Restricted Blend Feeding in Growing-Finishing Pigs: Effects on Productive Performance, Nitrogen Balance, Feed Cost and Feed-Related Carbon Footprint

Precision feeding can improve nutrient efficiency and reduce the environmental impact of pig production. This study evaluated a restricted blend feeding (R-BF) program based on weekly adjustments of two diets differing in crude protein and standardized ileal digestible lysine concentrations. A total of 520 growing-finishing pigs were assigned to either a conventional three-phase feeding program or R-BF, with R-BF adjusted by BW group. Compared with conventional feeding, observed SID lysine intake was approximately 2–9% lower in light pigs and 2–18% lower in heavy pigs, depending on growth phase. R-BF did not affect feed intake but reduced average daily gain by 5% and impaired feed efficiency, particularly in heavier pigs. R-BF significantly reduced nitrogen intake, calculated nitrogen excretion, and blood urea nitrogen. The low-crude-protein, low-lysine finisher formulation had a 16.6% lower estimated carbon footprint than the conventional finisher diet, resulting in a 3.8% lower feed-related carbon footprint per pig. R-BF also reduced feed cost by up to EUR 4.0 per pig and tended to lower feed cost per kilogram of BW gain under the low-feed-cost scenario. Overall, R-BF reduced nutrient inputs, feed-related environmental impacts, and feed cost per pig, although lower growth performance limited economic efficiency.