Alleviation of aflatoxin-BI toxicity by using mycotoxin adsorbents and their effect on growth and immune response in Nile tilapia (Oreochromis niloticus)

Abstract

Clays have been used for centuries as ‘ancient medicine’ for their therapeutic benefits. One specific clay, calcium montmorillonite, has historically been used as an anti-caking agent in animal feeds, but has also verified the ability to bind toxins and alleviate infectious diarrhea. Food borne toxin exposure, such as aflatoxin B1 (AFB1) is a serious problem facing by the aquaculture particularly with its intensification. Therefore, the purpose of this research was to explore novel therapeutic applications for 4TX, calcium montmorillonite clay to reduce the risk of AFB1 toxicity in farm-raised Nile tilapia through growth enhancement and better meat quality. For this purpose three trials were conducted. Trial I was regarding the “alleviation of AFB1 toxicity by 4TX bentonite clay supplementation and its effect on health performance and immunity in Nile tilapia (Oreochromis niloticus)”. Two levels of 4TX clay (0.5 and 1%) were assessed against 2 and 4 mg/kg AFB1 contaminated diets along with control group. The efficacy of 4TX clay was also compared in terms of its inclusion types (Water dispersal WD and powder mix PM). The results indicated there was a significant difference (P<0.05) observed in % weight gain and feed efficiency in all treatments. Control group showed maximum % weight gain (975.5±29.2) and feed efficiency (0.737±0.009) while treatment 4mg AFB1 + 0.5% 4TX WD showed minimum % weight gain (661.5±63.5) and feed efficiency (0.583±0.013). Regardless the inclusion of 4TX clay in the diets, the AFB1 has overall negative impact on the fish health performance. Maximum weight gain was observed in 0 mg AFB1 group (838.23 ± 28.87) and minimum in 4 mg AFB1 inclusion group (693.92±34.63). 1 % 4TX PM group showed higher growth (774.89±38.79) over 1% 4TX WD group (752.58±38.63). AFB1 also negatively affected the hepato-somatic index (HSI). 2 mg AFB1 treated diets showed a reduction (1.38 ± 0.03) in (HSI) as compared to 0 mg AFB1 (2.28 ± 0.11) supplemented diets. 0 mg AFB1 treated groups showed better protein energy efficiency (33.10±0.81) as compared to the 4mg AFB1 treated diets (29.41±0.74). Immunological response of tilapia showed a significant difference (p<0.05) towards the toxicity of AFB1 among all the treatments of all the three parameters tested. The maximum value of plasma lysozyme was observed in 4mg AFB1+0.5% 4TX WD group (224.65±10.96A) and minimum in 2mg AFB1+0.5% 4TX WD group (119.29±10.22). The results of NBT assay also showed a significant difference (p<0.05) among all the treatments. The maximum value was observed in 4mg AFB1+1% xv 4TX PM group (3.60±0.10) and minimum in 2mg AFB1+1% 4TX PM group (2.72± 0.07). Extracellular super oxide anion production in head and kidney macrophages of tilapia were also significantly higher (p<0.05) in control group (1.72±0.07) as compared to AFB1 treated fish with minimal in 4mg AFB1+0.5% 4TX WD group (0.57±0.10). AFB1 residues (ppb) in muscles was observed maximum in 4mg AFB1+0.5% 4TX WD group (1.87±1.32) and minimum in 4mg AFB1+1% 4TX PM group (0.43±0.03) showing the protective effect of 4TX clay, particularly in PM form against the toxic effects of AFB1. Histological analysis showed that fish fed AFB1 had greater liver pathological damage than those without AFB1. In trial ІІ effects of 4TX clay supplements on the nutrient digestibility of tilapia were evaluated. Results showed non-significant difference in apparent dry matter digestibility (ADMD), apparent crude protein digestibility (ACPD) and apparent crude lipid digestibility (ACLD) (P > 0.05). Apparent digestibility of essential amino acids was also found statistically non-significant except in the case of Methionine where 0.5% 4TX group showed maximum digestibility (97.63 ± 0.59) as compared to 1% 4TX group (83.30±8.17). Overall, 0.5% 4TX level showed higher nutrient digestibility of tilapia as compared to 1% and control group. The results of trial ІІІ showed almost the same trends in growth patterns as observed in trial І. AFB1 treated diets showed minimum % weight gain (222.3±57.86), feed efficiency (0.170±0.05) and % survival (66.67±3.82) as compared to control group (421.9±29.83), (0.320±0.01) and (87.50±2.50), respectively. Without the addition of AFB1 in the diets, 0.5% 4TX level showed better growth performance (328.6±24.65) over 1% 4TX (271.2±29.39). The results of proximate composition of whole body revealed that % moisture, ash and protein differ non-significantly in all the treatment while there observed a significant difference in % lipid in all the four treatments with minimum in AFB1 treated group (4.617±0.27) and maximum in control (5.927±0.39). These results could positively impact both human and animal populations with AFB1 exposure and decreasing the incidence of aflatoxicosis in farm-raised fish would ultimately prevent economic loss for the industry.