Effect of calcium and sodium bentonite clays from the Albertine Graben region of Uganda on performance of broiler and layer chickens fed aflatoxin-contaminated diets
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Aflatoxins are secondary metabolites of the species belonging to the genus aspergillus which are highly hepatocellular carcinogenic and are of great concern in the grain and feed industry. The most promising approach to detoxifying aflatoxin-contaminated feed is the use of high-affinity non-nutritive adsorbents like bentonite clays. This study was therefore conducted to assess the performance of broilers and layers fed aflatoxin-contaminated diets as influenced by the addition of bentonite clays from the Albertine Graben region of Uganda. Two experiments were conducted. In experiment 1, balanced diets for broiler growers and finishers were each laced with aflatoxins to levels of 250 ppb during weeks 3-4 and 5-7, respectively. Three aflatoxin binders including a commercial toxin binder (TB) as a control, and two Albertine bentonite clays (Calcium bentonite (CaB) and sodium bentonite (NaB)) were each separately added at graded levels of 0.0, 0.25, 0.5, 1.0, and 2.0% w/w to the contaminated diets. The treatments were then randomly assigned to a group of birds as experimental units in a completely randomized experimental design replicated 3 times (n = 20 birds per group replicate). The broilers were evaluated during weeks 3-7 after which they were slaughtered for relative organ weights, residual aflatoxins, and blood antibody titer determination. In experiment 2, assessment of layer performance as influenced by the level of binder inclusion to aflatoxin-contaminated diets was conducted during weeks 20-31. An experimental design similar to that of the broilers was used but with (n=15 birds per group replicate). Largely, voluntary dry matter intake increased quadratically (p<0.05) with increasing binder inclusion levels except for TB and NaB in the broiler grower phase which showed a linear trend (p<0.05). Broiler daily weight gain (BWG) increased quadratically (p<0.05) with inclusion levels in grower and finisher. However, increase due to TB and CaB inclusion followed a linear trend (p<0.05) in the growers. Cumulative feed conversion ratio (FCR) decreased with increasing binder levels. Consequently, optimum cumulative FCR of 1.862, 1.864, and 1.877 g of feed/g of BWG was obtained at 1.35, 1.70, and 1.5% inclusion levels of TB, CaB, and NaB, respectively. The infectious bursal disease antibody titer increased to optimum values of 2761, 2559, and 2532 corresponding to 1.33, 1.53, and 1.46% inclusion levels of TB, CaB, and NaB, respectively. The antibody titers of Newcastle disease increased to optima of 7.62, 6.89, and 6.91 corresponding to 1.37, 1.48, and 1.48% inclusion levels of TB, CaB, and NaB, respectively. While the decrease in broiler mortality tended towards linearity (p=0.07) due to increasing CaB inclusion levels, a quadratic decrease (p<0.05) was observed with both TB and NaB. The relative weight of liver decreased quadratically (p<0.05) while that of the kidney decreased linearly (p<0.01). However, the relative weight of the bursa of Fabricius increased linearly (p<0.001) with binder inclusions. Aflatoxin carry-over in the liver tissues generally decreased quadratically (p<0.05) with the binder inclusions while that of the kidney tissues decreased linearly (p<0.05). Whereas a quadratic increase (p<0.05) in hen day egg production was obtained with increasing levels of TB, CaB and NaB inclusion resulted into a linear increase (p<0.01). Consequently, FCR decreased for clay binders decreased linearly (p<0.05) except for the commercial binder which resulted in a quadratic response (p<0.05). As a result, optimum FCR of 3.99, 4.03, and 4.12 were obtained at inclusion levels of 1.30, 1.83, and 1.76% of TB, CaB, and NaB, respectively. Although commercial binder outperformed the Albertine bentonite clays, performance of layers and broilers improves with the addition of bentonite clays due to aflatoxin decontamination. This implies that, optimum performance can be obtained at 1.5 and 1.7% inclusion levels of NaB and CaB, respectively in the aflatoxin-contaminated broiler diets. For the case of layer chickens, however, optimum performance can be obtained at 1.76 and 1.83% inclusion levels of NaB and CaB, respectively.