Adequate levels of dietary sulphur amino acids impart improved liver and gut health in juvenile yellowtail kingfish (Seriola lalandi)

Abstract

The sulphur amino acids methionine and cysteine and their derivative taurine are metabolically active molecules with interlinked roles in nutritional requirements. Deficiencies in these nutrients are linked to poor growth and health; however, the impacts of these deficiencies on organ structure and function are largely unknown. This study examined the effects of dietary methionine, cysteine, and taurine fed at different levels on yellowtail kingfish liver histology and surface colour, plasma biochemistry, and posterior intestine histology. Samples were collected from two dose-response feeding trials that quantified (1) the taurine requirement and sparing effect of methionine by feeding yellowtail kingfish diets containing one of seven levels of taurine at one of two levels of methionine, and (2) the methionine requirement and sparing effect of cysteine by feeding yellowtail kingfish diets containing one of five levels of methionine at one of two levels of cysteine. Yellowtail kingfish fed inadequate levels of dietary methionine, cysteine, and taurine exhibited thicker bile ducts, less red livers, more intestinal acidic goblet cell mucus and supranuclear vacuoles, and less posterior intestinal absorptive surface area. Further, thicker bile ducts correlated with less red livers (a*, R), whereas increased hepatic fat correlated with a liver yellowing (b*). Our results indicate a shift toward histological properties and functions indicative of improved intrahepatic biliary condition, posterior intestinal nutrient absorption and homeostasis of yellowtail kingfish fed adequate amounts of methionine, cysteine, and taurine. These findings may assist in formulating aquafeed for optimized gastrointestinal and liver functions and maintaining good health in yellowtail kingfish.

Effects of cysteine addition to low-fishmeal diets on the growth, anti-oxidative stress, intestine immunity, and Streptococcus agalactiae resistance in juvenile golden pompano (Trachinotus ovatus)

“…Meanwhile, non-specific serum immune parameters were improved, and the levels of immunoglobulins (IgM, IgA, and IgG), complement 3, complement 4, and LZM activity were increased, which may help the fish cope with oxidative stress and immunity reduction caused by low-fishmeal diets, thus improving growth performance. Our findings are similar to those found in Seriola lalandi ( 47 ) and Scophthalmus maximus L ( 48 ), where cysteine enhanced growth performance by improving resistance to oxidative stress and intestine immunity.…”

“…Oxidative stress and immune capacity reduction caused by low fishmeal content are the main reasons for reduced growth performance ( 8 , 9 , 46 ). In the present study, there were many reasons that cysteine supplementation improved the growth performance of golden pompano in low fishmeal conditions, such as the increased abundance and diversity of gut microbes ( 31 ), increased antioxidant capacity ( 47 , 48 ), and improved immune ability ( 27 ). Our results showed that dietary supplementation with 0.6%–1.2% cysteine could increase the activity of serum antioxidant enzymes (T-AOC, CAT, and GSH-PX) and decrease the serum MDA and ROS levels in juvenile golden pompano.…”