The effects of aflatoxin contaminated feed with or without a commercial binder on broiler performance

Abstract

Agriculture plays a prominent role in Kenya’s economy with livestock production contributing significantly to the gross domestic product (GDP). Among the challenges faced in this sector is the contamination of agricultural produce, mainly cereals, grains and their by-products, with mycotoxins, secondary fungal metabolites. This contamination could occur both pre and post - harvest depending on harvesting, storage and transportation methods. Aflatoxins (AFs) are mycotoxins produced by fungi of the genus Aspergillus (A), mainly A. flavus and A. parasiticus in agricultural produce when conditions are favorable. Poultry are the species most sensitive to the toxic effects of AFs. These effects are mainly on performance parameters, such as feed intake, growth rate and feed conversion efficiency, and health due to immunity suppression. Aflatoxins contamination of feeds is both of economic importance and a threat to public health as there is a risk of residual AFs in broiler tissues and organs. Aflatoxins are classified as number one cancer causing agents by the International Agency for Research on Cancer (IARC), they have also been reported to be immunosupressant, teratogenic and mutagenic. However, in Kenya there is inadequate data on the prevalence of AFs in commercial broiler feeds, effects of the AFs levels in commercial broiler feeds on broiler performance and digestibility and the if Mycosorb® AFs binder added in feeds is effective. Objective one was therefore a survey that determined the levels of total AFs in common commercial broiler feeds among feed manufacturers in Nakuru town and effects of these AFs levels in diet and AFs binder (Mycosorb®) inclusion in diets on broiler performance, organ weights and digestibility. The first objective was achieved by carrying out a survey in Nakuru town where forty commercial broiler feed samples were randomly collected from ten feed mill companies in two phases (April to May and June to July). Analysis for total aflatoxin levels in the feed samples was by Enzyme-linked immunosorbent assay (ELISA) technique following manufacturer’s instructions (Helica Biosystems Inc). Thermo Scientific™ microtiter plate reader read the absorbance optical density (OD) of each microwell with at 450 nm and the data recorded. The OD data conversion into parts per billion (ppb) was by Graphpad prism 7 software. The ppb data were subjected to two way analysis of variance using the GLM procedures of Statistical Analysis System (SAS) (version 9.13). All the feeds collected contained aflatoxins with total AFs levels ranging from 1.07ppb to 41.01 ppb. Of the samples collected, 92.5% and 52.5% contained total aflatoxin levels that exceeded the World Health Organization (WHO) limits of 5 ppb in animal feeds and Food and Drug Administration (FDA) limits of 20 ppb in poultry feeds respectively. For the second and third objectives, two feeding trial experiments were conducted in Completely Randomized Design. In both experiments, six treatments were tested. The treatments were own compounded broiler starter (fed from day 1 to day 21) and finisher (fed from day 22 to day 35 for experiment two and day 28 to 48 for experiment two), formulated to meet the nutritional requirement as recommended by NRC (1994). The treatments were three levels of AFs (6, 14 and 22 ppb) and two levels of Mycosorb® AFs binder addition for each AFs level (0 and 1 Kg/ tonne of feed). For the first experiment, two hundred one-day-old Arbo Acre broiler chicks purchased were randomly distributed into six experimental groups with four replicates each. Broilers watering and feeding was done daily, weighing on weekly basis to determine growth rate while, total feed given less the total left over feed determined daily feed intake. On day 36, eight broilers per treatment (two per replicate) were slaughtered and their liver, gizzard and heart weights recorded. For the second experiment, twelve broilers of uniform weight (0.8Kg± 0.05) were purchased at four weeks of age and the six treatments allocated randomly with replication. The broilers were allowed to acclimatize to the feeds for seven days then data collected for the next three days. The process was then repeated while ensuring that no broiler got the previously allocated diet. Daily feed intake was determined as feeds given less leftovers. Dry matter and aflatoxins digestibility were determined as; ((Total amount consumed less total amount in feaces) divided by total amount consumed) multiplied by 100. Data on mean separation was done using general linear model (GLM) procedure in SAS (version 9.0) at (p <0.05). Feed efficiency differed significantly (p<0.05) among the diets during the grower period. Diets had no significant effects (p>0.05) on feed intake, growth rate and organ weights. Moreover, inclusion of Mycosorb® AFs binder had no effect (p>0.05) in daily feed intake, daily growth, feed efficiency, organ weights and dry matter and AFs digestibility. In conclusion, feed conversion efficiency at grower stage was affected by AFs at 14.06 and 21.95 ppb in the treatment diets. Mycosorb® AFs binder was effective in binding the AFs in the treatments. Feed manufacturers should test for aflatoxins in the raw materials and avoid the fungal contamination in the broiler feeds at all stages of handling.