERIALS AND METHODS

Aflatoxin was produced using the fungal strain Aspergillus flavus NRRL 6513 that was obtained from US Department of Agriculture, Illinois, USA. To get the fresh spores, the culture was regularly sub-cultured on potato dextrose agar medium slants and stored at 5°C. Aflatoxin was produced on maize substrate. Fermentations were carried out in batches as per Shotwell et al. (1996). The extraction and estimation of aflatoxin was done as per Pons et al. (1966). Aqueous acetone was used for extraction of the toxin. Aflatoxin contents were finally quantified using spectrophotometry. The AFB₁ concentration in fermented maize was 990 mg/kg of maize.

Day-old broiler chicks (n=240) were obtained from experimental hatchery, CARI, Izatnagar. The chicks were wing banded, weighed individually and distributed randomly into 6 treatment groups adopting completely randomised design. Each dietary treatment consisted of five replicates and each replicate had 8 chicks. The experiment was conducted in broiler chickens from day-old to 6 weeks of age. The basal diet was mixed with the required quantity of mouldy maize to get the desired concentration of 250 ppb AFB₁. The six dietary treatments were T₁ : Control (basal diet); T₂ : T₁ +250 ppb AFB₁ ; T₃ : T₁ +0.05% Met; T₄ : T₁ +0.1% Met; T₅ : T₂ +0.05% Met; T₆ : T₂ +0.1% Met).

All the birds were reared under standard managemental conditions from 0-6 weeks. All birds were fed with broiler starter ration from 1-21d and broiler finisher ration from 22-42d. Weekly individual BW and feed consumption of each group were recorded. At the end of experiment, ten birds per dietary treatment were sacrificed at random in order to record organ weights. The relative weights of liver, spleen, bursa of Fabricius and thymus as per cent of body weight were calculated. The composition of broiler starter and finisher ration are presented in Table 1.

Effect of Methionine Supplementation in Ameliorating Aflatoxicosis in Broiler Chickens - Image 1

The crude protein (AOAC, 1990) and calcium (Talapatra et al., 1940) contents were estimated, while the concentration of lysine, methionine, available P and metabolizable energy value were calculated. Data were analyzed following completely randomized design (Snedecor and Cochan, 1980) the statistical analysis was done using SPSS 16.0 version.

RESULTS AND DISCUSSION

Significant (P<0.05) differences in body weight gain (BWG) among various dietary treatments were recorded from second week of age onward (Table 2). During starter (0-3 wk) and finisher (4-6 wk) phases, the BWG in groups T₂ and T₅ was significantly (P<0.05) lower than that of control. The BWG in groups T₃, T₄ and T₆ was statistically similar to that of control. During overall growth period (0-6 week), the BWG of groups T₂ and T₅ was significantly (P<0.05) lower than that of control but the BWG in other groups was statistically similar to that of control.

The presented study indicated that inclusion of 250 ppb of aflatoxin in the diet of broilers resulted in significant reduction in BWG. Significant reduction in BWG of broiler at 300 ppb level of dietary aflatoxin was also reported by previous researchers (Silambarasan et al., 2013; Sapocota et al., 2007). Earlier studies also indicated that dietary aflatoxin at 0.5 ppm or more in commercial broiler diet adversely affected growth in a dose-dependent fashion (Rosa et al., 2001). The present study revealed that supplementation of Met at 0.05% levels failed to ameliorate the adverse effect of aflatoxicosis on BWG caused by 250 ppb aflatoxin B₁ , however, 0.1% Met supplementation to the aflatoxin contaminated diet significantly (P<0.05) increased the overall BWG and the gain was statistically similar to that of control. Naveenkumar et al. (2007) and Sapocota et al. (2007) also reported significant improvement in BWG of broiler chickens due to Met supplementation in diet during aflatoxicosis.

Significant (P<0.05) differences in feed consumption (FC) pattern among various dietary treatments were recorded from fourth week of age onwards (Table 2). During starter phase (0-3 wk), the FC did not vary significantly among various dietary treatment groups. During finisher (4-6wk) and overall growth (0-6 wk) phases, the FC in aflatoxin fed group was significantly (P<0.05) reduced compared to that of control. The FC in other treatment groups was statistically similar to that of control (T₁ ).

Effect of Methionine Supplementation in Ameliorating Aflatoxicosis in Broiler Chickens - Image 2

Effect of Methionine Supplementation in Ameliorating Aflatoxicosis in Broiler Chickens - Image 3

Effect of Methionine Supplementation in Ameliorating Aflatoxicosis in Broiler Chickens - Image 4

The present study revealed that aflatoxin contamination in diet resulted in significant reduction in feed consumption. Significantly reduced feed consumption at 0.3 ppm aflatoxin was also reported by Silambarasan et al. (2013) and Abaji (2012). In present study, Met supplementation (0.1%) to aflatoxin contaminated diet resulted in significant improvement in feed consumption of broilers equal to that of control. Sapocota et al. (2007) also reported significant improvement in feed consumption of broilers due to Met supplementation in aflatoxin contaminated diet.

Effect of Methionine Supplementation in Ameliorating Aflatoxicosis in Broiler Chickens - Image 5

During Starter phase, the FCR in groups T₂ and T₅ was significantly (P<0.05) higher than that of control (T₁ ), however, the FCR in other treatment groups was statistically similar to that of control. During finisher phase, the FCR of group T₂ was significantly (P<0.05) higher than that of T₁, however, the FCR in other treatment groups was statistically similar to that of control. During overall growth period (0-6 week), the FCR of T₅ was statistically similar to that of aflatoxin alone fed group (T₂ ), indicating that supplementation of 0.05% Met to the AF contaminated diet did not curb the ill effect of AF on overall FCR in broiler chickens. The overall FCR of T₃ and T₄ groups was statistically similar to that of control, suggesting that addition of Met to the basal diet did not produce any positive effect on FCR of broilers. The FCR of T₆ was statistically (P<0.05) similar to that of control, indicating that supplementation of 0.1% Met to the aflatoxin contaminated diet ameliorated the ill effect on AF on FCR in broiler chickens.

Impaired feed efficiency is the common feature in poultry during aflatoxicosis. In the present study, aflatoxin contamination in feed resulted in poor feed efficiency in broilers. Silambarasan et al. (2013) and Abaji (2012) also reported significantly poor feed efficiency in broiler chickens with 0.3 ppm level of dietary aflatoxin. Scheideler (1993) and Rosa et al. (2001) also reported impaired feed efficiency due to 2.5 ppm and 5.0 ppm aflatoxin feeding, respectively. Similarly, other researchers have also reported a dose dependent significant reduction in feed efficiency due to presence of aflatoxin in diet (Rosa et al., 2001). In the present study, supplementation of Met at 0.1% level to aflatoxin contaminated diet resulted in significant improvement in feed efficiency equal to that of control. These reports are in agreement with literature (Sapocota et al., 2007; Naveenkumar et al., 2007), wherein Met supplementation to the aflatoxin contaminated feed resulted in improved feed efficiency in broiler chickens.

The liveability percentage did not vary significantly among various dietary treatment groups. In the present study, 250 ppb aflatoxin level in the diet resulted in higher mortality compared to control. Inclusion of aflatoxin at 250 ppb did not produce heavy mortality, which might be due to the low level of aflatoxin inclusion in the diet. Silambarasan (2011) and Abaji (2012) also reported an increase in mortality due to 300 ppb level 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, Met supplementation to the aflatoxin contaminated feed resulted in improved liveability percentage in broiler chickens.

The data pertaining to relative organ weights (liver, spleen, bursa, and thymus) expressed as percentage of live weight and presented in Table 3. The relative weight of liver in the control group was significantly (P<0.05) lower than that of T₂ and T₅. The relative weight of liver in T₆ was statistically similar to that of control. In the present study, contamination of aflatoxin at 250 ppb level in the diet of broiler chickens resulted in significant (P<0.05) increased in the relative weight of liver. Similar observations were also reported by Silambarasan (2011). In the present study, supplementation of methionine at 0.1% level ameliorated the adverse effects of aflatoxin on relative weight of liver. These results are in agreement with Sapocota et al. (2007).

The relative weight of spleen in control group was lower (P<0.05) than that of T₂ and T₅. The relative weight of spleen in groups T₃, T₄ and T₆ was significantly (P<0.05) lower than that of T₂ and statistically similar to that of control. In the present study, a significant increase in the relative spleen weight was recorded at 250 ppb level of dietary aflatoxin. Abaji (2012) also reported a significant increase in the relative weight of spleen at 300 ppb level of dietary aflatoxin. Significant increase in relative spleen weight due to dietary aflatoxin content ranging from 3.5 to 5 ppm has also been reported by earlier researchers (Bailey et al., 1998; Kubena et al., 1998 and Rosa et al., 2001). In the present study, supplementation of methionine (0.1%) to the aflatoxin contaminated diet reversed the effect of aflatoxin on relative weight of spleen.

Effect of Methionine Supplementation in Ameliorating Aflatoxicosis in Broiler Chickens - Image 6

The relative weight of bursa of Fabricius in control group (T₁ ) was higher (P<0.05) than that of aflatoxin alone fed group (T₂ ). The relative weight of bursa of Fabricius in other treatment groups was statistically similar to that of control. In the present study, a significant (P<0.05) decrease in the weight of bursa was reported at 250 ppb level of dietary aflatoxin. These results corroborate well with earlier reports of Silambarasan (2011) and Abaji (2012). In their study, a significant decrease in the relative bursa weight was observed at 300 ppb level of aflatoxin in the diet. In the present study, supplementation of methionine to the aflatoxin contaminated diet ameliorated the ill effect of aflatoxin on relative weight of bursa of Fabricius. There was no significant difference in relative weight of thymus among various dietary treatments. Non-significant difference in relative weight of thymus was also reported by Ortatatli et al. (2001) when diet containing 100 ppb was fed to broiler chickens.

It was concluded that 250 ppb aflatoxin in broiler diet impaired the performance in terms of body weight gain, feed intake and feed conversion efficiency and relative organ weights. Supplementation of 0.1% methionine to the aflatoxin contaminated diet had pronounced ameliorative effect on performance of the birds.

This article was originally published in Animal Nutrition and Feed Technology (2015) 15: 161-169 doi: 10.5958/0974-181X.2015.00018.9.