Lipid Droplets in Poultry Lipid Metabolism: Characteristics, Regulatory Factors, and Implications for Fatty Liver and Muscle Lipid Deposition.

Lipid droplets (LDs) are dynamic metabolic platforms that integrate neutral-lipid storage, fatty-acid trafficking, organelle communication, cellular energy metabolism, and stress adaptation in poultry cells. Lipid metabolism plays a central role in poultry growth, reproductive function, production performance, meat quality, and metabolic health. Unlike mammals, de novo lipogenesis in poultry occurs predominantly in the liver, making hepatic lipid homeostasis particularly important for maintaining physiological function and production efficiency. Dysregulation of lipid metabolism contributes to excessive fat deposition, fatty liver hemorrhagic syndrome (FLHS), oxidative stress, and impaired meat quality in poultry production systems. At the cellular level, LDs partition fatty acids among neutral-lipid storage, VLDL assembly, membrane synthesis, mitochondrial oxidation, and stress-buffering pathways. Poultry studies show that hepatic LD accumulation and altered lipid handling are closely associated with fatty liver and muscle lipid deposition, while mechanistic studies from mammalian and cellular models provide useful hypotheses for LD turnover and LD-organelle communication. Because direct poultry-specific evidence for several LD-organelle mechanisms remains limited, these mechanisms are discussed cautiously as conceptual frameworks and future research directions rather than as established causal pathways in poultry. Nutritional interventions, including balanced dietary energy, fatty acid sources, amino acid balance, choline, methionine, antioxidants, trace elements, phytochemicals, probiotics, and bile acids, can influence LD-associated lipid handling and improve metabolic health in poultry. In this review, we summarize current evidence on LD formation, turnover, and LD-associated regulatory pathways in poultry lipid metabolism, with particular emphasis on fatty liver, muscle lipid deposition, and nutritional regulation. We further discuss unresolved questions and future perspectives for defining the causal roles of LD dynamics in poultry health and production. The review therefore treats laying hens and broilers as distinct physiological contexts: estrogen-driven VLDLy production and susceptibility to fatty liver hemorrhagic syndrome in laying hens, versus hepatic lipid export, abdominal fat deposition, muscle lipid utilization, and meat-quality formation in broilers.