3.1. Characterization of Species Included in the Study
Lolium perenne (
Figure 2) is a bunchgrass. The species is demanding of moisture and nutrients and easily undergoes freezing. It is a highly valuable forage grass with a high soluble carbohydrate content. The disadvantage is its susceptibility to fungal diseases. On the contrary
Festulolium pabulare, resulting from crossbreeding between
Festuca arundinacea and
Lolium multiflorum, shows higher resistance to fungal diseases. This species has short rhizomes, is drought resistant and capable of being dotted under low temperatures. Leaves dry easily in autumn and, unlike
Lolium perenne, are not so susceptible to rotting.
Festulolium braunii is derived from crossbreeding of
Lolium multiflorum and
Festuca pratensis. Its endurance is limited to a period of five years. There is high quality forage, but susceptibility to fungal diseases. Unlike the above mentioned species, this one belongs to the spring grass class (
Figure 3), thus, it tends to ear well in the second cut.
Festuca rubra can be included in the leptomorph grasses group (
Figure 4), which display slow development. This species is commonly used to fill the gaps in vegetation by its long rhizomes.
Poa pratensis is similar to this species (
Figure 5), and, unlike
Festuca rubra, provides higher quality forage.
3.2. The Content of Mycotoxins and Statistical Evaluation of the Data
Species did not have a significant effect on the content of mycotoxins (
Table 1), but it is clear that
Festulolium pabulare had lower amounts of ZEA in comparison with other species, however, the difference was not statistically significant.
The resistance of this species to this kind of fungal diseases is shown in the content of ergosterol. Its content was lower in
Festulolium pabulare (
P < 0.05) than in
Festulolium braunii. Ergosterol content gradually increased (
P < 0.05) from June till December. On the other hand, contents of mycotoxins such as DON in July (
P < 0.05) and ZEA (P < 0.05) in July and October were significantly higher. Despite the high (
P < 0.05) content of ergosterol in November and December, low (
P < 0.05) contents of ZEA were determined in these months. This may be associated with a decrease in temperature when the mould reduces the production of mycotoxins, which are generally a response to stress associated with higher temperatures. The content of DON ranged from 35.07 to 52.78 ppb in the evaluated species in summer (
Figure 6).
A lower (
P < 0.05) content of DON occurred in June than in July. The content of ZEA in
Lolium perenne and
Festulolium pabulare (
Figure 7) was under the limit of quantification (<LOQ). The highest content of ZEA was determined in mixtures with
Festuca rubra and
Poa pratensis, respectively. (102.07 ppb and 112.52 ppb, respectively). The major difference between species was not significant because of the high standard errors of the means. The contents of AFL and FUM were zero or under the limit of quantification. This phenomenon was observed in summer and autumn samples. Samples of grasses in autumn contained comparable amounts of DON as summer samples (
Figures 8 and
9). During of autumn the content of DON decreased (
P < 0.05). Differences between years of observation are also significant (
P < 0.05). The content of ZEA was lowest at
Festulolium braunii. Content of ZEA decreased from October to December (
P < 0.01), like for DON. The reason for the low production of mycotoxins can be the decreasing temperatures when mycotoxins are not produced while warm weather during autumn is suitable for mycotoxin production. The effect of not only biotic but also abiotic factors on the production of mycotoxins was observed and discussed by DeNijs
et al. [
39], and Engels and Krämer [
40]. The content of ZEA was considerable higher (173.0 ppb) in October than in summer (122 ppb and <LOQ, respectively). According to D’Mello [
41], a zearalenone concentration ranging from 0.2–1.0 mg kg
−1 is even toxic for rodents. Forage with a zearalenone content higher than 0.5 mg kg
−1 is not advised for feeding [
42].
Given the fact that fungi are able to create a number of mycotoxins, one mould species can form multiple mycotoxins. In addition mycotoxins are synthesized under stressful conditions, thus, the presence of ZEA and DON does not reflect the current state of content of mould. The content of ergosterol indicates in this context the presence of fungus in all samples. Ergosterol content was lowest in June (3.84 mg kg
−1 dry weight). During the summer no difference between the evaluated grasses was observed (
Figure 10).
Obvious differences between the species were determined in the fall (
Figure 11). Even in the case of mycotoxin contamination
Festulolium pabulare was less contaminated. The low content of ergosterol (
P < 0.05) statistically confirms
Festulolium pabulare resistance against mildew. Unlike mycotoxins, the content of ergosterol increases (
P < 0.05) from October to December. It is obvious that the higher humidity of the growing season contributes to the development of mould, but low temperatures inhibit formation of mycotoxins. Fall of temperature under 5 °C in November and December can lead to reduction of enzymatic activity of mould and lower production of secondary metabolites, particularly mycotoxins, which comprise stress reaction on the higher temperature. On the contrary temperatures lower than 5 °C are favourable for the growth of some moulds (
Fusarium nivale) and this can enhance the content of ergosterol without increase of mycotoxins.