The present disclosure relates oligosaccharide preparations suitable for use in nutritional compositions such as animal feed and methods of manufacturing the described oligosaccharide preparations. The present disclosure further relates to nutritional compositions that comprise the oligosaccharide preparations. The disclosed oligosaccharide preparations can be advantageous as an animal feed due to, at least in part, their prebiotic utility and the presence of anhydro-subunit containing oligosaccharides, which can be used to detect and/or determine the presence and content of the disclosed oligosaccharide preparations in the nutritional composition.