Detoxification of aflatoxins in feed ingredients for broiler Chicken feed through fermentation

Abstract

Aflatoxins (AFs) are some of the toxic and carcinogenic mycotoxins. Due to the high cost of most cereals and its competition for human food, chicken feeds are often formulated with mouldy and broken grains which are easily contaminated with mycotoxins. Kenya Bureau of Standards recommended 20ppb total AFs as the permissible level in poultry feed. The first objective of this study evaluated the effects of fermentation on the detoxification of AF contaminated maize flour using S. cerevisiae. This was achieved in 3 experiments where the first and second experiments, maize flour were fermented with and without S. cerevisiae for 5-8 days. In the third experiment, the flour to water ratio was adjusted from 1:1 to 2:3 and fermented for 72 hours. Fermentation reduced pH (from 6.9 to 5.0) and total AFs by 52 and 53.4% when fermented either with or with S. cerevisiae respectively. It is concluded that the best ratio of flour to water for fermentation was 2:3 and the fermentation period of 72 hours. The second objective evaluated the effect of fermented feed on the digestibility of dry matter, metabolizable energy content, and nitrogen utilisation in broiler chicken. Twenty-four, 28- day old male broiler chicken were assigned to six different dietary treatments which are: diet 1 (no AF and not fermented), diet 2 (no AF and fermented without S. cerevisiae), diet 3 (no AF and fermented with S. cerevisiae), diet 4 (contained 20.034ppb AF and not fermented), diet 5 (contained 20.034ppb AF and fermented without S. cerevisiae) and diet 6 (contained 20.034ppb AF and fermented with S. cerevisiae). Each diet was assigned to four chicken following a 7-day adaptation period and 7-day total faecal collection period. The results showed that dry matter digestibility and metabolizable energy were significantly (p<0.05) affected by fermentation types. The metabolizable energy and nitrogen were significantly (p<0.05) affected by the total AF level of 20.034ppb in the diet. The third objective evaluated the feed intake and growth of broiler chicken offered fermented feed with or without S. cerevisiae. One hundred and forty-four broiler chicks were fed six different diets for 21 days. The six diets were: diet I (no AF and unfermented), diet II (no AF and fermented without S. cerevisiae), diet III (no AF and fermented with S. cerevisiae), diet IV (30.08ppb AF and not fermented), diet V (30.08ppb AF and fermented without S. cerevisiae) and diet VI (30.08ppb AF and fermented with S. cerevisiae). The intake, growth, and gain: feed ratio was calculated. Mortality was recorded every day. Results showed no significant difference of six diets on intake and growth. However, gain: feed ratio was significantly (p=0.048) better in broilers fed diets which were fermented without yeast. The mortality rate was very high (75.0%) in chicks fed on the diet containing 30.08ppb, which was not fermented.