Partitioning of variance in true metabolizable energy determinations: an example using wheat data |
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| Affiliation: | 1. Rhone Poulenc Animal Nutrition 42, Avenue Aristide Briand, BP 100 92164, Antony Cedex, France;2. Department of Agricultural and Biological Engineering, Penn State University, University Park PA 16802, USA;3. Department of Poultry Science, Penn State University, University Park PA 16802, USA;1. Tiergesundheitsdienst Bayern e. V., Senator-Gerauer-Str. 23, 85586, Poing, Germany;2. Zinpro Animal Nutrition Inc., Akkerdistel 2 E, 5831 PJ Boxmeer, The Netherlands;3. Universität Leipzig, Veterinär-Anatomisches Institut, An den Tierkliniken 43, 04103, Leipzig, Germany;4. Stiftung Tierärztliche Hochschule Hannover, Institut für Pharmakologie, Toxikologie und Pharmazie, Bünteweg 17, 30559, Hannover, Germany;5. Stiftung Tierärztliche Hochschule Hannover, Institut für Biometrie, Epidemiologie und Informationsverarbeitung, Bünteweg 2, 30559, Hannover, Germany;6. Stiftung Tierärztliche Hochschule Hannover, Klinik für kleine Klauentiere und forensische Medizin und Ambulatorische Klinik, Bischofsholer Damm 15, 30173, Hannover, Germany;1. Department of Animal Nutrition and Feed Science, National Research Institute of Animal Production, Krakowska Street 1, Balice 32-083, Poland;2. Department of Animal Molecular Biology, National Research Institute of Animal Production, Krakowska Street 1, Balice 32-083, Poland;3. University Centre of Veterinary Medicine, University of Agriculture, Mickiewicza Ave. 24/28, Krakow 30-059, Poland;1. School of Public Health, Guizhou Medical University, Guian New Region, China;2. The Affiliated Hospital of Guizhou Medical University, Guiyang, China;3. Key Laboratory of Environmental Pollution Monitoring and Disease Control, Ministry of Education, Guizhou Medical University, Guian New Region, China;4. Toxicity Testing Center of Guizhou Medical University, Guiyang, China;5. Guiyang University, Guiyang, China;6. Guizhou Institute of Geo-Environment Monitoring, Guiyang, China;7. Department of Geosciences, University of Texas, Dallas Richardson, TX, USA;2. DuPont Industrial Biosciences-Danisco Animal Nutrition, Marlborough, Wiltshire, United Kingdom SN8 1XN;3. DuPont Nutrition Biosciences-Enzyme Research & Development, Brabrand, Arhus, Denmark, DK-8220;4. Institute for Veterinary, Animal and Biomedical Sciences, Massey University, Palmerston North, New Zealand 4442 |
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| Abstract: | A variance statistic was used to partition the total variance into that attributable to each step of a TMEN assay procedure. Estimation of the TMEN of wheat was used as an example. The variance statistic can also be used to optimize the design of a TMEN experiment with respect to cost of the experiment and desired accuracy of the result. Experimental design optimization is accomplished by providing a functional relationship between the accuracy of the estimate and the number of replicates of feed, the number of birds used in the experiment, and the cost of each step. The variance statistic is also a useful tool for identifying and removing outliers and highly variable measurements. This feature was demonstrated with the chosen example data. Gross energy of the feed will explain approximately 50% of the variance of the TMEN estimate depending on how many replicates are evaluated. Nitrogen content of the feed sample will explain approximately 40% of the total variance. It is recommended to replicate this measurement as many times as possible. Ten replicates were recommended for the example data. The energy content of excreta from fed birds represented the next largest source of variance, at approximately 4% of the total variance, respectively. If within-bird variance is large, better homogenization of the sample and more replicates are recommended. If among-bird variance is significantly different, more birds should be used. Nitrogen content of excreta from fed birds represented less than 2.5% of the total variance. Energy and nitrogen content of excreta from unfed birds combined represented less than 2% of the total variance, suggesting that the number of unfed birds and the amount of excreta sub-samples may be reduced without adversely affecting the accuracy of the TMEN estimate. Variance due to the amount of excreta collected from the fed birds, and variance due to the amount of feed consumed by the birds, are expected to be small. This result suggested that force-feeding may not be necessary for accurate TMEN estimates. |
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