Dietary conjugated linoleic acid in poultry diets and its implications for hatchability, egg quality and immune function: a review

1. This paper reviews the importance of dietary conjugated linoleic acid (CLA) in poultry nutrition, with particular emphasis on its effects on hatchability, egg quality, fatty acid composition and immune function across different poultry species.2. Poultry meat and eggs naturally contain low concentrations of CLA compared with ruminant-derived meat. However, dietary supplementation effectively increases CLA, resulting in value-added functional products.3. Data from chickens, quail and pigeons consistently shows that high dietary inclusion of CLA in breeder diets can negatively affect hatchability, mainly through alterations in yolk fatty acid (FA) composition rather than through direct effects on fertility.4. Dietary CLA supplementation has been associated with an increase in saturated fatty acids, particularly palmitic (C16:0) and stearic acid (C18:0) and a concomitant reduction in monounsaturated FA such as palmitoleic (C16:1, n-7) and oleic acid (C18:1, n-9). These changes are due to the inhibition of stearoyl-CoA desaturase, which disrupts yolk lipid homoeostasis and impairs embryonic lipid utilisation.5. Supplementation with CLA can reverse storage-related egg quality defects, including increased yolk firmness, discolouration of both yolk and albumen and reduced peelability following refrigeration. These effects are dose-dependent and may be partially mitigated by co-supplementation with unsaturated lipid sources that help restore yolk fatty acid balance. Beyond reproductive traits, dietary CLA has been shown to influence body fat deposition, carcase characteristics and immune responses in poultry.