Effects of concentrated lipid sources on in vivo and in vitro digestibility of diets and net energy estimates of feed ingredients for growing pigs

The nutritional evaluation of concentrated lipid sources is essential for improving the precision of energy values used in pig diet formulation. This study evaluated the effects of soybean oil, poultry fat, and pork fat on in vivo digestibility, in vitro dry matter digestibility, and net energy estimates in growing pigs. Twenty castrated male pigs were assigned to a completely randomised design with four treatments and five replicates. The experimental diets consisted of a control diet without added oil or fat and diets with 8% replacement of the control diet with soybean oil, poultry fat, or pork fat. Mean values were compared with the control diet using Dunnett's test. Concentrated lipid sources increased ether extract digestibility and dietary energy values compared with the control diet. Estimated net energy values were 8,139, 8,222, and 8,161 kcal/kg for soybean oil, poultry fat, and pork fat, respectively. None of the lipid-containing diets differed from the control diet in in vitro dry matter digestibility, indicating limited sensitivity of the assay to detect effects of lipid source inclusion. Overall, the results suggest that concentrated lipid sources increase dietary energy utilisation in growing pigs. Net energy values should be considered experiment-specific estimates.