Apparent digestible energy content of commercial lipid sources fed to growing pigs

Abstract Text: This study was designed to evaluate lipid and GE digestibility of 7 commercial lipid sources varying in chemical composition (iodine value, IV; free fatty acids, FFA) and lipid peroxidation status (anisidine value, AnV; malondialdehyde, MDA). A total of 64 growing pigs (initial BW= 30.4 ± 0.43 kg) were housed individually and randomly allotted to one of 8 dietary treatments. Treatments consisted of a corn-soybean meal basal diet without added lipids and the basal diet supplemented with 8% of either soybean oil (IV=129, FFA=0%, AnV=3, MDA=1 mmol/L), tallow (IV=44, FFA=0%, AnV=2, MDA=0 mmol/L), poultry fat (IV=68, FFA=3%, AnV=4, MDA=7 mmol/L), pet food-grade poultry fat (IV=76, FFA=2%, AnV=1, MDA=14 mmol/L), yellow grease (IV=64, FFA=7%, AnV=19, MDA=28 mmol/L), brown grease (IV=65, FFA=23%, AnV=12, MDA=74 mmol/L) or restaurant grease (IV=98, FFA=8%, AnV=36, MDA=18 mmol/L). Lipid supplemented diets contained 1.03% standardized ileal digestible lysine and 3.69 Mcal ME/kg. Diets were fed ad libitum for 7 days followed by fecal collections for the next 3 days. Apparent total tract digestibility (ATTD) was calculated using TiO₂ as indigestible marker. On d 10, blood samples were collected for plasma MDA analysis as a marker of oxidative stress. Pigs fed yellow grease had a 64% lower ADFI (P<0.001; 0.62 vs. 1.73 kg/d) than pigs fed other diets, resulting in an overall BW loss during the 10 d feeding period (P<0.001; ADG of -0.14 vs. 0.95 kg/d). Concentrations of MDA in plasma of pigs fed yellow grease were 86% greater (P<0.001; 10.76 vs. 5.78 mmol/L) than those in pigs fed other lipid sources. Supplementation of lipids to the basal diet increased ATTD of crude fat (P<0.001; 81.3 vs. 40.0%) and GE (P<0.05; 88.4 vs. 85.8%).  For lipid supplemented diets, ATTD of crude fat ranged from 79.7 to 82.9% and ATTD of GE ranged from 87.5 to 90.0% and they were not different amongst lipid sources. Results indicate that there were no differences in the DE content of commercially available lipid sources that ranged widely in saturation level, content of FFA, and oxidative stability when fed to growing pigs. Nonetheless, caution is needed when feeding highly peroxidized lipid sources to pigs, as these can negatively impact performance.

Keywords: digestible energy, lipids, pigs