No abstract

An 8‐week feeding trial was conducted to investigate the effect of dietary selenium (Se) on feed intake, weight gain and antioxidant activity in juvenile grass carp (11.2 ± 0.03 g). Six Se levels (0.13, 0.41, 0.56, 1.12, 2.18 and 4.31 mg/kg) of semi‐purified diets were assayed in triplicate. The maximum weight gain, specific growth rate and feed intake were obtained in fish fed with 1.12 mg Se/kg diet. Hepatic glutathione peroxidase activity was markedly increased when dietary Se ≤1.12 mg/kg diet and reached a plateau when dietary Se ≥1.12 mg/kg diet. Hepatic superoxide dismutase and serum catalase activities in juvenile grass carp fed with 0.56, 1.12 and 2.18 mg Se/kg diets were all significantly higher than those in the other groups. The malondialdehyde content in liver and serum was firstly decreased and then increased with increasing dietary Se content, and the lowest content was observed in fish fed with 1.12 mg Se/kg diet. With the increase in Se level, the activities of serum alanine aminotransferase and aspartate aminotransferase were reduced. In addition, serum alkaline phosphatase activity and albumin content were highest in fish fed with 1.12 mg Se/kg diet. This study indicated that both the Se deficiency and excess of Se caused negative effect on the oxidative stress in juvenile grass carp and suggested that the health‐giving concentration of dietary inorganic Se was 1.12 mg/kg diet. Moreover, based on the broken‐line regression analysis of weight gain, the optimal concentration of dietary inorganic Se was 0.83 mg/kg for juvenile grass carp.

This study aimed to evaluate the fat deposition pattern and lipid metabolic strategies of grass carp in response to dietary lipid levels. Five isonitrogenous diets (260 g kg crude protein) containing five dietary lipid levels (0, 20, 40, 60, 80 g kg) were fed to quadruplicate groups of 15 fish with initial weight 200 g, for 8 weeks. The best growth performance and feed utilization was observed in fish fed with lipid level at 40 g kg. MFI and adipose tissue lipid content increased with increasing dietary lipid level up to 40 g kg, and higher lipid level in diet made no sense. Fish adapted to high lipid intake through integrated regulating mechanisms in several related tissues to maintain lipid homeostasis. In the present study, grass carp firstly increased PPARγ and CPT1 expressions in adipose tissue to elevate adipocyte differentiation and lipolysis to adapt to high lipid intake above 40 g kg. In liver, fish elevated hepatic lipid uptake but depressed biosynthesis of hepatic FAs, resulted in no difference in HSI and liver lipid content among the groups. Only in muscle, fish showed a significant fat deposition when the lipid intake above 40 g kg. The excess lipid, derived from enhanced serum TC and TG contents, was more likely to induce deposition in muscle rather than lipid uptake by adipose tissue in grass carp fed with high dietary lipid, indicating the muscle of grass carp might be the main responding organ to high lipid intake.

A feeding trial was conducted for 8 weeks to evaluate the effects of supplemental phytic acid (PA) on the apparent digestibility and utilization of dietary amino acids

Plant protein is the main substitution protein for fishmeal, especially rapeseed meal, and it contains anti-nutritional factors and toxicants such as tannin. Few studies have identified clear physiological or toxicological impacts of tannin on fish. Here, our experiment evaluated the physiological and toxicological effects of tannin on grass carp (Ctenopharyngodon idellus). Different concentrations of dietary tannin (1.5, 7.2, 19.9, 39.4, 83.2 and 162.0 g kg −1 diet) were tested. Dietary tannin (≥7.2 g kg −1 diet) inhibited feed intake, and the appetite-promoting gene expression (Grehlin, NPY, Y8a and Y8b), meanwhile, increased the appetite-inhibiting gene expression (CCK and CART).Moreover, tannin addition reduced feed utilization (dietary nutrient retention, fat depot, activity of protease, lipase and amylase) of grass carp (p < .05). Besides, high dietary tannin (≥39.4 g kg −1 diet) lowered immunity (serum superoxide dismutase and catalase activities and the contents of total protein, albumin, complement component C3 and C4) (p < .05) and damaged the hepatic structure of grass carp, leading to attenuated growth in grass carp. This suggests that grass carp could not tolerate dietary tannin of >19.9 g kg −1 . The second trial designed to test the alleviation the negative effect of tannin by tannase. After adding tannase with a dose of 1000 or 1500 U kg −1 to the diets, the weight gain of grass carp fed those diets was significantly increased compared with those fed the tannin and rapeseed meal addition groups (p < .05). Also, when high-level tannase was supplemented to the control diet, weight gain significantly improved. The decrease in feed intake by high dietary tannin and rapeseed meal was relieved through adding tannase in diet of grass carp, especially when tannase supplemented level reached 1000 U kg −1 diet (p < .05). This study indicates that dietary tannin (≥7.2 g kg −1 diet) negatively affects the growth of grass carp through changing feed intake, feed utilization, immunity and hepatic structure, and addition of tannase reached 1000 U kg −1 diet almost alleviate adverse effects of tannin and rapeseed meal (which included high contents of tannin) on grass carp.

Mandarin fish is a typical carnivorous fish, it can accept artificial diet after domestication, which is significantly essential to optimize its artificial diet. Nevertheless, only few studies were conducted on artificial diet of mandarin fish. Therefore, an 8-week feeding trial was conducted to evaluate the influence of feeding stimulants on growth performance, feed intake and appetite regulation of mandarin fish. In this trial, six diets were formulated, a basal diet contained 80% of Fish Meal without feeding stimulants, named as Control, 0.4% inosinic acid meal, 0.4% L-Alanine meal, 3%Yeast meal, 3% a commercial squid extract meal and 0.4% betaine meal were added into the basal diet to make five experimental diets, which were named as IM, AM, YM, SVO and BM respectively. At the end of feeding trial, SVO group showed higher feed intake, up-regulated mRNA expression of neuropeptide Y (NPY) and down-regulated mRNA expression of pro-opiomelanocorticoid (POMC) significantly as compared to control group, which suggested that squid extract improved feed acceptability and promoted appetite in mandarin fish. Similarly, compared to control group, SVO group showed low food conversion ratio, high weight gain and SGR, indicated that squid extract enhanced the growth performance. Our results suggested that the appropriate level of squid extract addition could contribute to optimize artificial diet in mandarin fish. K E Y W O R D Sfeed acceptability, growth performance, neuropeptide Y, pro-opiomelanocorticoid, Siniperca chuatsi, squid extract

No abstract

No abstract