Mycoflora of Layer Feed in Nairobi County and Their Toxigenic Potential

Abstract

Layer feeds consist mostly of grains such as maize which are susceptible to fungal growth and subsequent mycotoxin production. Under favorable environmental conditions, fungi are able to colonize the grain at any stage from processing to storage. Mycotoxins in feed are a health risk to both animals and humans. Mycotoxins negatively impact the feed intake, animal performance, reproductive rate, growth efficiency and immunity. This study aimed at investigating the mycoflora associated with layer feeds and quantify the aflatoxin and fumonisin content. One hundred and fifty feed samples comprising chick mash, grower mash and finisher mash were collected from five regions in Nairobi County where small-scale poultry farming is practiced. Dilution plate technique was used to isolate fungi in PDA and fungal colonies identified using both morphological and molecular methods. Toxigenic potential of Aspergillus flavus isolates were assessed using Coconut Agar Medium (CAM). Total aflatoxins (AF) and total fumonisins (FUM) levels in the samples were screened using the ELISA technique. The following genera of fungi were isolated from the feeds; Aspergillus (91%), Penicillium (77%), Fusarium (13%), Mucor (11%), Rhizopus (9%), Cladosporium (4%) and Cochliobolus (1%). Three strains of Aspergillus flavus were found to be toxigenic, among the Aspergillus flavus isolates, as confirmed by their blue fluorescence on CAM under UV light. AF contamination was detected in 65% of feed samples having a range of 0.22 μg/kg to 157.89 μg/kg while FUM contamination was detected in 91% of feed samples with a range of 210 μg/ kg to 15173 μg/kg. Sixty-two samples (42%) had AF levels greater than the Kenya Bureau of standards (KEBS) recommended limit of 10 μg/kg in finished poultry feed while no sample contained total FUM levels higher than the recommended European Union (EU) maximum permitted limit of 20000 μg/kg. This study provides insights on the quality of layer feeds in Nairobi County and will play a role in formulating food and feed safety policies.