Aflatoxin B1 Contamination of Dairy Feeds after Storage in Farm Practice in Tropical Environmen.

　The objective of this study was to determine the contamination of aflatoxin B1 (AF-B1) when keeping various dairy feeds in a farm environment. The study was carried out from March to May 2011 and involved 63 small holder dairy farms belonging to a single dairy cooperative in Chiang Mai province, Thailand. All feed samples used for milking cows including 4 commercial concentrates (CC1 to CC4), by-products from local corn processing factories fermented in plastic bags (SIL), and corn and cob meal or corn dust (CCD). Feed samples were collected 2 times at before and after storage. Farmers were requested to store CC1 to CC4 and CCD for a month and SIL for a week using their routine on-farm storage arrangements. All samples were measured for their AF-B1 concentrations by ELISA. Results showed that AF-B1 concentrations of CC1 to CC4, SIL and CCD before storage were 5.1, 4.1, 4.0, 4.2, 5.5 and 5.5 µg/kg, respectively, and after storage the concentration of AF-B1 were 9.7, 6.5, 9.8, 12.3, 11.4 and 20.0 µg/kg, respectively. CCD at after storage was the only feed that had mean level more than 20 µg/kg. Concentrations of AF- B1 at before storage in all feeds were significantly lower than after storage (P<0.01), and the increased ratio of AF-B1 levels was approximately 2 to 3 times. The study concluded that increased AF-B1 levels are related to feed types and farm conditions.

Use of blue-greenish yellow fluorescence test on feeds and its association with aflatoxin M1 contamination in bulk tank milk.

The objectives of this study were to use the blue-greenish yellow fluorescence (BY) test for aflatoxin M1 (AFM1) contamination in bulk milk and to examine the association between AFM1 contamination and environmental and feed management factors. The study was conducted March to May of 2011 with samples from 82 small holder dairy farms belonging to a single dairy cooperative in Chiang Mai province, Thailand. On the day of milk sample collection, samples of all feed used for milking cows and data on feed characteristics, feed management, and environmental factors also were collected at each farm. High-performance liquid chromatography was used to determine AFM1 concentrations in milk samples, and samples with AFM1 concentrations above the limit of detection were considered AFM1 contaminated. Fisher's exact tests were used to determine the association between AFM1 contamination in milk and farm management factors, feed management factors, and fungal contamination in feeds (as determined with the BY test). A multilevel logistic regression model was used to create the final model of factors associated with AFM1 contamination in milk. Feeds with fungal contamination (as determined by the BY test), high levels of cracked particles of commercial concentrate pellets, sunlight in the feed storage room, storage of commercial concentrates on the farm for more than 1 month, and more than 5% difference in relative humidity between the feed storage room and the barn holding lactating cows were associated with AFM1 contamination in milk. The BY test was useful for screening cattle feed for fungal contamination, and the results of this test in conjunction with other factors can be used to monitor and prevent AFM1 contamination in milk on small holder dairy farms.