237. Evaluation of Energy Utilization and Net Energy Efficiency of Novel Corn-derived Protein Ingredients in Growing Pigs.

Abstract This study evaluated the energy contribution and utilization efficiency of novel corn-derived products in growing pigs. Forty-eight (48) growing barrows (35 ± 5 kg BW; PIC 337 × 1050) were housed in metabolism crates across two replicates and assigned to one of five dietary treatments: a conventional corn-soybean meal control (CON), or diets in which PZ, PX, or PY replaced 35% of the basal diet, and corn liquor (CL) replaced 21%. The CON diet was formulated to meet or exceed requirements according to NRC (2012). Following a 9 day adaptation period, total feces and urine were collected over 5 days. Gross energy (GE) of diets, feces, and urine was determined by bomb calorimetry, and digestible energy (DE), metabolizable energy (ME), and net energy (NE) were calculated. Apparent total tract digestibility (ATTD) of GE and energy utilization ratios (DE:GE, ME:DE, NE:ME) were also evaluated. Data were analyzed using SAS 9.4 with treatment as a fixed effect and replication and block within replication as random effects. Pigs were the experimental unit, and significance was declared at P < 0.05. Feed intake did not differ (P = 0.16). Apparent Total Tract Digestibility of Gross Energy was similar (PZ = 92%, CON = 89%, PY = 92%, PX = 90%, CL = 91%; P = 0.16), indicating comparable digestive efficiency. Diet GE, DE, and ME differed (P < 0.01), with CL highest and CON lowest. Ratios of DE:GE and ME:DE were similar (P > 0.10), demonstrating comparable conversion of GE to DE and ME. The NE:ME ratio (72.% (PZ), 73.% (CON), 72.% (PY), 72.% (PX), and 73.% (CL) P < 0.01) were reduced in diets containing corn protein products compared with CON (P < 0.01) reflecting dietary crude protein supply may have exceeded the pig’s biological capacity for lean tissue deposition. When amino acid intake surpasses anabolic requirements, surplus amino acids are deaminated and nitrogen excreted as urea, increasing metabolic heat production. The energetic cost of this catabolism reduces the proportion of ME recovered as NE, reflecting physiological limitation rather than inherent ingredient inefficiency. Estimated ingredient ME values (Mcal/kg DM) were 5.569 for PZ, 4.432 for PX, 4.552 for PY, and 6.979 for CL. These results demonstrate that novel corn-derived protein ingredients provide substantial ME and digestibility comparable to corn-soybean meal diets. However, lower NE:ME ratios indicate reduced net energy efficiency, underscoring the importance of NE-based formulation and practical inclusion levels in growing pig diets.