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Protection of lysozyme with chitosan using radiant energy vacuum dehydration for control of clostridial necrotic enteritis in broiler chickens Zhang, Guopeng


The aim of this study was to develop a heat-stable and slow-release lysozyme-based product using radiant energy under vacuum (REV) technology by formulating lysozyme in a chitosan matrix so that the product could be used as a feed additive for more effective control of clostridial necrotic enteritis (NE) in broiler chickens. Lysozyme/chitosan was made into pastes with water at 25-45% solids content. These were dried with REV technology (300 watts microwave power under 4 KPa absolute pressure). Lysozyme retained its full activity during this process. A REV-treated sample produced with a paste containing 25% solids had a Tm of 124.6°C, which was substantially higher than that of spray-dried lysozyme (101.7°C). Thermal destruction curves constructed over a range of 100-130°C were used to determine D- and z-values of lysozyme and the REV-treated samples. REV products were consistently more heat-resistant than native lysozyme powder. A small scale feed pelleting study showed significantly better recovery of lysozyme in the chitosan protected REV product(P<0.05). The total porosity and pore size distribution of the REV products were analyzed with an Hg porosimeter. In the REV-treated samples, more than 80% of pore volume represented pore sizes ≥ 300 μm in radius, which were larger than those of native lysozyme powder. Surface structure analysis by scanning electron microscopy suggested the REV samples contained lysozyme evenly distributed inside the chitosan matrix. The REV samples released lysozyme more slowly in aqueous solution than lysozyme powder alone in water. A cage study was conducted to demonstrate the effect of Entegard™REV, the REV-treated lysozyme antimicrobial mixture, on the performance of broiler chickens and necrotic enteritis disease reduction of birds that were challenged with Eimeria maxima and Clostridium perfringens. Entegard™REV included in feed at 200 g/metric ton (MT) was very effective in reducing the negative health effects in the birds following NE challenge, and its ability to control the disease was not statistically different from a commonly used antibiotic growth promotant, bacitracin methylene disalicylate (BMD), at 55 g/MT.

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