A slope-ratio precision-fed rooster assay for determination of relative metabolizable energy values for fats and oils

Abstract

The precision-fed rooster assay (PFRA) frequently yields TME 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 TME 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 TME 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 TME linearly increased up to 20% RCO inclusion. There were some minor differences in TME 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 TME values.

Influence of the inclusion of co-products of the soy oil industry in poultry diets on nutrient digestibility, growth performance, and production

“…The available information, together with the results of the current research, suggest that within practical levels of use, the beneficial effects of fat on nutrient retention increase as the level of supplemental fat increases. Similar, results have been reported recently by Aardsma and Parsons (2016).…”

“…In this respect, Vieira et al (2002) and Peña et al (2014) reported in broilers that the AME of the experimental ASO source increased by 2.53 and 5.36 MJ/kg, when the level of the oil in the diet increased from 40 to 80 g/kg or from 20 to 60 g/kg, respectively. Aardsma and Parsons (2016) reported also that the TME of SO and maize oil increased by 1.01 and 2.33 MJ/kg, as the level of oil supplementation increased from 50 to 100 g/kg.…”

“…The contribution of fats to the energy content of the diet depends on the methodology used, with greater values when calculated by difference between the AME of the control and the oil containing diets than when calculated by multiplying the GE of the fat by the CTTAR of the EE of the experimental diet (Mateos et al, 1980cHuyghebaert et al, 1988;Irandoust et al, 2012;Aardsma and Parsons, 2016). In the current research, the difference in AME across fat sources between the two methods of estimation was, as an average, 1.94 MJ/kg in Exp.…”

“…Moreover, Aardsma and Parsons (2016) reported 2.60 MJ/kg higher true metabolizable energy (TME) for maize oil added at 50 g/kg, when calculated by difference than from GE and EE retention data.…”

“…Moreover, Aardsma and Parsons (2016) reported that the TME of eight different lipid sources, ranged from 35.31 to 45.36 MJ/kg (average of 41.32 MJ/kg). The reasons for the discrepancies observed among authors on the AME of a given fat source are probably related to variability in the quality of the fats as well as the age of the birds and the type of diets used in the different experiments.…”