Determination of metabolisable energy and digestible amino acids of canola meals and canola seed for broilers : a thesis presented in partial fulfilment of the requirements for the degree of Master of Science in Animal Science at Massey University, Manawatu, New Zealand

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Nutrient composition, apparent metabolisable energy (AME) and ileal amino acid (AA) digestibility of two canola meals (CM1 and CM2) and one canola seed (CS) sample were evaluated using laboratory analyses and animal studies. The AME assay was conducted with broilers using the classical total excreta collection between day 18 and 25 post-hatch. A maize-soybean meal basal diet was formulated and a test diet, containing CM or CS, was developed by replacing (w/w) 30% of the basal diet with CM or CS. The AME of CM and CS was calculated based on the difference between the AME values of basal and test diets. Ileal protein and amino acid (AA) digestibility of CM and CS were determined using direct method. In this method, the assay diets were formulated with the CM or CS serving as the sole source of AA. All diets contained titanium dioxide as an indigestible marker. The ratios between the titanium and AA in the diet and digesta were used to calculate the digestibility. The crude protein of CM1, CM2 and CS were determined to be 411, 393 and 235 g/kg (as received basis), respectively. Compared to both the CMs, CS had the highest neutral detergent fibre (NDF) and lowest total dietary fibre (TDF) value. Calcium was the major mineral in CS (17.7 g/kg), while major mineral in both the CM samples was potassium (13.6 and 13 g/kg, respectively). The overall concentration was low in CS compared to both the CM. Differences (P < 0.05) were observed in the AME and apparent metabolisable energy corrected for nitrogen (AMEn) value of CM and CS. The AMEn content of CM1, CM2 and CS were 7.22 and 6.78 and 10.29 MJ/kg DM, respectively. A tendency (P = 0.052) was observed for effect of dietary treatment on standardised ileal digestibility coefficient (SIDC) of protein and AA. The CS had highest (P < 0.05) digestibility compared to both CM samples, and no differences (P > 0.05) were observed between the two CM samples. The standardised ileal digestible protein content was highest (P < 0.05) in CM1 (293 g/kg), followed by CM2 (279 g/kg) and CS (176 g/kg). The digestible AA content, in general, followed the similar trend as digestible protein. In conclusion, the present study showed that the nutrient composition, AMEn, and standardised ileal digestibility of protein and AA vary between CM and CS samples. CM and CS are attractive feed ingredients for poultry and with careful considerations CS and CM can be used as a partial replacement for SBM in poultry diets. CS has high AMEn content, therefore, can be used as a potential energy source, while CM has high digestible AA content, therefore, can be added as a protein source in poultry diets.
Figures 2.3 (=Xu & Diosady, 2012 Fig 4.3 p. 66), 2.4 (=Chen & Andreasson, 2001 Fig 1), and 2.5 (=Tripathi & Mishra, 2007 Fig 2) were removed for copyright reasons.