380 Diet protein concentration does not influence dietary net energy by group housed growing pigs offered ad libitum access to feed

• Published in: Journal of animal science Vol. 102; no. Supplement_3; pp. 250 - 251
• Main Authors: Cristobal, Minoy, Lee, Su A, Mallea, Andrea P, Torres-Mendoza, Leidy J, Parsons, Carl M, Stein, Hans H
• Format: Journal Article
• Language: English
• Published: 14-09-2024
• ISSN: 0021-8812; 1525-3163
• DOI: 10.1093/jas/skae234.288

The objective was to test the hypothesis that net energy (NE) of diets is not increased by reducing soybean meal (SBM) and increasing crystalline amino acids (CAA) in diets fed to group-housed pigs on an ad libitum basis. Two “normal protein” diets with 17 and 14% crude protein (CP) were formulated. One diet was based on corn, SBM, and no CAA and the other diet was based on corn, SBM, and crystalline Lys, Met, and Thr. Four additional diets containing 13, 12, 11, or 10% CP were formulated by reducing SBM and increasing crystalline Lys, Met, Thr, Trp, Val, and Phe. Growing pigs (n = 24; initial body weight = 29.9 ± 2.4 kg) were randomly allocated to 6 calorimeter chambers with 4 pigs per chamber. The 6 chambers were allotted to the six diets using a 6 × 6 Latin square design with six 15-d periods providing 6 replicate chambers per diet. Pigs had ad libitum access to diets throughout the experiment except during the fasting periods. Consumption of O2 and production of CO2 and CH4 were measured, and fecal and urine samples were collected for 6 d after 7 d of adaptation. Fasting heat production (FHP) was determined for 12 h following a 24 h fasting period. Diets, fecal samples, and lyophilized urine samples were analyzed for gross energy (GE) and N. Data were analyzed using contrasts statements to determine linear and quadratic effects of reducing dietary protein. Results indicated that feed intake, fecal and urine GE output, the apparent total tract digestibility (ATTD) of dry matter and GE, total heat production (THP), FHP, and retained energy were not different between pigs fed the 17 and the 14% CP diets (Table 1). The respiratory quotient (RQ) of pigs fed the 17% CP diet was less (P = 0.045) compared with the 14% CP diet. Digestible energy (DE) and metabolizable energy (ME) in the 17% CP diet were greater (P < 0.05) than in the 14% CP diet, but NE was not different between these 2 diets. Feed intake, GE intake, and fecal GE output of pigs were linearly (P = 0.044) increased by reducing CP in diets, but reducing diet CP did not affect ATTD of dry matter or GE or urine GE excretion. Total heat production, FHP, retained energy, and DE, ME, and NE were also not affected by reducing CP in diets. In conclusion, reducing CP of diets for pigs by reducing SBM and increasing CAA did not increase NE of the diet when fed to group-housed pigs on an ad libitum basis, and dietary CP does not appear to influence diet NE.