Summary The present revision shows the early and current knowledge in the field of silage fungi and mycotoxins explaining the relevance of fungi and mycotoxins in silage. The problem does not end in animal disease or production losses as mycotoxins in feed can lead to the presence of their metabolic products in dairy products, which will be eventually affecting human health, mainly infants. Silage is green forage preserved by lactic fermentation under anaerobic conditions. This ecosystem maintains its quality and nutritional value depending on interactions among physical, chemical and biological agents. Forages used for ensilage are naturally in contact with yeasts and filamentous fungi, and the contamination often occurs in the field and can also occur during harvesting, transport, storage. Moreover, postharvest poor management can lead to a rapid spoilage. Studies on fungal contamination of dairy cattle feed have shown how corn silage influences the contamination degree of feed supplied to livestock. Increasing knowledge in this area will help elucidate the influence that this microbiota exerts on production and/or degradation of mycotoxins present in silage. Some of these fungi, although opportunist pathogens, are relevant epidemiologically and represent a high risk of contamination to farm workers who handle them improperly.

Aflatoxins (AF) are a major problem in broiler production and are significant economic and public health burdens worldwide. A commercial sodium bentonite (Na-B) adsorbent was used to prevent the effect of AF [50 µg of aflatoxin B₁ (AFB₁)/kg of feed] in broiler productivity, biochemical parameters, macroscopic and microscopic liver changes, and AFB₁ liver residues. The influence of Na-B (0.3%) and monensin (MON, 100 mg/kg), alone or in combination, was investigated in depth. The dietary treatments were as follows: treatment (T) 1: basal diet (B); T2: B + MON; T3: B + Na-B; T4: B + Na-B + MON; T5: B + AFB₁; T6: B + AFB₁ + Na-B + MON; T7: B + AFB₁ + MON; T8: B + AFB₁ + Na-B. Birds were fed dietary treatments for 28 d (d 18 to 46). No significant differences (P < 0.05) were observed among treatments with respect to broiler performance, biochemical parameters, or relative liver weights. With the exception of T8, all livers showed histopathological alterations, with accumulation of fat vacuoles. The normal appearance of livers from T8 showed the protective effect of Na-B against aflatoxicosis. The residual AFB₁ levels in livers from T5 to T8 ranged from 0.2 to 1.0 ng/g and were higher in livers from T6 (P < 0.05). Results of this study indicate a competition between AFB₁ and MON for adsorption sites on Na-B when feed contains low levels of the toxin, indicating a nonselective adsorption capacity of this particular Na-B. In addition, significant levels of AFB₁ in livers indicate that this determination is an important technique not only for diagnosis of aflatoxicosis in broilers, but also for quality control of avian products.

Synthetic zeolites (NaX, NaY, NaA, and CaA) were evaluated in vitro for their ability to sorb aflatoxin (AF) B1 from an aqueous solution. Zeolite NaA (ZN) was selected to be tested in vivo because of its high affinity and its stable association with AFB1. This sorbent was incorporated into diets (1%) containing 2.5 mg/kg AFB1. Male broiler chicks from 21 to 42 d of age received ad libitum access to their respective diets and water. When compared with controls, BW gains were lower (P < 0.05) for broilers that were fed AF in their diets. No differences were found between the BW gains of chicks fed diets without AF and those of chicks fed AF + ZN, indicating almost total protection against the effects caused by AF. Liver weights were considerably higher in chicks fed a diet containing AF, compared with those of controls, nevertheless, no significant differences were found in feed:gain ratio among the groups. The findings of this research suggest that ZN can counteract some of the toxic effects of AF in growing broiler chicks.

In vitro studies indicated that a sodium bentonite (SB) from southern Argentina had a high ability to sorb aflatoxin B1 (AFB1) from aqueous solution. We evaluated this compound for its ability to reduce the effects of total aflatoxins (AF; 5 mg AFB1/kg) in the diet of growing broiler chickens from 30 to 52 d of age. The diets were amended with 0.3% Argentinean SB to determine the effect of this compound during aflatoxicosis. When compared with the controls, BW gains were significantly (P < 0.05) lower for broilers fed diets containing AF alone (1,865 vs. 1,552 g). No differences were found between the BW gains of broiler chickens fed diets without AF (1,785 g) and those of chickens fed AF + SB (1,809 g). These results suggest that effects of AF treatment were ameliorated when SB was used in the broiler chick diets. The AF significantly (P < 0.05) decreased feed efficiency. Liver, kidney, and pancreas relative weights increased in chickens fed the diet containing AF alone. Alterations in the levels of serum total protein, albumin (ALB), and globulins (GLOB) were observed for AF diets, and moderate protection was provided by the sorbent. The ALB:GLOB ratio decreased in both groups of birds fed with the AF-contaminated diet, and we observed a moderate increase in this ratio by 0.3% addition of SB. The histopathological findings in liver sections of broiler fed diets with AF + SB indicated a nonprotective effect of this adsorbent, because a moderate hepatic steatosis was observed.

Sodium bentonite (SB) was evaluated for its ability to reduce the deleterious effects of fumonisin B1 (FB1) and aflatoxin B1 (AFB1) in broiler diets. It was incorporated into the diets (0.3%) containing 2.5 mg/kg AFB1, 200 mg/kg FB1, or a combination of 2.5 mg/kg AFB1 and 200 mg/kg FB1. Aflatoxin B1 significantly diminished body weight gain, whereas FB1 or the combination of FB1 and SB had no effect. Addition of SB in the diets significantly diminished the inhibitory effects of dietary AFB1. Feeding AFB1 alone caused significant increases in the relative weights of most observed organs. Feeding FB1 alone did not alter relative weights of any organs. In the combined diet (AFB1 plus FB1) relative weights of the liver, kidney, gizzard, and spleen were increased. Addition of SB to the diet containing AFB1 diminished the relative weights of liver, kidney, and spleen. Addition of SB to diets containing AFB1 and FB1 only decreased liver weights. In relation to the control, lower serum levels of total protein, albumin, and globulins were observed for all AFB, containing diets without SB addition, whereas all other treatments were not altered. Livers of birds fed diets containing AFB1 and a combination of AFB1 and FB1 were enlarged, yellowish, friable, and had rounded borders. The histopathology of them, stained with hematoxylin and eosin, showed multifocal and varied cytoplasmatic vacuolization with perilobular location. Incorporation of SB reduced the incidence and severity of the hepatic histopathology changes associated with aflatoxicosis.

Ochratoxin A (OA) is a mycotoxin detected in a variety of food and feeds mostly from countries with a temperate climate because of the fungi that produce it, mainly Aspergillus ochraceus and Penicillium verrucosum. In Argentina, there is no available information about the natural occurrence of OA and ochratoxigenic fungi from feedstuffs. The aim was to evaluate the natural occurrence of OA in poultry, pig and rabbit feeds over 8 months. Likewise, the capacity to produce OA by Aspergillus section Nigri was investigated. Mycotoxin analysis showed that in some months of sampling, OA was detected in three feeds. OA was found in 38% of the poultry feed samples tested with levels ranging from 25 to 30 ng g(-1). From rabbit feed samples, 25% contained OA and the levels ranged from 18.5 to 25 ng g(-1). Only 13% of the pig feed samples were contaminated with similar levels of toxins. Ninety-four black Aspergillus strains from feedstuffs were tested for OA production. Among these, the tested species were A. niger var. niger, A. niger var. awamori, A. japonicus var. japonicus, A. japonicus var. aculeatus and A. foetidus. For the detection of OA, three methodologies were applied: the two TLC methods used for the fast screening of the filamentous fungi for the production of OA were not sensitive enough to detect OA in any of the black Aspergillus strains. When an HPLC methodology was used, the results showed that 46% of the black Aspergillus strains were producers of OA, with levels ranging from 13 to 25 ng ml(-1) culture medium. The highest percentage of ochratoxicogenic strains was isolated from rabbit feeds with 100 and 78% of A. niger var. niger and A. niger var. awamori, with mean levels of 15.5 and 14.6 ng ml(-1), respectively. From pig feeds, 61% of the A. niger var. awamori were producers of this toxin with mean levels of 16 ng ml(-1). In poultry feeds, the lowest percentage of OA producer strains was detected. The results for the occurrence of OA in feeds from different sampling months depended on storage and humidity-temperature conditions. Therefore, a good storage practice becomes very important to prevent OA production

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Corn silage is an important feed source for dairy and beef cattle in central Argentina. The presence of thermophilic species Aspergillus fumigatus is among the major problem in silage, as many strains can produce several mycotoxins that affect the health of dairy cattle. The aims of the present study were to determine total fungal counts and relative density of A. fumigatus in silage samples, and to determine the natural incidence of gliotoxin in silage and ready dairy feed samples. The potential gliotoxin production of A. fumigatus isolated from silage was also recorded. A total of 90 samples were investigated, which were taken immediately after opening of the silo and the end of the ensiling period of about after 5 months. Sampling was performed manually through silos in transects at 3 levels per silo. Thirty samples of ready cattle feed (corn silage, ground corn, barley, cotton seed, brewer grains) were collected and investigated as well. Gliotoxin contamination was determined by HPLC. The ability of A. fumigatus to produce gliotoxin was measured using a TLC method. Results show that in all samples, the total number of yeasts and moulds exceeded 1×104 cfu/g. Aspergillus was the most prevalent genus followed by Fusarium and Penicillium spp. Investigations of the isolated A. fumigatus strains showed that many of these strains produced more than one mycotoxin. All samples showed gliotoxin contamination, but the strains isolated from ready cattle feed had higher gliotoxin levels than those isolated from corn silage. The gliotoxin concentrations found in this study exceeded the levels that are known to induce immunosuppressive and apoptotic effects in vitro. Although at present the oral bioavailability of gliotoxin in cattle is not known, the presented data suggest that its presence in feedstuffs could affect productivity and present a health risk for dairy cows.