Elevated sea temperature combined with dietary methionine levels affect feed intake and appetite-related neuropeptide expression in the brains of juvenile cobia (Rachycentron canadum)

This study aimed to determine the impact of elevated temperature combined with different levels of dietary methionine concentrations on feed intake (FI) and brain expression of selected neuropeptides and one receptor involved in appetite control in juvenile cobia (approximately 3.7 g body weight). The genes studies were neuropeptide y, npy; agouti-related protein, agrp; cocaine- and amphetamine-regulated transcript, cart; cholecystokinin, cck and melanocortin 4 receptor; mc4r. The cobia were reared at typical sea water temperature in Vietnam (30 degrees C) and elevated temperature (34 degrees C; selected as one of the predicted scenarios of climate change). The fish were fed diets with different levels of methionine: deficient (M9; 9.1 g/kg), sufficient (M12; 12.8 g/kg) and surplus (M16, 16.8 g/kg) for 6 weeks (triplicate tanks per treatment). Both dietary methionine concentration and temperature affected FI in cobia. Dietary methionine deficiency (i.e., M9) and elevated temperature reduced FI in cobia. Temperature significantly influenced the mRNA expression of agrp, cart, cck and mc4r. Expression of the orexigenic neuropeptide npy was consistently higher before the meal than after the meal for all diets and at both temperatures. At 30 degrees C, prefeeding levels of npy correlated with both increased methionine levels and FI. The interaction between dietary methionine and temperature on the levels of brain npy expression was significant (P<0.05). There was higher brain expression of agrp, cart and cck in cobia at 34 degrees C than in fish at 30 degrees C, which was correlated with a lower FI. In conclusion, both feeding, temperature and/or dietary methionine levels affected the brain expression of npy and agrp, cart, cck and mc4r. This suggests that these neuropeptides as well as the mc4r receptor are actively involved in adjusting feed intake to compensate for changing energetic demands, as well as metabolic adjustments due to the variable availability of methionine at elevated temperature.LA/P/0101/2020; QZA-0485 SRV-13/0010info:eu-repo/semantics/publishedVersio

Effect of increased rearing temperature on digestive function in cobia early juvenile

The present study is focused to elucidate the main characteristics of the digestive function of this carnivorous fast-growing fish living at high temperatures. With this aim, we have examined the effects of an increased temperature from 30 to 34 °C on the daily pattern of gastrointestinal pH, enzymatic proteolytic digestive activity and the feed transit time in early juveniles of cobia (Rachycentron canadum), a species living in tropical and subtropical waters with an increasing aquaculture production. Fish were fed two meals a day. Gastric luminal pH was permanently acidic (mean pH values: 2.76-4.74) while the intestinal pH increased from neutral/slightly acidic to slightly alkaline when the digesta was present, with an increasing alkalinity from proximal to distal intestine (mean pH values: 6.05 to 7.69). The temperature did not affect the gastric pH but a slightly higher acidity was induced in the intestine at 34 °C. Pepsin activity showed a daily rhythm at 30 °C with maximum in the middle of the light period, while at 34 °C some hourly changes coinciding with feed adding without a clear daily trend during the 24-h period were observed. The trypsin activity exhibited a daily rhythm at both temperatures with an increase after morning feeding to reach a maximum several hours later. Average pepsin activity during the daily cycle was slightly higher at 34 °C (6.1 and 7.3 U mg-1 BW at 30 and 34 °C respectively), but values were significantly different only at 8 and 24 h after the morning meal. Similarly, the trypsin activity was significantly affected by the temperature only at 8 and 16 h after the morning meal, but daily activity averages were similar (1.20 and 1.29 U g-1 BW at 30 and 34 °C respectively). The partial transit rates of the first meal in the stomach for each period inter-samplings were higher during the first 4-h period and decreased progressively along the rest of the 24-h cycle at both temperatures, but no significant differences were detected at 30 °C. In addition, the transit was notably faster at 34 °C particularly during the first 8 h after feeding, with rates between 100 and 65% of total volume displaced (intake or released) during each 4-h period. In the intestine the transit rate was relatively constant and similar at both temperatures during 12 h after feeding. Then the rates remained very low during the following 12 h. Residence time of the first meal was longer at 30 than at 34 °C, particularly in the stomach (12 h:02 min vs 4 h:54 min respectively). In the intestine the difference was not so large (8 h:18 min vs 6 h:24 min respectively). In a parallel study under same conditions, cobia reared at 30 °C grew faster and showed a more favorable feed conversion ratio than those at elevated temperature (34 °C). The present results indicate that at 34 °C, a subtle increase of proteolytic activity cannot compensate for the faster gut transit rate. Therefore, 30 °C is more appropriate temperature for the early on-growing of cobia because at higher temperatures the digestion efficiency decrease being one of the causes for a lower growth.Agência financiadora European Union (EU) 691150 MINECO, Spain + FEDER/ERDF contribution EFISHDIGESTAGL2014-52888 European Social Fund, the Operational Programme Human Potential IF/00482/2014/CP1217/CT0005 Portuguese Foundation for Science and Technology Portuguese Foundation for Science and Technology UDI/Multi/04326/2013 Norwegian Agency for Development Cooperation NORHED QZA-0485 SRV-13/0010info:eu-repo/semantics/publishedVersio

Cobia exhibits a permanent gastric acidity as digestion strategy

Póster presentado en el Aquaculture Europe 16 (Food for Thought), celebrado en Edimburgo del 20 al 23 de septiembre de 2016.This study examines the postprandial pH changes in the digestive tract of Cobia juveniles reared at 30° and 34° C. Cobia juveniles maintain a gastric luminal pH close to 4 throughout the day. A slight increase occurred after feeding due to the buffering and dilution effect of the ingested food and drinked sea water. In the intestine the luminal pH increased after the first meal and declines to neutral values by the end of the day. Higher alkalinization was observed in the intestine at 34° than at 30° C.Financed by Project WISEFEED funded by the EU H2020 programme (Marie Skłodowska-Curie grant No 691150). Additional funding from Norwegian Agency for Development Cooperation NORHED, No. QZA-0485 SRV-13/0010, and MINECO Spain, project EFISHDIGEST AGL2014-52888-R. S Engrola acknowledges a FCT investigator grant IF/00482/2014/CP1217/CT0005 funded by the European Social Fund, the Operational Programme Human Potential and the Foundation for Science and Technology of Portugal-FCT.Peer Reviewe

Effects of dietary methionine levels and temperaturas on feed intake and neuropeptide expressions in juvenile cobia (Rachycentron canadum)

Trabajo presentado al 10th International Fisheries Symposium celebrado en Vietnam entre el 5 y el 7 de diciembre de 2022.This study aims to explore the impact of dietary methionine concentrations combined with temperatures on feed intake (FI) and expressions of appetite neuropeptides (neuropeptide y, npy; agouti-related protein, agrp; cocaine- and amphetamine-regulated transcript, cart; and cholecystokinin, cck) and one receptor (melanocortin 4 receptor mc4r) in the brain of cobia. The juvenile cobia (ca 3.7g body weight) were reared in two recirculation systems at control temperature (30°C) and elevated temperature (34°C) at the Center for Aquatic Animal Health and Breeding Studies (Nha Trang University, Vietnam). The fish were fed diets with different levels of methionine; deficient (M9; 9 g/kg), sufficient (M12; 12 g/kg) and surplus (M16, 16 g/kg) for 6 weeks (triplicate tanks per treatment). Results showed that cobia fed M9 diet had a lower FI at both temperatures. Further, there was a significant interaction between dietary methionine levels and temperature on FI, with a lower FI in cobia at 34°C compared to fish kept at 30°C and fed the M12 diet and M16 diets. Feed intake was correlated to brain mRNA expression levels of npy and agrp, while temperature significantly influenced the mRNA expression of agrp, cart, cck and mc4r. Expression of the orexigenic neuropeptide npy were consistently higher before the meal compared to after the meal for all diets and at both temperatures. At 30°C pre-feeding levels of npy correlated with both increased methionine levels as well as FI. The interaction between dietary methionine and temperature on levels of brain npy expression was significant (P<0.05). There was a higher brain expression of agrp, cart and cck in cobia at 34 °C compared to fish at 30 °C that was correlated with a lower FI. In summary, both feeding, temperature and/or dietary methionine levels affected the brain expression of npy and agrp, cart and cck suggesting that these neuropeptides are actively involved in adjusting feed intake to compensate towards changing energetic demands as well as metabolic adjustments due to variable availability of methionine at elevated temperature

Feed intake and brain levels of appetite controlling neuropectides in cobia is affected by elevated water temperatures

Trabajo presentado en la International Conference and Exposition Aquaculture Europe 2017, celebrada en Dubrovnik del 17 al 20 de octubre de 2017.Increased sea temperature due to climate change will affect the physiology, behavior, and geographical distribution of marine species, including fish (Botkin et al., 2007). However, little information is available on the impact of elevated temperature and interactions with appetite, amino acid metabolism and growth in cobia (Rachycentron canadum), a candidate species in aquaculture. This work is part of a larger study aimed to determine whether there is a link and possibly a positive effect between the dietary methionine levels, elevated temperature and feed intake. Here we describe the effects on appetite and mRNA expression of the orexigenic (appetite stimulant) neuropeptide Y (NPY), agouti-related protein (AgRP), and the anorexigenic (appetite inhibiting) cocaine- and amphetamine-regulated transcript (CART) and cholecystokinin (CCK) in cobia brain.Project WISEFEED funded by the European Union’s H2020 programme (Marie Skłodowska-Curie grant No 691150). Additional funding from Norwegian Agency for Development Cooperation NORHED, No. QZA-0485 SRV-13/0010, MINECO Spain project EFISHDIGEST AGL2014-52888, and the European Social Fund FCT IF/00482/2014/CP1217/CT0005. Sofia Engrola cknowledges a FCT investigator grant IF/00482/2014/CP1217/CT0005 funded by the European Social Fund, the Operational Programme Human Potential and the Foundation for Science and Technology of Portugal (FCT).N

Growth, metabolism and N-retention in cobia at elevated water temperatures - The role of dietary methionine levels

Trabajo presentado en la International Conference and Exposition Aquaculture Europe 2017, celebrada en Dubrovnik del 17 al 20 de octubre de 2017.Increased sea temperature due to global warming will affect the physiology, behavior, and geographical distribution of marine fish (Botkin et al., 2007). Temperature is one of the vital factors affecting metabolism, growth and energy budget of fish, as for other ectothermic organisms (Hunter et al., 2016). Until now, there is no information available on the impact of temperature on amino acids metabolism on cobia (Rachycentron canadum), a candidate species in aquaculture. The present study aimed to determine the interactions of elevated temperature and dietary methionine on growth, metabolism and N-retention in cobia.Project WISEFEED funded by the European Union’s H2020 programme (Marie Skłodowska-Curie grant No 691150). Additional funding from Norwegian Agency for Development Cooperation NORHED, No. QZA-0485 SRV-13/0010; MINECO Spain, project EFISHDIGEST AGL2014-52888-R; and European Social Fund, IF/00482/2014/CP1217/CT0005. Sofia Engrola acknowledges a FCT investigator grant IF/00482/2014/CP1217/CT0005 funded by the European Social Fund, the Operational Programme Human Potential and the Foundation for Science and Technology of Portugal (FCT).N

Elevated sea temperature combined with dietary methionine levels affect feed intake and appetite-related neuropeptide expression in the brains of juvenile cobia (Rachycentron canadum)

This study aimed to determine the impact of elevated temperature combined with different levels of dietary methionine concentrations on feed intake (FI) and brain expression of selected neuropeptides and one receptor involved in appetite control in juvenile cobia (approximately 3.7 g body weight). The genes studies were neuropeptide y, npy; agouti-related protein, agrp; cocaine- and amphetamine-regulated transcript, cart; cholecystokinin, cck and melanocortin 4 receptor; mc4r. The cobia were reared at typical sea water temperature in Vietnam (30 °C) and elevated temperature (34°C; selected as one of the predicted scenarios of climate change). The fish were fed diets with different levels of methionine: deficient (M9; 9.1 g/kg), sufficient (M12; 12.8 g/kg) and surplus (M16, 16.8 g/kg) for 6 weeks (triplicate tanks per treatment). Both dietary methionine concentration and temperature affected FI in cobia. Dietary methionine deficiency (i.e., M9) and elevated temperature reduced FI in cobia. Temperature significantly influenced the mRNA expression of agrp, cart, cck and mc4r. Expression of the orexigenic neuropeptide npy was consistently higher before the meal than after the meal for all diets and at both temperatures. At 30°C, prefeeding levels of npy correlated with both increased methionine levels and FI. The interaction between dietary methionine and temperature on the levels of brain npy expression was significant (P<0.05). There was higher brain expression of agrp, cart and cck in cobia at 34°C than in fish at 30°C, which was correlated with a lower FI. In conclusion, both feeding, temperature and/or dietary methionine levels affected the brain expression of npy and agrp, cart, cck and mc4r. This suggests that these neuropeptides as well as the mc4r receptor are actively involved in adjusting feed intake to compensate for changing energetic demands, as well as metabolic adjustments due to the variable availability of methionine at elevated temperature.The study received funding from the European Union’s H2020 programme (Marie Skłodowska-Curie grant No 691150; WISEFEED). Additional funding was received from the Norwegian Agency for Development Cooperation NORHED, No. QZA-0485 SRV-13/0010, and MCIU-AEI + ERDF Spain project THERMODIGEST RTI2018-096134-B-I00. SE acknowledges an investigator grant IF/00482/2014/CP1217/CT0005 and national funds through projects UIDB/04326/2020, UIDP/04326/2020 and LA/P/0101/2020 from FCT. IR also acknowledges funds from the Research Council of Norway (grant No. 311627).Peer reviewe

Effect of rearing temperature on the digestive function in Cobia fry

Trabajo presentado en el 18th International Symposium on Fish Nutrition and Feeding (ISFNF. 40 years of research in fish nutrition), celebrado en Las Palmas de Gran Canaria del 3 al 7 de junio de 2018.Water temperature is a key factor affecting metabolic rates and therefore fish feeding physiology and behavior. These effects have a special significance in the scenario of the global warming. In this study we have examined effects of an increased water temperature on the daily pattern of gastrointestinal pH, enzymatic proteolytic digestive activity and the food transit time in early juveniles of cobia (Rachycentron canadum), a candidate species for aquaculture in tropical and subtropical waters. Juveniles (3.7±0.4 g wet BW) were randomly distributed to 6 experimental 200-L tanks (60 fish tank-1) and reared at two temperatures (30 and 34 °C) in recirculation systems for six weeks. Fish were fed twice a day (8:00 and 16:00h) with an experimental diet containing 47% protein and 10% lipid. At the end of the experiment, fish were sampled every 4 hours to obtain daily patterns of processes related to digestive activity. Cobia reared at 30oC grew faster and with higher FCR than those at elevated temperature (34oC). The fish reared at high temperature had lower intestinal luminal pH but similar gastric pH. Overall the pepsin activity during the complete daily cycle, but it was significantly different from the fish maintained at 30oC only at 8 hours post-feeding. Similarly, the trypsin activity was not significantly affected by the water temperature but tended to be higher at 34°C during the first hours postfeeding. The transit rate was notably faster 34°C in the stomach but similar in the intestine. These results indicate that the slight increase of proteolytic activity that was observed at 34°C cannot compensate for the faster gut transit rate. The reduced time the dietary proteins are available for hydrolysis can explain the lower growth observed at this temperature.Project WISEFEED funded by the European Union's H2020 program (Marie Skłodowska-Curie grant No 691150).N