Reproductive performance of female largemouth bass (Micropterus salmoides) broodstock was enhanced by dietary small peptides

Abstract

To research the effects of dietary small peptides on the reproductive performance of largemouth bass (Micropterus salmoides) broodstock, four isonitrogenous and isolipidic diets were prepared by adding 5 % small peptide (SP) on two fish meal levels (40 and 20 %), which were labeled as HF (40 % FM), HS (40 % FM+5 % SP), LF (20 % FM) and LS (20 % FM+5 % SP), respectively. 160 female largemouth bass broodstock (initial body weight: 452.36 ± 15.54 g) were randomly allocated to four groups with 4 tanks per group of 10 fish each. A 30-day feed experiment was conducted. Results showed that gonadosomatic index (GSI) of largemouth bass was higher in the 5 % SP group (8.51 ± 1.57 %) than that in the 0 % SP group (7.74 ± 1.82 %) (P < 0.05); GSI (6.83 ± 0.95 %) and relative fertility (RF, 90.64 ± 15.68 eggs/g) were significantly lower in the 20 % FM groups (P < 0.05), based on two-way ANOVA analysis. The contents of vitellogenin (VTG, 318.15 ± 26.15 μg/L), estradiol (E2, 42.90 ± 0.31 ng/L) and follicle-stimulating hormone (FSH, 23.04 ± 0.74 U/L) in serum were higher in the HS group than those in other groups (P < 0.05). The mRNA expression levels of vitellogenin receptor (vgr, 1.64 ± 0.41), follicle stimulating hormone receptor (fshr, 1.77 ± 0.35) and cytochrome P450 17a (cyp17a, 2.42 ± 1.02) in gonad were up-regulated in the 5 % SP group (P < 0.05). The mRNA expression levels of vgr (1.90 ± 0.29), insulin-like growth factor-1 (1.53 ± 0.67), steroidogenic acute regulatory protein (2.59 ± 0.78), fshr (1.97 ± 0.35) and cyp17a (2.78 ± 1.32) in gonad were up-regulated in the HS group (P < 0.05). The results indicated that the reproductive performance of female largemouth bass could be enhanced by adding 5 % SP to 40 % fish meal die. However, reproductive performance was negatively affected by 20 % fish meal in the diet, which provided a reference for the application of small peptides in the formulated feed for largemouth bass broodstock.