Nitrogen utilization is lower for sorghum-based diets compared with corn-based diets in pigs

Two experiments were conducted to compare the utilization of gross energy (GE) and N - in sorghum- or corn-based diets fed to pigs. In Experiment 1, 12 barrows (24.8 ± 1.5 kg) fitted with T-cannulas at the distal ileum were randomly assigned to 2 diets (6 barrows/diet) containing 966 g/kg of corn or sorghum as the sole source of N and GE to determine apparent ileal (AID) and total tract digestibility (ATTD) and hindgut disappearance (HGD) of GE and N in these 2 grains. There was no difference in ATTD of GE and N between corn and sorghum. The AID of GE tended to be lower in sorghum than in corn (P = 0.07), and conversely the HGD of GE tended to be greater in sorghum than in corn (P = 0.06). Sorghum had lower AID of N associated with greater HGD of N than corn (P < 0.05). In Experiment 2, 72 weaned pigs (8.8 ± 1.0 kg) were assigned to 2 treatments with 6 replicate pens per treatment and 6 pigs per pen in a randomized complete block design to determine the effects of sorghum as a potential substitute for corn on fecal energy and N output by pigs. During d 0 to 14, pigs fed the sorghum diet had similar GE intake and fecal energy output per day, but more fecal energy output per weight gain (P < 0.05), compared with pigs fed the corn diet. The N intake was not different in pigs between treatments; whereas N absorption was decreased in pigs fed the sorghum diet associated with increased fecal N output per day or weight gain (P < 0.05). During d 14 to 28, there was no difference in GE intake and utilization for pigs fed the 2 diets, but pigs fed the sorghum diet tended to have lower N absorption (P = 0.09) and greater fecal N output per weight gain (P = 0.07) than pigs fed the corn diet. There was no difference in serum metabolites and small intestine morphology between pigs fed the sorghum and corn diet. Pigs fed the sorghum diet tended to have greater total volatile fatty acids in cecum (P = 0.08) and rectum (P = 0.09). Overall, although sorghum could be an alternative energy source for corn in diets fed to pigs without negative effects on growth performance, N utilization could be decreased in pigs fed the sorghum-based diets because of the increased N loss via fecal excretion and hindgut disappearance.