Crude protein fractionation in feed analysis
One of the biggest cost and success factors in livestock farming is the feed used. This plays a decisive role in the subsequent composition and quality of animal products (meat, milk, eggs, etc.) and must be used as efficiently as possible in view of current cost increases. As different farm animals absorb and utilize feed differently, a targeted feed analysis is essential for a needs-based feeding strategy. Standard methods in feed analysis, such as the Weender analysis, differentiate the organic substances contained in the feed into the components crude protein, crude fat, crude fiber and nitrogen-free extractives. However, this breakdown of the ingredients is comparatively imprecise and only provides limited information about the digestibility and usability of the feed. Therefore, modern methods go one step further and divide the various parameters according to digestibility, digestibility and energy concentration and determine, for example, amino acid patterns, protein fractions, fiber components such as ADF or NDF, fatty acid spectrum and other parameters occurring in the samples.
Crude protein fractionation as a preparatory analysis for optimal ration calculation
On modern farms, ration calculations for feeding animals are now based on calculation models that work with the most detailed information possible, e.g. on amino acid patterns or crude protein fractions. One example is the Cornell Net Carbohydrate and Protein System (CNCPS) known from the USA, a calculation method for ration optimization that is constantly being further developed. Crude protein fractionation is necessary because the crude protein content of a sample is determined via the analyzed nitrogen content, e.g. the protein content in dairy products is calculated from the measured nitrogen content multiplied by the protein factor (factor 6.38 for dairy products). However, a certain proportion of the measured nitrogen represents protein that can either not be utilized at all, poorly or only moderately by the animal. In the analysis of crude protein fractions, proteins are therefore divided into different fractions or groups depending on their solubility and digestive reaction. The following parameters are analyzed according to the new VDLUFA method:
| Parameters | Abbreviation | Simplified analysis procedure |
| Crude protein | XP | Direct protein determination |
| Tungstate-insoluble crude protein | WUXP | 1. Incubation at pH2 overnight in a tungstate solution 2. Filtration with suitable filter paper or filter bags (e.g. FibreBags) 3. Protein determination of the filter residue |
| Borate-phosphate buffer-insoluble crude protein | BUXP | 1. Incubation for 3 hours at room temperature in a borate-phosphate buffer 2. Filtration with suitable filter paper or filter bags (e.g. FibreBags) 3. Protein determination of the filter residue |
| Neutral detergent insoluble crude protein | NDUXP | 1. Determination of aNDF 2. Filtration with suitable filter paper or filter bags (e.g. FibreBags) 3. Protein determination of the filter residue |
| Acid-detergent-insoluble crude protein | ADUXP | 1. Determination of ADF 2. Filtration with suitable filter paper or filter bags (e.g. FibreBags) 3. Protein determination of the filter residue |
| Crude protein fraction | Name | Enzymatic degradation | Calculation |
| A | Non-protein nitrogen (NPN) | Not applicable | XP - WUXP |
| B1 | Buffer soluble pure protein | Fast | WUXP - BUXP |
| B2 | Buffer-insoluble pure protein (ND-soluble) | Variable | BUXP - NDUXP |
| B3 | Cell wall-bound, soluble pure protein | Variable to slow | NDUXP - ADUXP |
| C | Cell wall bound, insoluble pure protein | Indigestible | ADUXP |
With the information obtained from crude protein fractionation, livestock can be supplied according to their needs and the available resources can be optimally utilized. The differentiated analysis of the protein content of feed brings several advantages to agricultural businesses:
- Effective use of feed and the associated cost savings
- Promotion of animal health by avoiding a shortfall in supply
- Minimization of negative environmental consequences, e.g. reduced excretion of ammonia or phosphate
