Flavour problems may also exist in freshly produced feeds. In many cases, it is impossible to produce high uniform palatability in different feed batches without flavour aids. This is due to varying by-products, different soil and crop conditions, and to varying manufacturing processes. The feed additives used in different batches may also contribute to the change of flavour. The fats, for example, may be provided from inedible animal greases with various impurities and contaminative feed vapidity. Likewise, minerals and vitamins may be provided in premixes having off-flavour carriers and bases, all of which factors are inductive to “taste shock” changes in feed intake.