About zearalenone levels in grass fodders and toxine producing activity of Fusarium fungi

Zearalenone, the Fusarium fungi metabolite with an estrogenic effect, can lead to significant economic losses in livestock due to fodder contamination. Pasture herbage and fodders from dried pasture plants can really cause intoxication. However, the reasons and mechanism of abnormally high accumulation of zearalenone in these fodders are not still found out. In this article we summarized the data on investigation of frequency and the level of zearalenone contamination in wild herbage and in hay. Also the ability to produce this mycotoxin was studied in vitro in 13 Fusarium strains from laboratory collection. Hay samples from different farms of 30 regions in Moscow Province were prepared from 120 hay batches in 2013. A total of 211 samples of wild herbage including ( Calamagrostis, dogstail grass, Anthoxanthum, reed canary grass, hedgehog, fire, bluegrass, fescue, bentgrass, bluegrass, timothy, foxtail) were collected in Kashirskii, Noginskii and Ruzskii regions of Moscow Province in 2014 from June to September. A total of 427 samples of pasture grasses were also repeatedly collected in North Karelia, Leningradskaya, Tverskaya and Astrakhanskaya provinces from 1998 to 2014 at different frequency for different plant species. In these samples, along with commonly grown grasses such as Bromus, bluegrass, fescue, bluegrass, timothy, some local plants were found, particularly reed, reed canary grass, hedgehog, bent grass, reeds, Leymus, dogtail grass, oats, ryegrass, clover, rank, peas, vetch, rye, pampasskaya grass, foxtail, alfalfa. An uneven zearalenone contamination of pasture grasses with rare overcontamination cases was shown to occur to the end of vegetation. In hay an increased frequency and more high level of contamination were found. The mycotoxin was detected in 54 samples of 120 those tested, and more than a half of them contained zearalenone at the level below 100 mg/kg, while the rest samples contained toxin at 1000 mg/kg, and in 13 % of the samples tested the contamination reached 1000 to 10000 mg/kg. After 7 day cultivation of F. graminearum, F. equiseti and F. semitectum on semi-synthetic agar medium more that 80 % of strains produced zearalenone, and the rate of strains with the high production reaching more than 10000 ng/ml was 5, 15 and 44 %, respectively. F. cerealis, F. culmorum, F. sporotrichioides, F. poae seemed to be less active producers, and among F. anguioides and F. langsethiae, as well as F. heterosporum, F. chlamydosporum and F. kyushuense the zearalenone producers were not found. In a strain of F. flocciferum which was tested a high biosynthetic ability and accumulation of zearalenoine at 15 500 ng/ml were detected. An involvement of Fusarium fungi having more pronounced metabolic response to environment changes in contamination of grass fodder with zearalenone is discussed. Also the possibility of forecasting hay contamination basing on pasture survey is under consideration.