Evaluation of nutritive value and in vitro rumen fermentation gas accumulation of de-oiled algal residues

Background：Algae are widely recognized for their high oil content and for exponentially accumulating biomass with particular potential to provide single cell protein for human consumption or animal feed.It is believed that along with biodiesel from algae,the high protein de-oiled algal residue may become an alternative feed supplement option in the future.This study was conducted to investigate de-oiled algal residue obtained from the common Chlorella species,Thalassiosira weissflogii,Selenarstrum capricornutum,Scenedesmus sp.,and Scenedesmus dimorphus for assessment as potential feed supplements for ruminants by comparing with soybean（Glycine max） meal and alfalfa（Medicago sativa） hay.Results：With the exception of T.weissflogii,algal residue had higher concentrations of Cu,Zn,and Mn and lower concentration of Ca,Mg,and K than soybean meal and alfalfa hay.The algal residue CP（crude protein）concentrations ranged from 140 to 445 g/kg DM and varied among the de-oiled residues.In vitro rumen fermentation gas accumulation curves indicated that algal biomass degradation potential was less than that of soybean meal or alfalfa hay by up to 41.7%.The gas production curve,interpreted with a dual pool logistic model,confirmed that the fraction sizes for fast fermenting and slow fermenting of de-oiled algal residues were smaller than those in soybean meal and alfalfa hay,and the fermenting rate of the fractions was also low.Conclusions：Inferior in vitro rumen gas accumulation from the five de-oiled algal residues suggests that these algal byproducts are less degradable in the rumen.

Selected dietary plant-based proteins for growth and health response of Nile tilapia Oreochromis niloticus

Tilapia culture is one of the largest sectors of global aquaculture.Among the different species of tilapia,Nile tilapia(Oreochromis niloticus)is perhaps the top cultured species.The production of Nile tilapia has been continually increasing throughout the years resulting in genetic deterioration.Several tilapia strains with better growth performance and adaptive capability to survive in different culture conditions have been developed to alleviate the crisis.Increased demand for Nile tilapia implies higher farming cost.Plant-based proteins are utilized as partial or complete fishmeal replacements to reduce feed cost.However,these proteins can adversely affect and alter growth and feed performance,carcass composition and indices,and gut and hepatic health.This review discusses the use of seven plant-based proteins:namely,soybean,copra,pea,corn,palm kernel,microalgae,and seaweed as a Nile tilapia aquafeed.Different processing methods are employed to produce several types of plant-based proteins.Processed plant-protein types,when utilized as an aquafeed ingredient,vary in its effect on the performance,hemato-immunological parameters,and gut and hepatic health of Nile tilapia.Studies have shown that Nile tilapia can effectively maximize plant-based protein diets based on the preparation method,type of plant source,amino acid supplementation,and inclusion levels of the plant proteins.These readily available crops should be considered as primary protein sources for aquaculture.Hindrances to the use of plant-based proteins as a main dietary protein are limiting amino acids,presence of anti-nutritional factors,and the competition between its demand as human food and as animal feed.