Ergotism
Rye grain is susceptible to contamination by ergot (Claviceps purpurea), which produces alkaloids with vasoconstrictor and neurotoxic properties that in humans result in necrosis of extremities, staggering, lameness, hyperthermia and sometimes death. Outbreaks of ergotism, also called Saint Anthony's Fire, were common in Northern Europe until the 19th century (Guerre, 2011; Bourke, 2000). The presence of ergot in rye grain is a causative agent for the poor performance of pigs and poultry. Ergot fed to pregnant sows has caused reproductive problems, abortion, agalactia and loss of piglets at farrowing. Levels of 1.0 or 2.0% ergot in pig rations severely reduce both feed intake and weight gains (Maner, 1987). Ergotism may become a major issue in rye by-products, such as distillers' grains, since mycotoxins are concentrated by starch removal (Newkirk, 2011).
Arabinoxylans and β-glucans
Rye grain contains large amounts of soluble arabinoxylans and β-glucans, which increase viscosity in the gut content in monogastrics, impairing the action of digestive enzymes, depressing nutrient bioavailability and thus resulting in a poor nutritive value (Rakowska, 1994). In poultry, this high soluble fibre content also results in sticky droppings. These problems can be alleviated by the use of enzymes (β-glucanases, xylanases, pentosanases), by extrusion or by fermentation processes (Korobov et al., 2005; Dendy et al., 2001; Rakowska, 1994).
Resorcinols
In the past, it was hypothetised that the poor performance of animal fed rye-based diets was due to the presence of alkyl- and alkenylresorcinols, which are in much higher concentrations in rye than in other grains, but experiments have failed so far to demonstrate this (Aman et al., 1997; Rakowska, 1994; Sosulski et al., 1988; Maner, 1987).
Dustiness
Dustiness may be a problem with rye. To prevent it, rye should be coarsely ground and/or fat or vegetable oil added (Sullivan et al., 2005).