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Duckweeds are fast-growing and nutritious plants, which are gaining increased attention in different fields of application. Especially for animal nutrition, alternative protein sources are needed to substitute soybean meal. The current bottleneck is the standardized production of biomass, which yields stable quantities of a defined product quality. To solve this problem, an indoor vertical farm (IVF) for duckweed biomass production was developed. It consists of nine vertically stacked basins with a total production area of 25.5 m2. The nutrient solution, a modified N-medium, re-circulated within the IVF with a maximum flow rate of 10 L min−1. Nutrients were automatically added based on electrical conductivity. In contrast, ammonium was continuously supplied. A water temperature of 23 °C and a light intensity of 105 μmol m−2 s−1 with a photoperiod of 12:12 h were applied. During a 40-day production phase, a total of 35.6 kg of fresh duckweed biomass (equals 2.1 kg of dried product) was harvested from the IVF. On average, 0.9 kg day−1 of fresh biomass was produced. The dried product contained 32% crude protein (CP) and high levels of proteinogenic amino acids (e.g. lysine: 5.42 g, threonine: 3.85 g and leucine: 7.59 g/100 g CP). Biomass of this quality could be used as a protein feed alternative to soybean meal. The described IVF represents a modular model system for duckweed biomass production in a controlled environment and further innovations and upscaling processes.
A project was initiated to apply dietary CP reduction under commercial conditions. The main objective was to demonstrate and validate that dietary CP can be reduced without compromising broiler performance in a production system which is already rather efficient. In addition, we wanted to demonstrate the potential of dietary CP reduction on reducing N-excretions especially in the context of German revised regulations and monitoring attempts. Finally, as previous research suggested, few further aspects such as impact of dietary CP reduction on litter quality and quantity, footpad health, change of ingredient inclusion levels and related impact on sustainability impact factors were evaluated.