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Title:Determination of relative metabolizable energy values for fats and oils via the slope-ratio precision-fed rooster assay
Author(s):Aardsma, Matthew Phillip
Department / Program:Animal Sciences
Discipline:Animal Sciences
Degree Granting Institution:University of Illinois at Urbana-Champaign
Abstract:Eight experiments were conducted to determine if the precision-fed rooster assay could be combined with a slope-ratio type assay to generate useful information on the nitrogen-corrected true metabolizable energy (TMEn) content of fats and oils (lipids) for poultry. In Experiment 1, refined corn oil (RCO) was fed to both conventional (CONV) and cecectomized (CEC) roosters. Lipids were fed in ground corn diets to CONV roosters in Experiments 2 through 6. Palomys®, stearidonic (SDA) soybean (soy) oil, three commercial animal/vegetable (A/V) blends (A/V blend 1, 2 and 3) and corn oil from distillers dried grains with solubles (DDGS) were evaluated. Experiments 7 and 8 were conducted to compare the measured available energy content of lipids generated from roosters (slope-ratio precision-fed rooster assay) and young growing broiler chicks (slope-ratio chick growth assay) to determine if values obtained from the roosters were applicable for use with broiler chicks. A variety of lipids that were expected to have low, medium, and high available energy contents were obtained. Lipids tested in each experiment were from the same batches, and were RCO, a 2:1 blend of stearic acid with RCO (Blend A), a 1:1 blend of stearic acid with RCO (Blend B), tallow, poultry fat, and DDGS corn oil. In the slope-ratio precision-fed rooster assays, roosters were tube-fed diets containing graded levels of supplemental lipid that were included at the expense of a ground corn basal. In the chick growth assay, diets consisted of graded levels of supplemental lipid added to a corn-soy basal diet at the expense of cellulose. Chicks were limit-fed from 10 to 20 d of age to ensure equal feed intake among treatment groups and to maintain energy as the growth-limiting factor. The TMEn of diets or body weight gain of chicks were regressed on supplemental lipid level or intake using multiple linear regression. Relative bioavailability values (RBV) for each lipid were calculated as the regression coefficient of the test lipid divided by the regression coefficient of the reference lipid (refined soy oil or RCO). The RCO was found to be a suitable reference material for use in the slope-ratio method as TMEn linearly increased up to 20% RCO inclusion in Experiment 1. Furthermore, there were no significant differences in TMEn of RCO between CONV and CEC bird types. Based on regression coefficients, Palomys® was found to have a lower (P < 0.05) RBV than RCO. There were no significant difference between SDA soy oil and refined soy oil. The RBV of A/V blend 2 was lower (P < 0.05) than RCO, while the RBV of A/V blend 1 was not significantly different than RCO. The RBV of DDGS corn oil was higher (P < 0.05) than RCO. The RBV of A/V blend 3 was lower (P < 0.001) than RCO; however, an interaction (P < 0.01) between lipid type and lipid supplementation level was observed, indicating that the RBV for A/V blend 3 may underestimate its available energy at low levels of inclusion. Excellent agreement was obtained for RBV between Experiments 7 and 8, with rooster and chick values being similar and the ranking of the lipids being similar for both bird types. Overall, these data indicate that the slope-ratio precision-fed rooster assay was able to detect and quantify differences in available energy among lipid types, and yielded values that were similar to those obtained with growing broiler chicks.
Issue Date:2015-04-24
Rights Information:Copyright 2015 Matthew Aardsma
Date Available in IDEALS:2015-07-22
Date Deposited:May 2015

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