Abstract:

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.