Corn silage quality for dairy cattle produced in southern Brazil regarding mycotoxins

Abstract

Silage corn (Zea mays L.) quality was evaluated from January 2010 to December 2012 for the presence of field (fumonisins-FBs and zearalenone-ZON) and storage (aflatoxins-AFLs) mycotoxins, supplied to dairy cattle in the Southern Brazil. A total analysis of 1,006, 1,077 and 1,080 for FBs, ZON and AFLs were performed by the immunoenzymatic (ELISA) methodology with LOQ of 500, 25 and 5 µg/kg, respectively. From the data obtained it was observed that there was contamination in different samples, the levels varied and so the toxin evaluated throughout the period of the year. Although, not much difference among the states that comprise the region (temperate climate) under study, was detected. The toxin produced by Fusarium graminearum, ZON, was present ranging from 28.2 to 1538 µg/kg indicating a large variability between levels (standard deviation-SD & relative standard deviation-RSD% of 131 & 65.4%) regardless of the origin of the sample or trial period. There is no ZON limit established in Brazil for feed. Out of these samples, 75.5% were above the maximum tolerable (LMT) established in Uruguay (200 µg/kg) for cereals for animal feed, although the country does not specify for silage. The FBs were the toxins that had the lowest percentage of contaminated samples (11.4 to 34.4%) between the years of study, with the  year 2011 presenting the highest levels yet, all below LMT U.S.A. (30,000 µg / kg) and 7.3% above the limit set by Switzerland (1,000 µg / kg). There are no limits set for FBs in Brazil feed. Regarding AFLs, the percentage of samples contaminated with levels higher than the Brazilian LMT (Ministry of Agriculture -  50 µg/kg) was 11.6% (125) of the total of 1080 tested silages. The levels varied among the positives samples with 9.7% (46-97), 11.3% (31-125.8) and 14.5% (48-105.4) for the states of PR, RS and SC, respectively. Although the levels detected for FBs were low, AFLs and ZON were higher, being some above the LMT of different countries. Therefore there is the need for agricultural practices adequacy in the production of silage for dairy cattle through several stages (harvesting / milling plant / fermentation / compression & silo type / size & closure) as well as its constant monitoring in order to avoid or minimize any economic losses. This is the first work reporting toxins of temperate climate in silage.