Abstract
Simple SummaryA standard nutritionally balanced diet is used as a reference diet into which test feedstuffs are added to determine metabolizable energy of the added test feedstuff either by difference or regression method. We hypothesized that if the composition of the reference diet changes, the metabolizable energy of the test feedstuff will also changes and that the difference and regression methods will not give similar metabolizable energy values for the test feedstuff under these circumstances. To test this hypothesis, we used two reference diets (corn-soybean meal and corn-canola meal), instead of using just one reference diet, to determine metabolizable energy of soybean meal and canola meal. The metabolizable energy of soybean meal and canola meal was greater when corn-canola meal was the reference diet compared with using corn-soybean meal reference diet. Compared with the difference method, the regression method gave greater metabolizable energy value for the test feedstuffs. Results from the current study show that the calculated metabolizable energy value of feedstuffs depends on the reference diet used and that the difference and regression methods did not give similar metabolizable energy value for the test feedstuffs.A 21-day experiment was conducted to study the effect of reference diet type and assay method on apparent metabolizable energy (AME) and nitrogen-corrected (AMEn) of soybean meal (SBM) and canola meal (CM). Broilers (n = 240) were allocated to 10 treatments with eight replicates/treatment and three birds/replicate. Treatments included corn-SBM or corn-CM reference diets (RD). To each RD, 300 or 450 g/kg of SBM or CM were added to make a total of eight test diets. For the difference method, AME of SBM and CM substituted at 300 g/kg in corn-CM RD gave greater AME values compared to inclusion in the corn-SBM RD. The AMEn of SBM increased with increase in inclusion level in the corn-CM RD but AMEn of CM decreased with increased inclusion level of CM in the corn-SBM RD. For the regression method, AME and AMEn of the test feedstuffs were greater with corn-CM RD compared with corn-SBM RD. The AME of SBM was not affected by assay method, whereas AME of CM was lower when determined using the regression method. In conclusion, both the reference diet type and assay method influenced assayed AME and AMEn value of test protein feedstuffs and should be considered in cross-studies comparisons.
Highlights
Feed represents 70% of the total cost of broiler production, of which the energy represents the greatest proportion
apparent metabolizable energy (AME) of canola meal (CM) was greater than AME of soybean meal (SBM), and the AME was greater (p < 0.01) when test feedstuffs were substituted at 300 g/kg compared to substitution at 450 g/kg
The apparent metabolizable energy (AMEn) of SBM was not influenced by an increasing inclusion level of SBM in the corn-SBM reference diet whereas AMEn of SBM increased (p < 0.05) as the inclusion level of SBM increased in corn-CM reference diet
Summary
Feed represents 70% of the total cost of broiler production, of which the energy represents the greatest proportion. Available energy from feedstuffs in broilers is determined using apparent metabolizable energy (AME) and as nitrogen corrected apparent metabolizable energy (AMEn). Accurate determination of AME value of feedstuffs and using these values in feed formulations are Animals 2020, 10, 2132; doi:10.3390/ani10112132 www.mdpi.com/journal/animals. There is wide variability in the reported AME and AMEn values for most feedstuffs making interpretation of the values and usage in feed formulation very challenging. Variation in reported AME values are often due to genetic factors, growing conditions, age, dietary factors and methods used in determining these AME values [3,4,5]. There are various methods used to determine the AME and AMEn of feedstuffs, among which methods basal diet substitution and multiple linear regression method are regularly employed
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