Developing efficient feeding and weaning protocols for Betta splendens informed by larval digestive physiology

Abstract

Betta splendens, also known as the Siamese fighting fish, is an anabantoid native to Southeast Asia and is among the top ten freshwater ornamental fish species imported into the USA for the aquarium trade. Although B. splendens is a staple in the ornamental aquaculture industry, larval production continues to rely heavily on the use of Artemia spp. nauplii. Digestive physiology data can be used to minimize the use of costly live feeds during larval production by indicating when larvae can digest complex feeds like microdiets (MDs). A 30-day trial was conducted to determine the timing of the maturation of the digestive tract. Standard microplate assays were conducted to quantify pepsin, trypsin, and lipase activities and histology was used to describe digestive tract morphology. Pepsin activity and the development of gastric glands indicated the presence of a functional stomach between 15 and 18 DPH (days post-hatch). Next, a 42-day dietetics trial was conducted to determine which of three commercially available MDs best promoted growth and survival in larval B. splendens compared to an Artemia spp. reference diet. Survival was statistically similar for larvae fed Gemma Micro compared to the Artemia spp. reference diet and all MD treatments yielded significantly higher growth compared with the reference diet. Finally, a 25-day weaning trial was conducted where MD was introduced at three timepoints surrounding the development of the digestive tract. Larvae were subjected to one of five treatments: Artemia spp. reference diet, MD from first-feeding, or MD introduction at 12, 15, or 18 DPH. MD introduction at 15 and 18 DPH yielded similar survival and growth compared to the Artemia spp. reference diet. MD from first-feeding yielded statistically lower survival and growth compared to all other treatments. These results suggest that B. splendens can transition to a MD as early as 15 DPH without reducing growth or survival.