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High-density pig production can create environmental risks due to ammonia emissions and nutrient leaching from slurry. Reducing dietary nitrogen with supplemental crystalline amino acids is effective in lowering nitrogen excretion, but low protein diets may impair growth if essential amino acid requirements are not fully met, especially in lean genetic lines.
Objective: The aim of this study was to investigate the effects of reducing dietary crude protein (CP) from 14.8% to 12.6% in finishing pigs (90–120 kg), on productive performance, nitrogen balance, blood protein markers, nutrient digestibility, carcass, and meat quality.
Methods: Eighty pigs were assigned to one of two dietary treatments: a standard or a low-protein diet with balanced amino acids. Body weight, carcass, and major cuts (ham, shoulder, loin, and belly) were monitored. Loin samples were analyzed for meat quality, including pH, color, cooking losses, tenderness, chemical composition (moisture, protein, fat, ash), and halothane gene status. Dietary treatment did not affect initial or final body weight or overall growth performance.
Results: The low-CP diet reduced nitrogen intake and excretion, improving nitrogen-use efficiency, while nitrogen retention remained similar across diets. Sex had no effect on nitrogen balance. Fecal dry matter tended to be higher in pigs fed the low-CP diet (30.1% vs. 27.9%), and phosphorus digestibility was lower, with a trend toward reduced neutral detergent fiber digestibility. Serum urea decreased in intact males fed the low-CP diet, with no effect in females, and total protein showed a similar pattern. Creatinine was lower in low-CP-fed pigs and in males at slaughter, while albumin was unaffected by diet or sex but increased over time. Diet did not influence carcass weight, dressing, or overall lean content, although intact males were heavier with a higher lean percentage, whereas females had larger proportions of individual cuts. The frequency of halothane gene carriers was similar across treatments. Meat quality parameters (pH, color, shear force) were largely unaffected by diet; however, low-CP meat tended to exhibit higher cooking losses and had lower moisture and protein content.
Conclusion: Reducing dietary crude protein with balanced amino acids improved nitrogen efficiency and lowered excretion without affecting growth or overall carcass quality.
Álvarez-Rodríguez J, Vigo-Morancho A, Miana-Mena FJ, Pérez-Ciria L, Latorre MA. Dietary Protein Reduction in Lean Pigs From Pietrain Paternal Line Under Commercial Setting: An Interplay Between Nitrogen Efficiency and Meat Attributes. Anim Sci J. 2025; Jan-Dec;96(1):e70033. https://doi.org/10.1111/asj.70033