PSVII-36 Late-Breaking Abstract: Protein concentrations in basal diets affect metabolizable energy of feed ingredients determined by difference procedure in pigs

Abstract

The objective was to investigate the influence of crude protein (CP) concentrations in the basal diet on the metabolizable energy (ME) of feed ingredients determined using the difference procedure in pigs. Twelve barrows (73.7 ± 5.5 kg body weight) individually housed in metabolism crates were used. A low-protein basal diet (LPBD, 7.4% CP) was composed of 97.5% corn as the sole energy source and a high-protein basal diet (HPBD, 14.3% CP) was composed of 78.0% corn and 19.6% soybean meal. Four additional diets were prepared by replacing 20% of the energy sources in the basal diets with full-fat soybean (FFSB, 37.7% CP) or soy protein isolate (SPI, 87.6% CP). The 6 experimental diets were fed to 12 pigs employing a replicated 6 × 4 incomplete Latin square design with 4 periods. Each period was consisted of 4 days of adaptation and 4 days of collection period and the marker-to-marker method was used for fecal collection. Urinary gross energy output was greater (243 vs. 176 kcal/d; P < 0.05) in the HPBD group compared with the LPBD group. While ME in the HPBD was greater (3,418 vs. 3,322 kcal/kg; P < 0.05) than in the LPBD, ME in FFSB diets (3,585 and 3,633 kcal/kg in the LPBD and HPBD group, respectively) and SPI diets (3,537 and 3,537 kcal/kg, respectively) were not different between the 2 basal diet groups. Metabolizable energy of the test ingredients was less (P < 0.05) in pigs fed the HPBD group (4,565 and 4,111 kcal/kg in FFSB and SPI, respectively) compared with pigs fed the LPBD group (4,756 and 4,517 kcal/kg in FFSB and SPI, respectively). In conclusion, as the protein in the basal diet increases, metabolizable energy in a test ingredient determined using the difference procedure decreases mainly due to greater urinary energy output in pigs.