Predicting disease-challenged pig performance and energy and nutrient requirements using the NRC 2012 modelling module

Abstract Text: Models can be used to estimate energy and nutrient requirements, evaluate feeding programs, and to compare pig performance modelling estimates to those actually observed. The objective of this study was to use the NRC 2012 modelling module to predict performance and energy and nutrient requirements of disease-challenged growing pigs. Growth and feed intake data from a previously conducted study consisting of healthy pigs (Control), porcine reproductive and respiratory syndrome (PRRS) virus, porcine epidemic diarrhea virus (PEDv), or a combination of PRRS and PEDv (PRP) challenged gilts were used as inputs. From this data a 14 d period was analyzed using observed BW gain (BWG) and ADFI. Within the modelling module, the selected nutrient systems were ME, standardized ileal digestibility (SID) of AA, and standardized total tract digestibility (STTD) of P, and the selected model for estimating nutrient requirements was for growing-finishing pigs. Treatment inputs for the 14 d test period for BWG and ADFI, respectively: Control 8.8 and 1.04 kg, PRRS 5.8 and 0.78 kg, PEDv 8.0 and 0.92 kg, and PRP 3.8 and 0.73 kg. The diet ME content was set at 3,388 kcal/kg and sex was specified as gilt so that the only adjustments made within the NRC 2012 modelling module were BWG and ADFI. Results for this 14 d challenge period predicted modelled Control gilt BWG (8.6 kg) to be similar to that we observed for these gilts. Compared to the observed BWG, the model overestimated BWG for PEDv (8.6 kg), PRRS (8.4 kg) and PRP (8.2 kg) disease-challenged gilts.  The model also overestimated ADFI for all treatments by 8 – 36% and this was also reflected in ME intake.  Utilizing observed BWG and ADFI, the model indicated no treatment differences in SID of AA (g/d) including: Lys, Met, Thr, and Trp. There were no differences in predicted whole body protein deposition rates between the control (105 g/d), PRRS (104 g/d), PEDv (101 g/d), and PRP (99 g/d) disease-challenged gilts. This module should be limited to healthy pigs as it does not consider the catabolic state of disease-challenged pigs as represented by the observed reduction in BWG and ADFI. In conclusion, the NRC 2012 modelling module is accurate in predicting BWG and ADFI of healthy gilts; however, it did not reflect the observed BWG and ADFI of disease-challenged gilts.

Keywords: energy and nutrient requirements, predictions, pigs