Models for energy utilization of feeds for nursery and growing pigs based on conventional and multi-sample simultaneous in vitro procedures

Objective:The objective of the present study was to develop prediction equations for energy digestibility and metabolizability in feedstuffs and diets for nursery and growing pigs based on in vitro total tract disappearance using the conventional procedure determined with the flask method (IVTTDflask) and the multi-sample simultaneous method (IVTTDDaisy) and chemical composition.Methods: Fourteen feedstuffs and 18 diets for nursery pigs and 35 feedstuffs and 42 diets for growing pigs were analyzed for gross energy, ether extract, crude protein (CP), ash, amylasetreated neutral detergent fiber (aNDF), and acid detergent fiber.In vitro procedures were performed to determine IVTTDflask and IVTTDDaisy of dry matter (DM) by mimicking digestion and absorption in the stomach, the small intestine, and the large intestine of pigs.Energy utilization of the feeds in nursery and growing pigs was from in-house data. Results:The most suitable equations for energy utilization (%) were: energy digestibilitynursery = 0.41×IVTTDDaisy of DM-0.28×aNDF+54.0(RMSE = 3.12, R 2 = 0.91, and p<0.001); energy metabolizabilitynursery = 0.38×IVTTDDaisy of DM-0.25×aNDF-0.09×CP+54.6(RMSE = 1.39,R 2 = 0.98, and p<0.001); energy digestibilitygrowing = 0.26×IVTTDDaisy of DM-0.36×aNDF+69.2(RMSE = 4.54, R 2 = 0.83, and p<0.001); energy metabolizabilitygrowing = 0.26×IVTTDDaisy of DM-0.33×aNDF-0.09×CP+68.2(RMSE = 4.77, R 2 = 0.80, and p<0.001),where all nutrients were in % on a DM basis. Conclusion:The energy utilization by nursery and growing pigs can be estimated using in vitro total tract disappearance of dry matter and chemical composition in feedstuffs and diets.