This study verified the effects of feeding frequency on growth, blood metabolites, digestive enzyme activities (alkaline protease, acid protease, amylase and lipase) and proximate composition of Lebranche mullet juveniles. Fish with initial weight of 13.6 ± 0.7 g were distributed in twelve tanks and fed one, three, five and seven times per day to apparent satiation for 60 days. While the final weight of fish fed only once a day attained just 15.4 ± 0.7 g, those fed five or seven times per day reached 54.0 ± 12.1 and 55.9 ± 6.1 g respectively. The feed consumption also increased at high frequencies, but feed efficiency was higher (76.7 ± 11.7%) when mullets were fed three times per day. In general, increasing feeding frequencies also increased blood content of metabolites (total protein, glucose, triglycerides and cholesterol), possibly due to increased intake and absorption of nutrients. The response of digestive enzymes correlated with feeding efficiency, with higher activity in fish fed three or five times per day. Concerning whole-body proximate composition, no significant difference was observed in protein, but lipid content increased significantly with feed frequency. Based on growth performance and biochemical responses, we recommend feeding Lebranche mullet juveniles three to five times per day. Filipe dos Santos Cipriano https://orcid.org/0000-0001-8333-9883 How to cite this article: Calixto da Silva E, Sterzelecki FC, Alves Musialak L, et al. Effect of feeding frequency on growth performance, blood metabolites, proximate composition and digestive enzymes of Lebranche mullet (Mugil liza) Juveniles.

The present study aimed to evaluate the activation characteristics of the lebranche mullet spermatozoa in natura and diluted with CF-HBSS for 96h at 4±2°C. The semen was collected from eight wild fish in Florianópolis -SC (Brazil) (27°S) in May, during reproductive migration. Three pools of semen were divided into two treatments: in natura and diluted with CF-HBSS 1:3. The semen was activated with seawater (salinity of 34, pH 8.7 and 4±2°C) to determine: motility time, motility rate and sperm cell membrane integrity. Dilution with CF-HBSS 1:3 increased motility time of diluted semen (15-20% for 6, 12 and 18h). Motility rate was equal to fresh semen for up to 24h of refrigeration and it was 30% higher than in natura semen at 12, 18 and 24h. Cell membrane integrity was maintained in fresh semen up to 6h, and it was 15-20% higher than in natura semen from 6 to 48h (p < 0.05). The use of CF-HBSS as diluent in the ratio 1:3 is recommended for semen refrigeration of lebranche mullet.

The feed provided to breeding fish is one of the main factors influencing the quality of fish gametes. This study was carried out to evaluate the influence of ascorbic acid on growth, haematological parameters and sperm quality of Lebranche mullet males (Mugil liza). Six diets with different levels of ascorbic acid (0; 53; 107; 216; 482 and 708 mg/kg) were tested in triplicate for 75 days. During spermiation (first gonadal maturation), 144 individuals (205.7 ± 11.5 g and 25.7 ± 0.4 cm) were randomly distributed in 18 experimental tanks. Growth parameters were evaluated at the beginning and end of the experiment. Fish blood was collected to analyse glucose, total protein and erythrocyte count (EC) (n = 9). Fish (n = 12) from each treatment were euthanized to determine hepatosomatic index (HSI) and gonadosomatic index (GSI). Semen was collected to evaluate spermatic density, cell membrane integrity and sperm motility. No difference (p > .05) was found on growth parameters, GSI, HSI and total protein. However, EC was lower in fish fed without ascorbic acid (the control group). Ascorbic acid supplementation provided positive effects on sperm characteristics. Fish from treatments with 53 and 107 mg/kg presented the best results for motility time (133.30 ± 4.25 and 135.00 ± 2.77 respectively). Treatments with 107, 216 and 708 mg/kg provided the best results for motility rate (92.0 ± 2.9%, 93.0 ± 5.8% and 93.0 ± 5.8% respectively). Supplementation with 107 and 216 mg/kg provided the best results for plasma membrane integrity (70.12 ± 9.10% and 76.3 ± 3.1% respectively). Lower spermatic density was observed in fish without ascorbic acid supplementation, although no difference was found in sperm density among the treatments with ascorbic acid (p < .05). Considering these results, supplementation of dietary ascorbic acid between 107 and 216 mg/kg optimizes the spermatic quality in males of lebranche mullet.

Conservation of fish gametes is critical to increasing the success of induced reproduction and is widely used in aquaculture farming . Refrigeration at temperatures close to 4°C is one of the techniques commonly adopted to preserve semen for short periods, to keep semen quality feasible for hours, days and even weeks, maintaining its fertilization capacity (Contreras et al., 2019;Shaliutina et al., 2013). For this to occur, it is necessary to use diluting solutions that provide a protective medium, while both nourishing and reducing cell metabolism of sperm during storage conditions (Silva et al., 2018).Studies with fish have demonstrated the positive effects of refrigeration associated with the use of cryoprotectants among which