The reliability of tabular values to estimate the composition and digestibility of pig feeds

Tabular values of feed ingredients are commonly used in pig feed formulation. It regroups mean values of chemical composition and digestibility coefficients. However, composition and digestibility within the same feed may vary to a large extent. To evaluate the reliability of the Dutch (CVB2016) and French (INRA 2017) tabular values of the ingredients, 20 compound feeds were formulated and the correlation (R²) and the mean absolute difference between the tabular and the determined chemical composition and digestibility coefficients was calculated (Excel 2016). The 20 compound feeds had a variable nutrient and ingredient composition and were fed to fattening pigs for a digestibility trial. Compounds feeds, feed ingredients and faeces were analyzed for chemical composition and were used to calculate the digestibility coefficients of organic matter (OM). The R² between the analyzed parameter on the compound feeds and the calculated values using the Dutch and French tables for the ingredients amounted to respectively 0.83 and 0.68 for moisture, 0.90 and 0.88 for crude protein, 0.95 and 0.95 for crude fat, 0.95 and 0.96 for starch, 0.78 and 0.52 for sugars, 0.79 and 0.76 for crude ash, 0.93 and 0.95 for nsp. The correlation between the in vivo digestion coefficients of the compounds and the digestibilities derived from the Dutch and French tables was 0.93 and 0.92 for OM, 0.91 and 0.86 for crude protein and 0.41 and 0.19 for crude fat. The Dutch and French tables are quite reliable to calculate the chemical composition of compound feeds, with somewhat lower accuracy for moisture, ash and sugar. These tables are also reliable to calculate the digestibility of OM and CP, but less for crude fat digestibility. For most parameters the Dutch tables appear slightly better than the French ones.