As fitases podem ser utilizadas como estratégia nutricional para reduzir a inclusão de alguns ingredientes, diminuir o custo de formulação da ração, a excreção de nutrientes ao ambiente e melhorar a disponibilidade de fósforo fitico, forma complexada nos ingredientes vegetais e que não é utilizada pelas aves. Inicialmente comercializada como ferramenta para os nutricionistas visando melhora no aproveitamento do fósforo, os efeitos extra-fosfóricos são cada vez mais evidentes 52-56.
Nos últimos anos, a comunidade científica tem discutido as características das moléculas do ácido fítico, demostrando uma grande interação com outras substâncias como minerais, amido e proteínas que podem reduzir ou indisponibilizar esses nutrientes aos animais, além de aumentar as perdas endógenas devido à elevação no turnover dos enterócitos e na secreção de mucina, ocasionando por sua vez, aumento do catabolismo e do requerimento energético1,4,10,11,18,20,21.
Por todo efeito anti-nutricional do fitato e seus reflexos na utilização dos nutrientes pelos animais, estudos com dosagens de fitase acima de 500 FTU/kg de ração têm sido realizados e contribuído para uma variabilidade de respostas na literatura. Assim, com a hidrólise dos grupos fosfatos, as fitases podem liberar o fósforo, reduzir os efeitos anti-nutricionais do fitato e disponibilizar outros minerais, proteínas e a energia das dietas9,20,36,37,38,39,155,156,157,158.
Pesquisadores também apontam que estratégias devem ser adotadas para diminuir o conteúdo de fitato ingerido pelos animais, seja pela desfitinização das matérias-primas, pela diminuição do conteúdo de fitato nos grãos vegetais através da modificação genética, ou pela utilização de fitases mais eficientes na nutrição animal1.
digestibildade ileal aparente dos aminoácidos e da energia metabolizavél, teor de cinzas na tíbia com a suplementação de fitase em doses logarítmicas de 150 FTU/kg a 24.000 FTU/kg de ração. Melhoria no ganho de peso e na eficiência alimentar em frangos de corte aos 28 dias de idade alimentados com dietas contendo baixo fósforo disponível e níveis de até 2.500 FTU/kg de ração foram relatados por Pirgozliev et al94.
Walk et al.36 mostraram que a suplementação com fitase em até 2.500 FTU/kg de ração aumentou linearmente a porcentagem de cinzas nas tíbias. A suplementação de níveis de 5.000 FTU/kg na dieta melhoraram a digestibilidade ileal aparente dos aminoácidos em frangos. Além disso, doses de fitase acima das recomendações feitas pela indústria pode permitir a redução de cálcio, manter o desempenho e a porcentagem de cinzas ósseas de frangos37.
Níveis de 1.500 FTU/kg de ração melhoraram o desempenho, particularmente a conversão alimentar em frangos aos 49 dias de idade alimentados com dietas contendo reduzido cálcio e fósforo disponível38.
Altos níveis de fitase resultaram na hidrólise quase completa do IP6, aumento das concentrações de inositol na moela e na melhoria do ganho de peso e da conversão alimentar de frangos sem efeitos adversos na porcentagem de cinzas na tíbia. Os benefícios com os maiores níveis de fitase podem estar associados com a destruição do fitato e no fornecimento de inositol em vez do excesso de fósforo e cálcio39.
Shirley e Edwards155 relataram que 12.000 FTU/kg de ração foi capaz de hidrolisar 95% do fósforo proveniente do fitato em dietas a base de milho e farelo de soja. Sugere-se que alguns destes resultados no desempenho, cinzas ósseas, digestibilidade ileal aparente dos aminoácidos e da energia com a suplementação de fitase podem estar associado à hidrólise da molécula de ácido fítico.
Com base no exposto, objetivou-se avaliar os efeitos da inclusão de diferentes níveis de fitase em dietas com redução de níveis nutricionais para frangos durante o período de 1 a 42 dias de idade.
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