| Popis: |
Six growers from each of five broiler companies were classified into equal numbers of good, mediocre, and poor growers based on a productivity index. Feed samples were collected weekly during the growout period of a flock from each grower and from the mill where the feed was produced. Samples of corn from which the feed was made were also collected. Aflatoxin, moisture contents, and bacterial, coliform, and fungal counts of the samples were determined. On the same weekly basis, the temperature and relative humidity of the chicken houses were measured and the age of the feed samples ascertained. Aflatoxin concentration in feed of good growers was 6.1 ppb with an 18.0% frequency of contamination while the values for poor growers were 14.0 ppb and 31.3%. Mean aflatoxin concentration in corn of 1.2 ppb increased to 8.8 ppb in feed from the farms. Optimum conditions for aflatoxin formation were 19 to 27 C, 79 to 89% relative humidity, and 10 to 13% moisture. Increasing age of feed was associated with low moisture and high aflatoxin. High aflatoxin was associated with high relative humidity but not with fungal, bacterial, or coliform counts. These data suggest that aflatoxin is produced during and after feed manufacture in apparently normal operations, that low levels of aflatoxin are associated with productivity losses in apparently healthy broilers, and that the aflatoxin formation is associated with high relative humidity in houses and with long residence time of the feed in the house. Because relative humidity and residence time in houses can be altered, aflatoxin formation might be limited by controlling these two factors. |
