From waste to feed resource: Evaluating shellfish by-products as alternative calcium sources for poultry

초록

Calcium is a cornerstone mineral in poultry nutrition, required for skeletal integrity, neuromuscular function, metabolic regulation, and eggshell formation. Commercial poultry production has traditionally relied on mined limestone as the principal calcium source; however, variability in limestone quality, environmental impacts of mining, and the growing need for sustainable feed resources have driven interest in alternative calcium sources. Concurrently, rapid expansion of shellfish aquaculture and seafood processing has resulted in the accumulation of large volumes of shell waste, composed primarily of calcium carbonate (85-95% CaCO3, equivalent to 33-40% elemental calcium depending on species and processing conditions). This study systematically reviews shellfish by-products, including oyster, mussel, clam, ark shell, periwinkle, and sea urchin shells, as alternative calcium source for poultry. Evidence from chemical characterization, in vitro solubility assays, and in vivo feeding trials in broilers, laying hens, and quail is critically synthesized. Reported ileal calcium digestibility values range widely from approximately 27-77%, depending on particle size, source, and bird age, highlighting substantial variability across studies. Particular attention is given to particle size effects, calcium bioavailability, growth performance, eggshell quality, bone mineralization, gastrointestinal responses, and interactions with dietary phosphorus and vitamin D. Importantly, the literature distinguishes between in vitro solubility (laboratory dissolution behavior in simulated gastric conditions) and in vivo digestibility (actual intestinal absorption in birds), which do not always correlate directly. Environmental and economic implications are discussed within a circular economy framework relevant to marine-dependent regions. Overall, the literature demonstrates that properly processed shellfish by-products can partially or fully replace limestone without compromising poultry performance, while contributing to waste valorization and sustainable feed systems.

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