Nitrate poisoning
Maize cultivation requires large amounts of N fertilizer (inorganic or manure). Under some conditions, such as extended dry periods ended by rains, nitrogen may accumulate in the plants in the form of nitrates that are toxic to livestock. This is particularly true for the first 5-7 days after the rain (Bagg, 2012; Brewbaker, 2003). However, ensiling and good practices can reduce the nitrate level in the silage. Maize plants at the time of harvest should be neither too wet nor too dry, in order to promote good fermentation and reduce the nitrate content of the silage. A well-managed 3-5 week ensiling period can reduce nitrate content by 40%. Cutting should be done above the bottom third of the stalk, where most nitrates are present (Bagg, 2012).
Silage spoilage and mycotoxins
Aerobic spoilage may occur at various stages of ensiling (see Processes on the "Description" tab for prevention methods). Aerobic spoilage causes the development of Fusarium, Penicillium or Aspergillus fungi. The most important issue with maize silage is the development of Fusarium, which produces vomitoxin (DON), fumonisin, zearalenone, and T-2 mycotoxins. Aspergillus is a source of aflatoxins (Tapia et al., 2005). Penicillium roqueforti produces penicillic acid, known for its antimicrobial activity, which impairs rumen health and reduces feed intake. Penicillium roqueforti is also responsible for the production of the neurotoxin roquefortine C and mycophenolic acid, a potent immunosuppressant (Berge, 2011). Other Penicillium species produce patulin, which affects rumen fermentation and is both a neurotoxin and a cell toxin (Berge, 2011).