RESUMEN
Our goal was to determine if relative bioavailability values (RBV) for fats and oils (lipids) determined in adult roosters are different than RBV determined with young broiler chickens. Lipids that were expected to have widely varying ME content were evaluated using a slope-ratio approach in adult roosters (Exp. 1) via the precision-fed rooster assay (PFRA) and broiler chicks via a growth assay (Exp. 2). The same lipids were tested in both experiments and were refined corn oil (RCO), a 2:1 blend of stearic acid (C18:0) with RCO (SAB1), a 1:1 blend of C18:0 with RCO (SAB2), tallow (TW), poultry fat (PF), and corn oil from a corn ethanol plant (DDGSCO). In Exp. 1, roosters were tube-fed diets containing 0, 5, and 10% of supplemental lipid in ground corn. In Exp. 2, diets consisted of 0, 5, and 10% supplemental lipid in an amino-acid fortified corn-soybean meal diet. Chicks were limit-fed test diets from 10 to 20 d posthatch to maintain energy as the growth-limiting factor. The TMEn of diets or BW gain of chicks were regressed on supplemental lipid level. The RBV were calculated as the regression coefficient of the test lipid divided by that of RCO. For Exp. 1 a non-linear response was observed for SAB2; however, the RBV for SAB1 (22%), TW (72%), PF (96%), and DDGSCO (90%) were as expected. The RBV of SAB1 and TW were lower (P < 0.001) than RCO, while PF and DDGSCO were not different than RCO. For Exp. 2, BW increased linearly in proportion to the energy content of the lipid sources. The RBV of SAB1 (22%), SAB2 (46%), and TW (76%), were lower (P < 0.001) than RCO, while PF (96%) and DDGSCO (97%) were not different than RCO. Excellent agreement was obtained for RBV between the two assays, with rooster and chick values being similar and the ranking of the lipids being the same for the two assays.
Asunto(s)
Alimentación Animal/análisis , Crianza de Animales Domésticos/métodos , Pollos/metabolismo , Metabolismo Energético , Metabolismo de los Lípidos , Fenómenos Fisiológicos Nutricionales de los Animales , Animales , Disponibilidad Biológica , Dieta/veterinaria , Masculino , Distribución AleatoriaRESUMEN
The precision-fed rooster assay (PFRA) frequently yields TMEn values for fats and oils in excess of their gross energies. Six experiments were conducted to determine if the PFRA could be combined with a slope-ratio type assay to yield more useful lipid TMEn values. In experiment (EXP) 1, refined corn oil (RCO) was fed to conventional and cecectomized roosters at zero, 5, 10, 15, and 20% of a ground corn diet. In EXP 2 through 6, lipids were fed to conventional roosters at zero, 5, and 10% in a ground corn diet. Palomys (a novel lipid), high stearidonic acid soybean oil (SDASO), 2 animal-vegetable blends (AV1, AV2), a vegetable-based oil blend (VB), and corn oil from an ethanol plant (DDGSCO) were evaluated and compared to refined soybean oil (RSO) or RCO as the reference lipid. Multiple linear regression of diet TMEn on supplemental lipid level generated regression coefficients that were used to calculate relative bioavailability values (RBV). In EXP 1, RCO was a suitable reference material as TMEn linearly increased up to 20% RCO inclusion. There were some minor differences in TMEn of RCO between conventional and cecetomized bird types. In EXP 2, Palomys was found to have a lower (P < 0.05) RBV (87%) than RCO. In EXP 3, there were no significant differences between SDASO and RSO. In EXP 4, the RBV of AV2 (79%) was lower (P < 0.05) than RCO, while the RBV of AV1 was not different from RCO. The RBV of DDGSCO (116%) was higher (P < 0.05) than RCO in EXP 5. The RBV of VB (84%) was lower (P < 0.001) than RCO in EXP 6; however, this may be an underestimation for low levels of VB, as there was an interaction (P < 0.01) between lipid type and lipid supplementation level. These results indicate that the precision-fed slope-ratio rooster assay can detect differences among lipids and yields practically useful lipid TMEn values.