Browsing by Person "Novotny, Moritz Sebastian Daniel"

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Phytate degradation and phosphorus digestibility in turkeys and broiler chickens fed maize-based diets
(2023) Novotny, Moritz Sebastian Daniel; Rodehutscord, Markus
A growing global human population, stagnation in available land for farming, and an increased interest in sustainable and eco-friendly food production necessitates a highly efficient and environmentally friendly food production. This includes the already very feed-efficient poultry meat production. Currently, using non-renewable mineral phosphate as feed additive is industry standard in poultry nutrition. This can lead to unwanted eutrophication of waterbodies by high faecal concentrations of unutilised plant-based phosphate. Degrading phytate via enzymatic hydrolysation by phytases drastically improves digestibility of plant-based phosphate. With dietary phytase supplementation, a tool is available to reduce necessity of dietary phosphate supplementation. However, predictability of the extent to which phytase supplementation can replace phosphate supplementation is not accurate enough to forego phosphate supplementation entirely. Subject of this doctoral thesis was to study the factors that can influence phytate degradation in the digestive tract of poultry, in order to improve predictability of plant-based phosphate digestibility. The focus was put on maize-based diets, as they are very common worldwide and phytate degradation is challenging due to low intrinsic phytase activity of maize. A literature review on the current state of knowledge on phytate degradation and phosphorus digestibility of chicken fed maize-based diets was conducted. Part of this review was to compare findings for chickens to findings in other poultry species. There is a plethora of studies that investigated the subject in broilers but comparatively little information on turkeys. There were indications of fundamental differences between broilers and turkeys. Consequently, the intention was to identify reasons for these differences and to evaluate to which extent knowledge transfer from chickens to turkeys is possible. Two consecutive trials comparing broilers and turkeys were designed. Factors studied were: supplemented phytase, dietary phosphorus and calcium concentration, age, and endogenous mucosal phosphatase activity. Broilers and turkeys studied were kept simultaneously and under identical conditions, including experimental diets. A total of 480 broiler and 480 turkey hatchlings were obtained at the same day and raised at the experimental facility. Halve of the animals of each species underwent the experiment from day 14 to day 21, the other halve from day 35 to day 42. This set up was chosen to study the influence of physiological development, as species with different maturation rates were compared. In 3-week-old broilers and turkeys, precaecal InsP6 disappearance was the same when no phytase was supplemented and dietary calcium and phosphorus level was low. This coincided with no differences in jejunal mucosal phosphatase activity. Without phytase supplementation, 6-week-old turkeys showed higher precaecal InsP6 disappearance than 6-week-old broilers. This coincided with higher jejunal mucosal phosphatase activity in turkeys than broilers. When phytase was supplemented, precaecal InsP6 disappearance was markedly increased in both species. This increase was always higher in broilers compared to turkeys of the same age. Increased dietary calcium and phosphorus levels led to decreased precaecal InsP6 disappearance in both species. This led to the conclusion that previously reported differences in precaecal InsP6 disappearance between broilers and turkeys were primarily due to the higher dietary calcium and phosphorus concentrations used in turkey diets, and secondly due to more phytate degradation by supplemented phytase in the crop of broilers compared to turkeys. The latter was attributed to more favourable conditions for the supplemented phytase. Although turkeys appeared to have compensated much of that in the more posterior parts of the digestive tract. Jejunal mucosal phosphatase activity was higher in treatments with phytase supplementation than without. As this coincided with high concentrations of lower inositol phosphates in the digesta, these might have triggered increased expression of phosphatases on the brush border membrane. In contrast, an increase in dietary calcium and phosphorus level coincided with a decrease in jejunal mucosal phosphatase activity, numerically in 3-week-old birds, but significantly in 6-week-old birds. This might indicate a downregulation of mucosal phosphatase expression based on phosphate concentration in the small intestine. In conclusion, fundamental mechanisms affecting phytate degradation in the digestive tract of broilers and turkeys seem to be the same. However, there is one big difference in recommended dietary calcium and phosphorus levels and many small differences in important details affecting phytate degradation and phosphate digestibility between the two species. These require dedicated attention to further improve phosphorus efficiency in poultry production.