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UBC Theses and Dissertations

Improving utilization of poultry feedstuffs with supplemental amino acids and enzymes Chong, Chen Hiung


Four studies were conducted to evaluate threonine and tryptophan requirements by poultry. A purified diet based on the ideal amino acid (AA) profile concept for 0-3 week old broilers was established in the first study. Different ratios of threonine and tryptophan to lysine were evaluated in the second study and the results indicated that dietary digestible threonine and tryptophan for 0-3 week old broilers should be targeted at 65% and 16% of digestible lysine, respectively. Studies using reduced protein (RP) diets based on practical ingredients indicated that dietary total threonine and tryptophan for 0-3 week or 3-6 week old broilers should be targeted at 0.74% (or 4.04% of crude protein (CP)) and 0.23% (or 1.22% of CP) or 0.67% (or 3.20% of CP) and 0.17% (or 0.89% of CP), respectively. The corresponding values for 42-50 week-old layers are 448 and 152 mg/hen/d, respectively. Crystalline AA supplementation of the RP diets improved the AA balance in the diet, thus improving protein utilization efficiency and resulting in reduced nitrogen in the excreta. The nutritive value of palm kernel cake (PKC) was investigated in several studies and it was found to contain low levels of metabolizable energy (ME) and moderate quantities of most nutrients. The low AA digestibility and the low ME of PKC were attributed to nutrient entrapment within the cell, lack of appropriate enzymes to break down mannan, as well as processing method. An enzyme mixture (mannanase, cc-galactosidase and protease) significantly increased the ME of PKC and improved the performance of both broilers and layers fed PKC-based diets. The results indicated that a 20% PKC diet could be used during the broiler starter or grower phase, but not during both phases unless supplemental enzymes were used. Laying hen performance was not different from controls when a 12.5% or 25% PKC-based diet was used. However, layers consumed more of the PKC diets and had poorer feed efficiency than the controls. Egg yolks were paler in birds fed the 25% PKC diets. A computerized feed formulation study showed that PKC is probably best suited for layer diets under the prevailing price situation in Malaysia.

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