Effects of β-hydroxy-β-methylbutyrate inclusion on growth performance and fillet quality of olive flounder Paralichthys olivaceus fed low fishmeal based diets

Abstract

β-Hydroxy-β-methylbutyrate (HMB) has been shown to improve animal growth and muscle quality. An 8-week feeding trial was thus performed to investigate whether HMB supplementation could improve the growth and fillet quality in olive flounder Paralichthys olivaceus fed low fishmeal based diets. Fish (body weight: 1.29 ± 0.00 g) were fed a fishmeal-based diet (named FM diet containing 60 % fishmeal), a low fishmeal based diet (named SM diet, 36 % fishmeal was replaced by soybean meal based on the FM diet) and the SM diet supplemented with 0.05 %, 0.1 %, 0.2 % and 0.4 % β-hydroxy-β-methylbutyrate calcium (named SMH0.05, SMH0.1, SMH0.2 and SMH0.4 diets respectively). Results showed that weight gain rate (WGR) and specific growth rate (SGR) of fish fed FM were significantly higher than those of the SM and HMB-supplemented groups. These parameters in the SMH0.1, SMH0.2 and SMH0.4 groups were significantly enhanced than in fish fed SM with the highest values observed in the SMH0.2 group. Fish fed SMH0.2 and FM shared similar feed efficiency ratio (FER) and protein efficiency ratio (PER) which were significantly higher than those of the SM and SMH0.05 groups. Meanwhile, fish fed SM displayed significantly lower fillet hardness, springiness and chewiness, while higher muscle liquid loss and water loss than those of the FM group. Inclusion of 0.2 % and 0.4 % HMB significantly increased above texture parameters of fish fed SM, though these values still did not reach to levels achieved in the FM group. But muscle liquid loss and water loss were both reduced to levels similar as those in fish fed FM by supplementing 0.2 % and 0.4 % HMB. Myofiber density and sarcomere length of fillet in the SMH0.2 group were significantly elevated than in fish fed SM, although these values were still significantly lower than in the FM group. Moreover, fish fed SM exhibited significantly lower expression of myogenic regulatory factors (myf5, myod and mrf4) and protein synthesis-related factors (igf1, pi3k, akt, tor, s6, P-TOR and PS6), while higher transcriptions of protein degradation-related genes (foxo1, murf-1 and mafbx) in muscle than those of the FM group. However, HMB inclusion in SM diet restored the expression of above genes and proteins to some extent with the maxima or minima found in the SMH0.2 group. In conclusion, dietary HMB improved growth and fillet texture of olive flounder fed low fishmeal based diets. The appropriate HMB level in SM diet for olive flounder was estimated to be 0.2 % based on the growth and feed performance parameters (WGR, SGR, FER and PER).