Acid Silage from Pirarucu (Arapaima gigas) By-Products Affects Performance, Physiological Parameters and Meat Quality of Slow-Growing Broilers

The increasing demand for sustainable and cost-effective feed alternatives has stimulated the use of agro-industrial by-products in poultry nutrition. This study evaluated the effects of acid silage from pirarucu (Arapaima gigas) by-products (ASP), derived from fish-processing waste, on growth performance, physiological responses, and meat quality of slow-growing broilers. A total of 240 male Label Rouge broilers were assigned to diets containing 0, 1, 2, or 3% ASP from 8 to 56 days of age. Moderate ASP inclusion levels (1–2%) improved (p ≤ 0.05) growth performance by increasing weight gain and improving feed conversion ratio, particularly during the grower and finisher stages. Hematological analyses demonstrated favorable physiological responses, including increased (p ≤ 0.05) hemoglobin concentration, hematocrit, mean corpuscular volume, and mean corpuscular hemoglobin. Plasma biochemical parameters indicated improved (p ≤ 0.05) protein metabolism, with higher total protein, albumin, and globulin concentrations, while glucose, cholesterol, and urea remained unaffected (p > 0.05). Carcass evaluation revealed improved (p ≤ 0.05) breast yield at 2% ASP inclusion, and breast composition showed increased (p ≤ 0.05) protein, lipid, and mineral deposition, accompanied by reduced (p ≤ 0.05) moisture content. However, the highest inclusion level (3%) did not promote additional productive benefits. These findings demonstrate that moderate ASP inclusion (1–2%) can improve productive efficiency and meat nutritional quality while promoting sustainable reuse of aquaculture by-products, supporting circular and environmentally responsible poultry production systems.