Nutritional quality assessment of commonly used oilseed meals in poultry feed
Figure 1: Number of soybean meal, full fat soy and rapeseed meal samples analyzed using Evonik AMINONIR® services (2017-19) in Asia South
It is a by-product of whole soybean seeds after oil extraction. It is the most preferred protein source for poultry and livestock feed due to high content of digestible AA. A poultry diet based on corn and SBM provides a good balance of all essential AA except methionine (Waldroup et al., 2008). It is usually classified and sold in poultry and livestock feed market on its crude protein (CP) content. It is classified into two main categories; high-protein (47-49% CP), obtained from dehulled seeds, and the conventional (44-46% CP), that contained the hulls. However, Evonik published regional data in the past under 3 categories; regular (40-46% CP), premium (46-49% CP) and hi-pro (>49% CP) to cover variation observed in SBM quality.
Quality and price of SBM has major effect on the feed quality and cost. More than 152,000 SBM samples were analyzed for AA, proximate parameters and AMEn using Evonik AMINONIR® services. Assessment of nutritive value only based on the CP content can be misleading and results in economic losses and reduction in poultry performance. Table 1 shows variation in AA profile of two SBM samples having same CP content (46.8%). This variation in AA profile has great impact on feed cost. The difference in feed cost of USD 4.10 per MT of starter broiler diet is due to difference in AA profile of above mentioned two SBM samples (Table 3). This effect of variation in AA profile at same CP content on feed cost is valid for other oilseed meals. Therefore, nutritional quality assessment of oilseed meals should be done on AA profile instead of CP content. Nutrient profile of SBM is changing with passage of time due to different varieties, growing conditions and processing technologies. Figure 2 shows broad variation in lysine and AMEn contents of analyzed SBM samples even at same CP content.
Figure 2: Relationship between (a) CP and lysine and (b) CP and AMEn of soybean meal samples analyzed in Asia South (2017-19).
Table 1: Variation in the amino acid profile (%) of two soybean meal (SBM) samples with same crude protein (CP) content
It is not only an excellent source of essential AA but also energy and fatty acids. During heat treatment, the trypsin inhibitor activity should be destroyed otherwise it reduces the digestibility of AA and poultry performance is compromised. The presence of anti-nutritional factors (trypsin inhibitors, lectins, antigenic proteins, and saponins) limits its use in poultry diets (Monari, 1996; Stein et al., 2008). Extrusion technology is considered as effective approach to inactivate the anti-nutritional substances in SFF (Bjorck, 1983). Overheating might also reduce the usable energy content (Willis, 2003).
There was broad variation in the AA profile and energy content of analyzed SFF samples. Figure 3 shows variation in lysine and AMEn contents of analyzed samples from 2017-19. Assessment based on AA profile and AMEn content provides opportunity to nutritionists and/or formulators for optimal use of SFF in poultry diets.
Figure 3: Relationship between (a) CP and lysine and (b) CP and AMEn of soybean full fat samples analyzed in Asia South (2017-19).
It is also an important AA/ protein source used in the diet of monogastric animals. Global production of RSM was 39.46 million ton in 2018-2019 (USDA, 2020). RSM is partially used as an alternate protein source for SBM in the livestock diets. The use of RSM in poultry feeds is limited because of low protein and essential AA contents, low digestibility coefficients and the presence of anti-nutritional factors such as glucosinolates and erucic acid compared to SBM (Newkirk, 2009). New varieties of rapeseed from North America, Europe and Australia contain less anti-nutritional factors. Canola is the improved variety of rapeseed. RSM can be included in broiler and layer diets up to 10-15% and 7-8%, respectively (Nega and Woldes, 2018).
Figure 4 shows variation in lysine and AMEn contents of RSM samples analyzed from 2017-19. Two clusters for lysine and AMEn contents of analyzed RSM samples are due to different origins. Samples from USA origin have high lysine and AMEn contents compared to samples from Indian subcontinent. Large variation in lysine and AMEn contents even at same CP confirms that quality assessment of RSM based on CP content is misleading.
Figure 4: Relationship between (a) CP and lysine and (b) CP and AMEn of rapeseed meal samples analyzed in Asia South (2017-19).
• NIR is a fast and reliable tool to assess the nutritional quality of oilseed meals and other raw materials.
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