One of the most intriguing comments came from Dr. Mick Hazzeldine (UK), who pointed out that when feed is contaminated with mycotoxins, it is possible to observe an increased requirement for sulfur-containing amino acids, methionine and cysteine. Most likely cysteine, which is required for the detoxification of toxins in the liver, but also methionine as levels of both amino acids decline rapidly in mouldy feed.
Nevertheless, as methionine can be converted to cysteine, and it is through synthetic methionine that we can largely manage the level of total sulfur amino acids in feeds, it may be possible to reduce the impact of mycotoxins by adding extra synthetic methionine. Now, this is a very intriguing argument!
Perhaps, this line of argumentation could explain why in trials evaluating methionine and cysteine requirements (as a ratio to lysine) the results have been ranging from 50 to over 60%. If the cereals used in the trials were contaminated with mycotoxins, and we assume that animals used some of the supplied methionine for detoxification, it is logical to conclude that amino acid requirements for growth appeared to be elevated.
Again, all these are very interesting, but we need some actual trials to evaluate and quantify this observation and enhance our understanding on how to feed animals in the presence of mycotoxins.