Vitamin requirements: is there basis for re-evaluating dietary specifications?

Abstract

There has been little work conducted over the last 40 years on estimating vitamin requirements of poultry, and so consequently NRC (1994) values are still often quoted as standards. A review of this information indicates many values are estimates, or extrapolated from comparable species, or as with broiler breeders, simply not given. The current concern related to formulating vitamin levels in poultry diets is the assumption that change in genetic potential of layers and meat birds necessitates re-evaluation, and that parameters for assessing needs are now more complex than simple production metrics as used previously. Unfortunately information on maintenance needs for vitamins is lacking, and while there is now information available on vitamin content of eggs, comprehensive details of the vitamin level in poultry meat products is surprising lacking. With unprecedented egg output of modern layer strains, and ever improving feed efficiency in meat birds, vitamin intake per unit of output is continually declining. For layers the estimate is around a 1% yearly decline in vitamin intake per egg produced, while for meat birds there has been a 0.6-0.8% yearly decline per kg body gain. This reduced intake of vitamins is the basis for improved performance in layers and meat birds fed a higher than normal level of vitamins. However, an even more important basis for reevaluating vitamin needs is change in measurement criteria. Many vitamins and especially the fat soluble vitamins accumulate in eggs and meat in proportion to diet inclusion. Development of vitamin enriched designer poultry products therefore dictates elevated feeding levels of vitamins. Co-incidentally, increased levels of vitamin E in poultry products has led to the realization that increased antioxidant capacity of these tissues enhances shelf life and appearance. Of greatest impact in reevaluating diet vitamin specifications has been the effect of these nutrients on bird health and in particular immune response. For example dietary levels of vitamin E far in excess of NRC (1994) requirements have been shown to positively impact immune response in all ages of bird and also the performance of heat-stressed birds. Expectations of ever increasing performance dictate the need for continual reevaluation in determining vitamin levels within diet formulations as detailed in recent publications on optimum vitamin nutrition of poultry to improve health, welfare, performance and the quality of poultry products.

Effects of Maternal and Progeny Dietary Vitamin Regimens on the Performance of Ducklings

“…In this study, increased growth performance was observed in ducklings fed a diet with high-vitamin premix designed according to the recommendations in the DSM Vitamin Supplementation Guidelines. These observations clearly demonstrate a shortcoming in the current NRC (1994) vitamin recommendations for ducks and are highly consistent with the view of Leeson (2007) that the vitamin requirements of poultry require re-evaluation. Interestingly, maternal and progeny dietary vitamin regimens interactively affected growth performance in the first 14 days post hatching.…”

Níveis vitamínicos para frangos de corte

“…Vários estudos realizados para determinar as necessidades de vitaminas para frangos foram realizados em condições controladas e/ou com dietas purificadas ou semipurificadas, de alta digestibilidade, sendo compostas por ingredientes pouco usuais na alimentação de frangos, o que também demonstra a baixa correlação com a realidade no campo (LEESON, 2007). Além disso, poucos são os trabalhos conduzidos nos últimos 30 anos para estimar as exigências de vitaminas para frangos, os quais apresentam maior potencial genético de crescimento, com melhora superior a 20% na conversão alimentar (CA) (PÉREZ-VENDRELL et al, 2002) e ganho de peso médio diário 87% superior (de 26,8g dia -1 em 1970 a 50g dia -1 em 2000) (BARROETA et al, 2002).…”

“…Geralmente respostas significativas do sistema imune ocorrem apenas quando as vitaminas são suplementadas em níveis pelo menos 10 vezes superiores aos do NRC (1994) ou duas a três a vezes maiores que os utilizados comercialmente (LEESON, 2007).…”

“…A literatura apresenta grande variação acerca dos níveis de vitaminas empregados comercialmente para frangos (BASF, 1995;BARROETA et al 2002;LEESON, 2007). Sendo assim, em virtude das dificuldades em estabelecer os níveis vitamínicos para frangos, a presente revisão teve como objetivo apresentar os conceitos atuais na avaliação das exigências de vitaminas para frangos e os níveis sugeridos pela indústria e pelo meio científico.…”

Relação vitamina E: vitamina C sobre a qualidade da carne de frangos submetidos ao estresse pré-abate

“…Cortinas et al (2005) concluíram que a suplementação com até 200mg/kg de α-tocoferol previne até 88% da máxima oxidação lipídica, no entanto níveis superiores a este não apresentaram melhora na estabilidade da carne de coxas de frangos. Segundo Leeson (2007), geralmente a suplementação de 100-400UI de vitamina E/kg de dieta tem demonstrado promover a qualidade da carne na maioria dos estudos.…”