Investigation of nutritional profile, protein solubility and in vitro digestibility of various algae species as an alternative protein source for poultry feed

Abstract

Alternative protein sources, particularly seaweed and microalgae, have long been considered a potential source of protein for poultry feed. Currently, several species of algae are a special focus of animal nutrition in order to replace soybean meal (SBM) due to its high protein content and abundance of vitamins, minerals and pigments. Determining nutrient and digestibility of a new ingredient is the first step in evaluating its suitability for use in poultry feeds. This study aimed to evaluate nutritional composition and digestibility of five algae including Caulerpa lentillifera J. Agardh, Ulva rigida C. Agardh, Spirulina sp., Coelastrella sp. (KKUP1) and Scenedesmus sp. (KKUP2). We evaluated nutritive value, amino acid profiles and physical characteristics microscopically. Protein solubility and in vitro digestibility, i.e., dilute pepsin digestibility (DPD) and two-phase gastric pancreatic digestibility (GPD), were performed by incubating algae samples in porcine pepsin and porcine pancreatin with a protease, lipase and amylase enzyme solution to determine suitability of algae as a protein ingredient in poultry feed. Results showed that Spirulina sp. had the highest protein content (44.44 % of dry matter basis; P < 0.0001) and was rich in amino acids (Lys, Thr and Trp). Moreover, protein solubility, digestibility (DPD and GPDProtein) and digestible protein of Spirulina sp. were significantly higher than those of other species (52.35 %, 49–67 % and 20.70 %, respectively). On the other hand, energy digestibility (GPDEnergy) and digestible energy were highest in Ulva rigida (99.40 % and 15.29 MJ kg−1, respectively; P < 0.0001). These results imply that Spirulina sp. was more suitable for utilization as an alternative protein source for SBM substitution in poultry feed formulation. This characterization of biochemical composition and in vitro digestibility of algae represents the preliminary methodology used to initially select algae for use as a protein source in animal feed and additional in vivo tests are warranted.