Effects of feeding frequency on growth performance, feed intake, metabolism and expression of fgf21 in grass carp (Ctenopharyngodon idellus)

Abstract

Grass carp (Ctenopharyngodon idellus) is one of the most important freshwater cultural species in China. However, obesity, fatty liver and digestive tract inflammation commonly exist in commercial grass carp, which may be due to excessive food and energy intake in daily feeding. Therefore, the feeding strategy should adapt to fish appetite, nutrition requirements and welfare in intensive aquaculture. To investigate the effects of feeding frequency on growth, physiology and metabolism-related fgf21 expression to provide a reference for the selection of feeding strategy, healthy and homogeneous juvenile grass carp (45.2 ± 2.5 g) were randomly divided and adapted to four feeding frequencies of 1, 2, 3 or 4 times/day following satiated feeding for 8 weeks. The growth rate increased with increasing feeding frequency. The hepatosomatic and abdominal fat-somatic indexes were higher in the higher feeding frequency groups, while the gut-somatic index was higher in the low feeding frequency groups (P < 0.05). The actual feeding ration increased from 1.3% to 3.5% with increasing feeding frequency (P < 0.05), and the feed conservation ratio increased from 1.5 to 2.3, but there was no significant difference between 3 and 4 meals/day (P˃0.05). The levels of serum glucose, triglycerides and total cholesterol also increased with increasing feeding frequency, while glycogen levels were higher in the 1 time/day group in both liver and muscle. The activities of digestive enzymes were higher in the high feeding frequency groups. Fgf21 gene expression was relatively low in the low feeding frequency group in all tissues, and the expression levels increased with increasing feeding frequency in the liver and muscle. Overall, the optimal feeding frequency to enhance the growth and health of juvenile grass carp is 3 times/day under apparent satiation.