A review of the iron requirements and its determination in commercial poultry

Iron (Fe) is an essential mineral for poultry, playing a critical role in oxygen transport and energy metabolism. Consequently, it is routinely supplemented into commercial poultry diets to safeguard against deficiencies that can negatively impact productive performance. Conversely, excessive dietary Fe can compromise performance by inducing oxidative stress, reducing absorption of other nutrients and negatively disrupting the gastrointestinal microbiota. The bioavailability, and thus absorption, of Fe is dictated by the form it is present in the feed, with haem, the organic form of Fe, being preferentially absorbed. Modern poultry diets, depending on location or context, may be devoid of animal proteins, and therefore without haem. Inorganic Fe sulphates have been the primary source of supplemental Fe in poultry diets, via premixes. These sources may provide Fe in the ferric state (Fe³⁺), which must first be converted to a ferrous state (Fe²⁺) for uptake, though it is more commonly supplied as ferrous sulphate monohydrate (Fe²⁺). The poor bioavailability of inorganic Fe has led to increased interest in alternative organic Fe sources, such Fe-amino acid chelates and Fe proteinates, with higher absorption efficiency at lower active inclusion levels. Iron absorption is also dictated by interactions with anti-nutrients, notably phytic acid and mineral antagonists. There is considerable variation in recommended supplemental Fe levels for poultry across published guidelines, feeding standards and scientific articles. For example, in broilers and broiler breeders recommended total Fe ranges from 20 to 110 mg/kg and in laying hens from 30 to 80 mg/kg. Advances in feed formulation, including use of organic sources of Fe, reduced concentration of antagonistic trace minerals and phytase supplementation, has enhanced bioavailability of Fe, indicating that commercial poultry may now be over-supplemented with Fe. Updated and context-specific Fe recommendations are essential for optimising poultry productivity. This review examines how to assess Fe utilisation in poultry, including methods for determining Fe status, proposes Fe recommendations for broilers, broiler breeders and laying hens based on outputs from research trials, and explores how Fe interacts with other nutrients and the microbiota.